Short-term effects of an active heat-and-moisture exchanger during invasive ventilation

BACKGROUND: Humidification is a standard of care during invasive mechanical ventilation. Two types of devices are used for this purpose: heated humidifiers and heat-and-moisture exchangers (HME). AIM: To compare the short-term physiologic effects of an active HME, with those of heated humidifiers and HMEs in terms of respiratory effort, ventilatory pattern, and arterial blood gases during invasive mechanical ventilation. METHODS: We conducted a randomized crossover study with 3 different devices in 15 stable subjects who had a tracheostomy and were ventilator-dependent. Transdiaphragmatic pressure, ventilatory pattern, arterial blood gases, and dyspnea scale were recorded at baseline and at the end of a 20-min period with each device. RESULTS: Compared with heated humidifiers, the active HME was associated with higher diaphragmatic pressure-time product per minute (117.10 [interquartile range IQR 34.58 –298.60]) versus 80.86 (IQR, 25.46 –110.55) cm H2Oμs/min, P = .01), higher PaCO2 (48.50 [IQR, 40.65–53.70] vs 39.60 [IQR, 37.50 – 49.95]) mm Hg, P = .02) and lower pH (7.41 [IQR, 7.36 –7.49] vs 7.45 [IQR, 7.40 –7.51], P = .030) without any significant difference in ventilatory pattern. A significantly worse dyspnea scale score (active HME, 3 (2– 4) vs heated humidifiers: 4 (3–5); P = .009) was also observed. No significant differences were seen between active HME and HME. CONCLUSIONS: This study indicated that, compared with the heated humidifiers, the use of the active HME or the HME increased inspiratory effort, PaCO2, pH, and dyspnea in stable subjects who were tracheostomized and ventilator-dependent. (ClinicalTrials.gov registration NCT02499796.)