Previous studies have typically concerned other patient categories and involved the use of cold-water humidifiers. To increase air moistening, the temperature must be raised as moisture absorption capability increases with temperature. The 2009 study of Rea et al. (9) examined the effect of warm humidification on COPD and bronchiectasis patients, who used a warm humidifier (MR 880) on average for two hours per day. LTOT was not an inclusion criterion in the study, and the severity of COPD varied. Despite the relatively short time of use the study demonstrated the beneficial effect of humidification on exacerbation frequency.