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.