Dräger Babylog 8000 plus Instructions For Use Manual page 168

Principles of operation
Because the device only recognizes the airway
pressure and not the pleural or esophageal
pressure, spontaneous breathing cannot be taken
into consideration. If strong spontaneous breathing
is overlaid on ventilation, the results of the
evaluation are distorted.
The same applies in the event of a large leakage.
The displayed resistance and compliance values
are then too high.
A possible distortion of the measured values
resulting from the above-mentioned conditions is
indicated by a warning symbol on the screen. The
warning symbol indicates that the correlation
coefficient r is less than 0.95 or the leakage is
greater than 20 % or strong spontaneous
breathing is present.
For the overinflation index the C20 ratio is
determined from the volume increase of the last
20 % of the inspiratory pressure and related to the
*
dynamic compliance :
C20 = (V(T ) – V(t80)) / (0.2 x Ppeak)
I
The results are displayed until the next evaluation
is completed. If, however, no new measured
values are available within one minute, the display
is cleared.
* Identifying lung overdistention during mechanical
ventilation by using volume-pressure loops by
Joel B. Fisher, Mark C. Mammel, Michael C. Coleman,
Dennis R. Bing, Stephen J. Boros. Pediatric
Pulmonology, 5:10-14 (1988)
168
Rate-Volume Ratio (RVR)
The quotient of respiratory rate and tidal volume
can help in evaluating the chances of success of
weaning the patient off ventilation
prevent fluctuations in the measured value
resulting from changing between spontaneous and
mandatory respiratory cycles, the ratio is not
calculated directly from the respiratory rate and
tidal volume.
Rather, the RVR is calculated using the following
formula:
2
RVR = f / VT = f / MV
This corresponds to the averaging of RVR values
over a period of approx. 10 to 15 seconds.
** A prospective study of indexes predicting the outcome of
trials of weaning from mechanical ventilation; by
Karl L. Yang, Martin J. Tobin. The New England Journal
of Medicine, Vol. 324, 21, 1991
Instructions for use Babylog 8000 plus SW 5.n
**
. In order to