These commonly used devices are usually contaminated with environmental Gram negative bacteria that like moist environments – eg. Pseudomonas species, Alcaligenes, coliforms and other. These organisms may be multi-resistant. The physics of humidification show that these room temperature devices do NOT significantly increase the humidity of the gas. Furthermore, patients on short-term low-flow oxygen therapy via mask or nasal prongs do NOT require humidification of oxygen – this is definitely not a practice followed in developed world situations. There are high flow oxygen circuits used, but these have heated humidification chambers with sterile water added, managed under strict asepsis.
Darin J et al. Respir Care. 1982 Jan;27(1):41-50. An evaluation of water-vapor output from four brands of unheated, prefilled bubble humidifiers.
Weber MW et al. Pediatr Pulmonol. 1996 Aug;22(2):125-8. Humidification of oxygen with unheated humidifiers in tropical climates.
I’d be keen to hear of your views ! If you use the devices, then get your lab to culture the water to see what is there – you will be horrified!