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Introduction: The influence of controlled mechanical volume ventilation (CMVV) on cardiovascular system in critically ill patients depends on predominant cardio-respiratory status. Overall, CMVV lessens RV preload while improving the LV afterload, hence in the presence of acute or chronic pulmonary disease; CMVV has to be carefully adjusted. CMVV adjustments should be made in real-time. In this study, recording of the right ventricular (RV) pressure-volume (PV) was made to characterize hemodynamic differences of CMVV with occurrence of spontaneous breathing (SB) compared to noninvasive ventilation (NIV), using mouse model.
Methods and Aims: During NIV, face mask was used while RV PV was measured using 1.2 F PV catheter accessing RV through right jugular vein navigated by transthoracic echocardiography. Next, transpharyngeal intubation and invasive CMVV using diaphragm opening and RV apical stab was used. Volume-ventilation setting (Vt and RR) was based on body weight. Isoflurane mono-anesthesia was used without any premedication.
Results: Both ventilation conditions had specific effects on RV pressurevolume. In case of blood pressure gradient caused by effects of respiratory pump during CMVV in open chest setting with periodic SB, variations of RV stroke volume (SVV) and (or) RV CO were less significant as compared to NIV. Additionally, marked increase of RV dp/dt was observed during NIV. Furthermore, increase of RV dp/dt in 2 following cycles by 23% (596 mmHg/sec) and 68% (1736 mmHg/sec) were noticed. Interestingly, both RV EDP and RV EDV were found to be temporarily increased during NIV. Later, 100 cardiac cycles were compared to CMVV for RV CO and RV SV. In case of CMVV with recurrent periods of SB (RV SV was 26.1 ± 0.4 μl, and RV CO=13.2 ± 0.2 ml/min) as compared to NIV (32.5 ± 0.6 and 16.3 ± 0.3 ml/ min); p<0.001 for both.
Conclusions: The study revealed distinctive role of the respiratory pump action during close chest setting on RV preload. CMVV with periodic SB showed lesser variations of RV stroke volume (SVV) and RV CO supporting use of this ventilatory mode in patients with respiratory failure associated with afterload-dependent LV dysfunction. Hemodynamic influence of ITP/ TPP and other pressures generated by the action of CMVV needs to be studied using multiple pressure/PV sensors.
