Nosocomial pneumonia accounts for the vast majority of healthcare-associated infections (HAI) [1]. Although numerous medical devices have been discussed as potential vehicles for microorganisms, very little is known about the role played by oxygen humidifiers as potential sources of nosocomial pathogens [2]. In order to administer low-flow oxygen therapy, it is currently common practice in many acute care hospitals to exclusively use clean water in humidifier reservoirs. The "Guideline for the Prevention of Nosocomial Pneumonia" published by the Centers for Disease Control in 1982 serves as the main foundation for this approach [3].

The current pandemic of mucormycosis infections has sparked concern about the likelihood of this fungus infection owing to inappropriate oxygen humidification and substandard humidifier maintenance [4]. Indian Council of Medical Research suggested the use of clean, sterile water for humidifiers during oxygen treatment and released evidence-based recommendations for its administration [5]. In addition, the Government of Telangana in India's Director of Public Health Department of Health, Medical and Family Welfare also released a recommendation for the prevention of mucormycosis in COVID-19 patients that specifically mentions the use of clean, sterile water for humidifiers during oxygen therapy [6]. A minister in Karnataka attributed the rising prevalence of mucormycosis infections during the COVID-19 epidemic on the utilization of tap water in the humidifier for oxygen treatment [7]. However, the issue of whether there is enough scientific evidence to compel the use of sterile water for oxygen humidification in nations with limited resources, such as India, is significant. However, the patient who is in need must eventually pay this increased expense [8]. A heated bubble humidifier was advised for the prevention of nosocomial infection in the Centers for Disease Control and Prevention's (CDC) recommendations for the prevention of nosocomial pneumonia (1997). However, the most current CDC Advisory Committee Report (1997) advises against using distilled water in bubbling humidifiers and instead suggests using sterile water [9]. On the other hand, a research by Cahill and Heath comparing tap water with sterile water for bacterial contamination discovered that culture after 5 days demonstrated increased microorganism growth in the sterile water reservoirs [10]. In addition, humidifiers that don't employ bubble-through technology to create water vapour do not induce microbial transmission by aerosolizing the solutes or microbiota that are present in water [11]. In addition, Wenzel et al came to the conclusion that nonsterile tap water may be a secure substitute for sterile water in convection-type humidifiers used in continuous positive airway pressure treatment [11, 12]. The WHO UNICEF, Manual on Oxygen Therapy (2016) suggests that the humidifier be filled with safe, clean, boiled tap water or distilled water that has to be replaced often since the likelihood of contamination may rise with time [13]. Koss et al. said that prefilled nebulizer units need to be replaced every 24 hours but that sterile water, distilled water, and saline were possibly less polluted up to 72 hours when used for oxygen humidification [14]. Data showed that the majority of COVID-19 patients only needed low-flow oxygen therapy, with just 20% of patients needing hospitalization [15]. The issue of whether humidification is advantageous in low-flow oxygen treatment therefore becomes crucial. In their investigation, Wen et al. provided the response that oxygen humidification was not required at low flow rates [9]. Literature has also shown that oxygen humidification is only necessary when supplied at high flow rates through the nasopharynx [16]. The heat and moisture exchanger approach, however, is more advantageous for ventilator patients since it lowers the risk of infection and lowers costs by reducing the need for frequent breathing circuit changes [17]. The conclusion is that there isn't enough data to back up any one technique of oxygen humidification. In healthcare settings with limited resources and affordability, sterilized water may be the preferable option; however, boiling tap water combined with a convection-style humidifier may also be a reliable alternative [18]. To reduce the possibility of microbial colonization and illness, it is more crucial to periodically replace the humidifying solution and clean and disinfect the humidifier reservoir.

I would like to thank my husband Mr Aadil Mudasir for his constant support and help to search the literature database.

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