1995 OPEN FORUM Abstracts
BICORE CP-100 ANALYSIS-VOLUME V/S PRESSURE AUGMENTATION MAX (PAM) ON THE BEAR1000.
John Emberger BS RRT, Herbert Patrick MD, Department of Respiratory Care, Thomas Jefferson University Hospital, Philadelphia PA
BACKGROUND: Since last year, we have studied pressure versus volume [PAM, and PAM with inspiratory pause (PAM&IP) versus A/C with decelerating flow] using Bear 1000 ventilators (Bear Medical Systems-Riverside, CA). We examined if an airway pressure plateau yields a pressure plateau (PP) in the lungs (thus better air distribution, better oxygenation/ventilation).
Methods: A computer connected to a Bicore CP-100 (BICORE Monitoring Systems, Irvine CA) (with portex jet adapter instead of an esophageal balloon) collected waveform data on PAM study patients.
SEE ORIGINAL GRAPH
1) The flow of PAM is higher than AC, and more aggressive (flow rises quicker at inspiration). 2) AC tracheal pressure (TP) rises linearly to the tracheal peak inspiratory pressure (TPIP), but PAM TP decelerates as it approaches TPIP. 3) AC airway peak inspiratory pressure (APIP) is higher than PAM APIP, but PAM TPIP is higher than AC TPIP. 4) No TP waves reach PP even when airway pressure (AP) wave has a long PP. 5) On exhalation, AP reverts quickly back to baseline but TP slowly drops back to baseline.
Conclusions: 1) PAM's higher initial flow meets the demands of a critically ill air hungry patient. 2) AC forces pressure quickly into the lungs (linear TP rise) even when the lungs are near maximal stretch. With PAM, TP rise decelerates during maximal lung stretch (end of inspiration) thus PAM has a decreased shear force. 3) PAM pressure more effectively crosses the endotracheal tube than AC. 4) Despite a long AP plateau, airway to alveolus is not statically equilibrated. 5) Frequent AutoPEEP checks are important when lengthening the inspiratory time (PAM&IP).