Respiratory insufficiency of any cause has significant effects on the nervous system.
Headache, mental status changes,
papilledema, and numerous motor abnormalities including
asterixis are commonly seen. Abnormalities in ventilation and gas exchange result in
hypoxia,
hypercapnia, and
respiratory acidosis, and these, in turn, interfere with cerebral metabolism, increase CBF, and may raise intracranial pressure. Chronic
respiratory insufficiency can persist for many months with minimal
neurologic symptoms, as numerous compensatory mechanisms, particularly renal, may take effect. Treatment includes restoring adequate ventilation and improving gas exchange and may require tracheal intubation and assisted ventilation. Supplemental
oxygen therapy should be carefully monitored, as high rates of flow may suppress the hypoxic drive for respiration and lead to significant
carbon dioxide retention. The
sleep apnea syndromes are a group of disorders in which abnormal respiratory patterns during sleep result in
hypercapnia and
hypoxemia. Intermittent obstruction of the upper airway and abnormalities of brainstem respiratory centers cause frequent nocturnal awakenings and
apneas in these patients. Treatments vary and include
weight loss in obese subjects,
respiratory stimulants,
tracheostomy, and diaphragmatic pacing. Rapid ascent to high altitudes may result in
headache, changes in mental status,
papilledema, and other
neurologic symptoms in certain individuals: a syndrome known as high-
altitude sickness.
Hypoxia leading to
cerebral edema, nocturnal periodic breathing, and hypobaria produces
neurologic symptoms in these individuals.
Acetazolamide and
dexamethasone may be effective in minimizing symptoms of this disorder. Sustained
hyperventilation produces acral and circumoral
paresthesias and
lightheadedness in anxious individuals and can be maintained by relatively normal ventilatory patterns once established. These symptoms are due to
hypophosphatemia and
respiratory alkalosis, the latter reducing CBF and causing localized tissue
hypoxia. Rebreathing into a paper bag at the first awareness of symptoms is the most effective form of treatment.