Comparing TwoHeatandMoisture Exchangers WithOneVaporizing Humidifier inPatients WithMinute Ventilation Greater Than10L/min*

Studyobjective: Toevaluate inpatients submitted to minuteventilation >10L/mintheability topreserve patients' heatandhumidity oftwoheatandmoisture exchangers (HMEs)andone vaporizing humidifier (VH). Design: Prospective, randomized, comparative, nonblinded study. Setting: Intensive care unitofa university hospital. Patients: Ninetracheally intubated, mechanically ventilated patients, sedated andsubmitted tomechanical ventilation withminuteventilation >10L/min. Interventions: Usingthepsychrometric method, relativehumidity (RH)andabsolute humidity (AH)of inspired gas were obtained as well as temperature of inspired gas andtracheal temperatures (maximal and minimal). Following a randomized order, eachpatient was ventilated fortwo24-hperiods with a vaporizing humidifier (Bennett Cascade 2,Bennett; France) and one oftwoHMEs:PallUltipor filter BB50(Pall Biomedical; France) or DAR Hygroster filter (Peters; France). Bothwere first tested for a 45-min period and thentheHME thatachieved thebestperformance in termsoftemperature andwaterpreservation was tested for24h. Measurements andresults: Duringthe45-min testperiod, thePallUltipor HME achieved a lowerperformance thantheother twosystemsfor any ofthestudied 3he importance ofdelivering warm, humidified gas topatients ventilated through an endotracheal or tracheostomy tubeiswidely accepted.'-3 Mechanical ventilation withendotracheal intubation ortracheostomy bypasses theupper airway andthe normal heat andmoisture exchanging processofinspired gases.A continuous loss ofmoisture andheat occurs andpredisposes patients toserious airway damage.'-7 Inaddition, medical gasesare dried to avoid condensation damage tovalves andregulators inthedistribution network. Complications following ventilation withdryandcold gasesmay beprevented bytheaddition ofexogenousheatandhumidity by parameters (p 10 L/min, theDARHygroster HME showed athermic and humidification capability similar tothereference system,theBennett Cascade 2VH.Inthese patients, the Pall Ultipor HME hada significantly lowercapability. (Chest 1995; 107:1411-15)