Continuous Positive Airway Pressure And Cardiovascular Outcomes

The present evidence for a significant protective or ameliorating effect of CPAP against adverse cardiovascular outcomes in OSA is mixed, especially in the management of mild OSA. In a large observational cohort study, there was an increased risk of stroke and death, which persisted after allowing for other risk factors including hypertension; however, CPAP use did not appear to provide protection against adverse outcomes in this study (112). In contrast, in case-control studies, there is some evidence of cardiovascular benefit from nasal CPAP therapy in severe sleep apnea. Long-term CPAP therapy seemed to provide a protective benefit against death from established cardiovascular disease though there was no difference in the development of new cases of hypertension, cardiac disorder or stroke between CPAP-treated and untreated groups (113). In a large Spanish study patients with untreated severe OSA had a higher incidence of both fatal and nonfatal cardiovascular events than untreated patients with mild-moderate OSA, simple snorers, healthy subjects, and patients treated with CPAP (114). CPAP also appears to provide a protective benefit against new vascular events after stroke or transient ischaemic attack in moderate-severe OSA subjects (115). These results suggest a protective benefit of CPAP against these adverse cardiovascular outcomes, but better designed RCTs are needed to convincingly demonstrate this benefit.

Cardiovascular-protective benefits of CPAP have been demonstrated mainly against hypertension. Short-term improvements in hypertension control have been shown in a randomized parallel trial of CPAP-treated OSA patients when compared to sub-therapeutic-CPAP, and cardiovascular risk benefits imputed therefrom (106). In a RCT of CPAP, sham-CPAP and nocturnal oxygen, two weeks of CPAP therapy resulted in a significant reduction in daytime mean arterial and diastolic blood pressure and night-time systolic, mean, and diastolic blood pressure (116). In a small study of nonrandomized OSA subjects measures of muscle sympathetic traffic were improved over time with CPAP treatment although blood pressure did not change (117). However, recent data question the ability of CPAP to decrease blood pressure over longer time periods, particularly in nonsleepy patients (118).

Although acute auto-CPAP use did not alter systolic nor diastolic blood pressure, nor heart rate, from diagnostic (pretreatment) values in 12 OSA patients, CPAP treatment was associated with a stabilizing effect by reducing night-time but not daytime variability of pressure parameters (119). Nearly half of a group of moderate-severe OSA patients experienced severe, mainly nocturnal, cardiac arrhythmia documented by use of an insertable loop recorder (but largely not documented by Holter monitor); and long-term CPAP treatment was associated with marked reduction of arrhythmia (120).

Preeclamptic women exhibited sleep-induced decrements of heart rate, stroke volume and cardiac output, and exacerbated increase of total peripheral resistance, and these changes were minimized and reduced, respectively in subjects treated with CPAP (121). There is an apparent linkage between untreated OSA and left-to-right cardiac shunt (LRS) via a patent foramen ovale, and a case report documents reversal of wake LRS with institution of CPAP therapy (122).

In summary, although there is tantalizing evidence from small physiological and case studies of potential cardiovascular benefit from treating OSA patients with CPAP, and epidemiological evidence of significant cardiovascular and mortality risk from OSA, there is a continuing need for large-scale RCTs to support the idea that we provide cardiovascular benefit to our OSA patients on CPAP, beyond merely reducing the level of respiratory disturbances.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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