Appeasing the Carotid Body After Chronic Intermittent Hypoxia
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See related article, pp 436-445
I recall vividly a conversation with the late Professor C. John Dickinson DM, FRCP, ARCO (Professor of Medicine and Chairman of the Department of Medicine at St. Bartholomew’s Hospital, London, 1975–1992) who remarked that in the majority of cases cardiovascular pathology occurred at night while asleep. John’s great hypothesis was that a shortage of oxygen to the brain because of high cerebrovascular resistance, triggered hypertension, and that was worsened by the diurnal falls in blood pressure further compromising cerebral perfusion. Clearly, such a mechanism would be thoroughly agonised during sleep-disordered breathing.
Sleep-disordered breathing occurs in ≈1 in 5 men and 1 in 10 women aged between 50 and 70 years.1 With an increasing incidence between 14% and 55% over the past 2 decades,1 sleep-disordered breathing is growing into a huge clinical and economic problem. Associated with sleep-disordered breathing is narcolepsy, cardiovascular disease including heart failure and hypertension, autonomic imbalance, baroreceptor resetting, and inflammation. The causes of sleep apnea are partly dependent on whether the apneas are obstructive or central in origin but many patients have a combination of both. Continuous positive airway pressure has been shown to reduce peripheral chemosensitivity (as seen as a reduction in the hypoxic ventilatory response2) and abolish hypopneas and apneas in patients with obstructive sleep apnea.3 However, the associated hypertension, which is found in at least 50% of cases, is typically not ameliorated.3 Central sleep apneas are controlled using adaptive servo ventilation: a recent study by Cowie et al4 in heart failure patients with reduced left ventricular ejection fraction used adaptive servocontrolled inspiratory pressure and expiratory positive airway pressure (SERVE-HF). Unexpectedly, all-cause mortality and cardiovascular mortality were significantly higher relative to the control group. Thus, alternative strategies for the treatment of sleep-disordered breathing and …