British journal of anaesthesia
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Carbon dioxide clearance during high frequency jet ventilation. Effect of deadspace in a lung model.
The effects of the volume and length of deadspace on the clearance of carbon dioxide from a lung model have been investigated during high frequency jet ventilation (HFJV) at 1, 3 and 5 Hz. At 1 Hz, increasing the volume of the deadspace without changing the length caused a reduction in the clearance of carbon dioxide. ⋯ Furthermore, the clearance of carbon dioxide at 5 Hz was very inefficient compared with that at 1 Hz. It is concluded that, during HFJV, carbon dioxide is cleared most efficiently when the frequency is low enough for the delivered tidal volume to be greater than the volume of the morphological deadspace.
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The performance of cricoid pressure was studied in three groups of medical personnel likely to be involved in its application using the cricoid yoke and a test rig. The instrument enabled individuals who had no previous experience in the application of cricoid pressure to achieve results as good as those obtained by experienced anaesthetic staff. Furthermore, the instrument improved the consistency of the applied force in all groups, particularly if cricoid pressure was required for sustained periods of 30 s or more.