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- Title
P LOW OF 0 CMH20 MAXIMIZES PEAK EXPIRATORY FLOW RATE WHILE OPTIMIZING CARBON DIOXIDE REMOVAL IN AIRWAY PRESSURE RELEASE VENTILATION.
- Authors
Madden, Maria; Andrews, Penny; Thurber, Melissa; Mellies, Benjamin; Williams, Kendall; Satalin, Josh; Gatto, Louis; Nieman, Gary; Habashi, Nader
- Abstract
BACKGROUND Airway Pressure Release Ventilation (APRV) is described as continuous positive airway pressure (CPAP) with a brief release to augment carbon dioxide (CO2) removal. Based on 2005 APRV published guidelines, clinical studies and multiple experimental models have validated setting a pressure low (P Low) of 0 cm H2O and time low (T Low) to terminate (T) at 75% of the Peak Expiratory Flow Rate (PEFR) maintains adequate end expiratory lung volume without a subsequent increase in CO2. Because diffusion of CO2 occurs during the prolonged CPAP phase (^90% of the total respiratory cycle) and convective removal during the sub-second release phase (T Low), increasing P Low >0 cmH2O could increase the expiratory resistance resulting in an increase in CO2 A previously published abstract using a single comparment test lung model demonstrated that a P Low >0 cmH2O would increase the PEFR. Our hypothesis was that a P Low >0 cmH2O with a T Low set to 75% T-PEFR in patients would decrease PEFR and subsequently cause an increase in CO2 as measured by end tidal CO2 (etCO2). METHOD After receiving IRB approval, we studied 20 patients on APRV with initial settings of P Low of 0 cmH2O and T Low of 75% T-PEFR. The P Low was increased in increments of 5 cmH2O from 0 to 15. Three (3) minutes between each P Low level was used as an equilbration period and the following data was collected: PEFR, T-PEFR, release volumes, etCO2, MV and assessment of patient comfort using a scale of 0-5 where 0 was no change in level of comfort and 5 was most uncomfortable. RESULTS In each case, a P Low of 0 cmH2O demonstrated the highest PEFR as compared to P Low >0 cmH2O with statistical difference seen as a decrease in PEFR when changing P Low from 0-15, 5-15 and 0-10 cmH2O (see Table 1). The etCO2 increased in 16 of the 20 patients while decreasing in the remaining 4 patients: however, a concomitant increase in respiratory frequency and signs of increased work of breathing was noted in these 4 patients, which may caused a decrease in etCO2 due to increase respiratory frequency. Visual assessment and patient comfort scores demonstrated 13 of the 20 patients became uncomfortable, agitated, coughing, and and exhibited increased respiratory frequency and use of accessory muscles to actively exhale. CONCLUSION Setting a P Low of 0 cmH2O in APRV maximizes PEFR while efficiently removing CO2 as assessed by etCO2 and was associated with the greatest comfort.
- Publication
Respiratory Care, 2016, Vol 61, Issue 10, pOF9
- ISSN
0020-1324
- Publication type
Academic Journal