Evaluation of the Humidification Performances of New Generation of Heated Wire Humidifiers

BACKGROUND: At high ambient temperatures in ICU rooms, the humidification performances of heated-wire humidifiers are significantly reduced, with delivered gas humidity well below 30 mg H₂O/L, which leads to an increased risk of endotracheal occlusions, subocclusions, or mucociliary dysfunction. The objective of the study was to evaluate the humidity delivered at the Y-piece with new-generation heated-wire humidifiers with advanced algorithm (FP950 [Fisher & Paykel Healthcare, Auckland, New Zealand] and VHB20 [Vincent Medical, Inspired, Hong Kong]) while varying ambient temperatures.

METHODS: We measured, on the bench, the hygrometry of inspiratory gases delivered by a new generation of heated-wire humidifiers (i) FP950, (ii) VHB20 and a previous generation of heated-wire humidifiers, (iii) MR850 (Fisher & Paykel) with the usual settings (37°C at the chamber/40°C at the Y-piece), (iv) MR850 with no temperature gradient (40°C/40°C), and (v) MR850 with the automatic compensation algorithm activated. Hygrometry was measured with the psychrometric method after 1 h of stability while varying the room temperature from 20 to 30°C.

RESULTS: Two hundred ninety-four hygrometric bench measurements were performed at steady state for the different tested conditions. With the new heated-wire humidifiers (FP950 and VHB20), gas humidity delivered remained > 30 mg H₂O/L in all tested conditions, even at high ambient temperatures (>25°C). With previous generations of heated-wire humidifiers (MR850), at high ambient temperature, humidity delivered was adequate in only 26% (11/42) of the measurements when the usual settings were used (37°C/40°C) and 30% (11/37) with automatic compensation. When no temperature gradient was set (40°C/40°C), humidity delivered was > 30 mg H₂O/L in 91% (30/33) of the measurements at a high ambient temperature. With an ambient temperature < 25°C, almost all devices and settings provided adequate humidity.

CONCLUSIONS: The new FP950 and VHB20 heated-wire humidifiers by using advanced algorithms demonstrated stable performance while varying the ambient temperature by 20–30°C, better than the previous generation of heated humidifiers when ambient temperatures were high.