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Numerical Analysis of Flow Rate Effect on Heating and Humidifying Efficiencies of a Heat and Moisture Exchanger FREE TO VIEW

Pezhman Payami*, MS; Masud Behnia, PhD; Barry Dixon, MD; Mehrdad Behnia, MD
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Sydney University, Sydney, NSW, Australia

Chest. 2012;142(4_MeetingAbstracts):943A. doi:10.1378/chest.1388805
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SESSION TYPE: Respiratory Support Posters

PRESENTED ON: Wednesday, October 24, 2012 at 01:30 PM - 02:30 PM

PURPOSE: Warming and humidification of the inspired gas cause significant limitations for a patient on mechanical ventilation. Heat and Moisture Exchanger (HME) is designed to overcome these limitations. The device acts as a passive humidifier that traps the expiratory heat and moisture in a porous medium and returns a portion of them through the subsequent inspiratory cycle. The purpose of this study was to investigate the effect of flow rate on heat and moisture conserving capacities of a HME by developing the first computational model.

METHODS: To investigate heat and humidifying efficiencies of the device, a computational fluid dynamics (CFD) model was developed. CFD is the numerical analysis of systems based on fluid flow, heat transfer and associated phenomena by computer-based simulation. Three dimensional distributions of temperature and absolute humidity inside the HME were obtained during expiratory phase of the respiratory cycle to evaluate heat and moisture conserving efficiencies.

RESULTS: The moisture and temperature gradient across the HME at a flow rate of 5 L/min was 18.7 mg H2O/L and 5.2 OC, respectively. At a flow rate of 30 L/min the moisture and temperature gradient fell to 1.6 mg H2O/L and 1.3 OC, respectively.

CONCLUSIONS: Studying temperature and humidity demonstrated that greater flow rates through the HME were associated with reduced heat and moisture conserving efficiencies. At a flow rate of 30 L/min humidification was inadequate. The calculated variables were correlated with flow rate and showed a reasonable degree of agreement with previous clinical studies.

CLINICAL IMPLICATIONS: The CFD model provides a simple method to predict the performance of a HME over a range of clinical settings. Adequate humidification is important to avoid prolonged mechanical ventilation and ventilator-associated pneumonia.

DISCLOSURE: The following authors have nothing to disclose: Pezhman Payami, Masud Behnia, Barry Dixon, Mehrdad Behnia, Mehrdad Behnia

No Product/Research Disclosure Information

Sydney University, Sydney, NSW, Australia




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