Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring

Kenneth Martin Brady*, R. Blaine Easley, Kathleen Kibler, David W. Kaczka, Dean Andropoulos, Charles D. Fraser, Peter Smielewski, Marek Czosnyka, Gerald J. Adams, Christopher J. Rhee, Craig G. Rusin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


The pressure reactivity index (PRx) identifies optimal cerebral perfusion pressure after traumatic brain injury. We describe a method to improve PRx precision by induced variations in arterial blood pressure (ABP) using positive end-expiratory pressure (PEEP) modulation (iPRx). Neonatal swine (n = 10) were ventilated with static PEEP and then with PEEP oscillated between 5 and 10 cmH2O at a frequency of 1/min. PRx was recorded as a moving correlation coefficient between ABP and intracranial pressure (ICP) from spontaneous ABP activity (0.05-0.003 Hz) during static PEEP. iPRx was similarly recorded with PEEP oscillation-induced ABP waves. The lower limit of autoregulation (LLA) was delineated with continuous cortical laser Doppler flux monitoring. PEEP oscillation increased autoregulation-monitoring precision. The ratios of median absolute deviations to range of possible values for the PRx and iPRx were 9.5% (8.3-13.7%) and 6.2% (4.2- 8.7%), respectively (P = 0.006; median, interquartile range). The phase-angle difference between ABP and ICP above LLA was 161° (150°-166°) and below LLA, -31° (-42° to 12°, P < 0.0001). iPRx above LLA was -0.42 (-0.67 to -0.29) and below LLA, 0.32 (0.22- 0.43, P = 0.0004). A positive iPRx was 97% specific and 91% sensitive for perfusion pressure below LLA. PEEP oscillation caused stable, low-frequency ABP oscillations that reduced noise in the PRx. Safe translation of these findings to clinical settings is expected to yield more accurate and rapid delineation of individualized optimal perfusion-pressure goals for patients.

Original languageEnglish (US)
Pages (from-to)1362-1368
Number of pages7
JournalJournal of applied physiology
Issue number9
StatePublished - Nov 1 2012


  • Cerebrovascular autoregulation
  • Neonatal
  • Positive end-expiratory pressure
  • Pressure reactivity

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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