Management of the Engström Respirator in Early Infancy.

High tracheostomy through the second or third tracheal cartilage is performed using the widest possible silver cannula, i.e. usually 3 to 4 mm. in diameter at the distal opening, to fit tightly into the tracheal lumen. The cannula is double-lumen unfenestrated and protrudes beyond the guard plate so that the small standard tubings of the respirator can easily be connected to it. The patient is intubated, if necessary under general anaesthesia given with the respirator. Thus respirator treatment is instituted even before tracheostomy. The respirator treatment is started with an approximate volume for alveolar ventilation, which is determined from the size of the child's body, i.e. for a case in early infancy about 0-5-10 1./minute. The total volume of the tubings, etc., of the apparatus is a known constant, and the compressible gas volume of the apparatus which does not reach the lungs can easily be determined for each case from the actual peak pressures in the airways. This volume will increase the total volume in the average case by 1I7-2 1./minute. The settings on the respirator are the sum of the alveolar ventilation, the anatomical dead space and the compressible volume of 1./min.; this is the total volume and is usually 2 2-3-5 1./minute. At the same time, the rate of ventilation is chosen and is usually kept around 26-28/min., which has been shown by experience to be best, despite the fact that the infant's respiratory rate is higher. This frequency has given good results, because it allows sufficient time for physiological expansion and gas exchange in the alveoli. Finer adjustments are made by a further control of the rate and volume. The peak insufflating pressure in the patient's airways is usually around 25-30 cm. H20, but occasionally the peak pressure