EVALUATION OF RESPIRATORY INDUCTIVE PLETHYSMOGRAPHY - ACCURACY FOR ANALYSIS OF RESPIRATORY WAVE-FORMS

Objective: To assess the accuracy of respiratory inductive plethysmogr aphy (RIP) waveforms to those obtained with whole body plethysmograph (BP) as this device gives a plethysmographic signal and a pneumotachog raph (PNT). Design: Randomized controlled trial. Setting: Physiologic laboratory in a university hospital. Participants: Eleven subjects fro m the laboratory staff. Interventions: This study was achieved during four consecutive periods in subjects breathing spontaneously and throu gh different added resistive loads. Using the least square method cali bration, two RIP waveforms, VRIP.BP(t) and VRIP.PNT(t), were simultane ously calculated with coefficients obtained from BP and from PNT volum e waveforms, respectively VBP(t) and VPNT(t). For each recording, to c ompare volume waveforms, we calculated their differences in term of di stances, DRIP-BP and DRIP-PNT, between the normalized RIP volume signa l (respectively, (V) under bar RIP.BP[t] and (V) under bar RIP.PNT[t]) and its normalized reference (respectively, (V) under bar BP[t] and ( V) under bar PNT[t]). We also calculated the distance DPNT-BP between the two normalized references (V) under bar BP(t) and (V) under bar PN T(t). Results: No significant effect of load or time on the distance o ccurred. Including all the recordings, the mean distance DRIP-BP (3.4 +/- 1.1%) appears significantly lower than both the mean distance DRIP -PNT (4.5 +/- 1.3%; p < 0.04) and the mean distance DPNT-BP (4.6 +/- 0 .9%; p < 0.008), For each period or load level, DRIP-BP appears to be lower than DRIP-PNT and DPNT-BP. Conclusion: The RIP seems reasonably accurate for analysis of respiratory waveform while subjects subsequen tly breathe against resistive loads.