Effect of intermittent positive pressure ventilation on the skeletal muscle and small intestine microcirculation in rats

Introduction

Intermittent positive pressure ventilation (IPPV) may be accompanied by alteration of microcirculation [1, 2]; however, the effect of IPPV is not mentioned in the interpretation of the results of studies evaluating microcirculation using orthogonal polarization spectral or sidestream dark-field imaging. This study aimed to evaluate the effect of IPPV on microcirculation in the skeleton muscles and in the serosa of the small intestine in rats.

Methods

Ten animals were tracheostomized and prepared for microcirculation study; after tissue preparation, five rats were allowed to breath spontaneously (Group SB = spontaneous breathing), and five rats (Group IPPV) were connected to a small animal ventilator (IPPV: FiO₂ 0.21, respiratory rate 60/min, tidal volume 10 ml/kg, inspiratory time 50% of respiratory cycle, and 2 cmH₂O PEEP). Sidestream dark-field images were obtained from the quadriceps femoris muscle (QFM) and serosa surface of the ileum. The arterial blood pressure and rectal temperature were also recorded. The functional capillary density (FCD) and small and medium vessels rate were analysed offline using AVA V1.0 software (AMC, University of Amsterdam, The Netherlands), P ≤ 0.05.

Results

The FCD was decreased significantly in QFM in rats with IPPV with respect to Group SB (184 ± 27 resp. 197 ± 61 cm/cm²), but the FCD of the intestinal serosa was not affected by IPPV (265 ± 46 resp. 267 ± 25 cm/cm²). There were no differences in mean blood pressure and temperature between groups (128 ± 7 Torr and 36.6 ± 0.1°C in Group SB, or 128 ± 10 Torr and 36.5 ± 0.1°C in Group IPPV).

Conclusion

The use of IPPV should be taken into account in the interpretation of the studies examining the changes in microcirculation in rats.