Mechanical impedances of lungs and chest wall in the cat

Z. Hantos, A. Adamicza, E. Govaerts, B. Daroczy

Research output: Contribution to journalArticle

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Abstract

In nine anesthetized and paralyzed cats, the mechanical impedances of the total respiratory system (Zrs) and the lungs (ZL) were measured with small- volume pseudorandom forced oscillations between 0.2 and 20 Hz. ZL was measured after thoracotomy, and chest wall impedance (Zw) was calculated as Zw = Zrs - ZL. All impedances were determined by using input airflow [input impedance (Z(i))] and output flow measured with a body box [transfer impedance (Z(t))]. The differences between Z(i) and Z(t) were small for Zrs and negligible for ZL. At 0.2 Hz, the real and imaginary parts of ZL amounted to 33 ± 4 and 35 ± 3% (SD), respectively, of Zrs. Up to 8 Hz, all impedances were consistent with a model containing a frequency-independent resistance and inertance and a constant-phase tissue part (G - jH)/ω(α), where G and H are coefficients for damping and elastance, respectively, ω is angular frequency, and α determines the frequency dependence of the real and imaginary parts. G/H was higher for Zw than for ZL (0.29 ± 0.05 vs. 0.22 ± 0.04, P <0.01). In four cats, the amplitude dependence of impedances was studied: between oscillation volumes of 0.8 and 3 ml, GL, HL, Gw, and Hw decreased on average by 3, 9, 26, and 29%, respectively, whereas the change in G/H was small for both ZL (7%) and Zw (-4%). The values of H were two to three times higher than the quasi-static elastances estimated with greater volume changes (>20 ml).

Original languageEnglish
Pages (from-to)427-433
Number of pages7
JournalJournal of Applied Physiology
Volume73
Issue number2
Publication statusPublished - 1992

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Thoracic Wall
Electric Impedance
Cats
Lung
Thoracotomy
Respiratory System

Keywords

  • chest wall elastance
  • chest wall resistance
  • forced oscillations
  • pulmonary elastance
  • pulmonary resistance
  • tissue hysteresivity
  • tissue nonlinearity

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Mechanical impedances of lungs and chest wall in the cat. / Hantos, Z.; Adamicza, A.; Govaerts, E.; Daroczy, B.

In: Journal of Applied Physiology, Vol. 73, No. 2, 1992, p. 427-433.

Research output: Contribution to journalArticle

Hantos, Z. ; Adamicza, A. ; Govaerts, E. ; Daroczy, B. / Mechanical impedances of lungs and chest wall in the cat. In: Journal of Applied Physiology. 1992 ; Vol. 73, No. 2. pp. 427-433.
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