Pulmonary pathophysiology development of COVID-19 assessed by serial Electrical Impedance Tomography in the MaastrICCht cohort

Abstract

Patients with SARS-CoV-2 infection present with different lung compliance and progression of disease differs. Measures of lung mechanics in SARS-CoV-2 patients may unravel different pathophysiologic mechanisms during mechanical ventilation. The objective of this prospective observational study is to describe whether Electrical Impedance Tomography (EIT) guided positive end-expiratory pressure (PEEP) levels unravel changes in EIT-derived parameters over time and whether the changes differ between survivors and non-survivors. Serial EIT-measurements of alveolar overdistension, collapse, and compliance change in ventilated SARS-CoV-2 patients were analysed. In 80 out of 94 patients, we took 283 EIT measurements (93 from day 1-3 after intubation, 66 from day 4-6, and 124 from day 7 and beyond). Fifty-one patients (64%) survived the ICU. At admission mean PaO₂/FiO₂-ratio was 184.3 (SD 61.4) vs. 151.3 (SD 54.4) mmHg, (p = 0.017) and PEEP was 11.8 (SD 2.8) cmH₂O vs. 11.3 (SD 3.4) cmH₂O, (p = 0.475), for ICU survivors and non-survivors. At day 1-3, compliance was ~ 55 mL/cmH₂O vs. ~ 45 mL/cmH₂O in survivors vs. non-survivors. The intersection of overdistension and collapse curves appeared similar at a PEEP of ~ 12-13 cmH₂O. At day 4-6 compliance changed to ~ 50 mL/cmH₂O vs. ~ 38 mL/cmH₂O. At day 7 and beyond, compliance was ~ 38 mL/cmH₂O with the intersection at a PEEP of ~ 9 cmH₂O vs. ~ 25 mL/cmH₂O with overdistension intersecting at collapse curves at a PEEP of ~ 7 cmH₂O. Surviving SARS-CoV-2 patients show more favourable EIT-derived parameters and a higher compliance compared to non-survivors over time. This knowledge is valuable for discovering the different groups.

Figure 1

Study sample. Patients and good and intermediate quality serial EIT measurements during pressure control mode ventilation. Observations > 7 may include a range of 8 to 17 EIT observations, resulting in a total of 334. ICU, intensive care unit; EIT, electrical impedance tomography; PC, pressure control mode ventilation; PS, pressure support mode ventilation; CPAP, continuous positive airway pressure mode ventilation.

Figure 2

PaO₂/FiO₂-ratio (mmHg) and PEEP (cmH₂O) for survivors and non-survivors over time. (A): PaO₂/FiO₂-ratio for survivors (black) and non-survivors (red) over time; (B): positive end-expiratory pressure (PEEP) for survivors and non-survivors over time; (C): driving pressure for survivors and non-survivors over time.

Figure 3

Dynamic respiratory system compliance, alveolar overdistension, and alveolar collapse for the whole population from admission to beyond a week after. EIT population curves that show mean (solid lines), dynamic compliance (green), overdistension (blue), and collapse (yellow) with 95% confidence intervals (dashed lines) for the whole population from PEEP steps 28 to 8 cmH₂O over time for the first 3 days (A), day 4, 5 and 6 (B) and day 7 and above (C).

Figure 4

Dynamic respiratory system compliance, alveolar overdistension, and alveolar collapse for the whole population from admission to beyond a week after in ICU survivors and ICU non-survivors. EIT population curves that show mean (solid lines), dynamic compliance (green), overdistension (blue), and collapse (yellow) with 95% confidence intervals (dashed lines) from PEEP steps 28 to 8 cmH₂O for ICU non-survivors over time for the first 3 days (A), for day 4, 5 and 6 (B) and for day 7 and above (C); and for ICU survivors over time for the first 3 days (D), for day 4, 5 and 6 (E) and for day 7 and above (F).