Effects of CPAP therapy on cardiovascular variability in obstructive sleep apnea: a closed-loop analysis

Abstract

. Effects of CPAP therapy on cardiovascular variability in obstructive sleep apnea: a closed-loop analysis. Am J Physiol Heart Circ Physiol 282: H110-H121.-To determine the long-term effects of continuous positive airway pressure (CPAP) therapy on cardiovascular variability, we measured R-R interval (RR), systolic blood pressure (SBP) and respiration (⌬V) in 13 awake, supine patients with moderate-to-severe obstructive sleep apnea (OSA), before and after ϳ6 mo of treatment. Using these data, we estimated the dynamics of the following components of a closed-loop circulatory control model: 1) the baroreflex component, 2) the neural coupling of ⌬V to RR or respiratory sinus arrhythmia (RSA), 3) the mechanical effects of respiration (MER) on SBP, and 4) the circulatory dynamics (CID) component, which is responsible for the feedforward effect of RR fluctuations on SBP. Baroreflex and RSA gains increased whereas MER and CID gains decreased in compliant subjects whose average CPAP use was Ͼ3 h/night. In contrast, baroreflex, RSA, and MER gains remained unchanged and CID gain increased in noncompliant subjects. Other summary measures were unchanged in both groups, except for mean RR, which increased in compliant patients. Closed-loop analysis provides a simple but sensitive means for quantitatively assessing cardiovascular control in OSA by using data collected from a single, nonintrusive test procedure.heart rate variability; blood pressure regulation; sleep-disordered breathing; baroreflex sensitivity; respiratory sinus arrhythmia; mathematical model; autonomic function THERE IS A GROWING BODY of evidence (35, 44) that suggests a causal link between obstructive sleep apnea (OSA) and cardiovascular disease. Although the exact mechanisms that underlie this relationship remain unresolved, the acute cardiovascular effects of repetitive upper airway obstruction in sleep are well established. The alternating cycles of OSA and subsequent arousals with accompanying hyperpnea produce large fluctuations in intrathoracic pressure and recurring episodes of hypoxia and hypercapnia. These periodic events lead to dramatic alterations in hemodynamics and elevations in catecholamine level and sympathetic neural activity (43, 44). The neural and humoral consequences of nocturnal apnea carry over into wakefulness in the daytime (7, 12). Increased sympathetic drive is believed to be responsible for the elevated heart rate, decreased heart rate variability (HRV) and increased blood pressure variability observed in alert patients with moderate-to-severe OSA (26,36). The nocturnal application of continuous positive airway pressure (CPAP) over several months has been found to reduce muscle sympathetic nerve activity and plasma catecholamine levels (14, 27,42) and to increase heart rate variability (34). Consistent with these changes, autonomic stress tests also demonstrate improvements in cardiovascular function (41). Furthermore, daytime blood pressure is lowered significantly in hypertensive OSA patients after long-term CPAP therapy (22).A...

Baroreflex control of heart rate during sleep in severe obstructive sleep apnoea: effects of acute CPAP

“…The observations during sleep appear to be in line with the selective impairment of baroreflex response to hypotensive agents found in untreated OSA during wakefulness [38]. Overall, the current study confirms that long-term CPAP treatment is necessary to reverse chronic autonomic dysfunction during sleep [1,4,5,8] and wakefulness [6,8,39,40], possibly in relation to recovery of cardiac vagal fibres after protracted resolution of intermittent hypoxia [41]. Thus, the autonomic dysfunction associated with severe OSA appears not to be as readily reversible as the decreased BRS in snorers [17].…”

“…Long-term treatment with continuous positive airway pressure (CPAP) is effective in counteracting the detrimental effects of OSA on the cardiovascular system. In addition, baroreflex control of heart rate was found to increase [1,4,5] sympathetic and hyperactivity decreased [9,10], after prolonged CPAP treatment.…”

“…evere obstructive sleep apnoea (OSA) is a known cause of autonomic dysfunction [1][2][3][4][5][6] and increased cardiovascular risk and mortality [7,8]. Long-term treatment with continuous positive airway pressure (CPAP) is effective in counteracting the detrimental effects of OSA on the cardiovascular system.…”

Sleep: A Window Into Autonomic Control in Children Born Preterm and Growth Restricted

“…During expiration, intrathoracic pressure becomes less negative, thereby counteracting the earlier increase in SAP. 46,47 The intrathoracic pressure swing that results from a given tidal volume depends on lung volume and/or lung compliance. An increase in HF oscillations may arise from reduced lung compliance in these individuals, possibly due to respiratory distress syndrome which is known to have longterm effects on respiratory flow rates, diffusion capacity, and airway reactivity in children born preterm.…”

Perioperative Risk Modification in Patients with Obstructive Sleep Apnea

“…The initiation of positive airway pressure (PAP) therapy has a rapid effect on SNA, resulting in a significant reduction in hypertension and improvement in heart rate variability [22]. Patient compliance with PAP therapy is extremely important, as cessation of treatment is associated with an immediate return of increased SNA and all of its physiological manifestations [23].…”