title: Noninvasive monitoring of blood pressure in the critically ill: reliability according to the cuff site (arm, thigh, or ankle).
abstract: OBJECTIVE
  In the critically ill, blood pressure measurements mostly rely on automated oscillometric devices pending the intra-arterial catheter insertion or after its removal. If the arms are inaccessible, the cuff is placed at the ankle or the thigh, but this common practice has never been assessed. We evaluated the reliability of noninvasive blood pressure readings at these anatomic sites.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Medical-surgical intensive care unit.
  
  
  METHODS
  Patients carrying an arterial line with no severe occlusive arterial disease.
  
  
  METHODS
  Each patient underwent a set of three pairs of noninvasive and intra-arterial measurements at each site (arm, ankle, thigh [if Ramsay sedation scale >4]) and, in case of circulatory failure, a second set of measurements after a cardiovascular intervention (volume expansion, change in catecholamine dosage).
  
  
  RESULTS
  In 150 patients, whatever the cuff site, the agreement between invasive and noninvasive readings was markedly higher for mean arterial pressure than for systolic or diastolic pressure. For mean arterial pressure measurement, arm noninvasive blood pressure was reliable (mean bias of 3.4 ± 5.0 mm Hg, lower/upper limit of agreement of -6.3/13.1 mm Hg) contrary to ankle or thigh noninvasive blood pressure (mean bias of 3.1 ± 7.7 mm Hg and 5.7 ± 6.8 mm Hg and lower/upper limits of agreement of -12.1/18.3 mm Hg and -7.7/19.2 mm Hg, respectively). During acute circulatory failure (n = 83), arm noninvasive blood pressure but also ankle and thigh noninvasive blood pressure allowed a reliable detection of 1) invasive mean arterial pressure <65 mm Hg (area under the receiver operating characteristic curve of 0.98 [0.92-1], 0.93 [0.85-0.97], and 0.93 [0.85-0.98] for arm, ankle, and thigh noninvasive blood pressure, respectively); and 2) a significant (>10%) increase in invasive mean arterial pressure after a cardiovascular intervention (area under the receiver operating characteristic curve of 0.99 [0.92-1], 0.90 [0.80-0.97], and 0.96 [0.87-0.99], respectively).
  
  
  CONCLUSIONS
  In our population, arm noninvasive mean arterial pressure readings were accurate. Either the ankle or the thigh may be reliable alternatives, only to detect hypotensive and therapy-responding patients.
authors.affiliation: Service de Réanimation Polyvalente, SAR Lapeyronie, Centre Hospitalier Universitaire, Montpellier, France. lakhal_karim@yahoo.fr
authors.forename: Karim
authors.initials: K
authors.lastname: Lakhal
authors.forename: Christine
authors.initials: C
authors.lastname: Macq
authors.forename: Stephan
authors.initials: S
authors.lastname: Ehrmann
authors.forename: Thierry
authors.initials: T
authors.lastname: Boulain
authors.forename: Xavier
authors.initials: X
authors.lastname: Capdevila
mesh_terms: D000842:Ankle / Q000098:blood supply; D001132:Arm / Q000098:blood supply; D001794:Blood Pressure / Q000502:physiology; D001795:Blood Pressure Determination / Q000379:methods* / Q000592:standards; D016638:Critical Illness; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D011446:Prospective Studies; D015203:Reproducibility of Results; D013848:Thigh / Q000098:blood supply