# 2002 OPEN FORUM Abstracts

### Laboratory Evaluation of an Automated Pressure-Volume Curve Maneuver

#### Robert S. Campbell, RRT, FAARC; Bradley R. Davis, MD; Jay A. Johannigman, MD; Kenneth Davis, Jr., MD; Sandra L. Miller,MD; Richard D. Branson, RRT, FAARC; University of Cincinnati College of Medicine, Cincinnati, OH.

**Background: **The pressure-volume
(P-V) curve describes the mechanical properties of the respiratory system. Current
techniques for P-V curve measurement include the supersyringe technique, multiple
occlusion technique, and low-flow technique. The Galileo gold ventilator (Hamilton)
incorporates an automated PV maneuver (pre-clinical software) that uses a constant
pressure rise, which is adjustable between 2 and 5 cmH2O/sec. We evaluated the
accuracy and reproducibility of this automated PV maneuver in the laboratory.

**Method: **We designed a bench
study to evaluate the accuracy and reproducibility of the automated PV maneuver
using the Galileo. We also assessed Galileo's ability to deliver the set pressure
rise and any effect of varying lung mechanics. Five automated PV curves were
performed on one side of a two-chamber test lung (TTL) for each of eight combinations
of resistance (5 and 20 cmH2O/L/sec), compliance (20 and 50 ml/cmH2O), and pressure
rise setting (2 and 5 cmH2O/sec). Pressure, volume, and flow delivery was measured
at the prox airway at a sampling rate of 70/sec and recorded to a PC with commercially
available monitoring package (Datalogger), from which, PV and Pressure-Tim (PT)
curves wee generated. The measured PT curve was plotted against a mathematically
determined curve and any deviations were noted. Peak and mean flowrate during
each maneuver were also measured and recorded. Three manual PV curves were performed
at each combination of R and C using 100 ml aliquots from a 0.5L calibration
syringe. Automated and manual PV curves were overlapped and any deviations noted.

**Results: **Figure 1 reveals
the overlapped automated and manual PV curves. Figure 2 reveals the PT curves
plotted against the mathematically determined PT curve. Pressure rise setting
of 5 cmH2O/sec at high C resulted in a mean flow >14 L/min. Mean flow at
all other combinations was ² 6 L/min. The PT curve of the automated PV curve
deviated from the mathematical curve (undershoot) in the first 0.8 seconds of
the maneuver. Reproducibility of the automated PV curve was excellent. There
was good correlation between the automated and manual PV curves.

**Conclusions: **The automated
PV curve maneuver on the Galileo Gold ventilator yields reproducible and accurate
measurement of lung mechanics. Benefits associated with use of an automated
PV measurement include elimination of interoperator variability, faster completion
of the maneuver, and avoidance of patient-ventilator disconnection. Clinical
evaluation of the automated PV maneuver appears warranted.

**OF-02-172**