PxV curve behavior inside and outside the thorax in normal rats

Introduction

PxV curve is a good way to study the mechanical behavior of the respiratory system in animal models; however, it is important to distinguish between the behavior of the PxV curve inside the thorax (PxV curve of the respiratory system) and outside the thorax (PxV curve of the lung) as we studied in isolated lungs models.

Methods

In order to evaluate the behavior of the curve inside and outside the thorax, we studied 42 Wistar normal rats. In 21 rats we performed the PxV curve of the respiratory system with a constant flow of 1.66 ml after the rats were anesthetized and paralyzed. In the other 21 rats, after we had anesthetized the rats, we excised the lungs from the thorax and performed the PxV curve of the isolated lung with a syringe (Figure). We recorded the curve in a PC computer and then calculated the L-Pflex and the U-Pflex.

Results

In the 21 rats with closed thoracic cage the mean U-Pflex of the PxV curves was 13.5 ± 1.90. None of the 21 normal rats had L-Pflex. In contrast the isolated lungs showed a mean L-Pflex of 12.05 ± 3.03 and a mean U-Pflex 16.96 ± 2.93 (Figure).

Conclusion

The PxV curve has a completely different shape inside and outside the thorax, and this fact has to be taken into account during mechanical measurements in rats experimental models. FAPESP-LIM-FMUSP.