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

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.