Download Name Chapter 26: Alterations of Pulmonary Function I. Clinical

PATHOPHYSIOLOGY
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Chapter 26: Alterations of Pulmonary Function
I. Clinical Manifestations of Pulmonary Alterations
A. Signs and Symptoms of Pulmonary Disease
1. Dyspnea

Dyspnea is the subjective sensation of uncomfortable breathing, including breathlessness and
increased respiratory effort.

Causes - disturbances of ventilation, gas exchange, or ventilation-perfusion relationships,
increased work of breathing or any disease that damages lung tissue (lung parenchyma).

Pathophysiology - may be due to a mismatch between sensory and motor input from the
respiratory center such that there is more urge to breathe than there is response by the
respiratory muscles.
o
Other causes include stimulation of central and peripheral chemoreceptors, and
stimulation of afferent receptors in the lung and chest wall.

Orthopnea - dyspnea when a person is lying down.

Paroxysmal nocturnal dyspnea (PND) – occurs at night, patients wake up gasping for air and
have to sit up or stand to relieve the dyspnea.
o
Often occurs with pulmonary or cardiac disease with heart failure.
2. Abnormal breathing patterns

Kussmaul respirations (hyperpnea) - characterized by a slightly increased ventilatory rate,
very large tidal volumes, and no expiratory pause.
o

Occur during strenuous exercise or metabolic acidosis.
Cheyne-Stokes respirations - characterized by alternating periods of rapid, deep breathing and
shallow breathing or apnea.
o
Result from any condition that slows the blood flow to the brain stem, which in turn
slows impulses sending information to the respiratory centers; or from neurologic
impairment above the brain stem.
3. Hypoventilation/hyperventilation

Background –ventilation is measured as the minute ventilation rate.
o
Minute ventilation rate = tidal volume x ventilation rate (in breaths per minute).
a. Hypoventilation – inadequate alveolar ventilation in relation to metabolic demands.

Causes - airway obstruction, chest wall restriction, or altered neurologic control of breathing.

Pathophysiology - CO2 removal does not keep up with CO2 production and the level of
CO2 in the arterial blood (PaCO2) increases.
o
Hypercapnia - PaCO2 more than 44mm Hg
o
Results in respiratory acidosis.
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b. Hyperventilation - alveolar ventilation exceeding metabolic demands.

Causes - severe anxiety, acute head injury, pain, and in response to conditions that cause
insufficient oxygenation of the blood.

Pathophysiology - the lungs remove CO2 faster than it is produced by cellular
metabolism, resulting in decreased PaCO2.
o
Hypocapnia - PaCO2 less than 36mm Hg
o
Results in a respiratory alkalosis.
4. Cyanosis

Bluish discoloration of the skin and mucous membranes caused by increasing amounts of
deoxygenated hemoglobin.

Causes - decreased arterial oxygenation (low PaO2), pulmonary or cardiac right-to-left
shunts, decreased cardiac output, cold environment, or anxiety.

Central cyanosis - decreased oxygen saturation of hemoglobin in arterial blood; best seen in
buccal mucous membranes and lips.

Peripheral cyanosis - slow blood circulation in fingers and toes; best seen in nail beds.
ACTIVITY 1: Answer the following questions.
1. A symptom of brain stem impairment is:
a. Kussmaul respirations
b. Cheyne-Stokes respirations
2. A symptom of metabolic acidosis is:
a. Kussmaul respirations
b. Cheyne-Stokes respirations
3. An increase in PaCO2 could be due to:
a. hyperventilation
b. hypoventilation
5. Clubbing

Selective bulbous enlargement of the end of a finger or toe.

Associated with diseases that cause chronic hypoxemia, such as lung cancer, bronchiectasis,
cystic fibrosis, pulmonary fibrosis, lung abscess, and congenital heart disease.
6. Cough

Protective reflex that expels secretions and irritants from the lower airways.

Caused by stimulation of irritant receptors, which are located in the upper airways and
proximal bronchi (few in the distal bronchi and alveoli).

Acute cough - resolves within 2 to 3 weeks of the onset of illness or resolves with treatment.
o
Usually the result of upper respiratory infections, allergic rhinitis, acute bronchitis,
pneumonia, congestive heart failure, pulmonary embolus, or aspiration.

Chronic cough - cough that has persisted for more than 3 weeks.
o
In nonsmokers – results from postnasal drainage syndrome, asthma, or gastroesophageal
reflux disease.
o
In smokers – usually due to chronic bronchitis, and less commonly lung cancer.
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7. Hemoptysis

Expectoration of bloody mucus

Causes - bronchitis, tuberculosis, abscess, neoplasms, and other conditions that cause
hemorrhage from damaged pulmonary vessels.
8. Pain

Chest pain can result from inflamed pleurae, trachea, bronchi, or respiratory muscles.
B. Conditions Caused by Pulmonary Disease or Injury
1. Hypercapnia

Increased PaCO2 caused by hypoventilation.

Causes – any disorder that decreases the drive to breathe or results in an inadequate ability to
respond to ventilatory stimulation, including drugs that depress the respiratory center, CNS
disorders like damage to the medulla or spinal cord, disorders of the muscles of ventilation, thoracic
deformities, airway obstruction, or advanced emphysema.
2. Hypoxemia

Reduced oxygenation of arterial blood (reduced PaO2) caused by respiratory alterations.

General causes – (a) decreased oxygen content of inspired gas, (b) hypoventilation,
(c) diffusion abnormality, (d) ventilation-perfusion mismatch, or (e) blood bypassing the lungs.

Diffusion of oxygen from the alveoli into the blood depends on the V/Q ratio and the status of
the respiratory membrane.
a. Ventilation-perfusion (V/Q) abnormalities
o
V/Q ratio - the balance between the amount of air getting into alveoli (V) and the
amount of blood perfusing the capillaries around the alveoli (Q).

o
An abnormal V/Q ratio is the most common cause of hypoxemia.
Low V/Q (Shunting) - inadequate ventilation of well-perfused areas of the lung.

Causes decreased systemic PaO2 and hypoxemia.

Occurs in atelectasis, emphysema, in asthma as a result of bronchoconstriction,
and in pulmonary edema and pneumonia when alveoli are filled with fluid.
o
High V/Q - Hypoxemia also can be caused by poor perfusion of well-ventilated
portions of the lung, resulting in wasted ventilation.

Alveolar dead space - an area where alveoli are ventilated but not perfused.

Usually due to a pulmonary embolus that impairs blood flow to a segment of lung.
b. Respiratory membrane impairment
o
Respiratory membrane (alveolocapillary barrier) – composed of the epithelial lining of
the alveolus, its basement membrane, and the epithelium of the neighboring capillary.
o
o
Diffusion of oxygen is impaired by:

Thickening of respiratory membrane - edema and fibrosis

Reduction in alveolar surface area - emphysema (causes destruction of alveoli)
Hypercapnia is seldom produced because CO2 diffuses easily across membrane.
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c. Circulatory bypass of lungs
o
Due to intracardiac defects that cause right to left shunting or because of intrapulmonary
arteriovenous malformations.

Symptoms of hypoxemia - cyanosis, confusion, tachycardia, edema, and decreased renal
output, and compensatory hyperventilation.
ACTIVITY 2: Identify the things that would be more likely to cause only hypoxemia with an “O” and
those that cause both hypoxemia and hypercapnia with a “B”.
1. Pulmonary edema
4. Breathing air with a low oxygen content
2. Circulatory bypass of lungs
5. Drug overdose
3. Airway obstruction
6. Thickening of respiratory membrane
3. Acute respiratory failure

Respiratory failure is defined as inadequate gas exchange such that PaO2 ≤50mm Hg or PaCO2
≥50mm Hg with pH ≤7.25. (Average normal values: PaO2 = 100, PaCO2 = 40, pH =7.4)

Can result from direct injury to the lungs, airways, or chest wall or indirectly because of
injury to another body system, such as the brain or spinal cord.

Hypercapnic failure - result of inadequate alveolar ventilation; requires ventilatory support.

Hypoxemic failure - result of inadequate exchange of oxygen between the alveoli and the
capillaries; requires supplemental oxygen therapy.
o

Often a combined hypercapnic and hypoxemic respiratory failure occurs.
Potential complication of any major surgical procedure, especially those that involve the
central nervous system, thorax, or upper abdomen.
4. Pulmonary edema

Excess water in the lungs.

Causes - disturbances of capillary hydrostatic pressure, capillary oncotic pressure, or
capillary permeability. Commonly results from:

o
Left heart failure - increases the hydrostatic pressure in the pulmonary circulation
o
Systemic infection - increases capillary permeability due to inflammatory cytokines.
Clinical manifestations - dyspnea, hypoxemia, and increased work of breathing; inspiratory
crackles (rales) and dullness to percussion over the lung bases. In severe edema, pink frothy
sputum is expectorated and PaCO2 increases.
5. Aspiration

Passage of fluid and solid particles into the lungs.

Tends to occur in people whose normal swallowing mechanism and cough reflex are impaired.

Aspiration of large food particles or foreign bodies can obstruct a bronchus, resulting in
bronchial inflammation and collapse of airways distal to the obstruction.
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
Aspiration of acidic gastric fluid may cause severe pneumonitis (lung inflammation) which
could progress to pneumonia.

Clinical manifestations - sudden onset of choking, cough, vomiting, dyspnea, and wheezing.
6. Atelectasis

Collapse of lung tissue.

Compression atelectasis - caused by external pressure exerted by tumor, fluid, or air in
pleural space or by abdominal distention pressing on a portion of lung, causing alveoli to
collapse.

Absorption atelectasis - results from removal of air from obstructed or hypoventilated alveoli
or from inhalation of concentrated oxygen or anesthetic agents.

Clinical manifestations - include dyspnea, cough, fever, and leukocytosis.

Atelectasis tends to occur after surgery.
7. Pleural Abnormalities
a. Pneumothorax - accumulation of air or gas in the pleural space.

Caused by a spontaneous rupture of weakened areas of the pleura, or it can be secondary
to pleural damage caused by disease, trauma, or mechanical ventilation.

Open pneumothorax - air is drawn in and out of pleural cavity through the rupture during
breathing, so the lung will only partially inflate.

Tension pneumothorax – the site of pleural rupture acts as a one-way valve, permitting air
to enter on inspiration but preventing its escape by closing up during expiration, so
pressure builds up in the pleural space.
o
Air pressure in the pleural space pushes against the lung, causing compression atelectasis,
and against the mediastinum, compressing and displacing the heart and great vessels.
o
Life threatening medical emergency.
b. Pleural effusion

Presence of fluid in the pleural space.

Results from migration of fluids and other blood components through the walls of intact
capillaries bordering the pleura or from blockage or injury that causes lymphatic vessels
to drain into the pleural space.

Transudative effusion – watery fluid.

Exudative effusion – contains high concentration of white blood cells and plasma proteins.

Hemothorax – blood in pleural space.

Chylothorax – chlye in pleural space.

Empyema (infected pleural effusion) – fluid contaminated with pus from an infection.
o
Develops when pulmonary lymphatics become blocked, leading to an outpouring of
contaminated lymphatic fluid into the pleural space.
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c. Pleurisy (pleuritis)

Inflammation of the pleura.

Usually results from an infection of the adjacent lung tissue, but could be caused by
thoracic trauma or an invading tumor.
II. Pulmonary Disorders
A. Restrictive Lung Diseases

Characterized by decreased compliance of lung tissue and resultant increased work of breathing.

Commonly affect the alveolocapillary membrane and cause decreased diffusion of oxygen
from the alveoli into the blood resulting in hypoxemia.

Includes pulmonary edema, atelectasis and pneumothorax, as well as the following.
1. Pulmonary fibrosis

Excessive amount of fibrous or connective tissue in the lung, which diminishes lung compliance
and diffusing capacity of alveolocapillary membrane.

May be idiopathic or caused by diseases such as infections, ARDS, autoimmune disorders or
inhalation of harmful substances.

Diffuse pulmonary fibrosis has a poor prognosis.
2. Pneumoconiosis

Any change in the lung caused by inhalation of inorganic dust particles.

Often occurs after years of exposure to the offending dust, with progressive fibrosis of lung tissue.

Causes – most commonly from inhalation of silica, asbestos, and coal (others are less common).

Pathophysiology – deposition of these materials in the lungs leads to chronic inflammation with
scarring of the alveolocapillary membrane leading to pulmonary fibrosis.
o

Dust deposits are permanent and lead to progressive pulmonary deterioration.
Clinical manifestations - cough, chronic sputum production, dyspnea, decreased lung volumes,
and hypoxemia.
3. Acute respiratory distress syndrome (ARDS)

A fulminant form of respiratory failure that results from acute lung inflammation, diffuse injury
to the alveolocapillary membrane, and membrane formation in the alveoli.

Often occurs as a complication of sepsis and multiple trauma; but also with many other disorders
including pneumonia, burns, aspiration, pancreatitis, inhalation of smoke or noxious gases,
oxygen toxicity, and disseminated intravascular coagulation.

Pathophysiology:
o
An insult to the body damages the alveolocapillary membrane, resulting in the systemic
release of high levels of inflammatory cytokines (especially TNF-alpha and IL-1).
o
Inflammation causes breakdown of the alveolar-capillary barrier, thus flooding the alveoli
with protein-rich exudate and cells, causing edema and development of a hyaline membrane.
o
Hyaline membrane - thick, gel-like layer that forms when protein deposits in the alveoli.
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o
Inflammation is complicated by loss of surfactant, causing atelectasis, and by
vasoconstriction of the alveolar capillaries and pulmonary thrombus formation.
o
The resultant V/Q mismatch is usually very severe, and the associated hypoxemia is not
responsive to administration of supplemental oxygen.
o
As the lungs become stiffer (decreasing lung compliance) due to fluid and atelectasis,
hypoventilation and hypercapnia follow.

Clinical manifestations - dyspnea; rapid, shallow breathing; inspiratory crackles; respiratory
alkalosis; decreased lung compliance; hypoxemia unresponsive to oxygen therapy (refractory
hypoxemia); and diffuse alveolar infiltrates on radiographs, without evidence of cardiac disease.

Patients frequently present with the symptoms of the original insult, followed in 24 to 48 hours
by increasing dyspnea. This may progress to complete respiratory failure and death.
ACTIVITY 3: Why is ARDS considered a restrictive lung disease rather than obstructive?
B. Obstructive Lung Diseases

Characterized by airway obstruction that is worse with expiration.
o
During inspiration airways stretch to allow air in.
o
During expiration excess mucus or loss of lung elasticity causes airways to collapse,
trapping air in the alveoli.

Patients exhibit dyspnea, and wheezing that is worse with expiration, with increased work of
breathing, V/Q mismatching, and a decreased forced expiratory volume in one second (FEV1).

Trapping of air in alveoli can cause less CO2 to be exhaled, resulting in hypercapnia.

The major obstructive lung diseases are asthma, chronic bronchitis, and emphysema.
1. Asthma

Asthma is a chronic inflammatory disorder of the airways.

Results from a type 1 hypersensitivity immune response involving the activity of lymphocytes,
IgE, mast cells, and eosinophils.

Occurs in individuals with a genetic predisposition to certain environmental antigens (allergens)
so that high levels of interleukin-4 (IL-4) and IgE are produced.

This causes the airways to be hyperresponsive to allergens, with excessive mast cell
degranulation, and resulting mucus secretion, bronchoconstriction, and pulmonary edema.

Clinical manifestations during attacks - tripod positioning, use of accessory muscles, tachypnea,
tachycardia, expiratory wheezing/prolonged expiratory phase, increased pulsus paradoxus (a
decrease in systolic blood pressure during inspiration of more than 10mm Hg).
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
Status asthmaticus - acute exacerbation of asthma that does not respond to standard treatments
of bronchodilators and steroids. The resulting hypoxemia and respiratory acidosis can be lifethreatening if not reversed rapidly.

Asthma staging is based on clinical severity from mild intermittent to severe persistent and is
used to determine therapy.
2. Chronic Obstructive Pulmonary Disease (COPD)

Syndrome that includes emphysema and chronic bronchitis.

Characterized by airflow limitation that is not fully reversible, is usually progressive, and is
associated with an abnormal inflammatory response of the lung to noxious particles or gases.

Primarily caused by cigarette smoke, though genetic susceptibilities also have been identified.
3. Chronic bronchitis

Hypersecretion of mucus and chronic productive cough that lasts for at least 3 months of the
year and for at least 2 consecutive years.

Pathophysiology:
o
Inhalation of irritants causes inflammation and hyperplasia of the mucus-producing goblet
cells of the bronchial epithelium and hypertrophy of smooth muscle.
o
Accumulated mucus facilitates growth of bacteria, which further contributes to airway
inflammation, bronchospasm, and eventual scarring.
o
Narrowed airways cause V/Q mismatching and expiratory airway obstruction with air
trapping, resulting in hypoxemia and hypercapnia.

Accumulations of thick mucus make patient at risk for recurrent pulmonary infections.

Clinical manifestations - productive cough of purulent sputum (earliest symptom), dyspnea,
prolonged expiratory phase, wheezing, cyanosis, and systemic edema.

Treatment – bronchodilators, expectorants, and chest physical therapy; during acute attacks
antibiotics, steroids and mechanical ventilation may be required.
o

If patient stops smoking, progression can be halted.
Prevention through smoking cessation is best option since damage is irreversible.
4. Emphysema

Abnormal permanent enlargement of the gas-exchange airways accompanied by destruction of
alveolar walls without obvious fibrosis.
o
Airflow limitation occurs due to loss of elastic recoil.

Major cause is cigarette smoking.

Primary emphysema (1-3% of cases) is linked to an inherited deficiency of the enzyme alpha 1antitrypsin, which normally inhibits the action of many proteolytic enzymes in the lungs.
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
Pathophysiology:
o
Inhaled irritants cause an imbalance between lung proteases (that break down lung tissue,
like elastin) and antiproteases (that preserve lung tissue, like alpha 1-antitrypsin) so that the
alveoli and bronchial walls are destroyed.
o
Alveolar destruction causes decreased surface area for gas exchange, leading to hypoxemia.
o
Bronchial wall damage causes loss of elastic recoil, leading to expiratory airway collapse,
air trapping, hypoventilation, and hypercapnia.
o
Air trapping causes hyperinflation of lungs and increased residual lung volume, with much
energy expended on breathing, and eventually increased thoracic diameter.

Clinical manifestations – severe dyspnea, nonproductive cough, weight loss, barrel chest,
prolonged expiratory phase, and wheezing.

Treatment - smoking cessation, bronchodilators, nutrition, breathing retraining, relaxation
exercises, anti-inflammatory medications, and antibiotics for acute infections.
ACTIVITY 4: Match each characteristic to the disorder it is most closely associated with.
a. Asthma
b. Chronic bronchitis
c. Emphysema
1. Involves a hypersensitivity reaction.
4. Productive cough
2. Involves destruction of alveolar septa.
5. Barrel chest
3. Involves hyperplasia and hypertrophy of
cells in airways.
6. Systemic edema
C. Respiratory Tract Infections
1. Pneumonia

Acute infection of the lung that is caused by bacteria, viruses, fungi, or parasites.

Risk factors - anything that compromises normal respiratory defense mechanisms, such as age,
smoking, compromised immune system, malnutrition, mechanical ventilation, and immobilization.

Categories:
o
Community Acquired Pneumonia (CAP)–most commonly caused by viruses (e.g., influenza)
or by bacteria (e.g., Streptococcus pneumoniae, Mycoplasma pneumoniae).
o
Nosocomial– acquired in hospital, often due to a dangerous organism that is difficult to treat
(e.g., Pseudomonas aeruginosa).
o
Immunocompromised Individuals– often due to opportunistic infections by the fungus
Pneumoncystis jiroveci (P. carinii) or by the cytomegalovirus.

Pathophysiology:
o
Organisms enter the respiratory tract, often by aspiration of infected oral secretions.
o
These organisms overwhelm the alveolar macrophages and set off an intense immunologic
and inflammatory response.
o
Inflammatory cytokines, white blood cells, and edema fluid flood the alveoli and bronchi.
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o
Exudates and fibrin are deposited in alveoli and interfere with gas exchange.
o
Ventilation/perfusion (V/Q) mismatching occurs with resultant hypoxemia.
o
The infection may spread to the bloodstream (bacteremia and sepsis), pleura (empyema), or
other organs (e.g., meningitis).

Clinical manifestations- fever, usually a productive cough, and dyspnea; infiltrates on chest
X-ray; leukocytosis.

Treatment – antibiotics for bacterial pneumonia; supportive care for viral pneumonia.
2. Tuberculosis

An infection caused by Mycobacterium tuberculosis that usually affects the lungs but may
invade other body systems.

In the U.S. most active cases are in AIDS patients and other immunocompromised individuals.

Transmitted from person to person in airborne droplets.

Pathophysiology:
o
Microorganisms lodge in the lung periphery, usually in the upper lobe.
o
Bacilli multiply and cause nonspecific pneumonitis (lung inflammation).
o
Bacilli are engulfed by macrophages and neutrophils which seal off the colonies of bacilli to
prevent spread, forming a granulomatous lesion called a tubercle.
o
Once the bacilli are isolated in tubercles and immunity develops, tuberculosis may remain
dormant for life.
o
If the immune system is impaired, or if live bacilli escape into the bronchi, active disease
occurs and may spread through the blood and lymphatics to other organs.

Clinical Manifestations
o
Latent tuberculosis is asymptomatic.
o
Active tuberculosis - fever, night sweats, dyspnea, productive cough (sometimes with
hemoptysis, i.e. blood in sputum), and weight loss.

Usually diagnosed by a positive tuberculin skin test (PPD), sputum culture, and chest radiographs.

Treatment - antibiotic therapy (6- to 9-month course of treatment)

Multidrug resistant strains of TB are arising which are very difficult to control.
3. Severe Acute Respiratory Syndrome (SARS)

A severe pneumonia that affected more than 300 people in China in 2002- 2003 and spread
rapidly around the world.

Caused by a strain of coronavirus.

Fatality rate was 4% to 6%.

Spread mainly by inhalation of droplet nuclei, or by contact with infected respiratory excretions.

Clinical manifestations - high fever, body aches, dry cough, and dyspnea.

Treatment - mainly supportive, although several antivirals are being tested.
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D. Pulmonary Vascular Disease
1. Pulmonary embolism

Occlusion of a portion of the pulmonary vascular bed by a thrombus, embolus, tissue fragment,
lipids, or an air bubble.

Pulmonary emboli most commonly arise from the deep veins in the legs or pelvis.

Thromboembolism – specifically due to a portion of a clot that has broken off into the bloodstream.

Risk factors – anything that promotes blood clotting, immobility, trauma and fractures of the head,
spine, legs and pelvis; incidence increases with age.

Pathophysiology:
o
An embolus, often from a deep leg vein, breaks off and travels through the venous circulation.
o
It travels through the right heart and lodges in the pulmonary arterial circulation, blocking
flow into the affected portion of the lungs.
o
This causes immediate V/Q mismatch, hypoxemia, and pulmonary hypertension.
o
Hypoxemia interferes with surfactant production, resulting in collapse of alveoli.
o
Small emboli often do not cause lung infarction.
o
Larger emboli often cause some infarction of lung tissue with associated hypoxic
vasoconstriction, atelectasis, and loss of functional lung tissue.
o

Very large emboli cause massive occlusion, resulting in cardiogenic shock and death.
Initial symptoms are typically sudden onset of dyspnea, pleuritic chest pain and hemoptysis.
2. Pulmonary hypertension

Mean pulmonary artery pressure 5 to 10 mm Hg above normal or above 20 mm Hg.

Primary pulmonary hypertension - rare idiopathic disorder involving the precapillary
pulmonary arteries; due to hereditary factors in some cases.
o
Decreased endogenous vasodilators, increased vasoconstrictors, and vascular remodeling
combine to cause vasoconstriction and fibrotic changes in the vessel walls.

Secondary pulmonary hypertension - results from diseases of the respiratory system that cause
hypoxemia and are characterized by pulmonary arteriolar vasoconstriction and arterial
remodeling.
o

Most commonly due to chronic pulmonary disease.
Pathophysiology:
o
Narrowing of the vessels increases resistance to pulmonary artery inflow to the lungs.
o
Pulmonary artery pressures rise, creating significant afterload to the right ventricle.
o
This results in right ventricular hypertrophy that usually progresses to right heart failure,
which is called cor pulmonale.
o
Pressures then back up into the systemic venous circulation.
3. Cor pulmonale

Right ventricular enlargement caused by chronic pulmonary hypertension.

Progresses to right ventricular failure if the pulmonary hypertension is not reversed.
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E. Respiratory Tract Malignancies
1. Lung Cancer

o
Most common cause of cancer death in the United States.
o
Commonly caused by cigarette smoking.
o
Heavy smokers have a 20 times’ greater chance of developing lung cancer than nonsmokers.
o
Other environmental factors can also contribute, such as asbestos and radiation exposure.
Bronchogenic carcinomas - primary lung cancers arising from the bronchi. Two major types:
o
Non–small cell lung carcinoma - 75-85% of lung cancers; different types have different
characteristics, but in general these are slower growing and slower to metastasize than
small cell tumors.
o

Small cell lung carcinoma - rarer; grow and metastasize rapidly. Very poor prognosis.
Lung cancers most frequently metastasize to the brain, bone marrow, and liver.