Measurement of tidal volume by using transthoracic impedance variations in rats

K. G. Davidson, A. D. Bersten, T. E. Nicholas, P. R. Ravenscroft, I. R. Doyle

    Research output: Contribution to journalArticlepeer-review

    15 Citations (Scopus)


    The application of impedance pneumography for monitoring respiration in small animals has been limited by problems with calibration. With improved instrumentation, we describe the calibration of tidal volume in anesthetized rats. The detection of changes in voltage, reflecting the electrical impedance variations associated with respiration, was optimized by using disposable adhesive silver-silver chloride electrodes, advanced circuitry, and analog-to-digital recording instrumentation. We found a linear relationship between change in impedance and tidal volume in individual rats (R2 ≥ 98%), which was strongly influenced by rat weight. Consequently, a calibration equation incorporating change in impedance and rat weight was derived to predict tidal volume. Comparison of the predicted and true tidal volumes revealed a mean R2 ≥ 98%, slopes of ~1, intercepts of ~0, and bias of ~0.07 ml. The predicted volumes were not significantly affected by either frequency of respiration or pulmonary edema. We conclude that impedance pneumography provides a valuable tool for the noninvasive measurement of tidal volume in anesthetized rats.

    Original languageEnglish
    Pages (from-to)759-766
    Number of pages8
    JournalJournal of Applied Physiology
    Issue number2
    Publication statusPublished - Feb 1999


    • Edema
    • Frequency
    • Impedance pneumography
    • Monitoring respiration
    • Spontaneous breathing


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