Abstract
Background:
Airway pressure release ventilation (APRV) is an alternative mode of ventilation for patients with severe hypoxemic failure. There is little evidence on how best to titrate APRV settings based on each patient's disease process, and thus limited consensus among practitioners for appropriate APRV settings. The purpose of this retrospective review was to determine if APRV is set according to recommendations established by a previously published protocol in adult patients admitted to the ICU. Such protocol recommends setting a pressure high (Phigh) equal to the plateau pressure on conventional ventilation or less than 35 cm H2O, pressure low (Plow): 0 cm H2O, time high (Thigh) : > 4.0 s, and initial time low (Tlow) between 0.5-1.0 s but titrated to keep at least 50% expiratory flow air trapping measured on the flow vs. time waveform.
Methods:
Electronic medical records (EMR) from 89 patients admitted to ICUs at a 496-bed university-affiliated institution in San Antonio, TX between January of 2014 and March of 2018. Ten patients were placed on APRV during that time and they were selected for analysis. The information obtained included the ventilator settings and clinical status of each patient. The four main APRV parameters were analyzed to determine if APRV was used as recommended.
Results:
The mean age of the patients selected for the study was 56.6 y (± 12.1). Most patients (40%) were transitioned to APRV from AC/VC with AutoFlow from a mean FIO2 of 77.5% (± 21.8%), P/F ratio 121.5 (± 74.4), OI 22.2 (± 12.5), Ppeak of 27.8 cm H2O (± 7.03), PEEP of cm H2O (± 3.9), and MAP 18.6 (± 4.3). Pplat was not recorded in the majority of patients prior to APRV. The mean values for APRV parameters obtained were P High 29.8 cm H2O (± 2.8; range 30.5-28.5), P low 0.55 cm H2O (± 1.57; range 0-5), T High: 3. 71 s (± 0.92; range 2.5-4.7), and T Low: 0.65 s (± 0.23; range 0.25-1.0). The average I:E ratio selected was 6.3:1. After 24 h, only 5 patients remained on APRV but the reasons for switching back to other modes were not documented.
Conclusions:
This preliminary evaluation of patients admitted for respiratory failure to these ICUs showed that, when selected, most APRV parameters were set in a similar fashion to recommended protocols. A larger number of patients and evaluation at different institutions is necessary to evaluate how consistently a protocol for this very unique mode is utilized.
APRV Parameters
PARAMETER
Phigh
Plow
Thigh
Tlow
MEAN (SD)
29.8 (+/-2.8)
0.55 (+/-1.57)
3.71 (+/-0.92)
0.65 (+/-0.23)
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