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K Zhu, S Aouf, G Roisman et al. CPAP Treatment Efficacy with Pressure-Relief Features
Figure 2 —Comparisons between effective treatment pressures of the same efficacy (device set pressure) with and without pressure relief feature.
Figure 3 —Mask airflow and pressure profiles of Remstar Auto with and without P-Flex at the beginning of the 4.2-h obstructive apnea sequence.
Pm, mask pressure; V’, airflow.
APAP resulted from both the specific autotitration algorithm and the reduced CPAP efficacy with pressure-relief feature. Regarding APAP treatment with pressure-relief features, Mulgrew et al. 10 found a nonsignificant trend of greater subjec - tive comfort with C-Flex. Kushida et al. 31 reported an equiva- lency in treatment adherence and efficacy between A-Flex and conventional CPAP after either 3 or 6 mo, but a higher AHI at the initiation phase. In a recent study, Chihara et al. 15 compared the adherence between conventional APAP, APAP with C-Flex and APAP with A-Flex, and found greater adherence in APAP with C-Flex. Of note, at the initiation of the studies of Kushida et al. 31 and Chihara et al., 15 the APAP autotitration was carried out with the allocated pressure-relief feature. Our results have an important clinical consequence for sleep apnea treatment. In clinical practice, the problem may arise when a pressure relief feature is later added to a convention- ally titrated patient without increasing the titration pressure of the device. However, the negative effects that we document in the current study may be mitigated in the case of fixed CPAP initially titrated to a pressure level that is high enough to cope with sleep in unfavorable circumstances such as supine pos- tures and rapid eye movement sleep stage because most SDB events will be abolished; or during “CPAP exploration”, when the pressure can be up to 5 cmH 2 O higher than that is just suf- ficient to abolish SDB events. 32 Similarly, in the case of APAP our findings could be relevant if the pressure range over which autotitration was allowed to occur had an upper limit that was set close to the effective (95 th or 90 th centile) pressure prior to
(A) Remstar Auto. (B) AirSense 10 AutoSet. (C) Prisma 20A. Conventional CPAP is continuous positive airway pressure without pressure-relief feature.
Figure 3 shows that despite the persistent apneas the autotitra- tion pressure of P-Flex decreased around the 19 th min after a foregoing pressure increase. This is a specificity of the algo - rithm of Remstar Auto (P-Flex) that intends to prevent inappro - priate pressure increase to central apneas and non-responding events. 30 With this specific algorithm, such improper pressure decrease may also occur during autotitration in the case of suc- cessive obstructive apneas with severe upper airway obstruc- tion. Compared to the conventional Remstar Auto APAP, the insufficient treatment pressure with P-Flex worsened such suc - cessive apneas and led to further decrease in autotitration pres- sure ( Figure 3 ). Thus, this inappropriate response of P-Flex
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Journal of Clinical Sleep Medicine, Vol. 12, No. 3, 2016
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