Study objectives: To quantify thoracoabdominal asynchrony (TAA) in children during anesthesia, and to measure the effect of continuous positive airway pressure (CPAP) on TAA, tidal volume (Vt), and minute ventilation (V̇e).
Design: Prospective, nonrandomized, controlled study.
Setting: Operating room of a university children’s hospital.
Participants: Ninety children aged 2 to 9 years scheduled for elective outpatient day surgery who were enrolled prospectively.
Methods: Each subject was anesthetized with sevoflurane 3% in equal parts O2 and N2O while breathing spontaneously through a facemask. Respiratory impedance plethysmography was used to calculate TAA indexes (phase angle [PA], phase relation in inspiration [PhRIB], phase relation in expiration, phase relation in total breath [PhRTB], and ratio of the inspiratory time to the total duration of the respiratory cycle [Ti/Ttot]), Vt, and V̇e. Tidal gas flows were measured with a dual-hotwire anemometer with the sensor inserted between the facemask and the Y-piece of the anesthetic breathing circuit. This enabled the volume calibration of the respiratory impedance plethysmography equipment. The following conditions were compared: (1) no CPAP, (2) CPAP of 5 cm H2O, and (3) CPAP of 10 cm H2O.
Results: Eighty-one children completed the study protocol. All measurements of TAA with an inspiratory component (PA, PhRIB, PhRTB, and Ti/Ttot) decreased significantly from baseline with the addition of CPAP to the circuit. Application of CPAP of 10 cm H2O decreased significantly mean Vts and V̇es compared with CPAP of 5 cm H2O and no CPAP. There were no differences in TAA for all conditions when comparing children scheduled for adenoidectomy with other surgical procedures.
Conclusions: With spontaneously breathing anesthetized children, TAA decreases with the application of CPAP. CPAP of 5 cm H2O was as effective as CPAP of 10 cm H2O in reducing PA, PhRIB, PhRTB, and Ti/Ttot. However, CPAP of 10 cm H2O also caused a significant decrease in Vt and V̇e.