Chapter 77: Sleep-Disordered Breathing and Cardiac Disease
Which of the following characteristics is associated with central sleep apnea (CSA)?
C. Ongoing respiratory effort
D. Cheyne–Stokes respiration (CSR)
E. Upper airway obstruction
The answer is D. (Hurst’s The Heart, 14th Edition, Chap. 77) Sleep-disordered breathing can present as either OSA, CSA, or a combination of both. In OSA, there is collapse of the pharynx during sleep with consequent upper airway obstruction (option E). Predisposing factors include obesity (option B), a short neck, and retrognathism (option A). In OSA, there is evidence of ongoing respiratory effort throughout the apneic-hypopneic event (option C), often with paradoxical movement of the chest and abdomen as breathing against a closed airway is attempted. In contrast, apneas and hypopneas in CSA are accompanied by a marked reduction or cessation of respiratory effort. In CSA, the underlying abnormality is in the regulation of breathing in the respiratory centers of the brainstem. In normal physiology, minute ventilation during sleep is primarily regulated by chemoreceptors in the brainstem and carotid bodies, which trigger an increase in respiratory drive in response to a rise in partial pressure of arterial carbon dioxide (PaCO2), thus maintaining PaCO2 within a narrow range. Patients with HF and CSA tend to have an exaggerated respiratory response to carbon dioxide, so that modest rises in PaCO2 that may occur during sleep result in inappropriate hyperventilation. One of the hallmarks of CSA is CSR (option D), characterized by a periodic pattern of hyperventilation followed by hypoventilation.
Which of the following techniques is considered the gold standard for diagnosing sleep-disordered breathing (SDB)?
A. Multichannel sleep polygraphy
C. Transthoracic impedance sensor
D. Nocturnal heart rate monitor
E. Epworth Sleepiness Scale
The answer is B. (Hurst’s The Heart, 14th Edition, Chap. 77) More than 50% of patients with OSA and cardiovascular disease (CVD) do not report symptoms of unrestful sleep, but rather present with symptoms of CVD.1 In addition, patients with HF and SDB do not tend to complain of daytime sleepiness, possibly because of the high sympathetic tone found in HF. Screening questionnaires that include questions about daytime sleepiness, such as the Epworth Sleepiness Scale, can thus be insensitive (option E).2 Attended in-hospital PSG, including the assessment of respiratory movement, oxygen saturation, nasal and oral airflow, snoring, electroencephalography, electrocardiography, electromyography, and ocular movement, has long been considered the gold ...