Effect of general anesthesia and controlled mechanical ventilation on pulmonary ventilation distribution assessed by electrical impedance tomography in healthy children

Abstract

Introduction: General anesthesia is associated with the development of atelectasis, which may affect lung ventilation. Electrical impedance tomography (EIT) is a noninvasive imaging tool that allows monitoring in real time the topographical changes in aeration and ventilation.

Objective: To evaluate the pattern of distribution of pulmonary ventilation through EIT before and after anesthesia induction in pediatric patients without lung disease undergoing nonthoracic surgery.

Methods: This was a prospective observational study including healthy children younger than 5 years who underwent nonthoracic surgery. Monitoring was performed continuously before and throughout the surgical period. Data analysis was divided into 5 periods: induction (spontaneous breathing, SB), ventilation-5min, ventilation-30min, ventilation-late and recovery-SB. In addition to demographic data, mechanical ventilation parameters were also collected. Ventilation impedance (Delta Z) and pulmonary ventilation distribution were analyzed cycle by cycle at the 5 periods.

Results: Twenty patients were included, and redistribution of ventilation from the posterior to the anterior region was observed with the beginning of mechanical ventilation: on average, the percentage ventilation distribution in the dorsal region decreased from 54%(IC95%:49-60%) to 49%(IC95%:44-54%). With the restoration of spontaneous breathing, ventilation in the posterior region was restored.

Conclusion: There were significant pulmonary changes observed during anesthesia and controlled mechanical ventilation in children younger than 5 years, mirroring the findings previously described adults. Monitoring these changes may contribute to guiding the individualized settings of the mechanical ventilator with the goal to prevent postoperative complications.

Conflict of interest statement

Letícia C. Corrêa and Glasiele C. Alcala are employees of Timpel S.A.; Eduardo Leite and Felipe S. Rossi are Timpel S.A. consultants, Marcelo B. P. Amato is Timpel S.A. consultant and minority shareholder. The other authors declare no competing interests. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Copyright: © 2023 Nascimento et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Figures

Fig 1. Plethysmogram representing the total monitoring time with EIT.

The white tracing represents the variation in ventilation over time. Delta Z (double arrow) represents the tidal variation in impedance and is associated with tidal volume. The vertical dashed lines indicate the periods studied during monitoring: induction-SB (spontaneous breathing before anesthesia induction), MV-5min (initial five minutes of controlled ventilation), MV-30min (after 30 minutes of controlled ventilation), MV-late (final 5 minutes of controlled ventilation) and recovery-SB (after removal of the artificial airway and resumption of spontaneous breathing).

Fig 2. Distribution of pulmonary ventilation assessed by the dorsal ventilation fraction in the anterior and posterior regions presented over the five time points: Induction-SB, MV-5min, MV-30min, MV-late and recovery-SB.

The dorsal ventilation fraction is calculated by the ratio of the Delta Z of the posterior region to the global Delta Z multiplied by 100. Significant variations were observed in the ventilation distribution measures demonstrated in percentage when compared MV-5min, MV-30min and MV-late to induction-SB.

Fig 3. Distribution of pulmonary ventilation assessed by center of ventilation (CoV) presented over the five time points: Induction-SB, MV-5min, MV-30min, MV-late and recovery-SB.

The CoV is a parameter that quantifies the distribution of ventilation. When we have a value of 50 it means that ventilation is equally distributed between the anterior and posterior regions of the thorax. Higher numbers indicate a shift towards the dorsal region, and lower numbers indicate a shift towards the ventral region. Significant variations were observed in the ventilation distribution measures demonstrated in percentage when compared MV-5min, MV-30min and MV-late to induction-SB.

Fig 4

Impedance change (Delta Z) in the global (A) and in the anterior (B) and posterior (C) regions over the five periods: induction-SB, MV-5min, MV-30min, MV-late and recovery-SB. Significant variations were observed in the measurements of global and anterior Delta Z compared all mechanical ventilation time to induction-SB. Gray dots represent multiple measurements (respiratory cycles) at each time point from all patients. Gray lines describe the average behavior from each patient. Error bars represent the confidence interval with mean (open red circle).