Electrical impedance tomography (EIT) is a recent monitoring technique that provides information on regional ventilation distribution. Following the injection of a hypertonic saline bolus, EIT can also assess regional pulmonary perfusion distribution, allowing evaluation of the ventilation/perfusion (V/Q) ratio.
In adults, protocols for assessing perfusion distribution require the injection of 10 mL of a 7.5% or 10% NaCl solution or sodium bicarbonate over a few seconds. Studies have reported good hemodynamic tolerance, adequate image quality, and no significant changes in serum sodium levels. However, this volume and sodium load are not appropriate for small children.
To date, no pediatric protocol exists for assessing pulmonary perfusion distribution and the ventilation/perfusion ratio using EIT. It is therefore proposed to conduct a pilot study to evaluate the feasibility of assessing pulmonary perfusion by EIT using a weight-adjusted bolus of hypertonic saline (NaCl or sodium bicarbonate).
patients < 12 years hospitalized in pediatric intensive care
intubated, under conventional invasive mechanical ventilation and sedated
between 3 and 40 kg
with central venous access in the superior vena cava
Patients with significant leaks > 20% around the endotracheal tube
Patients receiving spontaneous ventilation (inspiratory support, NIV, etc.)
Natremia > 150 mmol/L at inclusion
Hyperchloremia ≥ 115 mmol/L and/or hypokaliema ≤ 3 mmol/L
Sequential
Evaluation of perfusion with Electrical impedance tomography using sodium chloride or sodium bicarbonate
Other interventionAll patients will undergo EIT monitoring (Enlight 2100, Timpel, Brazil) using a belt adjusted to the thoracic circumference. Ventilation distribution will be assessed with a tidal volume of 8 mL/kg. Following a breath hold, a saline solution (sodium chloride or sodium bicarbonate) will be injected over a few seconds. Perfusion distribution, as well as impedance signal variation, will be recorded using dedicated software (Timpel, Brazil). Data acquisition will be considered valid if the impedance signal variation induced by the saline solution injection is at least equivalent to the amplitude variation observed during ventilation with a tidal volume of 8 mL/kg. 2 measurements at 4 to 6-hours intervals with volume or concentration adjustment after the first injection if needed in the group 1
Proportion of patients with pulmonary perfusion acquisition consider as valid
Data acquisition will be considered valid if the impedance signal variation induced by the saline solution injection is at least equivalent to the amplitude variation observed during ventilation with a tidal volume of 8 mL/kg.
Proportion of patients requiring an increase in volume and/or concentration of saline solution
Increase in the volume and/or concentration of the saline solution due to insufficient signal detection during the first injection (Group 1).
Proportion of respiratory acquisition failures explained by breathing movements
Data acquisition failure related to variations in the airway pressure waveform recorded by the software.
Distribution of pulmonary perfusion
Description of the distribution of regional pulmonary perfusion in children, expressed as percentages across predefined regions of interest (right versus left and anterior versus posterior).
Natremia variation after injection
Serum sodium concentration (mmol/L) measured before and after injection, with calculation of absolute (mmol/L) and relative (%) changes.
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