The purpose of this study was to compare the Jackson-Rees circuit with the pediatric circle and MERA F breathing system (MERA F system) for pediatric anesthesia from the viewpoint of work of breathing (WOB). Twenty-three children (2-10 yr old) were studied during spontaneous breathing under endotracheal anesthesia with 4 L/min nitrous oxide, 2 L/min oxygen, and 1% end-tidal concentration of sevoflurane. WOB, inspiratory and expiratory airway resistance, dynamic compliance (CDYN), pressure time product (PTP), and arterial blood gasses were measured in the three circuits. The inspiratory WOB was estimated directly by measuring the esophageal pressure-volume loop using the Campbell technique. In a laboratory study, we measured the compliances of the Jackson-Rees circuit, the pediatric circle, the MERA F system, and the adult circuit. WOB differed among the three circuits (MERA F system > pediatric circle > Jackson-Rees circuit). Inspiratory and expiratory resistances, and arterial carbon dioxide tension in the Jackson-Rees circuit were significantly lower than those of both the pediatric circle and MERA F system. The CDYN and PTP in the MERA F system were significantly higher than those in both the Jackson-Rees circuit and the pediatric circle. The MERA F system had significantly higher compliance than the Jackson-Rees circuit and pediatric circle. It is concluded that the Jackson-Rees circuit is most efficient, the pediatric circle is intermediate, and the MERA F system is the least efficient from the viewpoint of WOB during spontaneous breathing for pediatric anesthesia.

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Purpose: To compare the effectiveness of three patient-triggered ventilators by evaluating triggering delay time and pressure-volume loops during initiation of inspiration. Methods: In a two-part study, a model lung was used in part I and 20 children, after tracheal intubation, in part 2. Triggering delay time and work of breathing 0AIOB) during pressure support ventilation using three patient-triggered ventilators: Servo Ventilator 300 TM VIP Bird", and SLE 2000 Neonatal Ventilator TM. Triggering delay time was from the beginning of negative deflection in the oesophage~ pressure trace, to the onset of inspiration. The WOB was estimated directly by measuring the oesophageal pressure-volume loop. Objectif: Comparer l'efficacit~ de trois respirateurs d&lench& par le patient en ~valuant le d~lai et les courbes pression-volume durant la phase initiale de l'inspiration. M&hodes : Dans cette ~tude en 2 volets, un module pulrnonaire a ~t~ utilis~ pour la premi&e pattie et 20 enfants intub~s pour la deuxi~me. On a ~tudi~ le d~lai de d&lenchement de l'appareil et le travail respiratoire (-l-R) durant la ventilation selon le mode pression de support en utilisant trois respirateurs d&lench& par le patient : le ventilateur Servo 300@, le Bird VIP@ et le SLE 2000 Neonatal Ventilator~. Le d~lal de d~clenchement de l'appareil a ~t~ calcul~ ~ partit du d~but de la d~fection n~gative sur le trac~ de pression oesophagienne jusqu'au d~but de rinspiration. Le TR a ~t~ estim~ directement en mesurant la boucle pression-volume oesophagienne. RA.suitats : Le Servo a d~montrE un meilleur d~lai de d&lenchement et un TR rEduit darts l'&ude utilisant le module pulmonaire. Le Bird VIP a d~montr~ un d~lai plus court et un TR diminu~ darts la partie clinique de l'~tude. Dans le module pulmonaire, le d~lai de d&lenchement du Servo 300 (62 ___ 6 msec (moyenne + &art type)) a ~t~ plus court que celui du Bird VIP (76 • 7 msec) (P<0,05), et le TR avec le SLE 2000 (202 ___ 37 g.cm) a ~t~ plus grand qu'avec les deux autres ventilateurs (Servo 300, 112 ___ 32 g'cm et Bird VIP 72 • 41 g'cm) (P<0,05), Darts la partie clinique de r&ude, le d~lai de d&lenchement du Bird VIP (52 ___ 19 msec) a ~t~ plus court qu'avec les autres ventilateurs, Servo 300 (66 ---14 msec) et SLE 2000 (68 • 65 msec) (P<0,05). Le TR du Servo 300 (56 • 34 g.cm) a ~t~ plus ~lev~ que celui des deux autres ventilateurs : Bird VIP (22 ___ 12 g-cm) et SLE 2000 (14 ___ 3 g-cm) (P<0,05). Conclusion : La performance de ces ventilateurs dans le modEle pulmonaire ne correspond pas ~ leur performance clinique. Au cours de notre ~valuation clinique, le Bird VIP a d6montr6 une performance sup&ieure aux autres avec un d61ai de dEclenchement moindre, un faible TR pour initier l'inspiration et peu de fuite5 d'air.

The alveolar-arterial O2 difference (A-a DO2) decreased at severe metabolic acidosis in the three cyanotic infants.Case 1. A 47-day-old infant was diagnosed as Tetralogy of Fallot and operated on for a subclavian-pulmonary shunt. The A-a DO2 decreased from 120mmHg to 81mmHg at severe metabolic acidosis after the surgery.Case 2. A 9-day-old infant was diagnosed as giant hemangioma in the liver. The A-a DO2 decreased from 220mmHg to 80mmHg at severe metabolic acidosis after the angiography.Case 3. A 53-day-old infant was diagnosed as Tetralogy of Fallot and operated on for an aorto-pulmonary shunt. A cardiac arrest occured during the surgery but it was successful in a resuscitation. The A-a DO2 decreased from 650mmHg to 400mmHg at severe metabolic acidosis after the resuscitation.The A-a DO2 could be decreased by the increase of PvO2, the decrease of the intra cardiac right to left shunt and the improvement of V/Q. On the other hand, it also might be decreased directly by the H+ ion. The decrease of pH and the increase of PO2 were observed at the same time after a little addition of weak HC1 to the other patient's arterial blood.The A-a DO2 might be decreased by the right shift of the oxygen dissociation curve.