Respiratory Alkalosis Differential Diagnoses
- Author: Ryland P Byrd, Jr, MD; Chief Editor: Zab Mosenifar, MD, FACP, FCCP more...
Hyperthyroidism: Hyperthyroidism increases the ventilation chemoreflexes, thereby causing hyperventilation. These chemoreflexes return to normal with treatment of the hyperthyroidism.
Pregnancy: Progesterone levels are increased during pregnancy. Progesterone causes stimulation of the respiratory center, which can lead to respiratory alkalosis. Chronic respiratory alkalosis is a common finding in pregnant women.
Congestive heart failure: Patients with congestive heart failure (and other low cardiac-output states) hyperventilate at rest, during exercise, and during sleep. Owing to pulmonary congestion, pulmonary vascular and interstitial receptors are stimulated. Additionally, the low cardiac-output state and hypotension stimulate breathing via the arterial baroreceptors.
Chronic/severe liver disease: Several mechanisms have been hypothesized to explain the hyperventilation associated with liver disease. Increased levels of progesterone, ammonia, vasoactive intestinal peptide, and glutamine can stimulate respiration. Patients with severe disease or portal hypertension may have small pulmonary arteriovenous anastomoses in the lungs or portal-pulmonary shunts, which result in hypoxemia. This stimulates the peripheral chemoreceptors and leads to hyperventilation. The degree of respiratory alkalosis correlates with the severity of hepatic insufficiency.
Salicylate overdose: Initially, a respiratory alkalosis occurs, which is followed by a metabolic acidosis that induces secondary hyperventilation.
Fever and sepsis: Fever and sepsis may manifest as hyperventilation, even before hypotension develops. The exact mechanism is not known but is thought to be due to carotid body or hypothalamic stimulation by the increased temperature.
Gram-negative sepsis: Before fever, hypoxemia, or hypotension develops, acute respiratory alkalosis may be the only early finding.
Pain: Hyperventilation may be due to stimulation of the peripheral and central chemoreceptors, as well as the behavioral control system.
Hyperventilation syndrome: This is also known as psychogenic hyperventilation and was first described in 1935. It is due to stress and anxiety, both of which act on the behavioral respiratory control system. The hyperventilation ceases during sleep, when the behavioral control system is inactive and only the metabolic system is controlling breathing. The diagnosis of hyperventilation syndrome should be a diagnosis of exclusion. Rule out all organic medical conditions, including pulmonary embolism, cardiac ischemia, and hyperthyroidism, before establishing a diagnosis of hyperventilation syndrome.
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