Humidity during high-frequency oscillatory ventilation compared to intermittent positive pressure ventilation in extremely preterm neonates: An in vitro and in vivo observational study

Pediatr Pulmonol. 2023 Jan;58(1):66-72. doi: 10.1002/ppul.26157. Epub 2022 Sep 19.


Background: Inappropriate humidification of inspired gas during mechanical ventilation can impair lung development in extremely low birthweight (ELBW) infants. Humidification depends on multiple factors, such as the heater-humidifier device used, type of ventilation, and environmental factors. Few studies have examined inspired gas humidification in these infants, especially during high-frequency oscillatory ventilation (HFOV). Our objective was to compare humidity during HFOV and intermittent positive pressure ventilation (IPPV), in vitro and in vivo.

Methods: In vitro and in vivo studies used the same ventilator during both HFOV and IPPV. The bench study used a neonatal test lung and two heater-humidifiers with their specific circuits; the in vivo study prospectively included preterm infants born before 28 weeks of gestation.

Results: On bench testing, mean absolute (AH) and relative (RH) humidity values were significantly lower during HFOV than IPPV (RH = 79.4 ± 8.1% vs. 89.0 ± 6.2%, p < 0.001). Regardless of the ventilatory mode, mean RH significantly differed between the two heater-humidifiers (89.6 ± 6.7% vs 78.7 ± 6.8%, p = 0.003). The in vivo study included 10 neonates (mean ± SD gestational age: 25.7 ± 0.9 weeks and birthweight: 624.4 ± 96.1 g). Mean RH during HFOV was significantly lower than during IPPV (74.6 ± 5.7% vs. 83.0 ± 6.7%, p = 0.004).

Conclusion: RH was significantly lower during HFOV than IPPV, both in vitro and in vivo. The type of heater-humidifier also influenced humidification. More systematic measurements of humidity of inspired gas, especially during HFOV, should be considered to optimize humidification and consequently lung protection in ELBW infants.

Keywords: ELBW; HFOV; humidification.

Publication types

  • Observational Study

MeSH terms

  • High-Frequency Ventilation*
  • Humans
  • Humidity
  • Infant
  • Infant, Extremely Premature
  • Infant, Newborn
  • Intermittent Positive-Pressure Ventilation
  • Respiratory Distress Syndrome, Newborn* / therapy