Clinical Benefits & The Löwenstein Difference

S A N T È • LÖW E N S T E I N S L E E P T H E R A PY D E V I C E S

Appendix 9 Pgs. 3-4

K Zhu, S Aouf, G Roisman et al. CPAP Treatment Efficacy with Pressure-Relief Features

Table 2 —Comparison of pressure-relief features in fixed continuous positive airway pressure mode: residual apnea-hypopnea index, apnea index, and measured pressures during a 10-min obstructive apnea sequence (initial apnea index = 60/h). Residual AHI (events/h) Residual AI (events/h) Measured mean pressure (cmH 2 O) Remstar Auto: Manual titration pressure = 11 cmH 2 O Conv. CPAP 0 0 10.9 C-Flex 3 0 0 10.7 C-Flex+ 3 60 0 9.1 P-Flex 60 0 8.2 AirSense 10 Autoset: Manual titration pressure = 10.8 cmH 2 O Conv. CPAP 0 0 10.8 EPR 3 60 0 8.2 Prisma 20A: Manual titration pressure = 10.5 cmH 2 O Conv. CPAP 0 0 10.7 SoftPAP 2 0 0 9.6 SoftPAP 3 0 0 9.9 All results were identical for two independent repetitions. Titration pressure was noted as the device pressure and the pressure-relief feature was disabled during the continuous positive airway pressure (CPAP) titration. Conventional CPAP: fixed CPAP without pressure-relief feature. P-Flex is only available in autotitrating continuous positive airway pressure (APAP) mode; here the minimum pressure was set identical to the maximum to achieve a constant therapy pressure. AHI, apnea-hypopnea index; AI, apnea index.

Statistical Analysis One-way analysis of variance, preceded by Levene’s test for equality of variance, was applied to compare the AHI, AI, and pressure with and without pressure-relief feature. Kruskal- Wallis test was applied if Levene’s test was positive (Medcalc Software, Mariakerke, Belgium). Relationship between Conventional and Pressure-Relief CPAP Different severities of upper airway obstruction were simu - lated by changing the pressure inside the Starling resistor from 3 to 16 cmH 2 O with increment of 1 cmH 2 O. At each obstruc- tion level, the effective pressures (device pressure) obtained by the manual CPAP titration were compared between conven- tional and pressure-relief CPAP.

sufficient because fixed CPAP efficacy is time-independent. A 30-sec obstructive apnea occurred every minute, i.e., total apnea-hypopnea index (AHI) = 60/h. A similar reference test was carried out without pressure-relief feature (conventional CPAP) for each device. Tests were repeated twice for reproduc - ibility. A third test was executed if the coefficient of variance of the first two tests was higher than 10%. APAP: The devices were set to APAP mode with open pres - sure range (4–20 cmH 2 O), and subjected to a long obstruc- tive apneas sequence with pressure-relief features enabled. The long breathing sequence lasted 4.2 h, including a 6-min normal breathing session at the beginning, which was con- sidered as a baseline. A 20-sec obstructive apnea occurred every minute and thus the total AHI was 58.6/h. A simi - lar reference test was carried out for each device without pressure-relief feature (conventional APAP). Tests were re - peated twice for reproducibility. A third test was executed if the coefficient of variance of the first two tests was higher than 10%. Data Analysis For each test, mean or median pressure was calculated from the P m . Also, residual AHI and apnea index (AI) were derived from the peak-to-peak flow amplitude (ΔV’, derived by calcu - lating the upper and lower envelops of the flow curve). Each residual event was scored by considering both the amplitude reduction and the corresponding duration, i.e., ΔV’ ≤ 10% of baseline: apnea; 10% < ΔV’ ≤ 70%: hypopnea, with a dura - tion ≥ 10 sec. 25–27 In addition, the AHI, AI, and pressure data on the device report were also noted for comparison. Results were averaged on two tests for fixed CPAP and on three tests for APAP. All the analyses were performed with MATLAB (MathWorks Inc., Natick, MA, USA).

RESULTS Pressure-Relief CPAP/APAP Efficacy Fixed CPAP

Measured flow and pressure waveforms of each pressure- relief feature during normal breathing and obstructive ap- nea are shown in Figure 1 . The residual AHI and measured pressure are shown in Table 2 . Compared to conventional CPAP (without pressure relief ), the C-Flex+ 3, P-Flex and EPR 3 pressure-relief features were ineffective to normal - ize the breathing flow and to reduce the AHI. The measured pressures with these features were 1.8, 2.6, and 2.6 cmH 2 O respectively lower than that with the conventional CPAP. However, with C-Flex 3 and SoftPAP 2 and 3, the CPAP devices maintained the same treatment efficacy compared to the conventional CPAP and normalized the breathing flow ( Table 2 ), despite the fact that their mean pressures

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Journal of Clinical Sleep Medicine, Vol. 12, No. 3, 2016

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