PEEP Optimization After Elective Cardiac Surgery: A Pilot Study

Patients undergoing cardiothoracic surgical procedures face an elevated risk of
pulmonary complications, ranging from hypoxemia to acute respiratory distress
syndrome (ARDS). The most common complications include hypoxemia and the
development of atelectasis. Having atelectasis poses a risk for the onset of
pneumonia, a late complication of cardiothoracic surgery, which is associated
with a poorer outcome. Atelectasis manifests as a decrease in lung compliance
and a diminished ratio between arterial oxygen tension (pO2) and the fraction
of inspired oxygen (FiO2); the P/F ratio.

Atelectasis can occur during the period when the patient is sedated and
ventilated and/or during the post-extubation period. The risk of atelectasis
during the ventilation period increases when the time on pressure control
ventilation (PCV) is prolonged and/or when positive end-expiratory pressure
(PEEP) is set too low.

The current PEEP level for patients with ARDS is set according to the
ventilation protocol applicable in the Intensive Care Unit (ICU). This PEEP
level can be adjusted in complex-to-ventilate patients using Electrical
Impedance Tomography (EIT) or transesophageal pressure measurement (Pes). With
Pes, the transpulmonary pressure corresponding to pleural pressure (PL) is
measured.

Patients undergoing elective cardiothoracic surgical procedures rarely fall
into the complex or prolonged ventilation category. At the same time, their P/F
ratio is often equivalent to that associated with (mild) ARDS, given the
incidence of atelectasis. The hypothesis is that, considering the occurrence of
atelectasis, individually adjusting the optimal PEEP level using EIT or Pes in
this patient group will lead to a reduction in atelectasis and a concomitant
improvement in the P/F ratio.

This study will initially focus on gaining insight into the difference between
the current set PEEP level following cardiothoracic surgery compared to
individually adjusting the PEEP level using EIT or Pes.

Randomized Pilot Study at Erasmus MC in Pressure-Controlled Ventilated Patients
Following Elective Cardiothoracic Surgery in the ICU.

Participants will be randomly allocated into two groups. One group will have
their settings determined through Electrical Impedance Tomography (EIT)
measurements, while the other group will have their settings determined through
transesophageal pressure (Pes) measurements.

PCV (Pressure Control Ventilation) is standard care in the ICU after
cardiothoracic surgery. Patients typically remain sedated and ventilated for an
average of one to two hours before extubation. This study is not expected to
cause significant delays in this process. Blood gas analysis to calculate the
P/F ratio is routine care. Within the ventilation protocol, decremental PEEP
trials, EIT measurements, and Pes measurements are included as interventions
for challenging-to-ventilate patients. These interventions are not currently
applied to the study population since they are generally extubated within a few
hours. EIT and Pes measurements are used in this study because they provide the
most reliable information for adjusting the optimal PEEP level.

The assessment is that this pilot study has a low burden with low risks. The
interventions performed are already part of the ventilation protocol and are
commonly carried out. The only difference now is that these interventions are
performed in a different patient category. The risks of the interventions are:
* Risk of a nosebleed due to the insertion of the balloon catheter.
* A very small chance of pneumothorax due to the decremental PEEP trial that is
conducted.