抄録
Tidal volume measurement is widely used in both clinical practices and experimental researches. Although a flowmeter gives accurate tidal volume, it requires a facemask which makes a subject uncomfortable and even affects breathing pattern in the subject. Measurements using any methods other than the flowmeter must be calibrated by the flowmeter in each subject. To dispense with the facemask and the calibration, we developed a new method which measures the change in the body trunk volume, because it is established that the change in the body trunk volume is equal to that in the lung volume.
A curvature sensor using optical fibers was developed to yield a cross-sectional area of the body trunk. The shape of the cross section was reconstructed from 20 curvatures measured by the curvature sensors, to produce the area. Two cross-sectional areas were obtained as stated above, and two other areas were estimated from the two areas obtained already. The estimation was based on the relation between the area and the circumference length. The four cross-sectional area and three distances between them gave the body trunk volume related to respiration. The circumference lengths and the distances between the areas were measured by length sensors using optical fibers which we also developed. We named this method the curvature plethysmography (CP).
The change in the lung volume was measured by a flowmeter in six subjects, and the change in the body trunk volume was simultaneously measured by the CP without any calibration in each subject. The coefficient of the regression line between the two measured changes ranged from 0.8 to 1.2. The results obtained indicated that the CP can be used for tidal volume measurement without a facemask and a calibration.
