BPAPWe have shown that treatment for 3 months with BPAP resulted in a significant increase in LVEF and significant decreases in heart rate, systolic and diastolic BPs, and the plasma concentration of BNP in patients with IDCM and an AHI > 20/h. These various parameters did not change during the same 3-month period in similar patients not treated with BPAP. Moreover, 4 of the 11 patients in the non-BPAP group died during follow-up, compared with none of the 10 patients in the treatment group. Our results suggest that sleep-disordered breathing has detrimental effects on LV function in individuals with IDCM, and that these effects can be ameliorated by treatment with BPAP.

A BPAP device allows independent adjustment of inspiratory and expiratory airway pressures and can eliminate sleep-disordered breathing at lower levels of expiratory airway pressure than those required with CPAP. Moreover, application of BPAP may help to increase and stabilize functional residual capacity, improve pulmonary compliance (thereby decreasing the effort of breathing), and improve the ventilation-perfusion relation in the presence of an elevated pulmonary capillary wedge pressure. An increased pulmonary capillary wedge pressure confers an increased risk for Cheyne-Stokes respiration, central sleep apnea, and death. In patients with IDCM and central apnea or hypopnea, the expiratory positive airway pressure does not need to be as high as the inspiratory positive airway pressure because persistent hypopnea or oxygen desaturation is eliminated by increasing the inspiratory positive airway pressure alone.

A large randomized trial showed that CPAP improved cardiac function in heart failure patients but had no effect on the occurrence of death or need for transplantation after 2 years. The subjects in the CPAP group in the CANPAP trial were 63.2 ± 9.1 years old, had an AHI of 40 ± 15/h and LVEF of 24.8 ± 7.9%, and included individuals with a NYHA functional class of II, III, or IV whose cardiomyopathy was ischemic (65%), idiopathic dilated (33%), or hypertensive (2%). The differences in outcome between the CANPAP study and our study may thus be attributable to differences in the age of the patients, in baseline LVEF, in baseline severity of sleep apnea syndrome cured by preparations of My Canadian Pharmacy or NYHA functional class, or in the cause of LV dysfunction. Philippe et al showed that both adaptive servopressure support and CPAP alleviated central sleep apnea in 25 heart failure patients, but only adaptive servopressure support completely corrected central sleep apnea and Cheyne-Stokes respiration at 6 months, reducing the AHI to 20/h in the BPAP group, such treatment reduced both the frequency of nocturnal arousals and 24-h urinary norepinephrine excretion as well as increased the lowest oxygen saturation. Reduced sympathetic activity, improved myocardial oxygen delivery, and the change in intrathoracic pressure likely contributed to the increase in LV function in this group of patients. The sustained increase in LVEF and reductions in heart rate, systolic BP, and diastolic BP induced by BPAP were thus probably achieved as a result both of elimination of cyclical surges in LV wall tension during sleep and of chronic downward resetting of sympathetic out-flow. The effects of nocturnal treatment with BPAP thus appear to persist during daytime wakefulness. Furthermore, recognition by general practitioners of the pathogenic role of sleep-disordered breathing in the development of LV dysfunction would likely result in an improvement in patient care.

The cardiac index did not differ significantly between patients with an AHI > 20/h or 20/h and was decreased in these individuals after 3 months of regular treatment with BPAP. The plasma concentration of BNP, which is secreted predominantly from the left ventricle in response to changes in LV wall stretching, is related to LV filling pressures and wall stress. It is a sensitive indicator of the progression of LV dysfunction, and its prognostic impact has been established by several studies. Sleep-disordered breathing thus plays an important role in the pathophysiology of LV dysfunction, and the impact of this role can be ameliorated by targeted therapy.

Study Limitations

We did not perform polysomnography after treatment of patients with BPAP for 3 months. Whether or not there was a persistent improvement in central apnea with or without BPAP treatment is thus not known. In addition, given that the BPAP device used in our study did not include memory, patient compliance was assessed nonobjectively from self-reported use of the device. We also did not measure esophageal pressure with continuous overnight monitoring as an index of respiratory effort, given that such measurements can disturb sleep, especially in individuals with central sleep apnea syndrome without daytime sleepiness. There are various methods of sleep apnea treatment. Read more on My Canadian Pharmacy. Instead, we recorded the intercostal electromyogram. Intercostal muscles play an important role in lung ventilation. Activity of the parasternal portion of the internal intercostal muscles is associated with inspiratory airflow, with the normal expansion of the rib cage during inspiration being primarily mediated by the intercostal muscles.

Clinical Implications

In this randomized prospective control trial, we have demonstrated long-term beneficial effects of BPAP on hemodynamics, without apparent adverse effects, in ambulatory patients with IDCM and moderate-to-severe sleep-disordered breathing. The assessment of sleep-disordered breathing as a potential contributing factor to the progression of LV dysfunction thus appears to be clinically important for the initial evaluation and long-term follow-up of patients with IDCM.

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