Effects of Thoracotomy on Respiratory System, Lung, and Chest Wall Mechanics

The frequency (f) dependence of pulmonary and chest wall mechanics was assessed in nine kittens and four cats. Kittens and cats were anesthetized, paralyzed, and mechanically ventilated at various f between 0.13 and 1.6 Hz and 0.09 and 0.79 Hz, respectively. Resistance and dynamic compliance pertaining to the respiratory system (Rrs and Cdyn,rs), lungs (RL and Cdyn,L), and chest wall (RW and Cdyn,W) were estimated by fitting a single-compartment model to data obtained from regular ventilation. Static lung and chest wall compliances (Cst,L and Cst,W) were computed from quasi-static pressure-volume data. Lung tissue resistance (Rti) was estimated with alveolar capsules in open-chest animals. The f dependence of the two-compartment viscoelastic model of the respiratory system was assessed by computing the effective resistance [Rmod,rs(omega)] and compliance [Cmod,rs(omega)] from data obtained at the lowest experimental f. Both Cdyn,L and Cdyn,W decreased with increasing f in all animals. Cdyn,L/Cst,L and Cdyn,W/Cst,W were lower in kittens than in cats. RL and RW decreased markedly with f in all animals. Rti/RL showed a marked f dependence, its values being similar in both young and adult cats at their respective resting f. CstW/Cst,L ratio was higher in kittens than in cats. A better agreement was found between Cmod,rs(omega) and Cdyn,rs than between Rmod,rs(omega) and Rrs.

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Effects of longitudinal laparotomy on respiratory system, lung, and chest wall mechanics

Journal of Applied Physiology ◽

10.1152/jappl.1992.72.5.1985 ◽

1992 ◽

Vol 72 (5) ◽

pp. 1985-1990 ◽

Cited By ~ 2

Author(s):

R. L. Santos ◽

M. A. Santos ◽

R. S. Sakae ◽

P. H. Saldiva ◽

W. A. Zin

Keyword(s):

Chest Wall ◽

Respiratory System ◽

Guinea Pigs ◽

Inspiratory Flow ◽

Total Resistance ◽

Abdominal Incision ◽

Mechanically Ventilated ◽

Flow Method ◽

Chest Wall Mechanics ◽

Before And After

In six sedated, anesthetized, paralyzed, and mechanically ventilated guinea pigs, total respiratory system (RT,rs), lung, and chest wall resistances and respiratory system (Est,rs), lung, and chest wall (Est,w) elastances were determined before and after longitudinal laparotomy. Furthermore the resistances were also split into their initial and difference components, with the former reflecting the Newtonian resistances and the latter representing the viscoelastic/inhomogeneous pressure dissipations in the system. For such purpose the end-inflation occlusion during constant inspiratory flow method was used. During laparotomy, a statistically significant increase in respiratory system difference resistance (from 0.086 to 0.101 cmH2O.ml-1.s) significantly augmented RT,rs (from 0.157 to 0.167 cmH2O.ml-1.s). The former was entirely secondary to a significant increase in chest wall difference resistance (0.019 to 0.034 cmH2O.ml-1.s), which naturally raised chest wall total resistance (from 0.030 to 0.047 cmH2O.ml-1.s). Est,rs and Est,w also increased (14.7 and 13.1%, respectively) after abdominal incision. It can be concluded that the midline xiphipubic laparotomy accompanied by the bilateral ventrodorsal infracostal incision increases RT,rs as a consequence of augmented chest wall difference resistance and Est,rs as a result of higher Est,w.

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