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Main Techniques for Evaluating the Performances of Humidification Devices Used for Mechanical Ventilation

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Humidification in the Intensive Care Unit

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Abstract

Hygrometric measurement of gases conditioned by heat and moisture exchangers (HMEs) or heated humidifiers (HH) during mechanical ventilation is mainly used for research. The technique of the visual evaluation of the condensation on the flex tube or on the humidification chamber’s wall is feasible at the patient bedside but has many limitations. Several techniques to measure the moisture of gases exist. The most frequently used are the psychrometric method and the capacitance hygrometers that may be used in patients (during invasive or non-invasive ventilation) or on bench. The gravimetry (used by the standard ISO 9360) has technical limitations with high risk of errors and can only be used on bench. Psychrometry and capacitance hygrometers are generally used for clinical research, whereas the manufacturers of humidification systems often use gravimetry. This may explain the large differences in performance evaluation found for HMEs assessment. It was again observed during the pandemic that the humidity measurements conducted by the manufacturers with the ISO standards overestimated the humidity delivered to patients by their devices. Only independent measurements could discriminate between safe devices that should be used in patients from other devices. The large differences found between the manufacturer’s claim and the measured humidity by the psychrometric method call into question the validity of the ISO standard for detecting underperforming HMEs.

A new method to evaluate humidity delivered by heated wire humidifiers has been described recently. The heater plate temperature is closely correlated to the absolute humidity delivered to patients, and this temperature should be monitored in the case of high ambient temperature (that causes dysfunction of heated wire humidifiers). Heater plate temperature of above 62 °C predicts adequate humidity (above 30 mgH2O/L) in most situations with MR850.

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Authors and Affiliations

  1. Centre de recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec- Université Laval, Québec, QC, Canada

    François Lellouche

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  1. François Lellouche
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Correspondence to François Lellouche .

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  1. Intensive Care Unit, Hospital General Universitario Morales Meseguer, Murcia, Spain

    Antonio M. Esquinas

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Lellouche, F. (2023). Main Techniques for Evaluating the Performances of Humidification Devices Used for Mechanical Ventilation. In: Esquinas, A.M. (eds) Humidification in the Intensive Care Unit. Springer, Cham. https://doi.org/10.1007/978-3-031-23953-3_3

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  • DOI: https://doi.org/10.1007/978-3-031-23953-3_3

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