The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

HIGH INTERMITTENT POSITIVE END-EXPIRATORY PRESSURE (PEEPINT) SUPPORTS OXYGENATION DURING LOW TIDAL VOLUME (VT) VENTILATION IN THE ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS)

RH Kallet RRT, MS. Siobal RRT, EL Warnecke RRT, JA. Alonso RRT, JA. Katz MD, JD. Marks MD PhD. Department of Anesthesia, San Francisco General Hospital, 94110

Background: Low VT ventilation limits ventilator-induced lung injury in ARDS,(1) but may potentiate atelectasis, especially during hypercapnia.(2) High levels of PEEP may reduce atelectasis. Extra-pulmonary etiologies of ARDS (ARDSEXP) are noted both for PEEP-responsive lung recruitment and PEEP-sensitive hemodynamic instability.(3) PEEPINT raises set PEEP above baseline for 2 breaths every 3 minutes. Because lung recruitment with PEEP is sustained over time,(4) PEEPINT may support arterial oxygen tension (PaO2) without requiring high levels of set PEEP or high fractional concentrations of inspired oxygen (FIO2).
Case Summaries: Four ARDSEXP patients (2 with hemodynamic instability) were ventilated with a Drager E-2 ventilator at a VT (mean ± standard deviation) of 5.9 ± 1.3 mL/kg. An FIO2 of 0.93 ± 0.1 and PEEP of 17.5 ± 1.9 cm H2O were required to maintain a PaO2 of 81 ± 18.7 mm Hg. Lower inflection point (LIP) was 17.8 ± 7.2 cm H2O. PEEPINT was set at 25.5 ± 4.1 cm H2O. Over the next 24 hours, set PEEP was decreased to 13.5 ± 4.7 cm H2O while maintaining a VT of 5.8 ± 1.2 mL/kg and a PaO2 of 72.8 ± 10.8 mm Hg. However, the sample size was too small for inferential statistical analysis by Wilcoxon Sign Rank Test.
Conclusion: By exploiting sustained lung recruitment, PEEPINT set above LIP may permit low VT ventilation at a lower set PEEP and FIO2. PEEPINT may be a particularly useful approach to low VT ventilation in hemodynamically unstable ARDSEXP patients.
1. The ARDS Network. Ventilation with lower VT as compared to traditional VT for ALI and ARDS. N Engl J Med. 2000; 342 [in press].
2. Bendixen HH, Hedley-Whyte J. Impaired oxygenation in surgical patients during general anesthesia and controlled ventilation. N Engl J Med. 1963; 269 (19): 991-996.
3. Pelosi P, Cadringher P. Sigh in ARDS. Am J Respir Crit Care Med.1999;159: 872-880.
4. Katz JA, Ozanne GM, et al. Time course and mechanisms of lung volume increase with PEEP in acute respiratory failure. Anesthesiology 1981;54:9-16. (See Original for Figure)

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