Ac Theory And The Human Chest

The GR Type 1305-A Low-Frequency Oscillator was featured in an unusual demonstration last September at the XXII International Congress of Physiological Sciences at Leiden. In the exhibit, entitled "Interpretation of the Respiratory Pressure-Volume Lissajous figures," the oscillator was used to produce, on a dual-beam oscilloscope, Lissajous loops analogous to pressure-volume and pressure-volume flow in the human chest. The input data were taken from actual experiments performed on animals and human beings, part of a long-term program conducted by Drs. Wayland E. Hull and E. Croft Long at Duke University Medical Center.

The electrical analog of the human chest is an interesting example of the use of analogous systems to explain natural phenomena. The human chest and lungs are here visualized as a series circuit, containing capacitance (compliance of lung tissues and rib cage), inductance

Figure 1. Pressure-volume Lissajous patterns at fre- 20 quencies Indicated. System is asymmetrical at lower frequencies and resonant, | Q

in this particular case, at about 10 cycles/sec as seen from vertical loop indicat- q ing 90 degrees of phase shift. Data from anesthetized dog.

(by permission of the _20

Journal of Applied Physiology)

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