• J A Katz, R H Kallet, J A Alonso, and J D Marks.
• Department of Anesthesia, UCSF/Mount Zion Medical Center, San Francisco, CA 94143-1605, USA. katzj@anesthesia.ucsf.edu
• J Clin Anesth. 2000 Feb 1;12(1):40-7.

Study ObjectiveTo compare the flow and pressure capabilities of the Datex-Ohmeda SmartVent (Ohmeda 7900, Datex-Ohmeda, Madison, WI) to previous Ohmeda (7810 and 7000, Datex-Ohmeda, Madison, WI) anesthesia ventilators. To determine airway pressure and minute ventilation thresholds for intraoperative use of a critical care ventilator.DesignThree anesthesia ventilators and one critical care ventilator (Siemens Servo 900C, Siemens, Solna, Sweden) were studied in a lung model. Retrospective medical record review.SettingResearch Laboratory and Critical Care Unit of a Level I Trauma Center.Patients145 mechanically ventilated patients treated for acute respiratory failure who underwent 200 surgical procedures.InterventionsThe effect of increasing pressure on mean inspiratory flow was determined by cycling each ventilator through increasing restrictors. Maximum minute ventilation was measured at low compliance (10-30 mL/cm H2O), positive end-expiratory pressure (PEEP) (0-20 cm H2O), and increased airway resistance (approximately 19 and approximately 36 cm H2O/L/sec) in a mechanical lung model.Measurements And Main ResultsFlow, volume, and pressure were measured with a pulmonary mechanics monitor (BICORE CP-100, Thermo Respiratory Group, Yorba Linda, CA). Preoperative peak airway pressure and minute ventilation (VE) were extracted from the medical record. Mean inspiratory flow declined with increasing pressure in all anesthesia ventilators. The SmartVent and the 7810 produced greater mean inspiratory flow than did the 7000 ventilator. As compliance progressively decreased, the Siemens, the SmartVent, and the 7810 ventilators maintained VE compared to the 7000 ventilator. The Siemens and the SmartVent maintained VE with PEEP, compared to the 7810 and 7000 ventilators. During increased airway resistance, maximal VE was lower for all ventilators. The SmartVent met the ventilation requirements in 90% of the patients compared to 67% of patients with the 7000 ventilator.ConclusionThe improved pressure and flow capabilities of the SmartVent increase the threshold for using a critical care ventilator intraoperatively to a peak airway pressure > 65 cm H2O and/or VE > 18 L/min.

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