[Monitoring airway pressure in pediatric anesthesia: an experimental model of intratracheal medication and pressure-volume loops].
BACKGROUND
In the monitoring of anesthesia, airway pressure is measured in the ventilator or at the closest possible connection to the endotracheal tube.


OBJECTIVE
To compare the airway pressures and pressure-volume loops obtained before connection to the endotracheal tube with those obtained in the trachea.


METHODS
We carried out a single-blind prospective observational study on ASA 1 patients between the ages of 7 and 12 years ventilated in volume-control mode with an inspiration-to-expiration ratio of 1:2. Intratracheal and extratracheal peak and plateau pressures and pressure-volume loops were recorded. A special device was designed to monitor intratracheal pressure. Both sensors were connected to the same spirometric analysis system. The variables were measured on intubation and 5, 10, 15, 20, 30, 40, 50, and 60 minutes after intubation. The recorded pressures were compared using the t test, the Pearson product moment correlation coefficient (r), and the Spearman rank correlation coefficient (p), and regression models were fit to the data.


RESULTS
Seventy-one patients were enrolled. The mean (SD) pressure difference between the 2 systems was 3.5 (0.35) cm H2O (P < .01) and no differences between the endotracheal peak pressures and the plateau pressures were observed. The intratracheal areas of the pressure-volume loops were 15% lower than the extratracheal areas. The value of r for the correlation between the intratracheal peak and plateau pressures was 0.998 (P < .01). The value of r for the correlation between the intratracheal and extratracheal peak pressures was 0.981 (P < .01). Analysis of variance confirmed the linear relationship.


CONCLUSIONS
The difference between the intratracheal and extratracheal pressure measurements is due to the different locations at which the measurements are taken.
Abad Gurumeta
A
A
Servicio de Anestesiología, Hospital General Universitario Gregorio Marañón, Madrid. alfredo_abadg@hotmail.com
Calvo Vecino
J M
JM
San Norberto García
L
L
Muñoz Avalos
N
N
Pérez Gallardo
A
A
Gilsanz Rodríguez
F
F
D000769:Anesthesia, Inhalation / Q000379:methods*; D018685:Anesthetics, Inhalation; D002648:Child; D005260:Female; D005740:Gases; D006439:Hemodynamics; D006801:Humans; D007442:Intubation, Intratracheal; D008297:Male; D008365:Manometry / Q000295:instrumentation; D008738:Methyl Ethers; D008962:Models, Theoretical; D008991:Monitoring, Physiologic / Q000295:instrumentation; D009609:Nitrous Oxide; D011175:Positive-Pressure Respiration; D011229:Preanesthetic Medication; D011446:Prospective Studies; D015656:Respiratory Mechanics; D000077149:Sevoflurane; D016037:Single-Blind Method; D013147:Spirometry / Q000295:instrumentation; D014132:Trachea
D018685:Anesthetics, Inhalation; D005740:Gases; D008738:Methyl Ethers; D000077149:Sevoflurane; D009609:Nitrous Oxide