PT  - JOURNAL ARTICLE
AU  - Yusuke Chikata
AU  - Jun Oto
AU  - Mutsuo Onodera
AU  - Masaji Nishimura
TI  - Humidification performance of humidifying devices for tracheostomized patients with spontaneous breathing: a bench study
AID  - 10.4187/respcare.02093
DP  - 2013 Feb 05
TA  - Respiratory Care
PG  - respcare.02093
4099  - http://rc.rcjournal.com/content/early/2013/02/05/respcare.02093.short
4100  - http://rc.rcjournal.com/content/early/2013/02/05/respcare.02093.full
AB  - Background Heat and moisture exchangers (HMEs) are commonly used for humidifying respiratory gases administered to mechanically ventilated patients. While they are also applied to tracheostomized patients with spontaneous breathing (SB), their performance in this role has not yet been clarified. We carried out a bench study to investigate the effects of spontaneous breathing parameters and oxygen flow on the humidification performance of the HMEs. Methods We evaluated the humidification provided by 11 HMEs for tracheostomized patients, and also by a system delivering high-flow continuous positive air pressure (CPAP), and an oxygen mask with nebulizer heater. SB was simulated with a mechanical ventilator, model lung, and servo-controlled heated humidifier at tidal volumes (VT) of 300, 500 and 700 mL and respiratory rates of 10 and 20 breaths per minute. Expired gas was warmed to 37°C. The high-flow CPAP system was set to deliver 15, 30 and 45 L/min. With the 8 HMEs that were equipped with ports to deliver oxygen and with the high-flow CPAP system, measurements were taken when delivering 0 and 3 L/min of dry oxygen. After stabilization, we measured the absolute humidity (AH) of inspired gas with a hygrometer. Results AH differed among HMEs applied to tracheostomized patients with SB. For all HMEs, as VT increased, AH decreased. At 20 breaths a minute, AH was higher than it at 10. For all HMEs, when oxygen was delivered, AH decreased below 30 mg/L. With an oxygen mask and high-flow CPAP, at all settings, AH exceeded 30 mg/L. Conclusion No HME provided adequate humidification when supplemental oxygen was added. In the ICU, caution is required when applying HMEs to tracheostomized patients with SB, especially when supplemental oxygen is required.