Indirect measurement of tidal volume by multi-lead electrocardiograms: effect of filtering, deep breath, lead and posture.
We examined a new method for estimating tidal volume from the electrocardiogram (ECG) in order to dispense with the need for sensors used exclusively for tidal volume measurement. The direction of the vector loop in the QRS complex (DVL) was defined as the direction of the diagonal line of the rectangle which circumscribed the vector loop obtained from two orthogonal leads. Two leads of the ECG were transformed into the orthogonal leads using Einthoven's triangle. The peak-to-peak change in the direction (the change in the DVL) was highly correlated with tidal volume. Low-pass filtering of the ECG produced a better correlation between tidal volume and the change in the DVL, when the cutoff frequency was set at 20-45 Hz. A tidal volume of less than 1.21 was correlated more highly with the change in the DVL than a tidal volume of more than 1.21 A combination of leads I and III produced the best correlation between tidal volume and the change in the DVL, compared with other combinations. The posture of the subject had some effects on the slope of the linear regression between tidal volume and the change in the DVL.
Noshiro
M
M
Department of Clinical Engineering, School of Allied Health Sciences, Kitasato University, Kanagawa, Japan.
Inaoka
H
H
Yoshida
Y
Y
Ryumae
S
S
Shimizu
M
M
Hoshino
H
H
Hosaka
H
H
D004562:Electrocardiography; D006801:Humans; D011187:Posture / Q000502:physiology*; D012044:Regression Analysis; D012119:Respiration / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D013990:Tidal Volume / Q000502:physiology*