PEEP Incremental and Decremental Alveolar Recruitment of Critically Ill COVID-19 Patients Under Electric Impedance Tomography (EIT)

COVID-19 originated from Severe Acut Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection leads to critical condition in 5% of the cases due to hypoxemic respiratory failure with the background of viral pneumonia. 90% of these patients require invasive mechanical ventilation on critical care units. Both alevolar recruitment and the subsequent optimal positive end-expiratory pressure (PEEP) adjustment has a pivotal role in the eliminitaion of atelectasis developed by inflammation in the lung parenchyma.

The gold standard of the follow up of recruitment manoeuvre is the chest computed tomography (CT) examination. However, reduction of intrahospital transport and the exposure with healthcare workers are recommended because of the extremely virulent pathogen spreading easily by droplet infection. In this case bedside investigations have an utmost importance in the management of hygiene regulations.

Electric impedance tomography (EIT) is a non-invasive, radiation free functional imaging technique easily applicable at the bedside. With the help of EIT, intrathoracic impedance changes, resulting from air and blood volume variations, can be determined by circumferentially attached surface electrodes around the thorax, applying small alternating currents and measuring differences in surface potentials. The calculated difference in potential is utilised to reconstruct impedance images what is employed to assess ventilation and perfusion distribution. Several local and global variances can be estimated just like the ratio fo atelectatic/overdistended alveoli, the ratio of aeration in the anterior/posterior regions, the inhomogeneity of aeration or regional compliance.