Haemoglobin E and alpha-Thalassaemia.

Clinical Monitoring-Farman and 7uett BEDICA JoURNAL 29 respiratory waves are absent.In Fig. 4, recorded from the same relaxed patient, the airway is only partially obstructed, resulting in an obvious reduction of tidal volume.Fig. 5 shows the effect, again in the same apnoeic patient, of dis- connecting the ventilator.This pattern is indistinguishable from that shown in Fig. 4, demonstrating that this technique reveals the essential point-namely, that ventilation of the lungs has ceased.So far as we know this is the only method of monitoring which cannot give a wrong indication in these circumstances.It is also possible to study the shape of the respiratory wave- form with the impedance spirometer.The tracing follows closely all changes in the volume of air in the lungs, so that it is possible to measure not only the tidal volume but the rate of change of volume, both in inspiration and in expiration.Fig. 6 was recorded on a patient ventilated with a Barnet Mark III ventilator.This machine, though theoreti- cally a constant pressure generator, in practice operates as a Fiq.