Respiratory failure & ventilation
Absolute values of regional ventilation-perfusion mismatch in patients with acute respiratory distress syndrome (ARDS) monitored by electrical impedance tomography and the role of dead space and shunt compensation
Authors' conclusion
Regional V'/Q maps calibrated with a non-invasive EIT-only method closely approximate the ones obtained with invasive monitoring. Higher efficiency of shunt compensation improves oxygenation while compensation of dead space is less needed at lower airway pressure.
Study context
- Population
- ARDS patients on controlled mechanical ventilation
- Participants
- 21 patients
- Comparison
- Electrical impedance tomography (EIT)-only corrected V'/Q maps (V'/Q-CORR) and unadjusted maps (V'/Q-REL) vs maps calibrated with invasive MV/CO (V'/Q-ABS)
- Outcome
- Agreement of non-invasive EIT-derived calibration factor (V'/Q-CORR) with invasive MV/CO ratio (V'/Q-ABS)
Main finding
As reported in the abstract
- Calibration factor correlated with invasive MV/CO (r)
- 0.65
- V'/Q-REL vs V'/Q-ABS: overestimated ventilation to low V'/Q units
- p = 0.013
- V'/Q-REL vs V'/Q-ABS: overestimated perfusion to low V'/Q units
- p = 0.002
- V'/Q-REL vs V'/Q-ABS: underestimated ventilation to high V'/Q units
- p = 0.011
- V'/Q-REL vs V'/Q-ABS: underestimated perfusion to high V'/Q units
- p = 0.008
- V'/Q-CORR eliminated all differences with V'/Q-ABS
- p > 0.05
Further findings
Shunt compensation index (V D ' /QSHUNT)
- Higher index correlated with higher PaO2/FiO2 (r)
- 0.49, p = 0.025
- Higher index correlated with lower shunt fraction (ρ)
- - 0.59, p = 0.005
- Lower index associated with fewer ventilator-free days
- P = 0.05
Dead space compensation index (QND/ V DS ' )
- Higher index correlated with lower PEEP (ρ)
- - 0.62, p = 0.003
- Higher index correlated with lower plateau pressure (ρ)
- - 0.59, p = 0.005
- Lower index associated with fewer ventilator-free days
- P = 0.03
Original publication
Absolute values of regional ventilation-perfusion mismatch in patients with ARDS monitored by electrical impedance tomography and the role of dead space and shunt compensation. Crit Care. Published 15 July 2024. doi:10.
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