History
The clinical manifestations of hypoventilation syndromes usually are nonspecific, and in most cases, they are secondary to the underlying clinical diagnosis. Manifestations vary depending on the severity of hypoventilation, the rate of development of hypercapnia, and the degree of compensation for respiratory acidosis that may be present.
Progression
During the early stages of hypoventilation with mild to moderate hypercapnia, patients usually are asymptomatic or have only minimal symptoms.
Patients may be anxious and complain of dyspnea with exertion. As the degree of hypoventilation progresses, patients develop dyspnea at rest. Some patients may have disturbed sleep and daytime hypersomnolence.
As the hypoventilation continues to progress, more patients develop increased hypercapnia and hypoxemia. Therefore, they may have clinical manifestations of hypoxemia, such as cyanosis, and they also may have signs related to their hypercapnia.
Other symptoms of worsening hypoventilation can include the progression of anxiety to delirium. In addition, patients can become increasingly confused, somnolent, and obtunded. This condition occasionally is referred to as carbon dioxide narcosis.
Patients may develop asterixis, myoclonus, and seizures in severe hypercapnia. Papilledema may be seen in some individuals secondary to increased intracranial pressure related to cerebral vasodilation. Conjunctival and superficial facial blood vessel dilation also may be noted.
Patients with respiratory muscle weakness usually display generalized weakness secondary to their underlying neuromuscular disorder. Respiratory muscle weakness also may lead to impaired cough and recurrent lower respiratory tract infections.
With advanced disease, patients may develop respiratory failure and require ventilatory support.
Central alveolar hypoventilation
Patients with central alveolar hypoventilation usually have no respiratory complaints. However, they may have symptoms of sleep disturbance and daytime hypersomnolence. In some patients, the diagnosis of central alveolar hypoventilation is made only after the development of respiratory failure.
Obesity-hypoventilation syndrome
Patients with OHS typically report symptoms of OSA, such as daytime hypersomnolence, fatigue, loud snoring, nocturnal choking, and morning headaches. They may also have pulmonary hypertension and chronic right-sided heart failure (cor pulmonale), with secondary peripheral edema in advanced disease.
Chronic obstructive pulmonary disease
Patients with COPD and hypoventilation usually have severe disease and complain of significant dyspnea. They also may have peripheral edema secondary to pulmonary hypertension with cor pulmonale.
Physical Examination
In patients with alveolar hypoventilation, the findings upon physical examination usually are nonspecific and are related to the underlying illness.
Thoracic examination
Upon thoracic examination, patients with obstructive lung disease have diffuse wheezing, hyperinflation (barrel chest), diffusely decreased breath sounds, hyperresonance upon percussion, and prolonged expiration.
Coarse crackles beginning with inspiration may be heard, and wheezes frequently are heard upon forced and unforced expiration. Cyanosis may be noted if accompanying hypoxia is present. Clubbing may be present.
Pulmonary hypertension
Patients with central alveolar hypoventilation, COPD, and OHS may show evidence of pulmonary hypertension from examination findings. These findings include a narrowly split and loud pulmonary component (P2) of the second heart sound, a large a-wave component in the jugular venous pulse, a left parasternal (right ventricular) heave, and an S4 of right ventricular origin. A diastolic murmur indicative of pulmonic valve regurgitation may be auscultated.
Advanced disease
Patients with advanced disease develop signs of right ventricular failure (cor pulmonale) and may have elevated jugular venous pressure with a prominent V wave, lower-extremity edema, and hepatomegaly. A pulsatile liver develops if tricuspid regurgitation is severe. Ascites may occur but is unusual. The systolic murmur of tricuspid valve regurgitation may be present.
Other
The patient's mental status may be depressed with severe elevations of PaCO2. Patients may have asterixis and papilledema upon examination, and conjunctival and superficial facial blood vessels may be dilated.
