Heated Humidification or Face Mask To Prevent Upper Airway Dryness During Continuous Positive Airway Pressure Therapy

The objectives of this study were (1)to evaluate the way in which nasal continuous positive airway pressure(CPAP) therapy influences the relative humidity (rH) of inspired air;and (2) to assess the impact on rH of the addition of an integratedheated humidifier or a full face mask to the CPAP circuitry. The studies were performed in 25 patients withobstructive sleep apnea syndrome receiving long-term nasal CPAP therapyand complaining of nasal discomfort. During CPAP administration, temperature and rH were measured in the mask either during a night'ssleep for 8 patients or during a daytime study in which the effects ofmouth leaks were simulated in 17 patients fitted with either a nasalmask (with or without humidification) or a face mask alone. University hospital sleep disorders center. Compared with the values obtainedwith CPAP alone, integrated heated humidification significantlyincreased rH during the sleep recording, both when the mouth was closed(60 ± 14% to 81 ± 14%, p < 0.01) and during mouth leaks(43 ± 12% to 64 ± 8%, p < 0.01). During the daytime study, asignificant decrease in rH was observed with CPAP alone. Compared withthe values measured during spontaneous breathing without CPAP(80 ± 2%), the mean rH was 63 ± 9% (p < 0.01) with the mouthclosed and 39 ± 9% (p < 0.01) with the mouth open. The additionof heated humidification to CPAP prevented rH changes when the mouthwas closed (82 ± 12%), but did not fully prevent the rH decreaseduring simulation of mouth leaks (63 ± 9%) compared with thecontrol period (80 ± 2%, p < 0.01). Finally, attachment of aface mask to the CPAP circuitry prevented rH changes both with themouth closed (82 ± 9%) and with the mouth open (84 ± 8%). These data indicate that inhaled air drynessduring CPAP therapy can be significantly attenuated by heatedhumidification, even during mouth leaks, and can be totally preventedby using a face mask.