Calibration of computer-assisted (Respicomp) respiratory inductive plethysmography in newborns

We investigated the accuracy of a computer-assisted, respiratory inductive plethysmograph (Respicomp) on 50 awake human newborns who were lying supine. Breaths were selected with different rib cage (RC) to pneumotach (PNT) and abdomen (AB) to pneumotach (PNT) values. The equation RC/PNT + AB/PNT = 1 was solved using the least squares method (LSQ) of calculation of calibration factors. Validation of the calibration factors was performed with a range of consecutive breaths between 6 and 22. Of the 1,128 validation or revalidation breaths, 628 (56%) were within 10% of the simultaneously measured PNT volume, 1,024 (91%) were within 20%, and 1,128 (100%) were within 30%. The RC or AB compartment contributions to ventilation changed spontaneously in the awake newborns. This change eliminated the need to wait for varying sleep states to obtain calibration factors and reduced total time required for calibration. (Some loss of accuracy is a compromise with this method; the calibration factors obtained do not remain accurate while the infant is asleep.) This method provided a reliable and rapid calibration and validation technique of the respiratory inductive plethysmograph (Respicomp) on awake newborns.