LETTER TO THE EDITORS Humidification during CPAP titration: an unresolved issue Antonio M. Esquinas & Ahmed S. BaHammam Received: 14 June 2012 / Revised: 14 June 2012 / Accepted: 10 July 2012 # Springer-Verlag 2012 Abbreviations AHI Apnea–hypopnea index CPAP Continuous positive airway pressure HH Heated humidifier OSA Obstructive sleep apnea Dear Editor, There is still a controversy over the role and positive effects of heated humidifier (HH) on nasopharyngeal symptoms and objective measures during continuous positive airway pres- sure (CPAP) titration [1, 2]. We read with interest the article by Yu et al. [3] who analyzed the effects of HH during CPAP titration in subjects with and without nasopharyngeal symp- toms. The investigators randomly assigned 52 patients with obstructive sleep apnea (OSA) during CPAP titration under polysomnographic monitoring into HH and non-HH groups. The authors assessed symptomatology (nasal cavity, pharynx, and nasopharynx) before and after CPAP titration, and evalu- ated leak, AHI reduction, and optimal CPAP pressure level in the two groups. They concluded that HH does not improve any of the objective measures during CPAP titration and did not recommend the use of HH during CPAP titration. We believe that the conclusion is overstated based on the pre- sented data. The results cannot be generalized to all OSA patients 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 in patients who can maintain adequate physiological levels of humidity. As the pressure needed to overcome the obstruc- tive respiratory events in the studied group was relatively low, it seems that the studied subjects were able to maintain adequate airway humidity without HH. The conclusions of the study of Yu et al. [3] cannot be generalized to OSA patients who require high positive airway pressure to over- come airway obstruction. Another important issue to con- sider when assessing the need for humidification is the presence of mouth breathing and mouth leaks. Mouth breathing may generate unidirectional nasal air flow and results in significant increase in nasal airway resistance and 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 CPAP and when there is unidirectional flow caused by mouth leaks. The potential effects of mouth breathing were not evaluated in the paper of Yu et al. [3]. Therefore, we think that the role of humidification during CPAP titration cannot be discarded. Humidifica- tion may be beneficial in selected OSA patients during CPAP titration such as patients with mouth breathing and patients requiring high positive airway pressure to eliminate airway obstruction. Future studies should as- sess the role of humidification during CPAP titration in patients with mouth breathing and patients requiring high positive airway pressure. A. M. Esquinas (*) Intensive Care Unit, Hospital Morales Meseguer, Avenida Marques Velez, s/n, Murcia 3008, Spain e-mail: antmesquinas@gmail.com A. S. BaHammam University Sleep Disorders Center, College of Medicine, King Saud University, Riyadh, Saudi Arabia e-mail: ashammam2@gmail.com Sleep Breath DOI 10.1007/s11325-012-0751-x