The purpose of this study was to document accurate calibration of respiratory inductive plethysmography (RIP) in piglets receiving various combinations of controlled mechanical ventilation. METHODS: We studied 10 healthy, sedated piglets weighing 2.7 ± 0.3 kg (mean ± standard deviation) at inspiratory flowrates of 83, 167, and 250 ml/s with peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) constant (Phase 1); at PIP settings of 10, 20, and 30 cm H2O with inspiratory flow and PEEP constant (Phase 2); and at PEEP settings of 3, 6, and 9 cm H2O with inspiratory flow and PIP constant (Phase 3). Throughout ventilator-setting evaluations, the respiratory frequency, inspiration-expiration ratio, and inspired oxygen fraction were constant. Calibration of RIP employed our single-position graphic technique. Validation of accuracy was determined by simultaneous volume measurement by integrated pneumotachography (PNT). RESULTS: We found that 58% of validation breaths were within 5% of PNT values, and 93% of validation breaths were within 10% of PNT values. Tidal volume and inspiratory flow measured by RIP demonstrated little change during the flow setting. These two variables increased during the PIP-setting evaluations, and they decreased during the PEEP evaluations. We conclude that RIP can accurately measure breathing patterns in piglets receiving controlled mechanical ventilation. (Respir Care 1988;33:846-851.)
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