Randomised short-term trial of high-span versus low-span APAP for treating sleep apnoea



Auto-titrating continuous positive airway pressure (APAP) devices were developed to improve treatment efficacy and compliance in patients with obstructive sleep apnoea syndrome (OSAS). Since there are insufficient data on the optimal pressure range setting, we aimed to compare the adherence, efficacy and tolerability of treatment with high-span versus low-span APAP.


Seventy-six newly diagnosed OSAS patients fulfilling the treatment criteria were randomised to receive high-span (HS, range 4–15cmH2O, n = 38) or low-span (LS, range 8–12cmH2O, n = 38) APAP. Patients were assessed at 1 and 3 months.


Median Epworth sleepiness scale (ESS) was 13 (IQR, 6–16) and median apnoea-hypopnoea index (AHI) was 35.9 (IQR, 27.6–56.3). There were no significant differences in baseline demographic and clinical characteristics between groups. Overall, no significant differences were found at the first month assessment. After 3 months of therapy, we found again no differences in residual AHI or ESS. However, the group HS proved less adherent than group LS, respectively, with median 87 % (IQR, 60.5–97.5) versus 94 % (IQR, 80.0–98.3) of the nights using ≥4 h (P = 0.014) and mean (±SD) usage 5.7 ± 1.6 versus 6.4 ± 1.2 h/night (P = 0.049). The group HS reported more frequently nasal congestion, excessive oronasal dryness and nocturnal awakenings of at least moderate intensity, the latter with statistical significance (P = 0.005).


Both pressure ranges appear to be equally effective to correct AHI and to improve symptoms. Though, patients with high-span APAP were less compliant to treatment, raising issues about the tolerability of wide pressure range settings of these devices.

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We thank Cristina Carrondo, Elisabete Santa Clara, Ermelinda Eusébio, Joana Pipa, Patrícia Dantas, Paulo Viana and Teresa Santiago for selecting the patients, performing the sleep studies and manually evaluating the records.

Conflict of interest

T Pinto has received financial support from Linde and Vitalaire (Healthcare Providers) for attending symposia and honoraria for speaking at symposia from Philips. After the conclusion of the study, JC Winck has started working in a global position for Linde. The remaining authors declare that they have no conflict of interest.

Ethical approval

The study protocol was approved by our institution’s Ethics Committee. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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Corresponding author

Correspondence to Helder Novais Bastos.

Additional information


In the era of increasing long-term auto-titrating positive airway pressure (APAP) device use for OSA treatment, this study helps sleep physicians improve adherence without substantive effects on OSA control. This randomised controlled trial evaluates the effect of high-span (4–15 cm water) and low-span (8–12 cm water) APAP initial settings on efficacy and adherence over a 3-month time span. The authors find that there is no difference in efficacy between the treatment arms and improved adherence with the low-span APAP settings. These findings indicate that there may be significant differences in long-term adherence based on initial PAP therapy settings. Long-term studies are needed to further clarify the issue; however, it may be prudent in selected patients at the start of therapy to do a trial of low-span APAP with short-term follow-up.

Anna May

Cleveland, OH

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Bastos, H.N., Cardoso, A.V., Castro, A.S. et al. Randomised short-term trial of high-span versus low-span APAP for treating sleep apnoea. Sleep Breath 20, 183–190 (2016). https://doi.org/10.1007/s11325-015-1203-1

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  • Obstructive sleep apnoea
  • Auto-titrating positive airway pressure
  • Pressure range
  • Treatment compliance