Hemodynamic effects due to the application of inspiratory pause in hyperinflation with mechanical ventilation in controlled volume: crossover and randomized study

Abstract

Introduction: Pulmonary hyperinflation is a physiotherapeutic technique commonly applied to critically ill patients with the purpose of clearance of pulmonary secretions, improvement of respiratory mechanics and oxygenation. Hyperinflation with the mechanical ventilator (VHI) has the same beneficial effects of hyperinflation with the manual resuscitator (MH) with the advantage of non-decoupling of the patient from the mechanical ventilator and better control of ventilatory parameters. Despite these advantages, there are still few studies evaluating the hemodynamic profile during the HVM; the studies evaluated the heart rate, the mean arterial pressure, the cardiac index and the oxygen consumption. Physiologically, changes in tidal volume during mechanical ventilation may cause hemodynamic repercussions, such as changes in pulmonary vascular resistance, pre and afterload of the right ventricle and left ventricle, and, finally, reflex bradycardia. Objective: This study aimed to evaluate two VHI protocols (without the application of the inspiratory pause – VHI-NP and the application of inspiratory pause – VHI-P) from a hemodynamic point of view measured by cardiothoracic bioimpedance. Methods: The study was a cross-over and randomized clinical trial, where 18 patients were analyzed at the Intensive Care Center of Santa Martha Hospital, Niterói /RJ. All family members of the research participants were asked to sign the informed consent form. Respiratory mechanics and hemodynamic repercussions were evaluated. Results: The mean age of the sample was 77 years and the median of the static complacency was 46.6 [33.3-55] cmH2O / mL. Statistically significant differences were found in the mean airway pressure (MPAW) between the rest moments vs intervention moments (p <0.001) and in the diastolic blood pressure (DBP) between the 3rd set of VHI-NP vs 3rd set of VHI-P (p = 0.009). There was a fall in the PAD in the 3rd set of VHI-P in relation to the 3rd set of VHI-NP with a magnitude of 6.5mmHg (Δ = 10%), however, with a median of normal limits. There was no correlation between MPAW changes and changes in cardiac output and/or DBP. Conclusion: The diastolic dysfunction of the elderly, the greater activation of the neurohumoral reflex and the greater difference in the pressure gradient between the thoracic and abdominal aorta during VHI-P, besides the reduced median Cst of the sample, may explain the results. VHI has been shown to be safe from the hemodynamic point of view, and VHI-NP is the safest mode of application, especially in elderly patients. Therefore, this study may allow greater training and better application of VHI by physiotherapists, based on current scientific literature.