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Development of a Novel Infant Volumetric Capnography Simulator: Making the Invisible Visible Improves Understanding
Marcelo D Campos1, Ariel Bonardi, Lucio H Palazzi
1From the Department of Anesthesiology (M.D.C.), Sanatorio Finochietto, Buenos Aires, Argentina; Simulation Center of Buenos Aires Association of Anesthesia (A.B.), Analgesia y Reanimation, Buenos Aires, Argentina; Department of Anesthesiology (L.H.P.), Children Hospital Dr. Orlando Alassia, Santa Fe, Argentina; Instituto Tecnológico Buenos Aires (ITBA) (M.M.), Buenos Aires, Argentina; Department of Anesthesiology and Intensive Care Medicine (S.H.B.), Rostock University Medical Center, Rostock, Germany; and Department of Anesthesia (G.T.), Hospital Privado de Comunidad, Mar del Plata, Argentina.
Introduction:
Volumetric capnography depicts volumetric capnograms [ie, the plot of expired carbon dioxide (CO 2 ) over the tidal volume]. This bench study aimed to determine the reliability, accuracy, and precision of a novel infant simulator for volumetric capnography. This simulator would be clinically valuable for teaching purposes because it reflects the entire cardiopulmonary physiology within 1 breath.
Methods:
An infant lung simulator was fed with CO 2 supplied by a mass flow controller (VCO 2-IN ) and ventilated using standard settings. A volumetric capnograph was placed between the endotracheal tube and the ventilatory circuit. We simulated ventilated babies of different body weights (2, 2.5, 3, and 5 kg) with a VCO 2 ranging from 12 to 30 mL/min. The correlation coefficient ( r2 ), bias, coefficient of variation (CV = SD/ x × 100), and precision (2 × CV) between the VCO 2-IN and the elimination of CO 2 recorded by the capnograph (VCO 2-OUT ) were calculated. The quality of the capnogram's waveforms was compared with real ones belonging to anesthetized infants using an 8-point scoring system, where 6 points or greater meant that the simulated capnogram showed good, 5 to 3 points acceptable, and less than 3 points an unacceptable shape.
Results:
The correlation between VCO 2-IN and VCO 2-OUT was r2 = 0.9953 ( P < 0.001), with a bias of 0.16 (95% confidence intervals from 0.12 to 0.20) mL/min. The CV was 5% or less and the precision was 10% or less. All simulated capnograms showed similar shapes compared with real babies, scoring 6 points for 3 kg and 6.5 points for 2-, 2.5-, and 5-kg babies.
Conclusions:
The simulator of volumetric capnograms was reliable, accurate, and precise for simulating the CO 2 kinetics of ventilated infants.
