Effects of Arterial and Tracheal Pressures During a Respiratory Mechanics Protocol in Spontaneously Hypertensive Rats

摘要

This work aims to evaluate the response of tracheal and arterial pressures during a Methacholine (MCh) dose-response curve. This drug is a bronchoconstrictor and, additionally, causes vasodilatation in cardiovascular system leading to reduction of arterial pressure. Spontaneously hypertensive rats (SHR) were used and each animal was anesthetized, tracheostomized and connected to a small animal ventilator (flexiVent version 5.2, SCIREQ, Canada). Whereas the animal was ventilated, a device developed by us was connected to the right carotid in order to assess blood pressure. This device is composed of a pressure sensor, a low-pass filter, an amplifier and an analog-to-digital converter. The two main variables studied in this work were the arterial and tracheal pressure, the latter assessed by the ventilator. Firstly, we depicted the temporal dynamics of both pressures. The blood pressure decreased while the tracheal pressure increased with the increment of the MCh doses. In a second analysis, we compared the pressure during (intra) and after (inter) perturbations used to mathematical modeling. There were no differences between intra vs. inter, only among doses for the first three measures of each dose (p < 0.0001). Thus, despite the shape of the arterial pressure being different between intra vs inter perturbation, the mean value did not alter. Finally, we indicate that the arterial pressure returns to basal after 2 and 4min after MCh injection, since that there was no statistical difference among doses or in 2 vs 4min comparison (p > 0.05), which may guide the recovery time given between doses in a dose-response curve.