Airway obstruction in heat & moisture exchanger filter: A case report

Heat and moisture exchanger filters (HMEF), used for humidification of patient respiratory gas and filtering microorganisms can cause airway obstruction. We experienced serious airway obstruction in a HMEF after making hydrothorax for high intensity focused ultrasound (HIFU) procedure. The airway obstruction was difficult to differentiate from severe bronchospasm irresponsive to bronchodilator therapy. It was relieved dramatically after we removed the filter from the breathing circuit as soon as we detected air-fluid meniscus in it.

Evaluating humidity recovery efficiency of currently available heat and moisture exchangers: a respiratory system model study

OBJECTIVES: To evaluate and compare the efficiency of humidification in available heat and moisture exchanger models under conditions of varying tidal volume, respiratory rate, and flow rate. INTRODUCTION: Inspired gases are routinely preconditioned by heat and moisture exchangers to provide a heat and water content similar to that provided normally by the nose and upper airways. The absolute humidity of air retrieved from and returned to the ventilated patient is an important measurable outcome of the heat and moisture exchangers' humidifying performance. METHODS: Eight different heat and moisture exchangers were studied using a respiratory system analog. The system included a heated chamber (acrylic glass, maintained at 37°C), a preserved swine lung, a hygrometer, circuitry and a ventilator. Humidity and temperature levels were measured using eight distinct interposed heat and moisture exchangers given different tidal volumes, respiratory frequencies and flow-rate conditions. Recovery of absolute humidity (%RAH) was calculated for each setting. RESULTS: Increasing tidal volumes led to a reduction in %RAH for all heat and moisture exchangers while no significant effect was demonstrated in the context of varying respiratory rate or inspiratory flow. CONCLUSIONS: Our data indicate that heat and moisture exchangers are more efficient when used with low tidal volume ventilation. The roles of flow and respiratory rate were of lesser importance, suggesting that their adjustment has a less significant effect on the performance of heat and moisture exchangers.

Effects of Six Heat and Miosture Exchange for Use during Endotracheal Anesthesia / 대한마취과학회지

Despite many theoretical advantages of humidification of anesthetic gas, the role and method of choice of humidification in anesthesia remains uncertain. With the recent introduction of disposable heat and moisture exchangers (HME), a paueity of information of the specific performance characteristics of various HMEs exists. Using an on-line humidity detector, based on the dry-wet bulb principle, with a fast response temperature sensor (0.l sec), I have reexamined the effectiveness in maintaining humidity and temperature of various commercially available HMEs in clinical settings, and the relationship of the effectiveness of the rate of fresh gas flow. Humid-Vent 2 demonstrated the best result that increased the inspired temperature from 22.78+/-0.2degrees C to 31.35+/-0.89degrees C (absolute humidity; 27.4+/-0.7mg H2O/L). Extreme low fresh gas flow(500ml/min) demonstrated low absolute humidity (18.87+/-1.28 mg H2O/L) that was lower than use of HME.

Effects of Six Heat and Miosture Exchange for Use during Endotracheal Anesthesia / 대한마취과학회지

Despite many theoretical advantages of humidification of anesthetic gas, the role and method of choice of humidification in anesthesia remains uncertain. With the recent introduction of disposable heat and moisture exchangers (HME), a paueity of information of the specific performance characteristics of various HMEs exists. Using an on-line humidity detector, based on the dry-wet bulb principle, with a fast response temperature sensor (0.l sec), I have reexamined the effectiveness in maintaining humidity and temperature of various commercially available HMEs in clinical settings, and the relationship of the effectiveness of the rate of fresh gas flow. Humid-Vent 2 demonstrated the best result that increased the inspired temperature from 22.78+/-0.2degrees C to 31.35+/-0.89degrees C (absolute humidity; 27.4+/-0.7mg H2O/L). Extreme low fresh gas flow(500ml/min) demonstrated low absolute humidity (18.87+/-1.28 mg H2O/L) that was lower than use of HME.