Usefulness of continuous monitoring of airway resistance and flow-volume curve in the perioperative management of infants with central airway obstruction: A case of vascular ring

Abstract

In the treatment of vascular ring, repair of the trachea and esophagus or aortopexy is often necessary in addition to resection of the vessels. 1,2 Although the decision is made mainly on the basis of the preoperative computed tomographic or magnetic resonance images or intraoperative bronchoscopic findings, the anatomic information may be insufficient.We report here the usefulness of expiratory airway resistance (Raw) and the flow-volume (FV) curve in a patient with vascular ring for the assessment of the immediate surgical effect during the operation and for deciding the timing of extubation. MethodPatients were anesthetized with fentanyl and pancuronium bromide. After intubation, measurement of pressure and flow was started and maintained by manual ventilation during the operation. The sensor was placed between the tracheal tube and the anesthesia equipment in the operating room or the respirator in the intensive care unit. Pressure and flow were measured simultaneously with a CO 2 SMO Plus! monitor (Novametrix Medical Systems Inc, Wallingford, Conn), and Raw was calculated as driving pressure divided by maximum expiratory flow. Raw and the FV curve were displayed in real time on a personal computer connected to the CO 2 SMO Plus! monitor. All digital data were stored. FV curves were sampled over a 5-minute period every 15 minutes, and all data were stored.Ten consecutive FV curves in which the tidal volume was between 50 and 60 mL were reproduced from the data, and the mean tidal volume and the mean minimum volume were calculated. The expiratory flow at the midpoint between the mean tidal volume and the mean minimum volume was measured, and the ratio to the maximum expiratory flow (V 50 ) was calculated (Figure 1, A and B). V 50 was determined preoperatively, immediately after intubation, after the tracheal tube was placed below the stenotic sites, before and after resection of the vascular ring, after withdrawal of the tracheal tube above the stenotic sites, and several times in the intensive care unit.For control values, after the induction of anesthesia, V 50 was measured in the same way, and mean Raw was determined from continuous measurements over 60 minutes (Figure 2) in 26 patients with congenital heart disease without airway obstruction (body weight 3.3-23.6 kg, mean 9.1 kg, SD 5.5 kg). Statistical AnalysisThe correlations between body weight and Raw and between body weight and V 50 were examined in control subjects, and the correlation between the data was tested by the F test. Clinical SummaryA 7-month-old girl with a previous diagnosis of corrected transposition of the great arteries, pulmonary stenosis, ventricular septal defect, and right aortic arch was admitted to our hospital for cardiac catheterization. Increased wheezing since birth had been noted, and