RESUMO
Pneumoperitoneum may give rise to several respiratory changes; nevertheless, no comprehensive analysis of respiratory mechanics has been performed under this condition. Respiratory mechanics and thoracoabdominal morphometry were evaluated in six sedated, anaesthetized, paralysed, and mechanically-ventilated rats before (control) and during pneumoperitoneum. After airway occlusion at end-inspiration, respiratory system, pulmonary, and chest wall resistive pressures (deltaP1,rs, deltaP1,L and deltaP1,cw, respectively) and viscoelastic/inhomogeneous pressures (deltaP2,rs, deltaP2,L and deltaP2,cw, respectively) were determined. Total pressure changes (deltaPtot) were calculated as the sum of deltaP1 and deltaP2, yielding the values of deltaPtot,rs, deltaPtot,L and deltaPtot,cw, respectively. Respiratory system, lung, and chest wall static (Est,rs, Est,L and Est,cw, respectively), and dynamic elastances (Edyn,rs, Edyn,L and Edyn,cw, respectively), and the corresponding changes in elastance (deltaE) (calculated as Edyn-Est) were also obtained. Chest wall configuration both at functional residual capacity (FRC) and end-inspiration (FRC + tidal volume (VT)) was also evaluated in another four rats. Pneumoperitoneum significantly increased deltaPtot,rs, deltaPtot,cw, deltaP2,rs, deltaP2,cw, deltaErs, deltaEcw, Est,rs, Est,L and Est,cw. Lateral and anteroposterior diameters increased significantly, with the exception of lateral diameters at the level of crista iliaca. Cephalocaudal diameter and FRC decreased. In conclusion, pneumoperitoneum augments elastances and increases the pressure dissipated against viscoelasticity/inhomogeneity of the respiratory system and chest wall. These changes are related to a cephalad displacement of the diaphragm plus changes in thoracoabdominal configuration.
Assuntos
Pulmão/anatomia & histologia , Pneumoperitônio Artificial , Mecânica Respiratória , Tórax/anatomia & histologia , Animais , Elasticidade , Capacidade Residual Funcional , Masculino , Ratos , Ratos Wistar , Fenômenos Fisiológicos Respiratórios , Volume de Ventilação PulmonarRESUMO
It has been demonstrated that respiratory resistance and elastance increase whilst the abdomen remains open during longitudinal laparotomy. We wished to determine whether changes also occur after abdominal closure in the same animal preparation. In 10 sedated, anaesthetized paralysed, and mechanically-ventilated rats (309 +/- 33 (SD) g), resistances and elastances of the respiratory system, lung, and chest wall were measured both before longitudinal laparotomy and directly after abdominal closure. Furthermore, the resistances were also split into their initial and difference components, the former reflecting the Newtonian resistances and the latter representing the viscoelastic/inhomogeneous pressure dissipations in the system. For this purpose, the end inflation occlusion during constant inspiratory flow method was used. After laparotomy, no statistically significant changes were found in elastances and resistances of the respiratory system, lungs and chest wall (paired Student's t-test, significance level = 5%). It can be concluded that after midline xiphipubic laparotomy accompanied by bilateral ventro-dorsal infracostal incision, respiratory resistances and elastances were not different from those found in the control condition.