British journal of anaesthesia
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Minute ventilation (VE) (ml min-1), respiratory frequency (f), mixed expired carbon dioxide fraction (FECO2) and end-tidal carbon dioxide concentration (E'CO2) (%) were measured, and alveolar ventilation (VA), deadspace (VD), deadspace/tidal volume ratio (VD/VT) and carbon dioxide output (VCO2) calculated in 58 anaesthetized, spontaneously breathing infants and children weighing 2.8-20.5 kg. Although minute volumes varied, tidal volume correlated well with weight (r = 0.83), with a mean tidal volume (+/- 1SD) of 5.2 +/- 1.2 ml kg-1. ⋯ Respiratory frequency, VD/VT and total VD per minute were higher in the younger age group, which explained the finding of a high VE in relation to VCO2 for these patients. This inefficiency of ventilation emphasizes the need to minimize apparatus deadspace in breathing systems used for small infants.
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Ebstein's anomaly is a rare congenital malformation of the tricuspid valve, often associated with an atrial septal defect. Death occurs usually from cardiac arrhythmias. The successful use of a two-catheter technique for elective Caesarean section with extradural analgesia is described and the hazards associated with Ebstein's anomaly in pregnancy and anaesthesia are discussed.
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Using the single breath test for carbon dioxide (SBT-CO2), the components of physiological deadspace were investigated during anaesthesia with IPPV in 58 patients. A square-wave inspiratory flow and an end-inspiratory pause (25% and 10% of cycle time, respectively) were used. At tidal volumes of 0.45 litre (f = 17 b.p.m.), and 0.75 litre (f = 9 b.p.m.), median values for VDphys/VT were 0.44 and 0.31. ⋯ The median arterial--end-tidal PCO2 difference, (PaCO2-PE'CO2), was 0.6 kPa at small and 0.3 kPa at large tidal volumes (P less than 0.001). Three patients had zero and four had negative (PaCO2-PE'CO2) values at large tidal volumes. When phase III slopes steeply, negative (PaCO2-PE'CO2) values may be observed in the presence of alveolar deadspace.