Partitioning of airway and lung tissue properties: Comparison of in situ and open-chest conditions

B. Suki, F. Petak, A. Adamicza, Z. Hantos, K. R. Lutchen

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The purpose of this study was to investigate under physiological breathing conditions whether airway and lung tissue properties are different in situ and in open-chest conditions. We measured lung input impedance in dogs from 0.2 to 8 Hz with an optimal ventilator waveform at four tidal volumes (VT; from 75 to 450 ml) in intact animals using an esophageal balloon as well as after opening the chest. The lung impedance from both conditions was partitioned into airway and tissue compartments as characterized by airway resistance and inertance (law) and tissue damping (G) and elastance (H) parameters respectively. All parameters except law depended to some extent on VT. The in situ tissue G and H slightly decreased with VT while in the open- chest condition; G decreased and H increased slightly with VT. We found small but significant differences between the mechanical properties of the airway and lung tissues in situ and in open-chest conditions. Over the total population, the G, airway resistance, and law parameters were 13% (not significant), 35% (P < 0.001), and 31% (P < 0.001) smaller, respectively, in situ than in the open-chest condition. However, the H was 15% larger in situ (P < 0.001). Although we cannot completely rule out certain artifacts, these differences most likely reflect real alterations in the lung due to the different configurations and possible differences in the distribution of pleural pressures in the two conditions. The G being smaller and E being larger in situ resulted in hysteresivity (G/H) 36% smaller in situ (P < 0.001). Consequently, energy dissipation in the lung tissues relative to energy storage as characterized by hysteresivity is somewhat increased in the open-chest configuration. This may be anticipated because the mechanical efficiency of the lungs is expected to be better in its natural state than in any artificially maintained condition that was the end result of an invasive intervention.

Original languageEnglish
Pages (from-to)861-869
Number of pages9
JournalJournal of Applied Physiology
Issue number3
Publication statusPublished - Jan 1 1995



  • airway resistance
  • amplitude dependence
  • esophageal balloon
  • hysteresivity
  • tissue elastance
  • tissue resistance

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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