Journal of Applied Physiology, Vol 51, Issue 1 154-159, Copyright © 1981 by American Physiological Society
Measurement of dead space ventilation using a pHa servo-controlled ventilator
R. L. Coon, E. J. Zuperku and J. P. Kampine
A control system for the systemic arterial pH (pHa) servo control of
mechanical ventilation has recently been developed. If pHa is maintained
constant by the change, separation of minute volume into alveolar
ventilation and physiological dead space ventilation (VE = fVA VDp) can be
manipulated to show that VDp = (VE1 - VE 2)/(f1 - fe) where f1 and f2 are
different ventilator frequencies and VE1 and VE2 are expired minute volumes
at these frequencies. Also, added dead space can be measured. VDadded =
(VE2 - VE1)/f where VE1 and VE2 are the minute volumes before and after the
dead space was added. The validity of these equations was tested in the
anesthetized dog. The measured added dead space was in close agreement with
the volume of dead space which was added and with that measured by another
independent method. The measurement of VDp, probably as a result of tidal
volume-related changes in VDp, did not agree as well with VDp measured by
an independent method.
