Humidification during CPAP titration: an unresolved issue

Abstract

AbbreviationsAHI Apnea–hypopnea indexCPAP Continuous positive airway pressureHH Heated humidifierOSA Obstructive sleep apneaDear Editor,Thereisstillacontroversyovertheroleandpositiveeffectsofheated humidifier (HH) on nasopharyngeal symptoms andobjective measures during continuous positive airway pres-sure(CPAP)titration[1,2].WereadwithinterestthearticlebyYu et al. [3] who analyzed the effects of HH during CPAPtitration in subjects with and without nasopharyngeal symp-toms. The investigators randomly assigned 52 patients withobstructive sleep apnea (OSA) during CPAP titration underpolysomnographic monitoring into HH and non-HH groups.The authorsassessedsymptomatology (nasalcavity, pharynx,and nasopharynx) before and after CPAP titration, and evalu-ated leak, AHI reduction, and optimal CPAP pressure level inthe two groups. They concluded that HH does not improveany of the objective measures during CPAP titration and didnot recommend the use of HH during CPAP titration. Webelieve that the conclusion is overstated based on the pre-sented data. The results cannot be generalized to all OSApatients undergoing CPAP titration. The need for humidifica-tion during positive airway pressure therapy through a nonin-vasive route is influenced by several factors such as air leaks,interface, room temperature, temperature of inhaled gas, air-flow, and pressure used [4].External humidification will have no added benefits inpatients who can maintain adequate physiological levels ofhumidity. As the pressure needed to overcome the obstruc-tive respiratory events in the studied group was relativelylow, it seems that the studied subjects were able to maintainadequate airway humidity without HH. The conclusions ofthe study of Yu et al. [3] cannot be generalized to OSApatients who require high positive airway pressure to over-come airway obstruction. Another important issue to con-sider when assessing the need for humidification is thepresence of mouth breathing and mouth leaks. Mouthbreathing may generate unidirectional nasal air flow andresults in significant increase in nasal airway resistanceand hence mouth leaks [5]. The nasal mucosa has a consid-erable ability for heating and humidifying inspired air; how-ever, it can be overwhelmed at high flow rates with CPAPand when there is unidirectional flow caused by mouthleaks. The potential effects of mouth breathing were notevaluated in the paper of Yu et al. [3].Therefore, we think that the role of humidificationduring CPAP titration cannot be discarded. Humidifica-tion may be beneficial in selected OSA patients duringCPAP titration such as patients with mouth breathingand patients requiring high positive airway pressure toeliminate airway obstruction. Future studies should as-sess the role of humidification during CPAP titration inpatients with mouth breathing and patients requiringhigh positive airway pressure.