Tidal volume (TV) post-process obtained with electrical impedance tomography on a group of chronic obstructive pulmonary disease (COPD) patients. Use of adjust equations

Abstract

Abstract. Equations used to estimate ventilation out of EIT images, validated on healthy volunteers show a significant bias and a larger variance when were applied on a COPD patients group. The differences in estimation values were found to be highly correlated with anthropometric parameters. Two groups of 13 and 4 COPD male patients (FEV1/FVC<70% and FVC ≥ 80%) were used in this study. We have measured different anthropometric parameters like age, weight, height and skinfolds. The EIT system (TIE4sys) and a pneumotach were simultaneously connected to monitor tidal volume. The main anthropometric parameters values of 13 COPD patients were: age: 67±9 years, height: 1.65±0.05 m, weight: 72±11 kg, BMI: 26.4±3.3; and the subscapular skinfold thickness was 23±9mm. The mean tidal volume estimated with TIE4sys and the pneumotach were: 0.580±0.212 L and 0.774±0.173 L r = 0.861 (p<0.01). The mean difference was 0.196±0.096 L (p<0.01). On this group we have found out an adjust equation and we have validated it on an independent group of 4 COPD patients. The equation was Diff=-1478+15.6(weight). The mean tidal volume values obtained with pneumotach and TIE4sys on the second group of COPD patients (M:4) were: 0.798±0.395 L and 0.732±0.327 L. The mean of the differences was 0.066±0.114L. The differences of determinations estimated with pneumotach and TIE4sys can be attributed to changes of anthropometric characteristics like subscapular skinfold.

Telemonitoring Techniques for Lung Volume Measurement: Accuracy, Artifacts and Effort

“… Bias and limits of agreement distribution in liters for tidal volume (TV) ( 37 , 39 , 47 , 49 , 52 , 53 , 55 , 58 , 64 , 65 , 71 – 90 ), end-expiratory lung volume (EELV) ( 36 , 37 , 87 , 91 ), forced expiratory volume in 1s (FEV 1 ) ( 26 , 27 , 64 , 69 , 74 , 92 – 94 ) and forced vital capacity (FVC) ( 69 , 74 , 92 , 93 ) per telemonitoring technique. Spiro; spirometry (including BbB-analyzers) in blue, RIP; respiratory inductance plethysmography in orange, RMP; respiratory magnetic plethysmography in gray, and EIT; electrical impedance tomography in yellow.…”

“…Only a few studies investigated the accuracy of volumetric measurements with EIT compared to spirometry. Balleza et al ( 88 , 89 ) Marco et al ( 90 ) studied differences between EIT and spirometry in multiple populations and found biases for TV between −0.003 L and 0.218 L. Ngo et al ( 64 ) found a bias of 0.243 L for TV. Sosio et al ( 65 ) found a bias of −0.095L.…”