title: Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring.
abstract: 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 cmH(2)O 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.
authors.affiliation: Anesthesiology, Texas Children's Hospital, Baylor College of Medicine, Houston, Texas 77030, USA. kbrady@texaschildrens.org
authors.forename: Ken M
authors.initials: KM
authors.lastname: Brady
authors.forename: R Blaine
authors.initials: RB
authors.lastname: Easley
authors.forename: Kathleen
authors.initials: K
authors.lastname: Kibler
authors.forename: David W
authors.initials: DW
authors.lastname: Kaczka
authors.forename: Dean
authors.initials: D
authors.lastname: Andropoulos
authors.forename: Charles D
authors.initials: CD
authors.lastname: Fraser
authors.forename: Peter
authors.initials: P
authors.lastname: Smielewski
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Adams
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Rhee
authors.forename: Craig G
authors.initials: CG
authors.lastname: Rusin
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D062186:Arterial Pressure / Q000502:physiology; D001921:Brain / Q000098:blood supply; D001930:Brain Injuries / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D006706:Homeostasis; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D023421:Models, Animal; D008991:Monitoring, Physiologic; D011175:Positive-Pressure Respiration; D013552:Swine