Exposure assessment by physiologic sampling pump - Prediction of minute ventilation using a portable respiratory inductive plethysmograph system

A study was conducted to evaluate a portable respiratory inductive plethysmograph (RIP) as a means to estimate minute ventilation (V̇_E) for use in controlling the flow rate of a physiologic sampling pump (PSP). Specific aims were to: (1) evaluate the ability of the portable RIP system to measure V̇_E using a direct (individual) fixed-volume calibration method (Direct RIP model), (2) develop and evaluate the performance of indirect (group) regression models for V̇_E prediction using output data from the portable RIP and subject demographic characteristics (Indirect RIP model), and (3) compare V̇_E estimates from indirect and direct portable RIP calibration with indirect estimation models published previously. Nine subjects (19-44 years) were divided into calibration (n = 6) and test (n = 3) datasets and performed step-tests on three different days while wearing the portable RIP and breathing through a pneumotachometer (reference). Minute ventilation and portable RIP output including heart rate, breathing rate, and a motion index were recorded simultaneously during the 80 minute sessions. Calibration data were used to develop a regression model for V̇_E prediction that was subsequently applied to the test dataset. Direct calibration of the portable RIP system produced highly variable estimates of V̇_E (R² = 0.62, average % error = 15 ± 50) while Indirect RIP model results were highly correlated with the reference (R² = 0.80-0.88) and estimates of total volume were within 10% of reference values on average. Although developed from a limited dataset, the Indirect RIP model provided an alternative approach to estimation of V̇_E and total volume with accuracy comparable to previously published models.