Pulmonary & Critical Care Medicine MOC Sample Questions

The correct answer is B. Central apnea

Explanation: Central apnea. TRUE: This polysomnogram demonstrates 2 central apneas with an associated arousal/leg movement. Central apnea is a loss of airflow with the absence of respiratory effort lasting at least 10 seconds. Central apnea suggests the brief loss of ventilatory drive, mediated by respiratory centers in the pons and medulla. In obstructive apnea, there is a physical blockage of the airway with a retained respiratory effort. Respiratory effort may be assessed during polysomnography by the use of thoracic and abdominal respiratory inductance plethysmography to detect movements of the chest and abdomen during inspiration and expiration. The thermistor, thorax, and abdominal channels of the polysomnography indicate the pauses in respiratory effort. These pauses typically result in oxygen desaturation or arousal. In this case, leg movements are time-locked to the central apneas and suggest an arousal response.

Obstructive apnea. FALSE: Obstructive apneas consist of ≥90% airflow reduction for at least 10 seconds with continued respiratory effort.

Mixed apnea. FALSE: Mixed apnea occurs when both central and obstructive components occur within the same breath. No respiratory effort occurs initially, followed by resumption of effort with persistently diminished or absent airflow.

Restless legs syndrome and periodic limb movements of sleep. FALSE: The associated apnea means that this patient's condition is not related to restless legs syndrome or periodic limb movements of sleep.