Do we need to humidify oxygen in ER ???

What is bubble humidifier ?

• These are simple, low cost device with  water containers in which gas is forced to escape through a tube placed at the bottom. The gas bubbles collect moisture as they move towards the water surface and pass through an outlet connected to an oxygen delivery device.
•  The resultant use of cold bubble humidification generates an absolute humidity of only 10–20 g/m³ at standard room temperature against the physiological requirements of at least 34 g/m³ in trachea and 44 g/m³ below carina.

Evidence

• Zhang et (Medicine.2022) had done a open lable, single centre , RCT (n=213) done to evaluate the effects and safety of humidified versus non humidified low-flow oxygen therapy in children with Pierre-Robin syndrome. Study found  no significant differences in the average arterial PaO₂ and PaCO₂ level on the postoperative day 1, 2, and ICU discharge between humidified group and non humidified group were found (all P > .05). There were no significant differences in the incidence of nasal cavity dryness, nasal mucosal bleeding, bacterial contamination and VAP, the duration of ICU stay between humidified group and non humidified group (all P > .05).

• Santana et al (Scientific Reports. 2021) in a small RCT(n=31)  showed that Cold bubble humidification is not able to reduced nasal inflammation, eNO, oxidative stress, mucociliary clearance, and nasal mucosa moisture. However, subjects report improvement of nasal dryness symptoms (P < 0.05). In the conclusion, cold bubble humidification of low flow oxygen therapy via a nasal cannula did not produce any effect on the nasal mucosa and did not attenuate the oxidative stress caused by oxygen. However, it was able to improve nasal symptoms arising from the use of oxygen therapy.

• Poiroux et al (Annals of Intensive Care. 2018) done a randomised, multicentric, non inferiority trial (n=354) to explore whether delivering dry oxygen instead of bubble-moistened oxygen had an impact on discomfort of ICU patients. study concluded that dry oxygen could not be demonstrated as non-inferior compared to bubble-moistened oxygen after 6–8 h of oxygen administration. At 24 h, dry oxygen was non-inferior compared to bubble-humidified oxygen for flows below 4 L/min.

• Franchini et al (Respiratory Care. 2016) had done a study to investigate the effects of dry- (Nasal Low Flow Oxygen) NLFO and cold bubble humidified-NLFO on nasal mucociliary clearance (MCC), mucus properties, inflammation, and symptoms in subjects with chronic hypoxemia requiring long-term domiciliary oxygen therapy. He concluded that subjects receiving chronic NLFO, cold bubble humidification does not adequately humidify inspired oxygen to prevent deterioration of MCC, mucus hydration, and pulmonary function. The unheated bubble humidification performed no better than no humidification.

BTS 2008 Emergency Oxygen Guidelines - Humidification 

• Humidification is not required for the delivery of low-flow oxygen (mask or nasal cannulae) or for the short-term use of high-flow oxygen. It is not therefore required in prehospital care.
•  It is reasonable to use humidified oxygen for patients who require high-flow oxygen systems for more than 24 hours or who report upper airway discomfort due to dryness.
• Bubble bottles which allow a stream of oxygen to bubble through a container of water should not be used because there is no evidence of a clinically significant benefit but there is a risk of infection.
• Consider use of a large volume oxygen humidifier device for patients requiring high-flow rates or longer term oxygen, especially if sputum retention is a clinical problem.

WHO Guidelines on using humidifiers

The water level in the humidifier should be checked twice daily and topped up as necessary.

• Humidifier equipment must be washed and disinfected regularly to prevent bacterial
• The water in the humidifier should be changed daily, and the humidifier, water jar and catheter should be washed in mild soapy water, rinsed with clean water and dried in air before reuse.
• Once a week (for the same patient) and in between patients, all the components of the humidifier should be soaked in a mild antiseptic solution for 30 minutes, rinsed with clean water and dried in air. Allowing the humidifier to dry completely will discourage bacterial colonization.
• At every change, check for leakages between the flowmeter and humidifier and between he humidifier and oxygen delivery device.
• A spare, clean humidifier filled with clean water should always be available, so that oxygen therapy is not interrupted while the humidifier is being cleaned.

Humidifier and Nosocomial infection

• Fauci et al (J Prev Med Hyg. 2017) done a study to evaluate the safety of the reuse of humidifiers by analysing the rate of microbial contamination in reusable and disposable oxygen humidifiers used during therapy.The study was done at University Hospital of Messina, Italy. They found high rates of microbial contamination were observed in samples from reusable oxygen humidifiers employed in medical (83%), surgical (77%) and emergency (50%) areas. The most relevant pathogens were Pseudomonas aeruginosa, amongst the Gram-negative bacteria, and Staphylococcus aureus, amongst the Gram-positive bacteria. Other pathogens were detected in lower percentage. The disposable oxygen humidifier samples showed no contamination.

• Jadhav et al (J Clin Diagn Res. 2013) done a study  to determine the rate of colonization by bacteria and fungi of the oxygen humidifier chambers of the portable cylinders and central lines at our hospital. The study found 53/70 (75.71%) samples showed fungal growth; out of which, 23/33 (69.70%) were from the ICU, 24/30(80%) were from the wards and 6/7 (85.71%) were from the OPDs. Study also found even after the 70% ethanol disinfection and strict compliance with the hand hygiene, the colonization rates reduced significantly. The fungal colonization rate was reduced and only 15% fungi grew after the disinfection, while only 12% bacterial colonization rate was found.

Conclusion

 Humidification of oxygen for low flow devices or high flow devices for short duration <24 hour is  not recommended. Humidification of oxygen can improve patient comfort, but when used appropriate precautions and guidelines should be followed to prevent infection.

Reference

• O'Driscoll BR, Howard LS, Earis J, Mak V. British Thoracic Society Guideline for oxygen use in adults in healthcare and emergency settings. BMJ Open Respir Res. 2017 May 15;4(1):e000170. doi: 10.1136/bmjresp-2016-000170. PMID: 28883921; PMCID: PMC5531304.
• Dasgupta S, Ghosh S, Chandra A. Cold Bubble Humidification of Oxygen: Old habits die hard. Sultan Qaboos Univ Med J. 2022 Aug;22(3):309-313. doi: 10.18295/squmj.1.2022.002. Epub 2022 Aug 25. PMID: 36072067; PMCID: PMC9423755.
• WHO-UNICEF Technical specifications and guidance for oxygen therapy devices.