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Longitudinal oesophageal temperature differences were measured in 160 anaesthetized and intubated children. All showed an area of ventilatory cooling similar to that already reported in adults. It is suggested that oesophageal temperature probes should be 2 x age in years inserted a distance of 104 5 cm below the corniculate cartilages, but that readings should be taken up to 2 cm above and below this point before fixing to confirm that the lead is below the area affected by ventilation. For infants, a lead packed off at the back of the pharynx 2 cm above the corniculate cartilages proved sufficiently accurate for routine monitoring.

Oesophageal temperature variations during anaesthesia were measured in a number of groups of adult patients. It was found that in the upper half of the oesophagus intubation and controlled ventilation produced a greater degree of cooling than spontaneous breathing through a face-mask. Partial withdrawal of the endotracheal tube resulted in an upward shift of the cooled segment. Reducing the controlled tidal volume increased the mean temperature at the tip of the endotracheal tube and in the related part of the oesophagus. Temperatures in the lower fourth remained stable and it is concluded that the sensing probe should be inserted at least 24 cm below the corniculate cartilages when measuring the oesophageal temperature during anaesthesia.

Continuous electrocardiography was performed during eighty operations on the posterior fossa of the skull and fifty-seven other neurosurgical operations, all in the sitting position. There was little difference between the two groups in the incidence of arrhythmia before operation and during the surgical approach; more serious irregularities were almost entirely confined to periods when the surgeon was operating in the vicinity of the pons, the medulla, and the roots of the fifth, ninth and tenth cranial nerves. Severe arrhythmias may indicate or be the cause of medullary failure in this position and may also give an early warning of air embolism. Therefore continuous electrocardiography is valuable provided that its limitations are understood.