Chelan & S. Douglas CountyCPAP – Continuous Positive Airway Pressure

Protocol

Presentation Goals• Our Goal in the Field using CPAP• The Physiological Effects• Delivery Systems• Indications/Contraindications

Definitions• “Learn the Lingo”

– NIPPV – Non-Invasive Positive Pressure Ventilation• Includes CPAP, BiPAP and BVM

– CPAP – Continuous Positive Airway Pressure• What we are going to be using

– PEEP – Positive End Expiratory Pressure• Used on Ventilators with Intubated PT’s

– BiPAP – Bi-Level Positive Airway Pressure

CPAP & BiPAP

CPAP• Continuous Pressure• Same pressure during exhalation

and inhalation

• Used in field• Uses simple device or

complicated• Needs little monitoring

– Set it and forget it• Cheaper than BiPAP

BiPAP• Continuous pressure• Pressures are different

between inhalation and exhalation– 5cmH20 Exhal; 15cmH20 Inhal

• Not commonly used in field• No simple devices• Needs monitoring of

delivered pressures• Expensive

CPAP• Pressurized air that is continuously delivered

throughout the entire respiratory cycle– Both inhalation and exhalation– Similar when you stick your head out of a moving

car window at constant Speed

Introduction• Non-Invasive• Easily Applied• Easily Discontinued• Used on CHF, COPD, Asthma, Near Drownings,

and Pneumonia• Still able to use with other medications• Is a bridge to keep patient going until

medications begin having effect

Key Points• “Alternative” to ETT Intubation

– “Prospective randomized trials demonstrated 50%-70% of patients with severe exacerbation of COPD and who receive non-invasive ventilation can avoid being intubated” 1

– “Paramedics can be trained to use CPAP for patients in severe respiratory failure. There was an absolute reduction in tracheal intubation rate of 30% and an absolute reduction in mortality of 21% in appropriately selected out-of-hospital patients who received CPAP instead of usual care.” 2

– COPD patients who do get intubated often are ventilator dependent for long periods

1 Consensus Conference. Noninvasive positive pressure ventilation. Respiratory Care 1997; 42:364-3692 Out-of-hospital continuous positive airway pressure ventilation versus usual care in acute respiratory failure: a randomized controlled trial. Thompson J, Petrie DA, Ackroyd-Stolarz S, Bardua DJ. Ann Emerg Med. 2008 Sep;52(3):232-41, 241.e1. doi: 0.1016/j.annemergmed.2008.01.006. Epub 2008 Apr 3.

Why Positive Pressure?• Redistributes lung fluids• Reduces work of breathing• Counteracts intrinsic PEEP

– (Pursed lip breathing)• Improved lung compliance• Reverses areas of Atelecatsis

– Collapsed aveoli• Decreases Preload/Afterload

– Good for CHF Patients• Decreased V/Q Mismatch• Improves Gas exchange

V/Q Mismatch• When ventilation and perfusion do not match• Causes:

– Pulmonary Edema– Pulmonary Embolism– Pneumonia– Dead space increase

Normal V/Q• Upper lungs

– V>P• Mid lungs

– V=P• Lower lungs

– V<P• Overall Avg: 80%

High V/Q Ratio• Caused by enough ventilation, but not enough

perfusion– Pulmonary Embolism– Cardiac Arrest– Hypovolemia

• Normal in dead space – Ventilation,

but no capillaries

Low V/Q Ratio• Caused by enough perfusion, but not enough

ventilation– Atelectasis– Increased secretions– Mucus plugging– Bronchial intubation

• Also called shunt perfusion

Partial Pressures• Hypothetical pressure of a gas were it to

occupy the same volume of space as the mixture it is in.– Air at sea level has a pressure of 1 atmosphere, or

760mmHg.– Air is 21% O2– The partial pressure of room air O2 is 760 x 0.21 =

159mmHg

Pressure Gradients• The differences in pressure between a higher

concentration of gas and a lower concentration of gas is called a pressure gradient– Gasses of a higher partial pressure have a

tendency to move towards areas of lower pressure, until equilibrium is reached.

– This pressure gradient is what causes O2 to enter the blood, and CO2 to leave it.

Why O2 Enters Blood• Since expired air is 16% O2, expired air O2 has

a partial pressure of 760mmHg x 0.16 = 121mmHg– (Room air was 139mmHg)

• This difference between the partial pressure of expired air and inspired air causes O2 from room air to enter the blood where the partial pressure is lower, moving towards equilibrium.

CPAP• So, how does this apply to CPAP?

– CPAP changes the pressure gradient!– We measure CPAP pressures with cmH20– 1 cmH20 = 0.735mmHg– On a typical patient, a CPAP of 10cmH20 will increase

the partial pressure of O2 by ~2.25%– This increase in pressure “forces” more oxygen into the

blood!– Even though it might seem small, the clinical

significance can be all that is needed

Mechanical Effects• Increased Pressure in Airways

– Stenting open of airways that are at risk of collapsing due to excess fluid

– Extends aveoli to prevent collapse during expiration

• Causes greater surface area = more exchange– Easier for the patient to breathe air in– Maintains gas exchange

Physiological Effects of CPAP• Increased oxygen Levels• Reduced work of breathing• Reduced V/Q mismatch

Chelan/S.Douglas County Protocol• Indications – Severe respiratory distress from

the following:– Pulmonary Edema (including from near

drownings)– Asthma exacerbations not responding to normal

treatments– COPD failing conventional treatments– Pneumonia

Contraindications• Don’t use CPAP when patient is

– Unconscious– Unable to cooperate or maintain their own airway– Hypotensive (<90mmHG)– Vomiting– Suspected Pneumothorax– Trauma– Facial abnormalities– Unable to maintain mask seal– Extreme caution in pulmonary fibrosis

Procedure• Every CPAP system will be different

1. Overall goal is to increase airway pressure and gas exchange

2. Verbally coach patient, explain the procedure3. Apply waveform capnography (ETCO2)4. Apply CPAP with pressure of 5-10 cmH205. Coach and reassure the patient

• Watch for resistance and apprehension• Check for leaks around mask/face seal

6. Reassess lung sounds and vitals q 5 mins. at least

Procedure7. In line nebulizers can be administered at

same time as CPAP8. Nitroglycerin may be administered by

momentarily lifting facemask9. If patient continues to worsen consider

advanced airway measures

Precautions• CPAP may cause a drop in blood pressure due

to increased intrathoracic pressure• Watch for GI distention, which may lead to

vomiting• Patient may become claustrophobic or

unwilling to tolerate mask– Can be overcome with coaching

Special Notes• Proceed to advanced airway for patients with

worsening respiratory distress or decreasing level of consciousness.

• Not for use in children <12 Y/O• Advise receiving hospital of CPAP so they can

prepare

Important Points• Pulmonary Edema patients will improve within

minutes of administration– “CPAP to Pulmonary Edema is like D50 to

Hypoglycemia”• Visual inspection of chest wall movement

should demonstrate improved respiratory excursion– Bilateral chest wall movement, retractions, etc.– The look and feel of “Look, listen, and feel”

CPAP vs Intubate• When to do what:• Respiratory Distress – increased effort and

frequency of breathing in maintaining normal O2 and CO2 in blood

• Respiratory Failure – inability to maintain normal amounts of O2 and CO2 in blood

Respiratory Distress• Signs of Respiratory Distress:

– Tachypnea– Tachycardia– Accessory Muscle Use– Decreased Tidal Volume– Paradoxical Abdominal Motion

• CPAP can generally be used on these patients

Respiratory Failure• Declining tidal volume• Irregular/Gasping Breaths• Decline in LOC• CO2 levels will climb, reducing LOC• High CO2 lowers pH, causing acidosis

Summary• CPAP can provide a patient adjunct to allow

medications to take effect – B2 agonists, Steroids, etc.

• CPAP Reverses CHF induced pulmonary edema• Is less invasive than ET Intubation• Helps COPD patients avoid ventilator dependency• Fixes V/Q mismatch, opens airways, increases O2

pressure gradient, etc.