Abstract
The relationship between chest cage movements and changes in the transthoracic electrical impedance was studied with respect to three parts of the thorax, comparing the findings with simultaneously recorded respired air volume changes measured with a spirometer. The inductance pneumometer detected the dorso-ventral thoracic movements by measuring the mutual inductance. between two coils, distance of which varies with diameter changes of the chest cage associated with respiration. Transthoracic impedance was measured with a two-terminal, constant-current impedance pneumograph.
Coils and electrodes were placed on the upper, middle and lower part of the right thorax along the mid-clavicular line for the anterior chest wall and median side of the scapula for the posterior.. Dorso-ventral changes of the thoracic diameter and the transthoracic impedance for the total lung volume in a normal male subject were smaller at the top and larger at the bottom of the thorax.
The relationships between transthoracic impedance changes (Y) and thoracic diameter changes (X) were
Y= 3. 23 X (r =0. 95) in the upper part,
Y= 4. 00 X (r =0. 97) in the middle,
Y= 4. 68 X (r =0. 96) in the lower.
Transthoracic impedance changes per unit thoracic diameter change were also larger and grew larger towards the lower part of the thorax.
