Occlusion maneuver to detect the relative contribution of the rib cage and abdomen to tidal volume using respiratory inductive plethysmography in infants.
Respiratory inductive plethysmography (RIP) records movements of the rib cage (RC) and abdomen (AB). A calibration procedure is needed to determine their relative contribution to tidal volume. We evaluated the hypothesis that the relative contribution of the RC and AB could be defined from respiratory efforts made during a brief occlusion of the airways in 10 infants aged 6.5-19 months, who were studied in quiet sleep. Six occlusions were performed during tidal breathing, with and without a pneumotachograph (PNT) and face mask in place. We analyzed the periods of occluded respiratory effort when RC and AB were in opposite directions (paradoxical movements), plotting RC vs. AB and performing a least-squares linear regression to estimate the ratio of the coefficients of AB/RC. Multiple linear regression of AB and RC over tidal volume during about 100 seconds of tidal breathing provided a reference standard. A ratio of 1 means that AB and RC make equal contributions to tidal volume. The feasibility of the occlusion maneuver was poor; only 51% of occlusions with PNT and 54% without led to a paradoxical movement with a good fit (r > 0.9). The mean coefficient of variation (range) was 9.35% (3.9-15.3%) with PNT and 12.1% (2.5%-26.3%) without it. The accuracy was very poor, with the mean AB/RC value being 0.94 with occlusions and 2.39 with multiple linear regression. The mean difference was 1.45 (SD 0.80), yielding 95% confidence limits for the difference of 0.12-3.01. We concluded that, due to its very poor accuracy and feasibility, the occlusion technique is not a useful method to calibrate RIP in infancy.
Gagliardi
L
L
Department of Paediatrics and Neonatal Medicine, Royal Postgraduate Medical School, London, United Kingdom.
Rusconi
F
F
Aston
H
H
Silverman
M
M
D000005:Abdomen; D006801:Humans; D007223:Infant; D016014:Linear Models; D010991:Plethysmography / Q000379:methods*; D012119:Respiration / Q000502:physiology*; D012129:Respiratory Function Tests; D013909:Thorax; D013990:Tidal Volume