What syndrome is characterized by prolonged episodes of severe hypoxemia and elevated PaCO2 during sleep?

Obesity hypoventilation syndrome is characterized by prolonged episodes of severe hypoxemia (low blood oxygen levels) and elevated levels of carbon dioxide (PaCO2) during sleep. This condition typically affects individuals who are obese and often leads to hypoventilation, meaning that the body does not adequately ventilate to remove carbon dioxide effectively. During sleep, particularly non-REM stages, the respiratory drive can diminish further, causing significant drops in oxygen saturation and corresponding increases in carbon dioxide levels in the blood.

The defining feature of obesity hypoventilation syndrome is that it directly reflects the impaired ability to breathe properly due to excessive body weight, affecting ventilation during sleep. This is in contrast to other sleep disorders like obstructive sleep apnea, which involves repeated episodes of airway obstruction rather than an intrinsic problem with the body's ability to ventilate adequately. Understanding this syndrome is critical in polysomnography, as it informs both the diagnostics and treatment approaches for affected individuals.