C h a p t e r 2 3
Disorders of Ventilation and Gas Exchange
571
in persons with underlying lung disease in whom sec-
ondary spontaneous pneumothorax develops or in per-
sons with underlying heart disease who are unable to
compensate with an increase in heart rate and stroke
volumes. Regardless of etiology, the hypoxemia caused
by the partial or total loss of lung function can be
life-threatening. Without immediate intervention, the
increased thoracic pressure will further impair both car-
diac and pulmonary function, resulting in severe hypox-
emia and hypotension.
Diagnosis of pneumothorax can be confirmed by
chest radiograph, CT scan, or ultrasonography.
8,13,14
Pulse oximetry and blood gas analysis may be done to
determine the effect on blood oxygen levels. Treatment
of pneumothorax varies with the cause and extent of
the disorder. In small spontaneous pneumothoraces, the
air usually reabsorbs spontaneously, and only obser-
vation and follow-up chest radiographs are required.
Supplemental oxygen may be used to correct the
hypoxemia until the air is reabsorbed. In larger pneu-
mothoraces, the air is removed by needle aspiration or
a closed drainage system used with or without suction.
This type of drainage system uses a one-way valve to
allow air to exit the pleural space and prevent it from
reentering the chest.
Emergency treatment of tension pneumothorax
involves the prompt insertion of a large-bore needle or
chest tube into the affected side of the chest along with
one-way valve drainage or continuous chest suction
to aid in lung reexpansion.
8,13
Sucking chest wounds,
which allow air to pass in and out of the chest cavity,
should be treated by promptly covering the area with
an airtight covering. Chest tubes are inserted as soon
as possible.
Atelectasis
Atelectasis
refers to an incomplete expansion of a
lung or portion of a lung.
15,16
It can be caused by air-
way obstruction, lung compression such as occurs in
pneumothorax or pleural effusion, or increased recoil
of the lung due to loss of pulmonary surfactant (see
Chapter 21). The disorder may be present at birth
(i.e., primary atelectasis) or develop during the neo-
natal period or later in life (i.e., acquired or secondary
atelectasis).
Primary atelectasis of the newborn implies that the
lung has never been inflated. It is seen most frequently
in premature and high-risk infants. A secondary form of
atelectasis can occur in infants who established respira-
tion and subsequently experienced impairment of lung
expansion. Among the causes of secondary atelectasis in
the newborn is the respiratory distress syndrome associ-
ated with lack of surfactant and airway obstruction due
to aspiration of amniotic fluid or blood.
Acquired atelectasis occurs mainly in adults. It most
commonly results from airway obstruction, for example,
by a mucus plug in the airway or by external compres-
sion of the airway from fluid, a tumor mass, exudate, or
other matter in the pleural cavity or area surrounding the
airway (Fig. 23-3). Portions of alveoli, a small segment of
lung, or an entire lung lobe may be involved. Complete
obstruction of an airway is followed by the absorption
of air from the dependent alveoli and collapse of that
portion of the lung. Breathing high concentrations of
oxygen increases the rate at which gases are absorbed
from the alveoli and predisposes to atelectasis. The dan-
ger of obstructive atelectasis increases after surgery.
15
Anesthesia, pain, administration of narcotics, and
immobility tend to promote retention of viscid bron-
chial secretions and airway obstruction. The encourage-
ment of coughing and deep breathing, frequent change
of position, adequate hydration, and early ambulation
decrease the risk for atelectasis.
The clinical manifestations of atelectasis include
tachypnea, tachycardia, dyspnea, cyanosis, signs of
hypoxemia, diminished chest expansion, absence of
breath sounds, and intercostal retractions. Both chest
expansion and breath sounds are decreased on the
affected side. There may be intercostal retraction (pull-
ing in of the intercostal spaces) over the involved area
during inspiration. Signs of respiratory distress are pro-
portional to the extent of lung collapse. If the collapsed
area is large, the mediastinum and trachea shift to the
affected side. In compression atelectasis, the mediasti-
num shifts away from the affected lung.
The diagnosis of atelectasis is based on signs and
symptoms. Chest radiographs are used to confirm the
diagnosis. Computed tomography scans may be used to
show the exact location of the obstruction. Treatment
depends on the cause and extent of lung involvement.
It is directed at reducing the airway obstruction or lung
compression and at reinflation of the collapsed area of
the lung. Ambulation, deep breathing, and body posi-
tions that favor increased lung expansion are used when
appropriate. Administration of oxygen may be needed
to correct the hypoxemia. Bronchoscopy may be used as
both a diagnostic and treatment method.
Absorption
Compression
Obstructed
airway
Space-
occupying
lesion
FIGURE 23-3.
Atelectasis caused by airway obstruction and
absorption of air from the involved lung area (left) and by
compression of lung tissue (right).
