Dynamics of regional lung aeration determined by electrical impedance tomography in patients with acute respiratory distress syndrome

Abstract

BackgroundLung tissue of patients with acute respiratory distress syndrome (ARDS) is heterogeneously damaged and prone to develop atelectasis. During inflation, atelectatic regions may exhibit alveolar recruitment accompanied by prolonged filling with air in contrast to regions with already open alveoli with a fast increase in regional aeration. During deflation, derecruitment of injured regions is possible with ongoing loss in regional aeration. The aim of our study was to assess the dynamics of regional lung aeration in mechanically ventilated patients with ARDS and its dependency on positive end-expiratory pressure (PEEP) using electrical impedance tomography (EIT).MethodsTwelve lung healthy and twenty ARDS patients were examined by EIT during sustained step increases in airway pressure from 0, 8 and 15 cm H2O to 35 cm H2O and during subsequent step decrease to the corresponding PEEP. Regional EIT waveforms in the ventral and dorsal lung regions were fitted to bi-exponential equations. Regional fast and slow respiratory time constants and the sizes of the fast and slow compartments were subsequently calculated.ResultsARDS patients exhibited significantly lower fast and slow time constants than the lung healthy patients in ventral and dorsal regions. The time constants were significantly affected by PEEP and differed between the regions. The size of the fast compartment was significantly lower in ARDS patients than in patients with healthy lung under all studied conditions.ConclusionThese results show that regional lung mechanics can be assessed by EIT. They reflect the lower respiratory system compliance of injured lungs and imply more pronounced regional recruitment and derecruitment in ARDS patients.

Functional respiratory imaging, regional strain, and expiratory time constants at three levels of positive end expiratory pressure in an ex vivo pig model

“…Therefore, to mitigate VALI, investigators have attempted to more accurately measure important mechanical parameters of the lung such as e. Our results demonstrate that e RS decreased with increasing PEEP, an observation that has been previously documented and which was due to increased EELV RS in our experiment (Blankman et al 2016). More important than the fact that the techniques described in our study allow the measurement of e RS , is the ability to observe regional e. Heterogeneity in regional e has previously been observed using methods such as CT scans, electrical impedance plethysmography and forced oscillation techniques (Kaczka et al 2011b;Pulletz et al 2012;Wolf et al 2013;Cressoni et al 2014;da Paula et al 2016). We found that varied widely, with the highest strain lobes exposed to approximately threefold the strain of the lowest strain lobes (Fig.…”

Chest electrical impedance tomography examination, data analysis, terminology, clinical use and recommendations: consensus statement of the TRanslational EIT developmeNt stuDy group

“…58 The high scan rates allow the assessment of intratidal changes in regional C rs. 38 Another EIT measure of respiratory mechanics is the regional respiratory time constant 4459…”

“…Major heterogeneities in regional ventilation in diseases like ARDS,44 66 COPD,42 62 lung cancer76 or cystic fibrosis77 can be traced by EIT. The effects of ageing can also be detected 16…”

“…43 If EIT examination is performed during a stepwise inflation or deflation of the lungs then fitting of mathematical functions to pixel EIT waveforms may be used to calculate and image local respiratory time constants. 44 Combination of pixel EIT waveforms with other simultaneously registered signals like the airway pressure allows the generation of pixel pressure-volume curves 45 46 and generation of functional images showing, for example, regional lung opening and closing 47 or regional respiratory system compliance (C rs ). 48 Several types of functional images can be generated from a single EIT measurement.…”

Tomografia impedancyjna w diagnostyce i monitorowaniu zaburzeń funkcji płuc na oddziale intensywnej terapii — opis przypadku i przegląd piśmiennictwa

“…Moreover, it provides information about the side effects of mechanical ventilation enhanced by some diseases, i.e. ARDS, COPD, lung cancer, cystic fibrosis or ageing-associated processes [38][39][40]. Electrical impedance tomography has also been used to detect pleural oedema [41,42], changes in respiratory parameters after aspiration [43] and to evaluate onelung ventilation [44].…”