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K Zhu, S Aouf, G Roisman et al. CPAP Treatment Efficacy with Pressure-Relief Features
Figure 1 —Measured mask airflow and pressure waveforms of fixed CPAP.
Measured mask airflow and pressure waveforms of fixed continuous positive airway pressure (CPAP) with (black curves) and without (gray curves) pressure-relief feature during normal breathing and obstructive apnea. For each device, the pressure was set as the same value as the manual titration pressure of conventional CPAP (without pressure-relief feature). Panel A: recordings during normal breathing. Of note, with C-Flex+ 3, P-Flex and EPR 3, the device-delivered pressure curve was shown as a pressure support accompanied by a positive expiratory pressure that was about 3 cmH 2 O lower than the initial CPAP value. Panel B: recordings during obstructive apneas. The black and gray flow curves are superposed in C-Flex, and SoftPAP 2 and 3. With C-Flex+ 3, P-Flex, and EPR 3, the device-delivered pressure was around 3 cmH 2 O lower than the initial setting. As a consequence, breathing could not be normalized. The pressure oscillations observed in EPR 3 was due to the upper airway patency detection with forced oscillation technique. *C-Flex+: identical to A-Flex in APAP mode. **P-Flex: only available in APAP mode. Here the minimum pressure was set identical to the maximum in order to make the device work as a fixed CPAP. Pm, mask pressure; V’, airflow.
were 0.2, 1.1, and 0.8 cmH 2 O lower than the conventional CPAP values. APAP The residual AHI, AI, and pressure are shown in Table 3 . Re - garding the bench-assessed residual AHI, no clinically significant increase was found with any pressure-relief features included in this study except P-Flex: the bench-assessed AHI increased from 9.1/h with the conventional APAP (APAP without pressure relief) to 20.6/h with P-Flex (p < 0.05) whereas the initial AHI was 58.6/h. Similarly, the bench-assessed AI with A-Flex 3 and P-Flex slightly increased from 0.5/h with the conventional APAP to 1.4 and 1.8/h respectively (p < 0.05 for both). The AI with EPR 3 slightly in - creased from 0.2/h with the conventional APAP to 0.7/h (p < 0.05). In addition, the bench-measured mean pressure of P-Flex was 1.9 cmH 2 O lower than the conventional APAP (p < 0.05), whereas this pressure drop was only 0.3 cmH 2 O for EPR 3 (p < 0.01) and 0.4 cmH 2 O for SoftPAP 3 (p < 0.05). In the device reports of A-Flex 3, P-Flex, EPR 3, and SoftPAP 3,
respectively, the mean/median pressures were 1.9 (p = 0.002), 2.8 (p < 0.001), 2.5 (p < 0.001) and 0.9 cmH 2 O (p = 0.04) higher than the mean/median pressures measured on the bench. Relationship between Conventional and Pressure-Relief CPAP Comparisons of effective treatment pressures (device pressure) between conventional and pressure-relief CPAP are shown in Figure 2 . CPAP with C-Flex 3 ( Figure 2A ), and SoftPAP 2 and 3 ( Figure 2C ) were identical to the conventional CPAP in terms of efficacy. However, CPAP with C-Flex+ 3 ( Figure 2A ), P-Flex ( Figure 2A ), and EPR 3 ( Figure 2B ) should be set higher than conventional CPAP to achieve the same efficacy when CPAP > 4 cmH 2 O. D I SCUSS I ON This study demonstrates the effect of pressure-relief features on fixed CPAP and APAP treatment efficacy for OSA. Compared
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Journal of Clinical Sleep Medicine, Vol. 12, No. 3, 2016
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