Water accumulation in metered dose inhaler spacers under normal mechanical ventilation conditions.

OBJECTIVE: The purpose of this study was to compare the water accumulation in 3 types of metered dose inhaler (MDI) spacer shapes in-line in a ventilator circuit, in 2 positions over 2-, 4-, and 6-hour time periods through the use of heated- and nonheated-wire ventilator circuits. DESIGN: The study design was prospective, quasiexperimental, and random assignment. SETTING: The study was conducted in a university laboratory. MATERIALS: Three brands of MDI spacers (OptiVent, ACE, AeroVent) were tested. OUTCOME MEASURES: Grams of water accumulation were measured. INTERVENTION: Distilled water accumulation was measured in 3 brands of MDI spacers in 0 degrees and 45 degrees positions at 2-, 4-, and 6-hour time intervals. Water accumulation was measured in each spacer by calculating the differences between pretest (dry) weights and posttest (wet) weights through the use of an analytical balance. A Marquest SCT-3000 servo-controlled humidifier with heated-wire ventilator circuit was used with a room temperature range of 21.7 degrees C-22.8 degrees C (71 degrees -73 degrees F) and a relative humidity range of 57%-65%. RESULTS: Multivariate repeated measures analysis demonstrated a difference between brands (P <.001). The amount of water accumulated during 6 hours (time variable) was significantly different (P <.001), as was the interaction between time and "spacer brand" (with Greenhouse-Geisser adjustment). The interaction of time and position was also significantly different (P =.001). Water accumulations at a 45 degrees angle were: AeroVent 0.765 +/- 0.152 g; OptiVent 1.894 +/- 0.228 g; and ACE 4.043 +/- 0.665 g through 6 hours of use. CONCLUSIONS: We found that water accumulation was a result of the type of spacer, position of the spacer, and time that the spacer was left in-line. All 3 brands of spacer collected less than 5 mL of water over 6 hours in either position. Heated-wire circuits accumulated less water than nonheated-wire circuits and may be safer when using MDI spacers.

Surfactant treatment impairs gas exchange in a canine model of acute lung injury.

UNLABELLED: The effectiveness of surfactant (SURF) treatment in acute lung injury in the adult is controversial. In this study, we tested the effectiveness of early surfactant treatment in a commonly used animal model of acute lung injury, phorbol-myristate acetate (PMA), to see if it would attenuate the progression of lung injury. We measured the effect on lung compliance and whether positive end-expiratory pressure (PEEP) (10 cm H2O) during SURF administration had a synergistic effect. METHODS: Four groups of anesthetized dogs were studied: a) normals; b) PMA injury only; c) PMA injury + SURF; and d) PMA + SURF + PEEP. Lung injury was induced with 25-30 microg/kg of PMA. Responses were measured over 7 hrs. Surfactant was administered in the form of Survanta, 4 x 25 mg/kg doses via tracheal instillation 2.5 hrs after PMA. For the group receiving PEEP, 10 cm H2O PEEP was begun 1.5 hrs after PMA, 1 hr before SURF. Postmortem, the left lung was excised and inflated three times to total lung capacity (volume at 30 cm H2O) and expiratory compliance was measured with 25-100 mL volume increments. The trachea was then clamped and trapped volume was determined by water displacement. RESULTS: PMA-induced lung injury significantly reduced expiratory compliance and total lung capacity (p < .05 from normal). Wet/dry lung weights did not differ between groups. SURF without PEEP further decreased lung compliance as compared with PMA only. CONCLUSIONS: SURF administration after PMA injury causes marked reductions in lung compliance when no PEEP is coadministered. However, the loss of static expiratory lung compliance appears partly ameliorated by application of PEEP + SURF. Given that tracheal instillation of SURF is known to acutely elevate lung impedance in the first few hours after administration, coadministration of PEEP appears to be critically important in counteracting these early effects of surfactant instillation on the lung.

Bronchodilator response with use of OptiVent versus Aerosol Cloud Enhancer metered-dose inhaler spacers in patients receiving ventilatory assistance.

OBJECTIVE: This study compared the clinical effectiveness of the OptiVent (HealthScan Products, Inc, Cedar Grove, NJ) and the ACE (DHD, Inc, Canastota, NY) metered dose inhaler (MDI) in-line spacers. DESIGN: Two-group, split-plot design with subjects serving as their own controls. SETTING: Data were collected in a 1000-bed urban hospital. PATIENTS: A convenience sample of 7 intubated patients receiving mechanical ventilation. INTERVENTION: Patients received 4 and 8 puffs of albuterol with use of both the OptiVent and ACE devices. RESULTS: Changes in expiratory airway resistance (Raw), passive peak expiratory flow rate (PEFR), and total work-of-breathing (WOBTOT) were determined using a Bicore monitor (Bicore Monitoring System; Irvine, Calif). With the ACE, Raw decreased an average of 20.2% and 8.8% in patients receiving 4 and 8 puffs, respectively. With the OptiVent, Raw decreased an average of 34.6% and 10.8% in patients receiving 4 and 8 puffs, respectively. Improvements in WOBTOT were less than those seen in Raw, and PEFR did not trend with the other 2 variables. The performances of the 2 spacer brands were comparable, with no statistical difference (P values > 0.05) for all 3 variables with use of the nonparametric Kolmogorov-Smirnov test. CONCLUSIONS: These data suggest that use of the OptiVent spacer yields comparable clinical results with the ACE spacer in patients receiving mechanical ventilation and merits further evaluation.

High-dose furosemide alters gas exchange in a model of acute lung injury.

PURPOSE: Furosemide is often used to reduce edema in patients with acute respiratory distress syndrome (ARDS). It was hypothesized that furosemide would reduce lung water and improve gas exchange in a phorbol-myristate acetate (PMA) model of acute lung injury. METHODS: Two groups of mongrel dogs received PMA (25 to 30 micrograms/kg) and continuous saline at 10 mL/kg/h; one group received PMA plus two 1-mg/kg doses of furosemide at 1 and 2 hours after PMA. Arterial blood gases on F1O2 = 1.0 and double-dilution lung water were measured at intervals over 7 hours. RESULTS: In dogs receiving PMA+furosemide, AaDO2 and shunt fraction increased compared with dogs receiving PMA only (AaDO2, P = .014; shunt, P = .017). There were no significant differences between the groups in lung water (P = .34) during the experiment or in wet/dry weight postmortem. Urine flow was markedly reduced in both groups; the kidneys appeared unresponsive to the diuretic effects of furosemide. Significant elevations in hematocrit and pulmonary vascular resistance were seen in furosemide-treated compared with PMA-only dogs. CONCLUSIONS: In this model of ARDS, which results in the absence of effective kidney function and multiple organ failure, furosemide compromises alveolar-capillary gas exchange and fails to influence the time course of lung water accumulation. The results suggest that the nondiuretic affects of furosemide cannot explain its purported clinical utility in ARDS.