Personalized ventilation guided by electrical impedance tomography with increased PEEP improves ventilation-perfusion matching in asymmetrical airway

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Summary of “Personalized ventilation guided by electrical impedance tomography with increased PEEP improves ventilation‐perfusion matching in asymmetrical airway closure and contralateral pulmonary embolism during veno‐venous extracorporeal membrane oxygenation: A case report”

Abstract

This case report describes a novel use of electrical impedance tomography (EIT) to guide personalized PEEP adjustments in a 54-year-old patient on ECMO with right lung pneumonia and contralateral pulmonary embolism (PE). By using EIT to assess ventilation and perfusion in real time, clinicians adjusted PEEP to exceed the airway opening pressure (AOP) of the injured lung, improving V/Q matching, oxygenation, and hemodynamics without compromising cardiovascular stability. The findings illustrate the value of individualized, physiology-based ventilation strategies in complex critical care scenarios.

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Panels (a) and (b) illustrate electrical impedance tomography (EIT) recordings obtained over 15 min following a recruitment maneuver (RM). This RM consisted of two sustained inflations at 40 cmH₂O, each lasting 20 s, performed at PEEP levels of 12 cmH₂O and 20 cmH₂O, respectively. The regions of interest (ROIs) are designated as follows: ROI 1 and ROI 3 represent the ventral and dorsal regions of the right lung, while ROI 2 and ROI 4 correspond to the ventral and dorsal regions of the left lung. In Panel (a), the EIT recordings show an initial rise in end-expiratory lung impedance (EELI) immediately after the RM, which then rapidly decayed over time. Specifically, the right lung, affected by pneumonia, exhibited a progressive loss of EELI, as indicated by the marked decline in impedance signals over time in ROI 1 (ventral) and ROI 3 (dorsal). Conversely, in the left lung, which was affected by pulmonary embolism, ROI 2 (ventral) showed no significant increase in EELI post-recruitment, whereas ROI 4 (dorsal) displayed an initial rise in EELI, which gradually decreased over time. The tidal ventilation distribution images further highlight that ventilation was predominantly confined to the left lung. This is evidenced by clear impedance variations in ROI 2 and ROI 4, in contrast to the minimal impedance changes observed in ROI 1 and ROI 3 of the right lung. Panel (b) shows that the increased PEEP raised global EELI, which remained stable over time, though minor decay persisted in the dorsal region of the right lung (ROI 3). Tidal ventilation in ROI 1 and 3 of the right lung increased, as indicated by the greater amplitude of the impedance variation in these ROIs compared to PEEP of 12 cmH2O. However, the higher PEEP caused overdistension in ventral regions, as evidenced by reduced impedance variation in ROI 2 of the left lung. Regional compliance analysis further confirmed this pattern: At 12 cmH₂O PEEP, ventral compliance was 27 mL/cmH₂O compared to 21 mL/cmH₂O in dorsal regions; at 20 cmH₂O PEEP, ventral compliance decreased to 15 mL/cmH₂O, while dorsal compliance increased to 29 mL/cmH₂O.

Key Points:

  1. Clinical Background: The patient had severe refractory hypoxemia caused by asymmetrical lung injury—right-sided pneumonia and left-sided PE—complicating ventilator management and requiring VV-ECMO.

  2. Initial EIT Findings at PEEP 12 cmH₂O: EIT revealed ventilation was predominantly in the left lung, while perfusion remained primarily in the right lung, creating severe V/Q mismatch due to dead space and shunt physiology.

  3. PEEP Personalization Based on AOP: EIT-guided low-flow inflation identified differing AOPs: 8 cmH₂O in the left lung and 16 cmH₂O in the right (pneumonia-affected) lung. PEEP was increased to 20 cmH₂O to maintain right lung recruitment.

  4. Impact on Lung Mechanics: Higher PEEP improved EELI (end-expiratory lung impedance), especially in the right lung, indicating more sustained alveolar recruitment. Some overdistension was observed in ventral left lung regions.

  5. Ventilation-Perfusion Coupling Improvement: V/Q matching improved from 29% to 41.7%, while unmatched perfusion (shunt) dropped from 21.7% to 12.8%, and unmatched ventilation (dead space) decreased from 49.3% to 45.5%.

  6. Enhanced Gas Exchange: PaO₂ improved from 59 to 66 mmHg after PEEP titration, and SvO₂ rose from 84% to 85.5%, despite unchanged ECMO settings, suggesting improved pulmonary oxygenation efficiency.

  7. Cardiac Output and Hemodynamics: Cardiac output increased from 8.5 to 9.8 L/min with PEEP 20 cmH₂O, alongside a significant drop in pulmonary vascular resistance (from 169 to 122 dyn•s/cm⁵•m²), suggesting favorable right ventricular unloading.

  8. PE Confirmation and Resolution: EIT findings suggested a left-sided PE, which was later confirmed by CT scan. The patient underwent thromboaspiration, leading to further improvements in PaO₂ and FiO₂ weaning.

  9. Clinical Course and Outcome: The patient improved steadily, was weaned off ECMO by day 10, extubated by day 17, and discharged in stable condition on day 36. The underlying diagnosis was cryptogenic organizing pneumonia.

  10. Clinical Implication of EIT: EIT enabled real-time assessment of differential lung mechanics and perfusion, enabling physiology-based, bedside personalization of PEEP. It also served as a noninvasive early diagnostic clue for PE.

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The image shows the EIT recording obtained during a low flow inflation maneuver. It highlights the differential Airway Opening Pressure (AOP) in the right and left lungs (Rozé et al., 2024). Region of Interest 1 (ROI 1) represents the left lung, affected by pulmonary embolism (PE), with an AOP of 8 cmH₂O, while ROI 2 represents the right lung, affected by pneumonia, with an AOP of 16 cmH₂O.

Conclusion

This case highlights the clinical value of bedside EIT in tailoring mechanical ventilation in complex ICU patients. By adjusting PEEP to exceed the AOP of the consolidated lung, clinicians improved oxygenation and V/Q matching without compromising hemodynamics. Moreover, EIT identified perfusion defects consistent with PE, prompting timely imaging and intervention. This illustrates the potential of EIT as both a therapeutic and diagnostic tool in precision critical care.

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Panels (a) and (b) display ventilation at PEEP 12 and 20 cmH2O, respectively. Panels (c) and (d) display perfusion at PEEP 12 and 20 cmH2O, respectively. Panel (a) also includes a CT scan highlighting the lung parenchyma. The data indicate that ventilation was predominantly directed to the left lung, which was unaffected by pneumonia, while perfusion was primarily concentrated in the right lung. This mismatch was attributed to a pulmonary embolism affecting the left lung, a finding subsequently confirmed by a contrast-enhanced CT scan, shown in Panel (c). Panel (e) illustrates ventilation and perfusion matching at a clinical PEEP of 12 cmH₂O, while Panel

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Personalized ventilation guided by electrical impedance tomography with increased PEEP improves ventilation-perfusion matching in asymmetrical airway

Watch the following video on “Electrical Impedance Tomography Guided APRV” by Respiratory Associates

 

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