565
he major function of the lungs is to oxygenate the
blood and remove carbon dioxide as a means of
supporting the metabolic functions of the body’s tis-
sues. Many types of disease are capable of disrupting
the normal gas exchange function of the lungs. In some
cases the disruption is temporary and in other cases it is
marked and disabling. This chapter focuses on disorders
that disrupt ventilation and pulmonary gas exchange.
It is divided into six sections: the physiologic effects of
altered ventilation and gas exchange, disorders of lung
inflation, obstructive airway disorders, chronic intersti-
tial lung disorders, disorders of the pulmonary circula-
tion, and acute respiratory disorders.
Physiologic Effects of
Ventilation and Diffusion
Disorders
The primary function of the respiratory system is gas
exchange between the atmospheric air in the alveoli and
the blood in the pulmonary circulation.
1–3
In the process,
oxygen (O
2
) from air in the alveoli diffuses into the blood
in the pulmonary capillaries and carbon dioxide (CO
2
)
moves from the blood in pulmonary capillaries into the
alveoli (discussed in Chapter 21). This section provides
a brief overview of two abnormal states (hypoxemia
and hypercapnia) that develop as the result of impaired
ventilation and gas exchange that occur with many of
the disorders discussed in the chapter.
Respiration can be divided into three parts: ventila-
tion, perfusion, and diffusion.
Ventilation
involves the
movement of air into the lungs. However, not all inspired
air reaches the alveoli where gas exchange takes place.
Of each 500 mL of air, which is the typical volume of air
that is inhaled by the average-sized adult, about 150 mL
remains behind in the airways, with the remainder
(350 mL) moving into the alveoli. This is called
alveolar
ventilation
and represents the portion of ventilation that
participates in gas exchange. The actual movement or
diffusion
of O
2
and CO
2
takes place in the lung driven by
T
Disorders of
Ventilation and
Gas Exchange
23
C h a p t e r
Physiologic Effects of Ventilation and Diffusion
Disorders
Hypoxemia
Hypercapnia
Disorders of Lung Inflation
Disorders of the Pleura
Pleuritis
Pleural Effusion
Pneumothorax
Atelectasis
Obstructive Airway Disorders
Physiology of Airway Disease
Bronchial Asthma
Etiology and Pathogenesis
Manifestations
Diagnosis and Treatment
Severe Asthma
Bronchial Asthma in Children
Chronic Obstructive Pulmonary Disease
Emphysema
Chronic Bronchitis
Manifestations
Diagnosis and Treatment
Bronchiectasis
Etiology and Pathogenesis
Manifestations
Diagnosis and Treatment
Cystic Fibrosis
Etiology and Pathogenesis
Manifestations
Diagnosis and Treatment
Interstitial Lung Diseases
Pathogenesis
Clinical Features
Idiopathic Pulmonary Fibrosis
Sarcoidosis
Disorders of the Pulmonary Circulation
Pulmonary Embolism
Pathogenesis
Manifestations
Diagnosis and Treatment
Pulmonary Hypertension
Secondary Pulmonary Hypertension
Primary Pulmonary Arterial Hypertension
Cor Pulmonale
Acute Respiratory Disorders
Acute Lung Injury/Acute Respiratory Distress
Syndrome
Etiology and Pathogenesis
Clinical Features
Acute Respiratory Failure
Hypoxemic Respiratory Failure
Hypercapnic/Hypoxemic Respiratory Failure
Clinical Features
