Evaluation of the effect of a long inspiratory ramp time during pressure-controlled ventilation with volume guarantee: study protocol for a randomized, controlled trial.

Abstract

Background: The inspiration of pressure-controlled ventilation is characterized by an initial sharp increase of flow rate. The resulting peak flow rate could induce a disproportionately high mechanical load, transferred from the ventilator to the pulmonary structures. A higher inspiratory ramp time could decrease the peak inspiratory flow rate, which might reduce the mechanical power transmitted to the lungs. This study compares pressure-controlled ventilation with volume guarantee with low and high inspiratory ramp time and the effects on the mechanical load transferred from the ventilator to the patient's lungs.

Methods: This is a randomized, controlled single-center trial, in which patients receive pressure-controlled ventilation with volume guarantee with short (clinical standard) or increased inspiratory ramp time. Mechanical power will be compared between the two types of ventilation. Further, the effects of the respective ventilation setting will be evaluated with the Horowitz index, the mean airway pressure, and changes in respiratory system compliance. The occurrence of atelectasis will be investigated utilizing electrical impedance tomography. Additionally, lung-specific proteins in patients' blood will be measured, seeking indications of mechanical stress in their dynamics and postoperative pulmonary complications will be recorded and compared between groups.

Discussion: This trial aims to evaluate the feasibility of decreasing inspiratory flow rate during pressure-controlled ventilation with volume guarantee by increasing inspiratory ramp time and to analyze its effects on mechanical power, oxygenation, respiratory system mechanics, atelectasis, and postoperative pulmonary complications. Furthermore, lung-specific proteins in patients' blood will be examined in regard to find a novel, helpful biomarker, representing the mechanical load of the lungs. The results of this study could provide valuable information to improve perioperative mechanical ventilation with a reduced mechanical power through a simple an ubiquitously available modification of the breathing pattern, namely increasing inspiratory ramp time. Additionally, identification of a lung-specific biomarker reflecting mechanical load of the lungs might enhance research of lung-protective ventilation.

Trial registration: German Clinical Trials Register (DRKS), DRKS00035496. Registered on 12 November 2024; URL: https://drks.de/search/en/trial/DRKS00035496/details . Local Trials Register: Freiburger Register of Clinical Studies (FRKS), FRKS005304.