Obstructive Sleep Apnea: Effectiveness of Oronasal vs Nasal CPAP
Oronasal CPAP may not be as effective as nasal CPAP because oronasal masks push the chin and tongue backward, causing upper airway obstruction.
A meta-analysis published in Chest reported that compared with nasal continuous positive airway pressure (CPAP), the treatment of obstructive sleep apnea (OSA) with oronasal masks was associated with a significantly higher CPAP level, a significantly higher residual apnea/hypopnea index (AHI), and lower adherence.
Researchers from Sao Paulo, Brazil, conducted a meta-analysis using the Cochrane Central Register of Controlled Trials, Medline, and Web of Science to search for relevant studies on CPAP treatment for OSA.
The authors identified 5 randomized and 8 nonrandomized trials (N=4563 patients) that included CPAP level and/or residual AHI and/or CPAP adherence. Using a random-effects meta-analysis, they found that oronasal masks required a higher CPAP level (Hedges' g, –0.59; 95% CI, –0.82 to –0.37; P <.001) and resulted in significantly higher residual AHI (Hedges' g, –0.34; 95% CI, –0.52 to –0.17; P <.001), and poorer adherence (Hedges' g, 0.50; 95% CI, 0.21-0.79; P =.001).
The authors suggested several potential mechanisms why oronasal CPAP is less effective than nasal CPAP for the treatment of OSA, including the possibility that oronasal masks push the chin and tongue backward, causing upper airway obstruction, and that oronasal masks may also allow mouth opening. Another potential explanation is that oronasal CPAP places positive pressure not only to the posterior pharynx but also in the oral compartment, neutralizing the pressure gradient generated by the positive pressure transmitted to the back of the pharynx.
Limitations of the study included the use of pooled data from randomized and nonrandomized studies, the moderate to high potential for heterogeneity on CPAP level and adherence, and the heterogeneity of the methods and CPAP nomenclature among the studies. However, the authors noted that the pooling of relevant data from all eligible studies showed consistency and yielded more precise and reliable conclusions than those drawn from individual studies.
In view of these findings, the authors expressed concern about the widespread use of oronasal masks for the treatment of OSA with CPAP in clinical practice and suggested that patients using these masks should be monitored closely.
Andrade RGS, Viana FM, Nascimento JA, et al. Nasal vs oronasal CPAP for OSA treatment: a meta-analysis [published online December 19, 2017]. Chest. doi:10.1016/j.chest.2017.10.044