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Daytime hypoventilation in obstructive sleep apnoea syndrome
E Weitzenblum1, A Chaouat, R Kessler
1Department of Pulmonology and Sleep Unit, Hôpitaux Universitaires de Strasbourg, France.
Sleep Medicine Reviews
|August 18, 2004
Summary
Obesity-hypoventilation syndrome and obstructive sleep apnea syndrome (OSAS) can cause chronic alveolar hypoventilation in 10-20% of patients. The "overlap syndrome," combining OSAS and COPD, is a key factor, potentially leading to pulmonary hypertension.
Area of Science:
- Respiratory Medicine
- Sleep Medicine
- Pulmonology
Background:
- Chronic alveolar hypoventilation is a hallmark of obesity-hypoventilation syndrome.
- While hypercapnia is common in obesity-hypoventilation syndrome, it affects only a minority of obstructive sleep apnea syndrome (OSAS) patients.
- Recent studies indicate a 10-20% prevalence of alveolar hypoventilation in unselected OSAS patients.
Purpose of the Study:
- To investigate the mechanisms and contributing factors of hypercapnia in OSAS patients.
- To identify the prevalence and consequences of alveolar hypoventilation in OSAS.
- To explore management strategies for severe cases.
Main Methods:
- Analysis of prevalence data from large cohorts of OSAS patients.
- Evaluation of factors contributing to daytime respiratory insufficiency, including obesity and co-existing chronic obstructive pulmonary disease (COPD).
- Assessment of the role of nocturnal event severity and chemosensitivity.
Main Results:
- The primary drivers of daytime respiratory insufficiency in OSAS are severe obesity (leading to obesity-hypoventilation syndrome) and the "overlap syndrome" (OSAS with COPD), found in over 10% of OSAS patients.
- Mild to moderate bronchial obstruction, often asymptomatic, characterizes the overlap syndrome.
- Nocturnal event severity and diminished chemosensitivity do not appear to be primary determinants of hypercapnia.
- Pulmonary hypertension and subsequent right heart failure are significant consequences, observed in patients with daytime arterial blood gas disturbances.
Conclusions:
- The "overlap syndrome" (OSAS + COPD) is a critical factor in hypercapnia development in OSAS patients.
- Pulmonary hypertension is a major complication of chronic alveolar hypoventilation in OSAS, necessitating intervention.
- Management involves supplemental oxygen or assisted ventilation (BIPAP) when CPAP is insufficient, with continuous oxygen therapy required for severe cases.