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What is an ultrasound?

Ultrasound produces sound waves that are beamed into the body causing return echoes that are recorded to "visualize"structures beneath the skin. The ability to measure different echoes reflected from a variety of tissues allows a shadowpicture to be constructed. The technology is especially accurate at seeing the interface between solid and fluid filledspaces. These are actually the same principles that allow SONAR on boats to see the bottom of the ocean.

What is ultrasonography?

Ultrasonography is body imaging using ultrasound in medical diagnosis. A skilled ultrasound technician is able to see

inside the body using ultrasonography to answer questions that may be asked by the medical practitioner caring for thepatient. Usually, a radiologist will oversee the ultrasound test and report on the results, but other types of physicians mayuse ultrasound as a diagnostic tool. For example, obstetricians use ultrasound to assess the fetus during pregnancy.Surgeons and emergency physicians use ultrasound at the bedside to assess abdominal pain or other concerns.

A transducer, or probe, is used to project and receive the sound waves and the return signals. A gel is wiped onto thepatient's skin so that the sound waves are not distorted as they cross through the skin. Using their understanding ofhuman anatomy and the machine, the technician can evaluate specific structures and try to answer the question asked bythe patient's physician. This may take a fair amount of time and require the probe to be repositioned and pointed indifferent directions. As well, the technician may need to vary the amount of pressure used to push the probe into the skin.The goal will be to "paint" a shadow picture of the inner organ that the health care practitioner has asked to be visualized.

The physics of sound can place limits on the test. The quality of the picture depends on many factors.

y Sound waves cannot penetrate deeply, and an obese patient may be imaged poorly.

y Ultrasound does poorly when gas is present between the probe and the target organ. Should the intestine bedistended with bowel gas, organs behind it may not be easily seen. Similarly, ultrasound works poorly in thechest, where the lungs are filled with air.

y Ultrasound does not penetrate bone easily.

y The accuracy of the test is very much operator dependent. This means that the key to a good test is theultrasound technician.

Ultrasound can be enhanced by using Doppler technology which can measure whether an object is moving towards oraway from the probe. This can allow the technician to measure blood flow in organs such as the heart or liver, or within

specific blood vessels.

For what purposes are ultrasounds used?

Ultrasound is not limited to diagnosis, but can also be used in screening for disease and to aid in treatment of diseases orconditions.

Diagnostic uses

Obstetrics

Ultrasound routinely for assessing the progression of pregnancy. Pelvic ultrasounds can be obtained trans-abdominallywhere the probe is placed on the abdominal wall, or trans-vaginally, where the probe is placed in the vagina. For example

ultrasound in obstetrics is used to diagnose growths or tumors of the ovary, uterus, Fallopian tubes.

Cardiology

Echocardiography

Echocardiography (echo=sound + cardio=heart + graphy=study) evaluates the heart, the heart's valve function, and bloodflow through them. It also evaluates the heart wall motion and the amount of blood the heart pumps with each stroke.

Echocardiography can be performed in two ways:

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y trans-thoracic: the probe is place on chest wall to obtain images, and

y trans-esophageal: where the probe is placed through the mouth into the esophagus.

Anatomically, the esophagus sits near the heart and allows clearer images. However, this approach is a little moreinvasive.

Different groups of illnesses can be assessed by echocardiography:

y Valves in the heart keep blood flowing in one direction when the heart pumps. For example, when the heart beats,blood is pumped from the left ventricle through the aortic valve into the aorta and the rest of the body. The aorticvalve prevents blood from back-flowing into the heart as it fills for the next beat. Echocardiography can determineif the valve is narrow or leaking (regurgitating, insufficient). By following how the patient fares clinically, repeatedechocardiograms can help determine whether valve replacement or repair is warranted. The same principles applyto the mitral valve which keeps blood flowing from the left atrium to the left ventricle.

y The heart muscle pumps blood to the body. If the heart weakens, the amount of blood it pumps with each beat candecrease, leading to congestive heart failure. The echocardiogram can measure the efficiency of the heart beatand how much blood it pumps; which assists in determining whether medications are needed. It also is used tomonitor how well medications are working.

y Echocardiography can visualize the heart chambers to detect blood clots in conditions such as atrial fibrillation(an irregular heart rhythm). In other situations, the test can help diagnose endocarditis (an infection of the heartvalves) by visualizing "vegetations" (an infected mass) on the valves themselves.

y Echocardiography also can detect abnormal fluid collections (pericardial effusions) in the pericardium.

y Echocardiograms are used to diagnose and monitor pulmonary artery hypertension.

Blood vessels

Ultrasound can detect blood clots in veins (superficial or deep venous thrombosis) or artery blockage (stenosis) anddilatation (aneurysms). Some examples of ultrasound testing include:

y Carotid ultrasound is performed in patients with transient ischemic attacks (TIAs) or strokes to determine whetherthe major arteries in the neck are blocked causing the decreased blood supply to the brain.

y The aorta is the large blood vessel leaving the heart that supplies blood to the rest of the body. The walls of theaorta are under significant pressure from the force of the heartbeat and over time, may weaken and widen. This iscalled an aneurysm, and it can be detected in the abdomen by ultrasound (abdominal aortic aneurysm). For thosepatients with small aneurysm, observation may be recommended and the aneurysm size followed over time byrepeated tests.

y Veins can also be evaluated by ultrasound and it is a common test to assess whether swelling in a leg is due to ablood clot, deep vein thrombosis (DVT) or another cause.

Abdominal structures

Aside from its use in obstetrics, ultrasound can evaluate most of the solid structures in the abdominal cavity. Thisincludes the liver, gallbladder, pancreas, kidneys, bladder, prostate, testicles, uterus, and ovaries.

y Ultrasound is the preferred to test to screen for gallstones or an infected gallbladder. The ultrasound can revealthe stones as well as signs of infection, including thickening of the gallbladder wall and fluid surrounding thegallbladder. The ultrasound may find blockage in the bile ducts.

y For those patients where the radiation of a CT scan (computerized tomography) is a potential risk (pregnantpatients or children), ultrasound may be used to look for diseases like appendicitis or kidney stones.

y Ultrasound is the test of choice to diagnose testicular torsion.

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y Pelvic ultrasound is used in gynecology to help assess non-pregnancy related issues like lower abdominal pain,ovarian cysts, uterine fibroids, uterine growths, and endometriosis.

The neck

The thyroid gland can be imaged using ultrasound looking for nodules, growths, or tumors.

Knee joint

Ultrasound can be used to detect bulging of fluid from a swollen knee joint into the back of the knee, called a Baker's cyst.

Screening uses

Ultrasound may be used to screen for blood vessel diseases. By measuring blood flow and blockage in the carotidarteries, the test can predict potential risk for future stroke. Similarly, by measuring the diameter of the aorta in theabdomen, ultrasound can screen for aneurysm (abnormal dilatation) and the risk of rupture. These tests may be indicatedfor an individual patient or they may be offered as a community wide health screening assessment.

Therapeutic uses

Ultrasound may be used to help physicians guide needles into the body.

In situations where an intravenous line is required but it is difficult to find a vein, ultrasound guidance may be used toidentify larger veins in the neck, chest wall, or groin.

Ultrasound may be used to guide a needle into a cavity that needs to be drained (for example, an abscess) or a mass thatneeds to be biopsied, where a small bit of tissue is removed for analysis.

What are the risks of ultrasound?

There are no known risks to ultrasound, and as technology has improved, the machines have become smaller, portableand available for use at the patient's bedside.

How do patients prepare for an ultrasound?

Preparation for ultrasound is minimal. Generally, if internal organs such as the gallbladder are to be examined, patients arerequested to avoid eating and drinking with the exception of water for six to eight hours prior to the examination. This isbecause food causes gallbladder contraction, minimizing the size, which would be visible during the ultrasound.

In preparation for examination of the baby and womb during pregnancy, it is recommended that mothers drink at least fourto six glasses of water approximately one to two hours prior to the examination for the purpose of filling the bladder. Theextra fluid in the bladder moves air-filled bowel loops away from the womb so that the baby and womb are more visibleduring the ultrasound test.

How are the results of ultrasound interpreted and communicated to the physician?

The ultrasound is generally performed by a technician. The technician will notice preliminary structures and may point outseveral of these structures during the examination. The official reading of the ultrasound is given by a radiologist, aphysician who is an expert at interpreting ultrasound images. The radiologist records the interpretation and transmits it to

the practitioner requesting the test. Occasionally, during the ultrasound test the radiologist will ask questions of thepatient and/or perform an examination in order to further define the purpose for which the test is ordered, or to clarifypreliminary findings.

Plain x-rays might be ordered to further evaluate early findings.

A summary of results of all of the above is reported to the health care practitioner who requested the ultrasound. Theythen are discussed with the patient in the context of overall health status.

What is an electrocardiogram (ECG, EKG)?

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The electrocardiogram (ECG or EKG) is a noninvasive test that is used to reflect underlying heart conditions by measuringthe electrical activity of the heart. By positioning leads (electrical sensing devices) on the body in standardized locations,information about many heart conditions can be learned by looking for characteristic patterns on the EKG.

How is an ECG (EKG) performed?

EKG leads are attached to the body while the patient lies flat on a bed or table. Leads are attached to each extremity (fourtotal) and to six pre-defined positions on the front of the chest. A small amount of gel is applied to the skin, which allowsthe electrical impulses of the heart to be more easily transmitted to the EKG leads. The leads are attached by small suctioncups, Velcro straps, or by small adhesive patches attached loosely to the skin. The test takes about five minutes and ispainless. In some instances, men may require the shaving of a small amount of chest hair to obtain optimal contactbetween the leads and the skin.

What is measured or can be detected on the ECG (EKG)?

1. The underlying rate and rhythm mechanism of the heart.

2. The orientation of the heart (how it is placed) in the chest cavity.

3. Evidence of increased thickness (hypertrophy) of the heart muscle.

4. Evidence of damage to the various parts of the heart muscle.

5. Evidence of acutely impaired blood flow to the heart muscle.

6. Patterns of abnormal electric activity that may predispose the patient to abnormal cardiac rhythm disturbances.

What conditions may be diagnosed with an ECG (EKG)?

1. Abnormally fast or irregular heart rhythms.

2. Abnormally slow heart rhythms.

3. Abnormal conduction of cardiac impulses, which may suggest underlying cardiac or metabolic disorders.

4. Evidence of the occurrence of a prior heart attack (myocardial infarction).

5. Evidence of an evolving, acute heart attack.

6. Evidence of an acute impairment to blood flow to the heart during an episode of a threatened heart attack(unstable angina).

7. Adverse effects on the heart from various heart diseases or systemic diseases (such as high blood pressure,thyroid conditions, etc.).

8. Adverse effects on the heart from certain lung conditions (such as emphysema, pulmonary embolus (blood clotsto lung), etc.).

9. Certain congenital heart abnormalities.

10. Evidence of abnormal blood electrolytes (potassium, calcium, magnesium).

11. Evidence of inflammation of the heart or its lining (myocarditis, pericarditis).

What are the limitations of the ECG (EKG)?

1. The EKG is a static picture and may not reflect severe underlying heart problems at a time when the patient is nothaving any symptoms. The most common example of this is in a patient with a history of intermittent chest paindue to severe underlying coronary artery disease. This patient may have an entirely normal EKG at a time when heor she is not experiencing any symptoms. In such instances, the EKG as recorded during an exercise stress testmay reflect an underlying abnormality while the EKG taken at rest may be normal.

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2. Many abnormal patterns on an EKG may be non-specific, meaning that they may be observed with a variety ofdifferent conditions. They may even be a normal variant and not reflect any abnormality at all. These conditionscan often be sorted out by a physician with a detailed examination, and occasionally other cardiac tests (forexample, echocardiogram, exercise stress test).

3. In some instances, the EKG may be entirely normal despite the presence of an underlying cardiac condition thatnormally would be reflected in the EKG. The reasons for this are largely unknown, but it is important to rememberthat a normal EKG does not necessarily preclude the possibility of underlying heart disease. Furthermore, apatient with heart symptoms can frequently require additional evaluation and testing.

Echocardiogram (Echo, 2D echo, cardiac ultrasound, echocardiography)

Definition:

An echocardiogram (often called "echo") is a graphic outline of the heart's movement . During an echocardiogramtest, ultrasound ( high-frequency sound waves) that comes from a hand-held wand placed on your chest, is usedto provide pictures of the heart's valves and chambers and help the sonographer evaluate the pumping action ofthe heart. Echo is often combined with Doppler ultrasound and color Doppler to evaluate blood flow across thehearts valves.

Your doctor uses the echocardiogram to:

y Assess the hearts function

y Determine the presence of disease of the heart muscle, valves and pericardium, heart tumors, and congenitalheart disease

y Evaluate the effectiveness of medical or surgical treatments

y Follow the progress of valve disease

To prepare for echocardiography:

y You can wear whatever you like to your appointment for echocardiogram. You will need to change into a hospitalgown to wear during echocardiography. Do not bring valuables.

y You may eat and drink as you normally would on the day of the echocardiogram test.y Take all of your medications at the usual times, as prescribed by your doctor.

What to expect during an echocardiogram procedure:

y Before the echocardiogram test, a cardiac sonographer (an allied health professional who has been trainedspecifically to perform ultrasound examinations), nurse or physician will explain the procedure in detail, includingpossible complications and side effects. They will be available to answer any questions you may have. You will begiven a gown to wear for your echocardiography procedure. You will be asked to remove your clothing from thewaist up. A cardiac sonographer will place three electrodes (small, flat, sticky patches) on your chest. Theelectrodes are attached to an electrocardiograph monitor (ECG) that charts your hearts electrical activity.Thesonographer will ask you to lie on your left side on an exam table. The sonographer will place a wand (called asound-wave transducer) on several areas of your chest. The wand will have a small amount of cool gel on the end,which will not harm your skin. This gel helps get clearer pictures. Sounds are part of the Doppler signal. You mayor may not hear the sounds during the test. You may be asked to change positions during the exam in order totake pictures of different areas of your heart. You may be asked to hold your breath at times. You should feel nomajor discomfort during the test. You may feel coolness from the gel on the transducer and a slight pressure ofthe transducer on your chest.The echo test takes about 40 minutes. After the echocardiogram test, you may getdressed and go home or go to your other scheduled appointments.

y After the cardiologist reviews your test, the results will go into your electronic medical record. Your physician willhave access to the results and will discuss them with you.

A cardiac stress test is the recording of the heart's activity while you exercise. Your heart is monitored by using electrodesto record the electrical activity it makes. Your heart's activity will also be monitored by seeing how your blood pressureand pulse change over the course of the test.

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Reasons for Test

During physical activity, the body needs higher levels of oxygen, which it gets from blood. To get the blood to the organsfaster during exercise, the heart has to work harder. A cardiac stress test is used to see if your heart still works well, evenwhen it is working hard. The test is most often done:

y To evaluate if complaints of chest pain are related to the heart

y To determine if arteries to the heart have blockages or narrowing (coronary heart disease or CHD)

y To identify an irregular heart rhythm or passing out that occurs during or after exercisey To monitor the heart's response to treatment or proceduresy To determine a safe level of participation before the start of an exercise regimen

y To plan rehabilitation after a heart attack

ECGs Revealing Cardiac Muscle Damage

Possible Complications

A cardiac stress test presents minimal risk. Complications can include:

y Developing chest painy Developing an irregular heart rhythm

y Having a heart attack (extremely rare)

Technicians are alert for any signs of heart or lung problems. They are prepared to take immediate action if complicationsdevelop. A doctor (usually a cardiologist) will be readily available during the stress test as well.

What to Expect

Prior to Test

Your doctor may do the following:

y Physical exam

y Resting electrocardiogram (ECG, EKG)a test that records the heart's activity by measuring electrical currentsthrough the heart muscle

y Echocardiograma test that uses sound waves (ultrasound) to examine the size, shape, and motion of the heartand the function of its valves

y Review of your medicines. Some medicine should not be taken before testing.

In the time leading up to your procedure:

y Do not eat or drink products with caffeine for 12-24 hours before testing.y Do not eat or drink anything except water for four hours before testing.

y Do not smoke for several hours before testing.

y Wear comfortable clothing and walking shoes or exercise sneakers.y Bring a list of your current medicines to the test.

y If you have diabetes, bring your glucose monitor to the test.

Description of Test

ECG electrodes will be attached to your chest. The electrodes are small, sticky patches with wires. Your resting bloodpressure and ECG readings will be taken.

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The cardiac stress test is done on a treadmill (most common) or a stationary bike. You will slowly start walking or riding.At regular intervals, the speed and elevation will be increased. Your ECG, blood pressure, heart rate, and symptoms will beclosely monitored.

The test may be stopped early if you feel extremely tired, get chest pain, have trouble breathing, or have any symptomsthat suggest heart problems. Significant changes in the ECG will also stop the test. After exercise is complete, your bloodpressure, heart rate, and ECG will be monitored until levels return to normal.

A doctor may also order a blood-flow imaging exam, called a nuclear stress test. A small amount of radioactive chemicalwill be injected into a vein when you are exercising at your peak. Scans will be taken while you lie in different positionsunder a special camera. The images will help to identify areas of the heart muscle that may not be receiving enoughoxygen. A second set of images will be taken about an hour later, after you have rested.

A stress echocardiogram may also be done. This is an ultrasound to take pictures of the heart before and immediatelyafter exercise.

After Test

You may resume normal activities.

How Long Will It Take?

The exercise portion of the test generally takes less than 15 minutes. Your entire appointment will last about an hour. Anuclear stress test may take up to 3-4 hours.

Will It Hurt?

Exercise testing normally causes no pain.

Results

A cardiologist will review the test results and send a report to your doctor. The report is often sent within 24 hours.

One or more of the following are considered a positive stress test:

y ECG changes that show low oxygen supply to the heart muscle

y You develop chest pain or trouble breathing, especially if associated with ECG changes

y Nuclear stress test results which show areas of your heart which are not receiving enough oxygen during exercise

y Failure to adequately increase heart rate and/or blood pressure during exercise

A positive test may mean CHD, but not all patients who test positive have CHD. Based on the results of the test, yourdoctor will decide if further testing or treatment is needed.

Call Your Doctor

After the test, call your doctor if any of the following occurs:

y Chest pain

y Pounding in the chest

y Dizziness or lightheadedness

y Feeling extremely tired or having trouble breathing

Doppler Ultrasonography

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photoplethysmograph. It is often attached to a medical monitor so staff can see a patient's oxygenation at all times. Most

monitors also display the heart rate. Portable, battery-operated pulse oximeters are also available for home blood-oxygen

monitoring.

Advantages

A pulse oximeter is useful in any setting where a patient's oxygenation is unstable, including intensive care, operating,recovery, emergency and hospital ward settings, pilots in unpressurized aircraft, for assessment of any patient'soxygenation, and determining the effectiveness of or need for supplemental oxygen. Assessing a patient's need foroxygen is the most essential element to life; no human life thrives in the absence of oxygen (cellular or gross). Although a

pulse oximeter is used to monitor oxygenation, it cannot determine the metabolism of oxygen, or the amount of oxygenbeing used by a patient. For this purpose, it is necessary to also measure carbon dioxide (CO 2) levels. It is possible that itcan also be used to detect abnormalities in ventilation. However, the use of a pulse oximeter to detect hypoventilation isimpaired with the use of supplemental oxygen, as it is only when patients breathe room air that abnormalities inrespiratory function can be detected reliably with its use. Therefore, the routine administration of supplemental oxygenmay be unwarranted if the patient is able to maintain adequate oxygenation in room air, since it can result inhypoventilation going undetected.

Because of their simplicity and speed, pulse oximeters are of critical importance in emergency medicine and are also veryuseful for patients with respiratory or cardiac problems, especially COPD, or for diagnosis of some sleep disorders suchas apnea and hypopnea. Portable, battery operated pulse oximeters are useful for pilots operating in a non-pressurizedaircraft above 10,000 feet (12,500 feet in the US)

[4]where supplemental oxygen is required. Prior to the oximeter's

invention, many complicated blood tests needed to be performed. Portable pulse oximeters are also useful for mountainclimbers and athletes whose oxygen levels may decrease at high altitudes or with exercise. Those using portable pulseoximeters are also making use of blood oxygen charting software. These charting methods provide print outs for the

patients physician of blood oxygen and pulse, and reminders to check blood oxygen levels.

Invasive

a. Bronchoscopy-is a test to view the airways and diagnose lung disease. It may also be used during the treatment

of some lung conditions.

How the Test is Performed

A bronchoscope is a device used to see the inside of thelungs. It can be flexible or rigid. Usually, a flexiblebronchoscope is used. The flexible bronchoscope is a tube

less than 1/2 inch wide and about 2 feet long.

The scope is passed through your mouth or nose, throughyour windpipe (trachea), and then into your lungs. Goingthrough the nose is a good way to look at the upper airways.The mouth method allows the doctor to use a largerbronchoscope.

A rigid bronchoscope requires general anesthesia. You willbe asleep.

If a flexible bronchoscope is used, you will be awake. Thedoctor will spray a numbing drug (anesthetic) in your mouthand throat. This will cause coughing at first, which will stop as

the anesthetic begins to work. When the area feels thick, it isnumb enough. You may get medications through a vein(intravenously) to help you relax.

If the bronchoscopy is done through the nose, numbing jellywill be placed into one nostril.

Once you are numb, the tube will be inserted into the lungs.The doctor may send saline solution through the tube. Thiswashes the lungs and allows the doctor to collect samples oflung cells, fluids, and other materials inside the air sacs. Thispart of the procedure is called a lavage.

Sometimes, tiny brushes, needles, or forceps may be passedthrough the bronchoscope and used to take tissue samples(biopsies) from your lungs. The pieces of lung material thatare removed are small. The doctor can also place a stent inthe airway or view the lungs with ultrasound during abronchoscopy.

How to Prepare for the Test

Do not eat or drink anything 6 - 12 hours before the test. Yourdoctor may also want you to avoid any aspirin, ibuprofen, orother blood-thinning drugs before the procedure.

You may be sleepy after the test, so you should arrange fortransportation to and from the hospital.

Many people want to rest the following day, so makearrangements for work, child care, or other obligations.Usually, the test is done as an outpatient procedure, and youwill go home the same day. Some patients may need to stay

overnight in the hospital.

How the Test Will Feel

Local anesthesia is used to relax the throat muscles. Until theanesthetic begins to work, you may feel fluid running downthe back of your throat and have the need to cough or gag.

Once the anesthetic takes effect, you may have sensations ofpressure or mild tugging as the tube moves through thewindpipe (trachea). Although many patients feel like they

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might suffocate when the tube is in the throat, there is NOrisk of suffocation. If you cough during the test, you will getmore anesthetic.

When the anesthetic wears off, your throat may be scratchyfor several days. After the test, the cough reflex will return in1 - 2 hours. You will not be allowed to eat or drink until yourcough reflex returns.

Why the Test is Performed

You may have a bronchoscopy to help your doctor diagnoselung problems. Your doctor will be able to inspect the airwaysor take a biopsy sample.

Common reasons to perform a bronchoscopy are:

y Lung growth, lymph node, atelectasis, or otherchanges seen on an x-ray or other imaging test

y Suspected interstitial lung disease

y Coughing up blood (hemoptysis)y Possible foreign object in the airway

y Cough that has lasted more than 3 months without

any other explanationy Infections in the lungs and bronchi

y Inhaled toxic gas or chemical

You may also have a bronchoscopy to treat a lung or airwayproblem, such as:

y Remove fluid or mucus plugs from your airways

y Remove a foreign object from your airways

y Widen (dilate) an airway that is blocked or narrowedy Drain an abscess

y Treat cancer using a number of different techniques

y Wash out an airway (therapeutic lavage)

Normal Results

Normal cells and secretions are found. No foreignsubstances or blockages are seen.

Normal value ranges may vary slightly among differentlaboratories. Talk to your doctor about the meaning of yourspecific test results.

What Abnormal Results Mean

y Infections from bacteria, viruses, fungi, parasites, ortuberculosis

y Aspiration pneumonia

y CMV pneumonia

y Chronic pulmonary coccidioidomycosisy Cryptococcosis

y Chronic pulmonary histoplasmosisy Pneumonia in immunocompromised host

y Pneumonia with lung abscess

y Pulmonary actinomycosis

y Pulmonary aspergilloma (mycetoma)

y Pulmonary aspergillosis (invasive type)

y Pulmonary histiocytosis X (eosinophilic granuloma)

y Pulmonary nocardiosis

y Pulmonary tuberculosis

y Interstitial lung diseasey Lung cancer or cancer in the area between the

lungs

y Narrowing (stenosis) of the trachea or bronchi

B. ABG Analysis

Arterial Blood Gas Interpretation

(ABG) Arterial Blood Gas Analysis is used to measure thepartial pressures of oxygen (PaO2), carbon dioxide (PaCO2),and the pH of an arterial blood sample. Oxygen content(O2CT), oxygen saturation (SaO2), and bicarbonate (HCO3-)values are also measured. A blood sample for ABG analysismay be drawn by percutaneous arterial puncture from anarterial line.

The ABG analysis is mainly used to evaluate gas exchangein the lungs. It is also used to assess integrity of the

ventilatory control system and to determine the acid-bas levelof the blood. The ABG analysis is also used for monitoringrespiratory therapy (again by evaluating the gas exchange inthe lungs).

Nursing considerations:

Your first look at an ABG result might prove to be confusing.Any patient who is critically ill might be given this test atregular intervals. Arterial blood gas determinations willindicate two basic bodily functions:

1. acid-base balance of the blood2. oxygenation status of the blood

ABG's will also indicate other important facts about apatient's status. However, the two functions above are themost important.

In a clinical situation, most nurses need only to understandthese two basic concepts. When the results of an ABG areabnormal, most hospitals today will have a lab procedure fornotification of the MD or to the ICU staff. But if you should beone of those "lucky" nurses who is floated to a critical carearea or a respiratory care area, you may have to interpret theresults by yourself. If you are able to do this, and fast, it maymean that the patient will get help fast.

Hypoxemia, acidemia, and alkalemia are important conceptswhich should be understood before beginning.

Hypoxemia is a term which refers to a lowered blood oxygencontent. This term and the term hypoxia are probably quitefamiliar to most nurses. They both will be used as meaningexactly the same. Hypoxia is the basis of one part ofinterpretation process. From above, we know thatoxygenation status of the patient can be critical during certaindisease states.

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Acidemia or acidosis is a term which refers to excessiveamounts of acid in the blood. Acids are produced naturally inthe body as a product of metabolism and other specific bodyprocesses. If our blood acid levels rise too high, it willinterfere with the health of the individual. This will be inaddition to the disease which is already present causing theacidosis.

Alkalosis, or alkalemia is the term which refers to thecondition of excessive bicarbonate ions (bases) in the blood.

As we mentioned above, this imbalance in the blood pH will

then cause further problems as the normal body recoverymechanism may also be interrupted.

On the next pages you will find an explanation of what theABG test is all about. We will also present the nursingconsiderations surrounding their interpretation. Read eachsection of the following text in order. The text builds up fromthe simpler concepts to the more complex concepts so eachnurse will be able to easily follow the interpretation process.When you fully understand one section, then go on to thenext section until you finally are able to interpret the ABG withthe fullest understanding.

Since this course is very clinically oriented, we will

concentrate on the aspects of ABG interpretation that applyto direct patient care. The clinical uses of ABG studies will belisted on the following pages. ABG studies may be helpful todiagnose and treat the following: (Brunner 1994)

1. unexplained tachypnea, dyspnea (esp. in patientswith cardiopulmonary disease)

2. unexplained restlessness and anxiety in bedpatients

3. drowsiness and confusion in patients receivingoxygen therapy

4. assessment of surgical risk5. before and during prolonged oxygen therapy and

during ventilator support of patients

6. progression of cardiopulmonary disease

Collecting the ABG specimen

The ABG is performed on a sample of arterial blood. Thespecimen is then obtained in a syringe prepared with heparinso as to prevent coagulation from occurring. The sample isthen placed in crushed ice and rushed to the lab for analysis.Each institution will have a slight variation in the method ofthe collection and in which department the sample will behandled. The reason for rushing the specimen and for usingthe ice is to prevent coagulation of the specimen, andspecifically, ice slows the clotting of the blood. Be sure youare familiar with that procedure in your facility.

Terms used in connection with ABG's

Acid-Base Balance - a homeostatic mechanism in thehuman body that strives to maintain the optimal pH, so thatbody process may function optimally (normal pH of arterialblood = 7.35-7.45)

Buffer System - combination of body systems that work tokeep optimal acid-base balance

Partial Pressure - the amount of pressure exerted by eachgas in a mixture of gases

PO2 - partial pressure of oxygen

PCO2 - partial pressure of carbon dioxide

PAO2 - partial pressure of alveolar oxygen

PaO2 - partial pressure of arterial oxygen

PACO2 - partial pressure of alveolar carbon dioxide

PaCO2 - partial pressure of arterial carbon dioxide

PvO2 - partial pressure of venous oxygen

PvCO2 - partial pressure of venous carbon dioxide

P50 - oxygen tension at 50% hemoglobin saturation

Respiratory Acidosis - condition of lowered pH (acidosis)due to decreased respiratory rate (hypoventilation)

Respiratory Alkalosis - condition of increased pH (alkalosis)due to increased respiratory rate (hyperventilation)

Acid/Base Balance

pH is the measurement used to determine acidity or alkalinity

of arterial blood. pH is a measure of an acid or base solutionand the relative strength of that solution.

Below is the pH scale, 7 being the arbitrary center pointindicting a neutral solution. An example of an acid is carbonicacid. Carbonic Acid is formed when carbon dioxide (CO2)chemically combines with water (H2O) to form carbonic acid(H2CO3). The "H" at the beginning of a chemical formulausually designates and acid.

neutral

4 5 6 7 89 10death acidosis | | alkal

osis death7.35 7.45normal

The further away from 7 in either direction indicates thestrength of the acid or base. An acid can donate thehydrogen ion (H+) and the base is a substance which canaccept the ion. The pH then is the concentration of the ion insolution. Normal blood pH ranges from 7.35 to 7.45 this isslightly to the alkaline side of the scale. If the pH is at the low

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end of the scale or if it is actually below 7.35, the condition isacidemia. Thus if it above 7.45 it is described as alkalemia.

The body is in a state of constant change. Thus, the pH isconstantly changing within this range of values. This ofcourse is called the homeostatic process. Body wasteproducts are constantly being produced, and affecting the pHof the blood. As food is metabolized, these wastes aredumped into the blood and affect the pH. There are alsoconcurrent processes which act to balance these actions.They are known as buffers. If the body pH should start to

became too acid, the buffers work to neutralize them andbalance the pH at normal levels. The exact opposite occursin an alkaline pH situation. This buffer pair of acid-base workto maintain pH at an optimum 7.40. Carbonic acid and the ionbicarbonate is the buffer pair we refer to.

The buffer systems

The lungs, kidneys, and the buffer system are the primaryconsiderations in the homeostatic process. The lungs cancontrol certain small amounts of carbon dioxide in the blood.

Carbon dioxide in the blood chemically produces carbonicacid. Thus, in cases where the lungs do not function properly,CO2 builds up, causing increased carbonic acid. Thisincrease in acid can affect the blood pH, leading to acidosis.The main function of kidneys is retaining or excreting of thebicarbonate ion (HCO3). This is the ion which neutralizes theexcess acid in the blood. If both organs are working properly,the natural build?up of acids can be neutralized effectively bythe buffer system.

The buffer system in the body is able to work very quickly tomaintain proper pH of the blood and body tissues. The primebuffer system is the system of carbonic acid and bicarbonate.Bicarbonate will neutralize the correct numbers of carbonicacid molecules to maintain the correct ratio of 20:1 acidmolecules. This 20:1 ratio will preserve the blood pH at the

normal range of 7.35 to 7.45. Bicarbonate ions and carbonicacid are constantly being produced and combined in order tokeep the optimal pH.

The respiratory system also works to maintain the properblood pH. When the bicarbonate/carbonic acid buffer systemcannot work fast enough to compensate for pH disturbances,the respiratory system has a mechanism for buffering theblood. Hyperventilation and hypoventilation can be used bythe body to control the amount of carbonic acid in the blood.

The respiratory center in the brain responds to changinglevels of carbonic acid in the blood. When the acid level ofblood increases, and is not controlled by the first buffer

system, the respiratory system responds.

Hyperventilation causes the body to exhale and "get rid of"CO2 from the blood, through the lungs. This reduction ofCO2 causes the blood pH to become less acid. Reduce theCO2 and the acid level of the blood is reduced. This is howthe body responds to excess acid in the blood.

The opposite mechanism occurs with hypoventilation.Hypoventilation will cause the retention of CO2 in the blood.

As we discussed earlier, this CO2 becomes carbonic acidwhen it remains in the blood and mixes with water. If you

retain CO2, the acid level of the blood will go up. Thisincreased acid could "buffer" any excess base that is presentin the blood. If the blood becomes alkaline, thenhypoventilation may be another way to neutralize it and getthe blood pH back to normal. These respiratory conditionswill be discussed in more detail later in this text.

In the lab, pH is measured directly using an electrode placedin the blood sample. The "p" of pH is actually defined as"percent Hydrion" or called the negative logarithm of thehydrogen concentration. The concentrations can be

expressed as 10-7, for example; this means: 0.0000001. Thisnegative logarithm can also be expressed as the inverse ratio(Cooper 1987). The more hydrogen ions there are, the lowerthe pH, or acid. On the other hand, as the hydrogen ionconcentration decreases in the blood, the pH increases(alkalinity).

A third buffer system exists that will react if the first twomethods fail to correct an abnormal blood pH. This third andpowerful buffer system is the kidney. The kidneys will react tosustained and/or high levels of acid and/or alkalinity. Thekidney buffer system responds to these dangerous levels,called "metabolic" conditions. These conditions are metabolicacidosis and alkalosis, and will be discussed later.

CO2 + H2O H2CO3 HCO3- + H+

(Normal HCO3- is: 24 to 28 mEq/L)

NORMAL vs. ABNORMAL ABG VALUES

To continue the discussion from the previous section, wemust now look at the value of the carbon dioxide in the blood.CO2 levels are reported on the ABG test as the partialpressure of carbon dioxide. PCO2 levels will directly affectthe levels of acid in the blood.

PCO2 normal - 35 to 45 mm Hg

Increases above the levels indicated, could possibly meanthat the CO2 is building due to hypoventilation or respiratoryfailure of some kind. Decreased levels of CO2 can indicatethe opposite type of problem, hyperventilation, as discussedearlier.

Analysis of respiratory status

First: examine pH value; if HIGH (above 7.45), ALKALOSISis presentTHEN: examine CO2 LEVELS, If below 35 mmHg,RESPIRATORY ALKALOSIS present

IF: pH was low (below 7.35) and CO2 levels are High (above45 mm Hg),RESPIRATORY ACIDOSIS is present

As you see, the conditions of respiratory acidosis orrespiratory alkalosis can be determined by examining just thepH and the carbon dioxide levels in the blood. In fact, thereare two ways that the pH values can be affected. Earlier wedemonstrated that the respiratory system will increase ordecrease breathing when the acid levels are too high or toolow. The reverse condition can also occur.

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If some other factor(s) directly causes either hyperventilationor hypoventilation, then the acid content of the blood will beforced to go up or down. Examples of these conditions aredescribed below. So remember that respirations can beconsidered a buffer to help the body; or, if there is a primaryrespiratory problem, it can adversely affect the blood pH.

In most cases, the respiratory conditions of acidosis oralkalosis can be corrected quite simply, by merely improvingthe patient's respiratory status. Respiratory alkalosis can bereversed in most cases by merely stopping the

hyperventilation.

Nursing Considerations:

As we look at the medical conditions which can produce pHimbalances, we will first concentrate on respirations. Anydiagnosis which has decreased breathing as a symptom, canlead to either previously mentioned condition.

Respiratory Acid-Base Disorders

Respiratory Acidosis

Findings:

y excess CO2 retention

y pH 28 mEq/L (if compensating)

y PaCO2 > 45 mm Hg

Possible Causes:

y CNS depression from drugs, injury, or disease

y

asphyxiay hypoventilation due to pulmonary, cardiac,

musculoskeletal, or neuromuscular disease

Signs and Symptoms:

y diaphoresis

y headache

y tachycardiay confusion

y restlessness

y apprehension

Respiratory Alkalosis

Findings:

y excess CO2 excretion

y pH > 7.45

y HCO3- < 24 mEq/L (if compensating)

y PaCO2 < 35 mm Hg

Possible Causes:

y hyperventilation due to anxiety, pain, or improperventilator settings

y respiratory stimulation caused by drugs, disease,hypoxia, fever, or high room temperature

y gram-negative bacteremia

Signs and symptoms:

y rapid, deep breathing

y parasthesiay light-headedness

y twitching

y anxiety

y fear

Recognition of these conditions can be the key to prevention.When administering pain meds, remember possiblerespiratory problems which can occur. With fever, rememberhyperventilation can happen, quite subtly.

METABOLIC CONDITIONS:

Now we will discuss metabolic situations. Metabolic acidosis

and metabolic alkalosis conditions are determined by thelevels of bicarbonate ion in blood. The kidneys excrete theseions into the urine and out of the body when not needed. Asthe body demands the bicarbonates to neutralize acids, thekidneys conserve bicarb ions to keep the body in balance.Bicarb ions, are also metabolic by?products (normalby?products of metabolism).

To detect metabolic conditions:

FIRST: examine pH values------High pH (above 7.45)SECOND: examine CO2 levels (assumed to be normal)THIRD: examine bicarb levels-----high bicarbonate (above 22to 26 mEq/L)

Condition: METABOLIC ALKALOSIS

*opposite conditions indicate METABOLIC ACIDOSISFIRST: Low pH (below 7.35)SECOND: Normal CO2 levelsTHIRD: Low Bicarb levels

Nursing Considerations in Metabolic Conditions:

Metabolic Acidosis can be caused by many conditions:

renal failure, shock, severe diarrhea, dehydration , diabeticacidosis, salicylate poisoning, paraldehyde

The above conditions can all lead to metabolic acidosis.Patients who have had pancreatic drainage and have had aureterosigmoidostomy are also prone to develop a metabolicacidosis. The nurse should observe for any of the signs orsymptoms of dehydration, shock or diabetic acidosis. Mentalconfusion, disorientation, and other neurological signs shouldnot be overlooked, especially if the patient is an unstablediabetic. Remember, the kidneys will work to relieve theacidosis, but it may not be enough to fully compensate suchas in the case of aspirin overdose.

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With salicylate poisoning, initially there is a respiratoryalkalosis due to the stimulant effect of aspirin on therespiratory system. However, later ABG's will show the truedanger of salicylate poisoning, in the fact that metabolicacidosis will shortly follow.

Metabolic Alkalosis can be caused by many diseaseconditions as well as by iatrogenic causes.

The following are the most frequently seen causes ofmetabolic alkalosis:

severe and/or prolonged vomiting, Cushing's disease,administration of large amounts of sodium bicarbonate,diuretic therapy (long-term), steroid therapy (long-term),prolonged GI (gastrointestinal) suctioning

Every nurse should be aware of the great imbalances whichmight be brought on by suctioning of any kind. Especiallylong?term nasogastric suctioning can induce fluid andelectrolyte imbalances and can lead to alkalosis.

A common cause of alkalosis is hyperventilation. Thisrespiratory condition can lead to metabolic alkalosis

especially if another of the above disorders is present. One ofthe first symptoms seen in these cases is dizziness. Othersymptoms of increased alkalemia include numbness andtingling in extremities, weakness, twitching of the muscles,and some arrhythmias may be seen.

Metabolic Acid-Base Disorders

Metabolic Acidosis

Findings:

y HCO3- loss (acid retention)

y pH < 7.35

y HCO3- < 24 mEq/L

y PaCO2 > 35 mm Hg (if compensating)

Possible Causes:

y HCO3- depletion due to renal disease, diarrhea, orsmall-bowel fistulas

y excessive production of organic acids due to hepaticdisease

y endocrine disorders including diabetes mellitus,

hypoxia, shock, and drug intoxication

Signs and Symptoms

y rapid, deep breathing

y fatiguey fruity breath

y headache

y drowsiness

y lethargy

y nausea

y vomiting

y coma (if severe)

Metabolic Alkalosis

Findings:

y HCO3- retention (acid loss)

y pH > 7.45

y

HCO3- > 28 mEq/Ly PaCO2 > 45 mm Hg

Possible Causes:

Inadequate excretion of acids due to renal disease Loss of hydrochloric acid from prolonged vomiting orgastric suctioning Loss of potassium due to increased renal excretion (as indiuretic therapy) or steroid overdose excessive alkali ingestion

Signs and Symptoms:

y slow, shallow breathing

y confusiony hypertonic muscles

y twitching

y restlessness

y apathy

y irritability

y tetany

y coma (if severe)

y seizures

Oxygenation status

In the previous section, acid?base balance concepts werepresented. Those simple respiratory and metabolic diseaseconditions can be determined by analysis of the results of the

ABG. We also discussed the many clinical applications of thisknowledge. Next, we will present the oxygenation conceptsinvolved with interpretation of the ABG.

Oxygen as a gas in our atmosphere is in the concentration ofabout 21%. It is important to know that the patient wasbreathing room air when the ABG sample was obtained. Aswith all gases, oxygen is also measured in its partialpressure. Partial pressure of a gas refers to the pressure agas exerts as a result of its molecular activity in a mixture ofgases. The lab results of the ABG`s are reported aspercentages and partial pressures of these gases. For ourpurposes as nurses, these percentages and partial pressuresshould only be used as a comparison figure to the normwhen interpreting the results. As an example, the normalPO2 (partial pressure of oxygen) is 80?100 mmhg.

All this should really mean to us is that in arterial blood, 80 to100 mmHg represents the "amount" of oxygen that isdissolved in each 100 ml of the arterial blood. If a patient'sPO2 results are 70, then we know there is an insufficientamount of dissolved oxygen present. Clinically, there can be

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many different reasons for this. The patient may be anemic,or may have decreased respirations, or may havepneumonia. All or any of these conditions may lead to lowPO2.

Oxygen Content of the Blood:

Another term with which nurses should be familiar is FIO2.This term refers to fractional inspired oxygen (FIO2). If apatient is breathing other than 21% room air, the FIO2 is saidto be higher or at a greater percentage.

In some cases, ABG's are analyzed simply for the results ofthe oxygen content. Perhaps it might already be known thatthe patient does not have an acid-base imbalance, but thephysician is more interested in the amount of oxygen in theblood. Remember that many COPD patients will almostalways have a slight imbalance in the pH of the blood due toa chronically high CO2 level. In these cases the PO2 iscritically important for diagnosis.

Oxygen Saturation of the Blood:

Next we will present saturation of hemoglobin in determining

ABG results. The SO2 value is defined as the extent to whichoxygen saturates the hemoglobin molecules in the RBC's. Itis expressed in a percentage, compared to the full potentialof the blood to be saturated. Therefore, at full saturation thenormal SO2 is 95% to 100%. As you can then see, the SO2and PO2 are directly related to each other. As one increases,so does the other, usually. This holds true in the upper levelnumbers.

However, when the relationship between these two numberschanges, it also indicates that saturation is affected by otherfactors not just the amount of oxygen present. Rememberthat oxygen is present in the blood in two forms. Oxygen isdissolved in the blood and oxygen is combined withhemoglobin. The solubility of oxygen depends upon thepressure of oxygen and its solubility as a gas. Oxygendissolved in the blood represents only a very small part of thetotal oxygen in the blood. Most oxygen is carried on thehemoglobin.

Arterial oxygen pressure values (PaO2) are used to calculatethe hemoglobin saturation. These values are also used toestimate the availability of oxygen for the vital organs of thebody. The PaO2 is also used with the PaCO2, arterial carbondioxide pressure, can be used to estimate the alveolar-arterial oxygen gradient (Aagradient). Calculation of the

Aagradient serves as an index of lung effectiveness in gasexchange. The wider the difference, the greater the severityof the lung dysfunction.

As an example, even if the PO2 reaches as low as 50 to 60mmHg, the oxygen saturation can remain at 85% - 90%. Thatis an indication that even though the oxygen levels are quitelow, the saturation will be nearly normal. Clinically, thismeans that the patient has very little oxygen in reserve. Thepatient may seem quite normal while at rest, but even a slightexertion will be too much to handle and will probably cause acrisis. Again, this is due to the ability of the hemoglobin toremain saturated at relatively high levels, even though thereis actually a reduced amount of oxygen in the blood. (Forinstance, in anemia, where there is a reduced number of cells

and hemoglobin, but the cells that are present, are fullysaturated)

By this time, the clinical ramifications should be much clearer.A person who has a respiratory disease has the doubledanger of low oxygen levels, but also high CO2 levels. Nowwe see how these two problems can lead not only to anoxygen problem, but also an acid-base problem. We willdiscuss this further in the next section.

Pick an ABG result which indicates hypoxia:

Patient A Patient B

pH 7.32 pH 7.34

PCO2 48 PCO2 46

PO2 72 PO2 79

Answers: A & B are hypoxic

Compensation

We have seen how imbalance in the levels of CO2 and

HCO3 can disturb the blood pH. However, the body hasmechanisms to counteract these imbalances. Compensationis the process of the body's response to these imbalances,and tries to bring the pH back to normal.

If there is hypo- or hyperventilation causing a rise or fall in theCO2 levels, the pH will also change. The response of thekidneys would be to conserve or excrete bicarbonate, inorder to get the pH back to normal.

As an example: a patient is hyperventilating, CO2 is "blownoff" thus causing lowered acid levels, and alkalosis. Thekidneys respond by excreting HCO3, to try to restore thenormal pH.

The ABG's might be: pH 7.45 CO2-36 HCO3-22

As you see, the pH is high normal, indicating that the patientis borderline alkalotic. The low normal is trying tocompensate. Another ABG will be needed soon to see if thepatient has stabilized or if they are now in full blown alkalosis.If it was recognized that the patient was in compensation, thepatient would be watched very carefully and probably havefrequent ABG determinations to see if they were able tohandle the mild hyperventilation which lead to the alkalosis.

As another example, if we are dealing with a seriousmetabolic problem, the condition can be much more

unstable. For example, with renal failure, the kidneys will notbe able to excrete even normal amounts of HCO3. This renalfailure will cause alkalosis as bicarbonate builds up in theblood. The body's initial response will be hypoventilation, inan effort to build up CO2 and thus neutralize the bicarb withacid.

The ABG's might be: pH--7.45 CO2-45 HCO3-25

You can see that the patient is in compensation now, but ifthe kidneys continue to fail, the situation will become worse,

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rapidly. Compensation is a delicate situation. The patient caneasily go into acidosis or alkalosis with little or no reservepower to fight the situation. Also, compensatory situationscan last for only a short time.

When the lungs or the kidneys respond to a pH change, theyhave limits to what they can do to correct the situation. If theperson is already sick, and then they also develop a pHdisturbance, they are probably in serious trouble. The lungsand the kidneys will only be able to compensate for a shorttime, due to low body reserves.

In completing our discussion on compensation, we also haveto remember the patient. He/she will need to be treated assoon as possible. Since the body's own defense mechanismwill last just a short time, the nurse must look for andaccurately report symptoms. The susceptible patient must beidentified and observed for life-threatening complications inthe acid-base balance. However, do not forget the patient'soxygenation status. Up to this point, we have primarily beenconcerned with pH of the blood. We should also rememberthat changes in the acid-base balance may also effect theoxygen content.

In cases of compensation, the patient's respiratory status

may be severely compromised. For example, if the patientbegins to hypoventilate, it may be due to the primary cause ofreduced CO2 in the blood. However, hypoventilation may stilloccur in a person who is going into metabolic alkalosis. Inthat case, the patient may be severely hypoxic and needs tohyperventilate, but the overpowering effect of alkalosis stillcauses the patient to slow respirations instead of increasethem. Therefore, the patient may show signs of hypoxia(cyanosis, lethargy, etc.), but they may still be unable tobreathe on their own due to the pH problem which effects therespiratory center in the brain.

Clinically, the patient looks terrible, and cannot breathe well.In fact, the breathing may become erratic. First there may be

hyperventilation which changes rapidly to hypoventilation, thepatient may experience long periods of eupnea, even thoughthey may actually be hypoxic and in alkalosis. This is whynurses must also be aware of the delicate situation thecompensation creates.

The nurse should.........

1. Be aware of sudden changes in pH (especially ifborderline results)

2. Be aware of hypoxia (may develop suddenly)3. Be aware of clinical signs/symptoms of both of the

above:

confusion, lethargy, tremors, cyanosis, hypoventilation,hyperventilation, increased depth of respirations, decreasedurinary output, change in vital signs, sweating, nausea,vomiting, asymmetrical breathing pattern

Analyzing the ABG

This section is a guide to analysis of the ABG. Follow thesteps as indicated in order to best interpret the results.

step 1 - examine pH

if low, indicates acidosis --if high, indicates alkalosis --if normal, check to see if borderline (may be compensation)

step 2 - examine CO2

if high, indicates respiratory acidosis (with low pH)if low, indicates respiratory alkalosis (with high pH)

if normal, check for compensatory problem

step 3 - examine HCO3

if high, indicates metabolic alkalosis (with high pH)if low, indicates metabolic acidosis (with low pH)if normal, check for compensatory condition

step 4 - check PO2 levels

if low, indicates an interference with ventilation process(should evaluate the patient)if normal, indicates patient is getting enough oxygen

step 5 - check signs/symptoms of patient

This analysis is for the patient whose respiratory status isfairly stable clinically, but acid/base balance is questionable.Following is a step-by-step account of how to analyze ABG ifthe prime concern is oxygenation.

Patient 1pH 7.45 CO2 32 HCO3 23

identify:

a. (condition) ____________________

b. compensation YES or NO

c. name the possible diagnosis:

answers:a. resp alkalosisb. yes because HCO3 is less than 24c. possible hyperventilation

Possible causes: hyperventilation, respiratory stimulation,gram-negative bacteremia.

Signs & symptoms: rapid, deep breathing, twitching, anxiety,fear

Part B

Use this guide to analyze ABG's if the patient's primarydiagnosis is hypoxia or any condition where O2 may becompromised.

step 1 - Examine PO2

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if normal, go to step 2if high, go to step 2 (patient may be over ventilated)if low, indicates poor oxygenation

*may require immediate intervention, as in obstructed airway,COPD, or if on a ventilator.

step 2 - Examine pH

if normal, patient is either in no acute distress or is

compensatingif low, (and O2 is sufficient) go to step 2 prev pageif high, (with normal O2) go to step 2 prev page

step 3 - Examine patient symptoms:

If you have checked all of the above steps and they arewithin normal limits, then your patient is either incompensation or is adequately ventilated. If ABG's arenormal, but the patient still has symptoms of hypoxia, thenrepeat ABG's in a short time. Then the problem should beapparent

C. Thoracentesis

What Is Thoracentesis?

Thoracentesis (THOR-a-sen-TE-sis) is a procedure toremove excess fluid in the space between the lungs and thechest wall. This space is called the pleural space.

Normally, the pleural space is filled with a small amount offluidabout 4 teaspoons full. Some conditions, such as heartfailure, lung infections, and tumors, can cause more fluid tobuild up. When this happens, its called a pleural effusion

(PLUR-al e-FU-shun). A lot of extra fluid can press on thelungs, making it hard to breathe.

Overview

Thoracentesis is done to find the cause of a pleural effusion.It also may be done to help you breathe easier.

During the procedure, your doctor inserts a thin needle orplastic tube into the pleural space. He or she draws out theexcess fluid. Usually, doctors take only the amount of fluidneeded to find the cause of the pleural effusion. However, ifthere's a lot of fluid, they may take more. This helps the lungsexpand and take in more air, which allows you to breathe

easier.

After the fluid is removed from your chest, it's sent for testing.Once the cause of the pleural effusion is known, your doctorwill plan treatment. For example, if an infection is causing theexcess fluid, your doctor may prescribe antibiotics. If thecause is heart failure, you'll be treated for that condition.

Thoracentesis usually takes 10 to 15 minutes. It may takelonger if there's a lot of fluid in the pleural space. You'll be

watched for up to a few hours after the procedure forcomplications.

Outlook

The procedure usually doesn't cause serious problems, butsome risks are involved. These include pneumothorax (noo-mo-THOR-aks), or collapsed lung; pain, bleeding, bruising, orinfection where the needle or tube was inserted; and liver orspleen injury (very rare).

Most of these complications get better on their own, orthey're easily treated.

d. Pulmonary Angiography

A pulmonary angiography is a procedure that uses a specialdye (contrast material) and x-rays to see how blood flowsthrough the lungs.

How the Test is Performed

This test is done in a hospital. You will be asked to lie on an

x-ray table. Electrocardiogram (ECG) leads are taped to yourarms and legs to monitor the electrical impulses of the heart.

Before the test starts, you will be given a mild sedative tohelp you relax.

An area of your body, usually the arm or groin, is cleanedand numbed with a local numbing medicine (anesthetic). Theradiologist makes a small surgical cut in an vein in the areathat has been cleaned, and inserts a thin hollow tube called acatheter. The catheter is placed through the vein andcarefully moved up into and through the heart chambers andinto the pulmonary artery, which leads to the lungs.

The doctor can see live x-ray images of the area on a TV-likemonitor, and uses them as a guide.

Once the catheter is in place, dye (contrast material) isinjected into catheter. X-ray images are taken to see how thedye moves through the lung arteries. The dye helps highlightany blockages in blood flow.

The catheter is occasionally flushed with saline solutioncontaining a drug called heparin to help keep blood in thetube from clotting.

Your pulse, blood pressure, and breathing are monitoredduring the procedure.

After the x-rays are taken, the needle and catheter arewithdrawn.e

Pressure is immediately applied to the puncture site for 10-15minutes to stop the bleeding. After that time the area ischecked and a tight bandage is applied. The leg should bekept straight for 12 hours after the procedure.

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How to Prepare for the Test

You should not eat or drink anything for 4 - 8 hours beforethe test.

You will be asked to wear a hospital gown and sign a consentform for the procedure. Jewelry should be removed from thearea being imaged.

Tell your health care provider:

y If you are pregnant

y If you have ever had any allergic reactions to x-raycontrast material or iodine substances

y If you are allergic to any medications

y Which medications you are taking (including anyherbal preparations)

y If you have ever had any bleeding problems

How the Test Will Feel

The x-ray table is hard and cold, but you may ask for ablanket or pillow. You may feel a brief sting when the

numbing medicine is given and a brief, sharp, stick as thecatheter is inserted.

You may feel some pressure as the catheter moves up intothe lungs. The contrast dye can cause a feeling of warmthand flushing. This is normal and usually goes away in a fewseconds.

You may have some tenderness and bruising at the site ofthe injection after the test.

Why the Test is Performed

The test is used to detect blood clots and other blockages inthe blood flow in the lung (pulmonary embolism).

Normal Results

The x-ray will show normal structures for the age of thepatient.

What Abnormal Results Mean

Abnormal results may be due to:

y Blood clot in the lungs

y Narrowed blood vessel

y Primary pulmonary hypertension

y Pulmonary embolism

y Tumor

Risks

Occasionally abnormal cardiac rhythm can develop duringthe procedure. The doctors will monitor your heart and cantreat any abnormal rhythms that develop.

Other risks include:

y Allergic reaction to the contrast dye

y Blood vessel damagey Blood clot traveling to the lungs, causing an

embolism

y Excessive bleeding or blood clot, which can reduceblood flow to the leg

There is low radiation exposure. X-rays are monitored and

regulated to provide the minimum amount of radiationexposure needed to produce the image. Most experts feelthat the risk is low compared with the benefits.

Pregnant women and children are more sensitive to the risksof x-rays.

Alternative Names

Pulmonary arteriography