British Journal of Anaesthesia, Vol 80, Issue 4 422-433, Copyright © 1998 by The Board of Management and Trustees of the British Journal of Anaesthesia
J. S. Mecklenburgh and W. W. Mapleson
We have investigated the response of 12 normal, healthy subjects to
resistance loading and ventilator assistance of spontaneous breathing.
Three ventilators, the Hamilton Veolar, Engstrom Erica and Puritan Bennett
7200, were used to provide synchronized intermittent mandatory ventilation
and two levels of pressure assistance. Total respiratory elastance and
resistance were measured. The equivalent (negative) pressure of respiratory
muscle activity (pmus) was then calculated from measurement of flow and
pressure at the mouth. With ventilatory assistance, subjects maintained
frequency, decreased inspiratory time and the magnitude of pmus, but
increased tidal volume, thus not taking full advantage of ventilatory
assistance. The waveform of pmus varied in detail within and between
subjects and conditions, but the all- subject mean waveforms showed for all
conditions a consistency of trajectory. Increasing the level of assistance
decreased the duration and hence the (negative) peak value of pmus. The
results suggest that some waveforms of flow or pressure from the
ventilators may be more acceptable to patients than others, and that
different patients may prefer different waveforms.
CLINICAL INVESTIGATIONS
Ventilatory assistance and respiratory muscle activity. 1: Interaction in healthy volunteers
Department of Anaesthetics and Intensive Care Medicine, University of Wales College of Medicine, Heath Park, Cardiff CF4 4XN
![]()
CiteULike
Connotea
Del.icio.us What's this?