Abstract
BACKGROUND: Breathing through a tracheostomy results in insufficient warming and humidification of inspired air. This loss of air-conditioning can be partially compensated for with the application of a heat and moisture exchanger (HME) over the tracheostomy. In vitro (International Organization for Standardization [ISO] standard 9360–2:2001) and in vivo measurements of the effects of an HME are complex and technically challenging. The aim of this study was to develop a simple method to measure the ex vivo HME performance comparable with previous in vitro and in vivo results.
METHODS: HMEs were weighed at the end of inspiration and at the end of expiration at different breathing volumes. Four HMEs (Atos Medical, Hörby, Sweden) with known in vivo humidity and in vitro water loss values were tested. The associations between weight change, volume, and absolute humidity were determined using both linear and non-linear mixed effects models.
RESULTS: The rating between the 4 HMEs by weighing correlated with previous intra-tracheal measurements (R2 = 0.98), and the ISO standard (R2 = 0.77).
CONCLUSIONS: Assessment of the weight change between end of inhalation and end of exhalation is a valid and simple method of measuring the water exchange performance of an HME.
Footnotes
- Correspondence: Frans JM Hilgers MD PhD, Head and Neck Oncology and Surgery, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Plesmanlaa 121, Amsterdam 1066CX Netherlands. E-mail: f.hilgers{at}nki.nl.
Dr van den Boer presented a version of this paper at the 8th International Conference on Head and Neck Cancer, held by the American Head and Neck Society, in Toronto, Ontario, Canada, July 21–25, 2012.
Supplementary material related to this paper is available at http://www.rcjournal.com.
This study was partly funded by an unrestricted research grant from Atos Medical, the manufacturer of the tested heat and moisture exchangers. Atos Medical had no involvement in the study design, data collection, analysis, or interpretation; the writing or editing; or the decision to submit the manuscript for publication. The authors have disclosed no other conflicts of interest.
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