Monitoring of Breathing Effort Through Pressure Time Product Measurement Using Airway Occlusion Pressure

Overview

Mechanical ventilation is essential in the management of patients in Intensive Care. The approach to patients with prolonged weaning is challenging.In this context, it is vital to implement "diaphragmatic protection" strategies, which consist of programming the level of ventilator assistance focused on sustaining the muscular effort within an objective range. The reference method for measuring inspiratory effort is the Pressure-Time Product (PTP) of the esophagus. Recently, Bertoni et al. proposed the measurement of Occlusion Pressure as a non-invasive method, without the need to assess esophageal pressure, to estimate the magnitude of the effort and program assistance. Although it is a validated measurement for quantifying effort, it does not consider the duration of the effort performed by the patient, as well as the respiratory rate, two fundamental variables in terms of tolerance to the load. Therefore, the investigators propose the following study that will seek to validate the measurement of PTP in from the Occlusion Pressure, but considering inspiratory time and respiratory rate to obtain PTP per breath and per minute.

Mechanical ventilation (MV) is an essential support in the management of patients in Intensive Care Units (ICU). According to international epidemiological studies, around 40% of patients admitted to ICU require ventilatory support. International epidemiological data indicate that just over 55% of ICU patients are weaned from MV prematurely, and that approximately 20% experience difficult and prolonged weaning. In Argentina, our country, there are reports that this population amounts to 49.3%. One common denominator in the literature, international and national, regarding this section, is that such patients have more days of MV, ICU and hospital stay. During prolonged weaning, monitoring of muscular effort becomes essential: both excessive and deficient efforts usually lead to diaphragmatic dysfunction. The former predisposes to fatigue, while the latter to atrophy. In this context, it is vital to implement "diaphragmatic protection" strategies, which consist of programming the level of assistance with a focus on muscular effort or muscular pressure (PMUS) to keep it within a target range. The reference method for measuring inspiratory effort is the Pressure-Time Product of the esophagus (PTPESO), which involves the magnitude of PMUS measured through the change in esophageal pressure (PES) generated during inspiration, its duration, and respiratory rate (RR). For patients on partial ventilatory support, a PTP of 50 to 150 cmH2O/sec/min is recommended. Thus, PES becomes an everyday and reference tool for the management of patients with prolonged weaning from MV. Recently, Bertoni et al. proposed measuring Occlusion Pressure (POCC) as a non-invasive method, i.e., without the need to evaluate PES, to estimate the magnitude of PMUS and program assistance in PSV. By means of a tele-expiratory occlusion maneuver of the airway, the maximum negative deflection of the signal during the patient's inspiration is quantified. This maneuver is called POCC. Then, through a simple multiplication by a constant, the value of PMUS in one cycle is obtained. Given the ease of measurement and its non-invasive nature, this technique has taken a leading role in the approach to patients during partial support at present. Although the POCC is validated to quantify breathing effort, it has significant weaknesses. Some of these are that it only values the maximum deflection in an average of efforts, does not consider the time that the effort made by the patient lasts, nor the respiratory rate, two fundamental variables in terms of tolerance to the load (duration of contraction and frequency of repetition). In this context, having a method that can estimate PTPESO non-invasively would be extremely useful to titrate the level of assistance in the framework of diaphragmatic protection strategies in patients with difficulties in being weaned from MV. Therefore, the investigators propose the following study that will validate the measurement of PTPESO based on POCC, but considering the inspiratory time and respiratory rate to obtain PTP per breath and per minute. These variables will be called PTPPOCC-br and PTPPOCC-min, respectively.