Pressure-volume Curve:Automated Measurement of Respiratory Mechanics –A.R.M.Software

Overview

We developed software able to control mechanical ventilator (Adult Star TM Infrasonics,USA)via serial port and to simultaneously read data fromthe ventilator output.This enables to deliver randomly selected test tidal volumes under constant flow conditions with computer controlled expiratoryand inspiratory valve holds and to record the volume and respective pressures for automated pressure-volume curve measurements.We tested thesoftware performance in 4 patients suffered by a several lung injury on three different PEEP levels.Data obtained automatically from the ventilatorwere compared with independent calibrated measuring system consisting of airway and oesophageal pressure transducers (Validyne ±100 cmH2O,USA),and heated pneumotachograph (Hans Rudolph,USA)connected to differential pressure transducer (Validyne ±2 cmH2O,USA).Data wereprocessed and collected into the same computer operating the ventilator and analyzed.A.R.M.software driven ventilator is able to perform static respiratory mechanics measurements without disconnecting the patient from the ventilatorin 1 hour intervals.No additional equipment other than ventilator and external computer controlled end expiratory valve is needed.

Key words:
ARDS –ALI –automatization –mechanical ventilator