Impact of the type of mask on the effectiveness of and adherence to continuous positive airway pressure treatment for obstructive sleep apnea

Abstract

Continuous positive airway pressure (CPAP) is the gold standard for the treatment of obstructive sleep apnea (OSA). Although CPAP was originally applied with a nasal mask, various interfaces are currently available. This study reviews theoretical concepts and questions the premise that all types of interfaces produce similar results. We revised the evidence in the literature about the impact that the type of CPAP interface has on the effectiveness of and adherence to OSA treatment. We searched the PubMed database using the search terms "CPAP", "mask", and "obstructive sleep apnea". Although we identified 91 studies, only 12 described the impact of the type of CPAP interface on treatment effectiveness (n = 6) or adherence (n = 6). Despite conflicting results, we found no consistent evidence that nasal pillows and oral masks alter OSA treatment effectiveness or adherence. In contrast, most studies showed that oronasal masks are less effective and are more often associated with lower adherence and higher CPAP abandonment than are nasal masks. We concluded that oronasal masks can compromise CPAP OSA treatment adherence and effectiveness. Further studies are needed in order to understand the exact mechanisms involved in this effect.

Keywords: Continuous positive airway pressure; Masks; Sleep apnea, obstructive.

Figure 1 -. Photographs showing the types of continuous positive airway pressure masks currently available for the treatment of obstructive sleep apnea: nasal mask, in A; oronasal mask, in B; nasal pillows, in C; and oral mask, in D. Source: Sleep Laboratory, Heart Institute, University of São Paulo School of Medicine Hospital das Clínicas.

Figure 2 -. Schematic illustration of the Starling resistor. In A, the nose and the trachea are represented by two rigid tubes connected by a collapsible segment (the pharynx). In B, pharyngeal collapse occurs when the pharyngeal critical pressure (Pcrit) is greater than the upper airway pressure (Pnasal). In C, nasal continuous positive airway pressure (CPAP) applied to the upper airway is greater than Pcrit and can therefore maintain upper airway patency. In D, oronasal CPAP; the hypothesis is that upper airway collapse occurs when oral pressure (Poral) is greater than Pcrit. Source: Sleep Laboratory, Heart Institute, University of São Paulo School of Medicine Hospital das Clínicas.

Figure 3 -. In A, schematic illustration of the normal upper airway (left) of a patient with obstructive sleep apnea, showing retropalatal obstruction during negative pressure generated during inhalation (center) and during continuous positive airway pressure (right). In B, schematic illustration of a patient wearing an oronasal mask, and, in C, patient with significant mouth breathing. The tongue (red) is displaced posteriorly and obstructs the upper airway. Adapted from Sullivan et al.(21) Source: Schorr et al.(31)

Figure 4 -. In A, polysomnography summary of a continuous positive airway pressure (CPAP) titration study during natural sleep. In B and C, sleep endoscopy images showing the patient wearing a nasal mask and an oronasal mask, respectively. During the first half of the CPAP titration study, a nasal CPAP of 7 cmH2O was enough to control obstructive events. During the second half of the CPAP titration study, an oronasal mask was used. Obstructive events persist, despite the fact that the pressure was gradually increased to 16 cmH2O. The endoscopic image obtained when a nasal CPAP of 7 cmH2O was used (B) shows that the oropharynx is open. In contrast, the image obtained when an oronasal CPAP of 16 cmH2O was used (C) shows posterior displacement of the base of the tongue, which pushes the epiglottis and significantly narrows the airway lumen. Respiratory events are expressed in seconds (sec). SpO2 measured by pulse oximetry. CA: central apnea; OA: obstructive apnea; MA: mixed apnea; Hypo: hypopnea; PAP: pulmonary artery pressure; and REM: rapid eye movement.