[Measuring breathing pattern in patients with chronic obstructive pulmonary disease by electrical impedance tomography].
OBJECTIVE
The measurement of breathing pattern in patients with chronic obstructive pulmonary disease (COPD) by electrical impedance tomography (EIT) requires the use of a mathematical calibration model incorporating not only anthropometric characteristics (previously evaluated in healthy individuals) but probably functional alterations associated with COPD as well. The aim of this study was to analyze the association between EIT measurements and spirometry parameters, static lung volumes, and carbon monoxide diffusing capacity (DLCO) in a group of male patients to develop a calibration equation for converting EIT signals into volume signals.


METHODS
We measured forced vital capacity (FVC), forced expiratory volume in 1 second (FEV(1)), FEV(1)/FVC, residual volume, total lung capacity, DLCO, carbon monoxide transfer coefficient (KCO) and standard anthropometric parameters in 28 patients with a FEV(1)/FVC ratio of <70%. We then compared tidal volume measurements from a previously validated EIT unit and a standard pneumotachometer.


RESULTS
The mean (SD) lung function results were FVC, 72 (16%); FEV(1), 43% (14%); FEV(1)/FVC, 42% (9%); residual volume, 161% (44%); total lung capacity, 112% (17%); DLCO, 58% (17%); and KCO, 75% (25%). Mean (SD) tidal volumes measured by the pneumotachometer and the EIT unit were 0.697 (0.181)L and 0.515 (0.223)L, respectively (P<.001). Significant associations were found between EIT measurements and CO transfer parameters. The mathematical model developed to adjust for the differences between the 2 measurements (R(2)=0.568; P<.001) was compensation factor=1.81# - 0.82# height (m)# -0.004 x KCO (%).


CONCLUSIONS
The measurement of breathing pattern by EIT in patients with COPD requires the use of a previously calculated calibration equation that incorporates not only individual anthropometric characteristics but gas exchange parameters as well.
Balleza
Marco
M
Departament de Pneumologia, Hospital de la Santa Creu i de Sant Pau, Facultat de Medicina, Universitat Autònoma de Barcelona, Barcelona, España. jballeza@santpau.cat
Calaf
Núria
N
Feixas
Teresa
T
González
Mercedes
M
Antón
Daniel
D
Riu
Pere J
PJ
Casan
Pere
P
D000368:Aged; D000465:Algorithms; D002138:Calibration; D017097:Electric Impedance; D004867:Equipment Design; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D010507:Periodicity; D011653:Pulmonary Diffusing Capacity; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012129:Respiratory Function Tests / Q000295:instrumentation / Q000379:methods*; D012885:Skinfold Thickness; D013147:Spirometry; D014054:Tomography / Q000295:instrumentation / Q000379:methods*