Abstract
With electrical impedance tomography (EIT) recruitment and de-recruitment phenomena can be quantified and monitored at bedside. The aim was to examine the feasibility of EIT with respect to monitor atelectasis formation and resolution in the post anesthesia care unit (PACU). In this observational study, 107 postoperative patients were investigated regarding the presence and recovery of atelectasis described by the EIT-derived parameters Global Inhomogeneity Index (GI Index), tidal impedance variation (TIV), and the changes in end-expiratory lung impedance (ΔEELI). We examined whether the presence of obesity (ADP group) has an influence on pulmonary recovery compared to normal weight patients (NWP group). During the stay at PACU, measurements were taken every 15 min. GI Index, TIV, and ΔEELI were calculated for each time point. 107 patients were monitored and EIT-data of 16 patients were excluded for various reasons. EIT-data of 91 patients were analyzed off-line. Their length of stay averaged 80 min (25th and 75th quartile 52–112). The ADP group demonstrated a significantly higher GI Index at PACU arrival (p < 0.001). This finding disappeared during their stay at the PACU. Additionally, the ADP group showed a significant increase in ΔEELI between PACU arrival and discharge (p = 0.025). Furthermore, TIV showed a significantly lower value during the first 90 min of PACU stay as compared to the time period thereafter (p = 0.036). Our findings demonstrate that obesity has an influence on intraoperative atelectasis formation and de-recruitment during PACU stay. The application of EIT in spontaneously breathing PACU patients seems meaningful in monitoring pulmonary recovery.
Highlights
The risks for postoperative pulmonary complications are multifactorial, including patient-related factors like obesity [1]
The following three major findings of the current study should be discussed: (1) ΔEELI significantly increased during the post anesthesia care unit (PACU) stay in assigned to the obesity group (ADP); (2) when comparing the time periods of (A) the first 90 min and (B) 90 to 180 min, tidal impedance variation (TIV) was higher during (B) in the ADP group as well; (3) initially, GI differed between normal weight patient group (NWP) and ADP, but not anymore after discharge from PACU
Our data demonstrate the feasible use of Electrical impedance tomography (EIT) in postoperative patients in the PACU
Summary
The risks for postoperative pulmonary complications are multifactorial, including patient-related factors like obesity [1]. A more frequent postoperative pulmonary complication is atelectasis formation that occur usually in the dependent parts of the lungs of most anesthetized patients [2, 3]. In addition to the use of high oxygen concentration and the loss of muscle tone, surfactant depletion and the compression of lung tissue facilitate atelectasis formation. Parts of the study were presented in the doctoral theses of Torsten Kapell and Martin Dürbaum. Electrical impedance tomography (EIT) is a radiationfree, bedside-available, and non-invasive technique, which is able to visualize ventilation in time and spatial domains [8] and has already been studied in many areas related to ventilation [9, 10].
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