pulmonary pathophysiology · 2020. 1. 22. · pathophysiology a lower v/q ratio usually seen in...
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Pulmonary Pathophysiology
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Reduction of Pulmonary Function
1. Inadequate blood flow to the lungs –
hypoperfusion
2. Inadequate air flow to the alveoli -
hypoventilation
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Signs and Symptoms of Pulmonary
Disease
• Dyspnea – subjective sensation of
uncomfortable breathing, feeling “short of
breath”
• Ranges from mild discomfort after exertion
to extreme difficulty breathing at rest.
• Usually caused by diffuse and extensive
rather than focal pulmonary disease.
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Dyspnea cont. • Due to:
– Airway obstruction
• Greater force needed to provide adequate
ventilation
• Wheezing sound due to air being forced
through airways narrowed due to
constriction or fluid accumulation
– Decreased compliance of lung tissue
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Signs of dyspnea:
• Flaring nostrils
• Use of accessory muscles in breathing
• Retraction (pulling back) of intercostal
spaces
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Cough
• Attempt to clear the lower respiratory
passages by abrupt and forceful expulsion
of air
• Most common when fluid accumulates in
lower airways
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Cough may result from:
• Inflammation of lung tissue
• Increased secretion in response to mucosal irritation
– Inhalation of irritants
– Intrinsic source of mucosal disruption – such as tumor invasion of bronchial wall
• Excessive blood hydrostatic pressure in pulmonary capillaries
– Pulmonary edema – excess fluid passes into airways
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• When cough can raise fluid into pharynx,
the cough is described as a productive
cough, and the fluid is sputum.
– Production of bloody sputum is called
hemoptysis
• Usually involves only a small amount of
blood loss
• Not threatening, but can indicate a serious
pulmonary disease
–Tuberculosis, lung abscess, cancer,
pulmonary infarction.
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• If sputum is purulent, and infection of lung
or airway is indicated.
• Cough that does not produce sputum is
called a dry, nonproductive or hacking
cough.
• Acute cough is one that resolves in 2-3
weeks from onset of illness or treatment of
underlying condition.
– Us. caused by URT infections, allergic rhinitis,
acute bronchitis, pneumonia, congestive heart
failure, pulmonary embolus, or aspiration.
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• A chronic cough is one that persists for
more than 3 weeks.
• In nonsmokers, almost always due to
postnasal drainage syndrome, asthma, or
gastroesophageal reflux disease
• In smokers, chronic bronchitis is the most
common cause, although lung cancer
should be considered.
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Cyanosis • When blood contains a large amount of
unoxygenated hemoglobin, it has a dark red-
blue color which gives skin a characteristic
bluish appearance.
• Most cases arise as a result of peripheral
vasoconstriction – result is reduced blood flow,
which allows hemoglobin to give up more of its
oxygen to tissues- peripheral cyanosis.
• Best seen in nail beds
• Due to cold environment, anxiety, etc.
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• Central cyanosis can be due to :
– Abnormalities of the respiratory membrane
– Mismatch between air flow and blood flow
– Expressed as a ratio of change in ventilation
(V) to perfusion (Q) : V/Q ratio
• Pulmonary thromboembolus - reduced
blood flow
• Airway obstruction – reduced ventilation
• In persons with dark skin can be seen
in the whites of the eyes and mucous
membranes.
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Pain • Originates in pleurae, airways or chest
wall
• Inflammation of the parietal pleura causes
sharp or stabbing pain when pleura
stretches during inspiration
– Usually localized to an area of the chest wall,
where a pleural friction rub can be heard
– Laughing or coughing makes pain worse
– Common with pulmonary infarction due to
embolism
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Tests of Pulmonary Function
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Chest radiographs are among the most common examinations of the pulmonary system.
Chest x-ray Heart size Lung mass Pleural effusion Fibrosis Pneumonia Pneumothorax
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CT SCAN
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Spirometry
The diagnosis of COPD is confirmed by spirometry, a test that
measures breathing.
Spirometry measures the forced expiratory volume in one second
(FEV1) which is the greatest volume of air that can be breathed
out in the first second of a large breath and the forced vital
capacity (FVC) which is the greatest volume of air that can be
breathed out in a whole large breath. Normally at least 70% of
the FVC comes out in the first second (i.e. the FEV1/FVC ratio is
>70%).
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In COPD, this ratio is less than normal,
(i.e. FEV1/FVC ratio is <70%) even after a
bronchodilator medication has been
given.
Spirometry can help to determine the
severity of COPD.
The FEV1 (measured post-bronchodilator)
is expressed as a percent of a predicted
"normal" value based on a person's age,
gender, height and weight:
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Severity of
COPD FEV1 % predicted
Mild ≥80
Moderate 50-69
Severe 30-49
Very severe
<30 or Chronic
respiratory failure
symptoms
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Ventilation/perfusion ratio (or V/Q ratio) : It is defined as: the ratio of the amount of air reaching the alveoli to the amount of blood reaching the alveoli. "V" - ventilation - the air which reaches the alveoli "Q" - perfusion - the blood which reaches the alveoli These two variables constitute the main determinants of the blood oxygen concentration. In fact since V determines the quantity of oxygen mass reaching the alveoli per minute (g/min) and Q expresses the flow of blood in the lungs (l/min), the V/Q ratio refers to a concentration (g/l). Nuclear study
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Pathophysiology A lower V/Q ratio usually seen in chronic bronchitis, asthma and acute pulmonary edema. A high V/Q ratio increases paO2 and decreases paCO2. This finding is typically associated with pulmonary embolism (where blood circulation is impaired by an embolus).
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Pulmonary angiography
Laryngoscopy
Bronchoscopy
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Skin test (TB)
Microbiological (Sputum,Pleural
fluid,Throat swab)
Histopathological and
cytological
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Sputum : It is usually in air passages in diseased lungs, bronchi, pneumonia It can be associate with blood (hemoptysis) if a chronic cough is present, possibly from severe cases of tuberculosis.
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ABG – Arterial blood gas analysis – commonly performed for individuals with suggested or diagnosed pulmonary disease. Provides valuable information about an individual’s gas exchange & acid-base status.
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• Inflammation of trachea or bronchi
produce a central chest pain that is
pronounced after coughing
– Must be differentiated from cardiac pain
• High blood pressure in the pulmonary
circulation can cause pain during exercise
that often mistaken for cardiac pain
(angina pectoris)
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Respiratory Failure
• The inability of the lungs to adequately
oxygenate the blood and to clear it of
carbon dioxide.
• Can be acute:
– ARDS or pulmonary embolism
– Direct injury to the lungs, airways or chest
wall
– Indirect due to injury of another body system,
such as the brain or spinal cord.
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• Chronic respiratory failure
– Due to progressive hypoventilation from airway
obstruction or restrictive disease
• Respiratory failure always presents a serious
threat
– Dysnpea always present, but may be difficult to
detect a change in a chronic patient
– Since nervous tissue it highly oxygen-dependent,
see CNS signs and symptoms
– Memory loss, visual impairment, drowsiness
– Headache due to increased intracranial pressure
due to cerebral vasodilation
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Obstructive Pulmonary Disease
• Characterized by airway obstruction that is
worse with expiration. More force is required to
expire a given volume of air, or emptying of
lungs is slowed, or both.
• The most common obstructive diseases are
asthma, chronic bronchitis, and emphysema.
• Many people have both chronic bronchitis and
emphysema, and together these are often
called chronic obstructive pulmonary
disease - COPD
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• Major symptom of obstructive pulmonary
disease is dyspnea, and the unifying sign
is wheezing.
• Individuals have increased work of
breathing, V/Q mismatching, and a
decreased forced expiratory volume.
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COPD
• Pathological changes that cause reduced
expiratory air flow
• Does not change markedly over time
• Does not show major reversibility in
response to pharmacological agents
• Progressive
• Associated with abnormal inflammatory
response of the lungs to noxious particles
or gases.
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• Fourth leading cause of death in U.S.
• Increasing in incidence over the past 30
years
• Primary cause is cigarette smoking
• Both active and passive smoking have
been implicated
• Other risks are occupational exposures
and air pollution
• Genetic susceptibilities identified
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Infection of respiratory system
1-Upper resp tract inf
2-Pneumonia
3-TB
4-Fungal inf
5-Tumour and carcenoma
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