Application of electrical impedance principle in the diagnosis of diaphragm fatigue.

The chest and abdomen impedance respirographs (IRG), including the one dimensional IRG and the two dimensional IRG were designed and produced by applying the principle of bioelectrical impedance. Using IRG the non-synchronized chest and abdomen respiratory motions occurring in diaphragmatic fatigue were measured. The results showed that all 203 normal controls showed synchronized style of chest and abdomen respiratory motions. In 189 COPD patients 117 (61.9%) showed non-synchronized respiratory motions which could be further divided into three types: type I showed complete contra-directional respiratory movements of chest and abdomen respiration, with M > 24 % and alpha angel > 120 degrees; type II showed staggered peak of the chest and abdomen motion curves (13% < M < 24%), 50 degrees < alpha angle < 120 degrees; type III showed double peaks of abdomen trace in the one dimensional IRG and "8"-shaped double circles on the two dimensional IRG, (M < 13%, 50 degrees < alpha angle < 120 degrees. When compared with trans-diaphragmatic pressure (Pdi) and diaphragm myoelectricity frequency spectrum, the rates of conformity were 81.8% and 90%, respectively, suggesting that IRG could be reliably used for diagnosing diaphragmatic fatigue. This technique is simple, easy to use, cheap and pain-free.