The Accuracy of Respiratory Inductive Plethysmography in Measuring Breathing Patterns of Sedated Piglets Receiving Controlled Mechanical Ventilation

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.)