Topographic Distribution of Tidal Ventilation in Acute Respiratory Distress Syndrome

Abstract

In patients with acute respiratory distress syndrome undergoing pressure support ventilation, higher positive end-expiratory pressure and lower support levels increase the fraction of tidal ventilation reaching dependent lung regions, yielding more homogeneous ventilation and, possibly, better ventilation/perfusion coupling.

Ocena regionalnej wentylacji w zespole ostrej niewydolności oddechowej za pomocą elektrycznej tomografii impedancyjnej

“…A similar observation was made by Blankmann et al showing that lower inspiration support, both in PCV and neurally adjusted ventilatory assist mode (NAVA), provided better conditions of ventilation in dependent regions [24]. EIT imaging demonstrated that improvement of aeration of dependent lung sectors could be achieved by recruitment with positive end-expiratory pressure or by increased involvement of the diaphragm in initiation of inspiration [23,24].…”

Effects of Sigh on Regional Lung Strain and Ventilation Heterogeneity in Acute Respiratory Failure Patients Undergoing Assisted Mechanical Ventilation*

“…EIT data were generated by application of small alternate electrical currents rotating around patient's thorax and stored for offline analysis, as previously described (16)(17)(18). Airway pressure, flow, and volume tracings were continuously recorded.…”

“…For this purpose, we assessed regional dynamic lung imaging by electrical impedance tomography (EIT): a noninvasive, radiation-free, bedside lung imaging technique, which tracks changes in regional lung impedance, corresponding to changes in regional gas content (16)(17)(18). By EIT, we measured the changes induced by Sigh on regional Vt, regional EELV, and the heterogeneity of ventilation distribution.…”

“…By EIT, we measured the changes induced by Sigh on regional Vt, regional EELV, and the heterogeneity of ventilation distribution. Thus, in this study, we directly assessed regional strain (i.e., regional Vt/EELV ratio) while, based on sound physiological background and previous studies (4), heterogeneity of ventilation distribution (18) was considered close surrogate of regional heterogeneity of lung structure (3). Finally, we delivered Sigh at different mandatory rates in an effort to identify its "minimum effective dose.…”

Lung imaging: how to get better look inside the lung

“…In ARDS patients, EIT can visualize directly and non-invasively the effects of mechanical ventilation at the bedside, potentially helping the clinician to titrate ventilation parameters (52,53). In ARDS, interstitial oedema increases the effects of gravity dependent lung regions, and EIT can detect such loss of aeration along with compensatory increases in ventilation of ventral regions (49,50,53).…”