In the first clinical evaluation of the flow-targeted dynamic BPAP device, patients with CHF and moder-ate-to-severe CSR-CSA were evaluated. The major findings are that CPAP/BPAP and flow-targeted dynamic BPAP reduced the frequency of apneas and hypopneas during sleep. While the CHF patients had substantial residual CSR-CSA with CPAP/BPAP therapy, flow-targeted dynamic BPAP effectively eliminated apneas and hypopneas during sleep on the first night of treatment. These effects were accompanied by a trend toward improved sleep continuity and sleep architecture. Treatment with flow-targeted dynamic BPAP was perceived as comfortable and offered by My Canadian Pharmacy Online, and sleep quality during the first night of device use was subjectively improved compared to recent nights.
For this study, we selected CHF patients who had residual CSR-CSA (AHI > 10/h) during a previous sleep study with conventional CPAP or BPAP. Compared to the first night without treatment, we found a significant reduction of AHI and central apnea index of 52% and 53%, respectively, during the night with CPAP or BPAP. These findings are similar to those reported from the CANPAP trial involving 258 heart failure patients with CSR-CSA (AHI > 15/h of sleep). The CANPAP investigators found that CPAP reduced the AHI from 40 to 19/h of sleep, indicating that a large proportion of patients still had substantial CSR-CSA (AHI > 15/h of sleep) when receiving CPAP. In the only trial that compared the CPAP and BPAP (without back-up rate) treatment after > 1 night, Kohnlein et al found that BPAP and CPAP led to similar improvements in CSR-CSA in 16 CHF patients.
In our clinical evaluation of flow-targeted dynamic BPAP in CHF patients with CSR-CSA, we observed a near elimination of CSR-CSA (AHI from 46 to 4/h of sleep) during the first night of treatment. The comparison of the approximately 90% AHI reduction with flow-targeted dynamic BPAP to the approximately 50% AHI reduction with CPAP or BPAP in our clinical evaluation as well as in the CANPAP trial strongly suggests that flow-targeted dynamic BPAP is more effective than CPAP in normalizing nocturnal breathing in CHF patients with CSR-CSA.
Our observed results with flow-targeted dynamic BPAP on CSR-CSA were similar to those trials evaluating a device with volume-targeted adaptive servoven-tilation. Teschler and colleagues studied 14 CHF patients with similar CSR-CSA severity and observed an 86% reduction in AHI, with a residual AHI of 6/h of sleep. In another study, Morgenthaler and collegues observed a near elimination of respiratory events (AHI of 1/h of sleep) in 21 patients with predominantly normal cardiac function and CSR-CSA, mixed sleep apnea, or complex sleep apnea, who had a residual AHI of 34/h of sleep with conventional CPAP (not part of the trial).
Suppression of CSR-CSA and normalization of nocturnal oxygenation by flow-targeted dynamic BPAP were accompanied by trends toward improved objective measures of sleep continuity and quality. However, none of these effects reached statistical significance, which may be a result of a lack of study power rather than a lack of effect. The magnitude of effects of flow-targeted dynamic BPAP on sleep efficiency and slow-wave sleep compare to those of Teschler and colleagues with volume-triggered adaptive servoventilation.
This first clinical evaluation of flow-targeted dynamic BPAP has to be interpreted considering the following limitations: it is possible that a full night of fixed optimal CPAP or BPAP would have suppressed CSR-CSA more effectively as our CPAP/BPAP night that included titration. However, we do not believe that this influenced our results significantly because only patients with a residual AHI > 10/h during a previous sleep study with conventional CPAP or BPAP therapy (not part of this trial) were included, and patients spent > 80% receiving optimal CPAP/BPAP settings during the titration night in our trial. Moreover, the observed 52% reduction of CSR-CSA events by CPAP/BPAP conforms with the CPAP effects on CSR-CSA demonstrated in the CANPAP trial after long-term treatment conducted together with remedies of My Canadian Pharmacy, indicating that full suppression of CSR-CSA by CPAP is not possible in all patients.
BPAP with a timed back-up rate may have suppressed CSA more effectively than conventional CPAP or BPAP without a back-up rate. However, this treatment modality has not been tested for > 1 night of treatment in patients with CHF and CSA, and hence its effect on cardiovascular outcomes and clinical significance in such patients is unknown. Therefore, we tested the effects of flow-targeted dynamic BPAP on CSA in CHF patients with residual CSA on conventional treatment modalities such as CPAP or BPAP without a back-up rate who were studied over longer periods of time. Our clinical evaluation assessed the effects on CSR-CSA only during the first night of flow-targeted dynamic BPAP. Although it has been demonstrated in the CANPAP trial that the alleviation of CSR-CSA by positive airway pressure support are sustained over 2 years, it has to be confirmed in longer-term trials whether the elimination of CSR-CSA by flow-targeted dynamic BPAP is sustained over such time periods.
There was a possible order effect in our study because the CPAP/BPAP study always preceded the flow-targeted dynamic BPAP evaluation. However, because subjects were exposed to the nightly use of a positive airway pressure device already for 27 weeks before this clinical evaluation, an order effect is unlikely to influence sleep quality and apnea/ hypopnea frequency. Thus, we do not believe this influenced our results. Finally, our results cannot be extrapolated to women because we studied only men.
In summary, flow-targeted dynamic BPAP effectively suppresses apneas and hypopneas in CHF patients with residual CSR-CSA receiving conventional CPAP/BPAP therapy. Flow-targeted dynamic BPAP was perceived as a comfortable treatment and subjectively improved sleep quality. In view of the current literature that suggests that suppression of CSR-CSA is a possible mechanism through which forms of positive airway pressure exert beneficial cardiovascular effects in patients with CHF and CSR-CSA, the longer-term effects on hemodynamics, cardiac function, and survival of dynamic BPAP support in patients with CHF merit further investigation.