Bacterial Contamination of Circuit Inner Surfaces After High-Flow Oxygen Therapy

Abstract

BACKGROUND: During high-flow oxygen therapy, heated humidified gas is delivered at high flow. Although the warmth and humidity of this gas facilitates mucociliary function in the lower airway, warm and humid conditions also promote bacterial growth. Bacterial contamination of high-flow oxygen therapy circuits has not been well investigated. We examined the incidence of bacterial contamination in high-flow oxygen therapy circuits. METHODS: This was a prospective observational study in a university hospital 10-bed general ICU. After final high-flow oxygen therapy discontinuation, samples were obtained from the interface and the chamber ends of the circuit. Initially, a half circumference of each inner surface was swabbed, after which the whole circuit was left in the ICU at room temperature for 6 h. The samples were then, in the same way, taken from the previously unswabbed arcs of the end inner surfaces. All the samples were sent to a biology laboratory and cultured. RESULTS: In all, 118 samples were collected from 31 circuits. The median duration of high-flow oxygen therapy was 48 h (interquartile range, 26-96 h). Of 31 circuits, contamination occurred in 5 circuits (16.1% [95% CI 5.5-33.7%]). CONCLUSIONS: Bacterial contamination of inner surfaces of the circuit after high-flow oxygen therapy was relatively high.

COVID-19 pandemic and non invasive respiratory management: Every Goliath needs a David. An evidence based evaluation of problems

“…This figure is as high as for anesthetic breathing circuits, but can be decreased by circuits fitted with heating wires, which greatly reduce condensation. 54 Although the evidence from the recent series is lacking (with no single mention of transmission to professionals through these techniques), there are authors that do not recommend NIV or HFNC until the patients is cleared of COVID-19. 55 However some other experiments from China suggest that early intervention with HFNC and NIV associated or not with prone positioning can lead to lower mortality, less than 1% of cases needing intubation (versus 2.3% of National average).…”

Guidelines for high‐flow nasal cannula oxygen therapy in neonates (2022)

“…Evidence summary: This recommendation includes two references: one guideline 115 and one prospective study. 116 The warmth and humidity of the flow improves mucociliary function, but warm and humid conditions also promote bacterial growth. The included prospective study explored the occurrence of contamination in the pipeline after discontinuation of HFNC by sampling from the interface and the chamber ends of the circuit, revealing five positive cultures among the 31 collected samples, indicating circuit contamination.…”

“…Evidence summary : This recommendation includes two references: one guideline 115 and one prospective study 116 . The warmth and humidity of the flow improves mucociliary function, but warm and humid conditions also promote bacterial growth.…”

“…The warmth and humidity of the flow improves mucociliary function, but warm and humid conditions also promote bacterial growth. The included prospective study explored the occurrence of contamination in the pipeline after discontinuation of HFNC by sampling from the interface and the chamber ends of the circuit, revealing five positive cultures among the 31 collected samples, indicating circuit contamination 116 . The Guidelines for the Prevention and Treatment of Ventilator‐Associated Pneumonia in China stated that ventilation circuits do not need to be replaced regularly, but should be promptly replaced if damaged or contaminated, and that disposable components should be discarded after its use in accordance with relevant regulations and in an environmentally safe manner 115…”