title: Accuracy of invasive arterial pressure monitoring in cardiovascular patients: an observational study.
abstract: BACKGROUND
  Critically ill patients and patients undergoing high-risk and major surgery, are instrumented with intra-arterial catheters and invasive blood pressure is considered the "gold standard" for arterial pressure monitoring. Nonetheless, artifacts due to inappropriate dynamic response of the fluid-filled monitoring systems may lead to clinically relevant differences between actual and displayed pressure values. We sought to analyze the incidence and causes of resonance/underdamping phenomena in patients undergoing major vascular and cardiac surgery.
  
  
  METHODS
  Arterial pressures were measured invasively and, according to the fast-flush Gardner's test, each patient was attributed to one of two groups depending on the presence (R-group) or absence (NR-group) of resonance/underdamping. Invasive pressure values were then compared with the non-invasive ones.
  
  
  RESULTS
  A total of 11,610 pulses and 1,200 non-invasive blood pressure measurements were analyzed in 300 patients. Ninety-two out of 300 (30.7%) underdamping/resonance arterial signals were found. In these cases (R-group) systolic invasive blood pressure (IBP) average overestimation of non-invasive blood pressure (NIBP) was 28.5 (15.9) mmHg (P <0.0001) while in the NR-group the overestimation was 4.1(5.3) mmHg (P < 0.0001). The mean IBP-NIBP difference in diastolic pressure in the R-group was -2.2 (10.6) mmHg and, in the NR-group -1.1 (5.8) mmHg. The mean arterial pressure difference was 7.4 (11.2) mmHg in the R-group and 2.3 (6.4) mmHg in the NR-group. A multivariate logistic regression identified five parameters independently associated with underdamping/resonance: polydistrectual arteriopathy (P = 0.0023; OR = 2.82), history of arterial hypertension (P = 0.0214; OR = 2.09), chronic obstructive pulmonary disease (P = 0.198; OR = 2.61), arterial catheter diameter (20 vs. 18 gauge) (P < 0.0001; OR = 0.35) and sedation (P = 0.0131; OR = 0.5). The ROC curve for the maximal pressure-time ratio, showed an optimum selected cut-off point of 1.67 mmHg/msec with a specificity of 97% (95% CI: 95.13 to 99.47%) and a sensitivity of 77% (95% CI: 67.25 to 85.28%) and an area under the ROC curve by extended trapezoidal rule of 0.88.
  
  
  CONCLUSIONS
  Physicians should be aware of the possibility that IBP can be inaccurate in a consistent number of patients due to underdamping/resonance phenomena. NIBP measurement may help to confirm/exclude the presence of this artifact avoiding inappropriate treatments.
authors.affiliation: Department of Anesthesia and Intensive Care, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. stefano-romagnoli@hotmail.com.
authors.forename: Stefano
authors.initials: S
authors.lastname: Romagnoli
authors.affiliation: Department of Pediatric Cardiac Surgery, Bambino Gesù Children's Hospital, Rome, Italy. zaccaria.ricci@gmail.com.
authors.forename: Zaccaria
authors.initials: Z
authors.lastname: Ricci
authors.affiliation: Department of Anesthesia and Intensive Care, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. diegoquattrone@hotmail.it.
authors.forename: Diego
authors.initials: D
authors.lastname: Quattrone
authors.affiliation: Department of Neurosciences, Psychology, Drug Research and Child Health, University of Florence, Florence, Italy. lorenzo120787@gmail.com.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Tofani
authors.affiliation: Department of Anesthesia and Intensive Care, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. omartujjar@hotmail.com.
authors.forename: Omar
authors.initials: O
authors.lastname: Tujjar
authors.affiliation: Department of Anesthesia and Intensive Care, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. gianlucavilla1@gmail.com.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Villa
authors.affiliation: Department of Heart and Vessels, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. sm.romanov@gmail.com.
authors.forename: Salvatore M
authors.initials: SM
authors.lastname: Romano
authors.affiliation: Department of Anesthesia and Intensive Care, University of Florence, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy. araffaele.degaudio@unifi.it.
authors.forename: A Raffaele
authors.initials: AR
authors.lastname: De Gaudio
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D062186:Arterial Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000592:standards*; D015924:Blood Pressure Monitors / Q000592:standards*; D002406:Catheterization, Peripheral / Q000379:methods / Q000592:standards*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D055815:Young Adult