Short-Term Effects of an Active Heat-and-Moisture Exchanger During Invasive Ventilation

Respir Care. 2019 Oct;64(10):1215-1221. doi: 10.4187/respcare.06799. Epub 2019 Jul 3.


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 H2O×s/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. ( registration NCT02499796.).

Keywords: critical care; critically ill subjects; humidifiers; prolonged mechanical ventilation; tracheostomy; work of breathing.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Aged
  • Aged, 80 and over
  • Arteries
  • Blood Gas Analysis
  • Carbon Dioxide / blood
  • Cross-Over Studies
  • Diaphragm / physiopathology
  • Dyspnea / physiopathology
  • Female
  • Hot Temperature
  • Humans
  • Humidifiers*
  • Humidity
  • Hydrogen-Ion Concentration
  • Male
  • Middle Aged
  • Partial Pressure
  • Pulmonary Ventilation
  • Respiration, Artificial / instrumentation*
  • Severity of Illness Index
  • Time Factors
  • Tracheostomy
  • Work of Breathing*


  • Carbon Dioxide

Associated data