Clinical outcome associated with the use of different inhalation method with and without humidification in asthmatic mechanically ventilated patients.

BACKGROUND: Inhaled-medication delivered during mechanical-ventilation is affected by type of aerosol-generator and humidity-condition. Despite many in-vitro studies related to aerosol-delivery to mechanically-ventilated patients, little has been reported on clinical effects of these variables. The aim of this study was to determine effect of humidification and type of aerosol-generator on clinical status of mechanically ventilated asthmatics. METHOD: 72 (36 females) asthmatic subjects receiving invasive mechanical ventilation were enrolled and assigned randomly to 6 treatment groups of 12 (6 females) subjects each received, as possible, all inhaled medication using their assigned aerosol generator and humidity condition during delivery. Aerosol-generators were placed immediately after humidifier within inspiratory limb of mechanical ventilation circuit. First group used vibrating-mesh-nebulizer (Aerogen Solo; VMN) with humidification; Second used VMN without humidification; Third used metered-dose-inhaler with AeroChamber Vent (MDI-AV) with humidification; Forth used MDI-AV without humidification; Fifth used Oxycare jet-nebulizer (JN) with humidification; Sixth used JN without humidification. Measured parameters included clinical-parameters reflected patient response (CP) and endpoint parameters e.g. length-of-stay in the intensive-care-unit (ICU-days) and mechanical-ventilation days (MV-days). RESULTS: There was no significant difference between studied subjects in the 6 groups in baseline of CP. VMN resulted in trend to shorter ICU-days (∼1.42days) compared to MDI-AV (p = 0.39) and relatively but not significantly shorter ICU-days (∼0.75days) compared JN. Aerosol-delivery with or without humidification did not have any significant effect on any of parameters studied with very light insignificant tendency of delivery at humid condition to decrease MV-days and ICU-days. No significant effect was found of changing humidity during aerosol-delivery to ventilated-patient. CONCLUSIONS: VMN to deliver aerosol in ventilated patient resulted in trend to decreased ICU-days compared to JN and MDI-AV. Aerosol-delivery with or without humidification did not have any significant effect on any of parameters studied. However, we recommend increasing the number of patients studied to corroborate this finding.

Lung deposition and systemic bioavailability of different aerosol devices with and without humidification in mechanically ventilated patients.

BACKGROUND: During mechanical ventilation medical aerosol delivery has been reported to be upto two fold greater with dry inhaled gas than with heated humidity. Urine levels at 0.5 h post dose (URSAL0.5%) has been confirmed as an index of lung deposition and 24 h (URSAL24%) as index of systemic absorption. Our aim was to determine the effect of humidification and aerosol device type on drug delivery to ventilated patients using urine levels. METHODS: In a randomized crossover design, 36 (18female) mechanically ventilated patients were assigned to one of three groups. Groups 1 and 2 received 5000 µg salbutamol using vibrating mesh (VM) and jet nebulizers (JN), respectively, while group 3 received 1600 µg (16 puffs) of salbutamol via metered dose inhaler with AeroChamber Vent (MDI-AV). All devices were placed in the inspiratory limb of ventilator downstream from the humidifier. Each subject received aerosol with and without humidity at >24 h intervals with >12 h washout periods between salbutamol doses. Patients voided urine 15 min before each study dose and urine samples were collected at 0.5 h post dosing and pooled for the next 24 h. RESULTS: The MDI-AV and VM resulted in a higher percentage of urinary salbutamol levels compared to the JN (p < 0.05). Urine levels were similar between humidity and dry conditions. CONCLUSIONS: Our findings suggest that in-vitro reports overestimate the impact of dry vs. heated humidified conditions on the delivery of aerosol during invasive mechanical ventilation.