Anaesthesia
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Comparative Study
The importance of the expiratory pause. Comparison of the Mapleson A, C and D breathing systems using a lung model.
A physical lung model simulating spontaneous respiration was used to investigate the influence of the respiratory pattern on the efficiency of the Mapleson A, C and D breathing systems. It is shown that the Mapleson A system is always the most efficient breathing system and that its performance is relatively independent of the respiratory pattern. When the expiratory pause is minimal, the Mapleson C system is almost as efficient as the Mapleson A, but becomes ever less efficient as the expiratory pause increases. ⋯ With a longer expiratory pause, this system's efficiency approaches that of the Mapleson A. The experimental results are compared with predictions generated by a mathematical model. There is good agreement between the two, validating the mathematics used.
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In order to improve arterial oxygenation and venous admixture during one lung ventilation, the effect of selective infusion of prostaglandin E1 into the pulmonary artery of the ventilated lung was investigated in 12 adult patients undergoing thoracotomy. Patients' bronchi were intubated with a Mallinckrodt bronchial tube and ventilated with 66% oxygen in air. Cardiopulmonary factors such as systemic and pulmonary arterial pressures, pulmonary vascular resistance, blood gas analyses, cardiac output and airway pressure were measured before and during one-lung ventilation; venous admixture (Qs/Qt) was calculated. ⋯ The plasma endothelin-1 concentration reached a plateau between the end of one lung ventilation (before closing the thorax) and 6 h postoperatively. This correlated inversely with the pre-operative forced expiratory volume in one second (r = -0.68, p < 0.005), declining to normal values 72 h after operation. The selective infusion of PGE1 into the pulmonary artery of the ventilated lung corrected pulmonary vasoconstriction and improved both arterial oxygenation and venous admixture during one lung ventilation for thoracotomy.
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Letter Case Reports
Is caudal anaesthesia a safe-choice for infant hernia repair?