title: Non-invasive measurement of pulse pressure variation and systolic pressure variation using a finger cuff corresponds with intra-arterial measurement.
abstract: BACKGROUND
  Pulse pressure variation (PPV) and systolic pressure variation (SPV) are reliable predictors of fluid responsiveness in patients undergoing controlled mechanical ventilation. Currently, PPV and SPV are measured invasively and it is unknown if an arterial pressure (AP) signal obtained with a finger cuff can be used as an alternative. The aim of this study was to validate PPV and SPV measured using a finger cuff.
  
  
  METHODS
  Patients receiving mechanical ventilation under sedation after cardiac artery bypass graft (CABG) surgery were included after arrival on the intensive care unit. AP was measured invasively in the radial artery and non-invasively using the finger cuff of the Nexfin™ monitor. I.V. fluid challenges were administered according to clinical need. The mean value of PPV and SVV was calculated before and after administration of a fluid challenge. Agreement of the calculated PPV and SPV from both methods was assessed using the Bland-Altman analysis.
  
  
  RESULTS
  Nineteen patients were included and 28 volume challenges were analysed. Correlation between the two methods for PPV and SPV [mean (sd)=6.9 (4.3)% and 5.3 (2.6)%, respectively] was r=0.96 (P<0.0001) and r=0.95 (P<0.0001), respectively. The mean bias was -0.95% for PPV and -0.22% for SPV. Limits of agreement were -4.3% and 2.4% for PPV and -2.2% and 1.7% for SPV. The correlation between changes in PPV and SPV as a result of volume expansion measured by the two different methods was r=0.88 (P<0.0001) and r=0.87 (P<0.0001), respectively.
  
  
  CONCLUSIONS
  In patients receiving controlled mechanical ventilation after CABG, PPV and SPV can be measured reliably non-invasively using the inflatable finger cuff of the Nexfin™ monitor.
authors.affiliation: MIRA-Institute for Biomedical Technology and Technical Medicine, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. b.lansdorp@utwente.nl
authors.forename: B
authors.initials: B
authors.lastname: Lansdorp
authors.forename: D
authors.initials: D
authors.lastname: Ouweneel
authors.forename: A
authors.initials: A
authors.lastname: de Keijzer
authors.forename: J G
authors.initials: JG
authors.lastname: van der Hoeven
authors.forename: J
authors.initials: J
authors.lastname: Lemson
authors.forename: P
authors.initials: P
authors.lastname: Pickkers
mesh_terms: D000368:Aged; D000465:Algorithms; D001158:Arteries / Q000502:physiology*; D015982:Bias; D001794:Blood Pressure / Q000502:physiology*; D001916:Brachial Artery / Q000502:physiology; D001026:Coronary Artery Bypass; D003627:Data Interpretation, Statistical; D005260:Female; D005385:Fingers / Q000098:blood supply*; D005440:Fluid Therapy; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D011184:Postoperative Period; D011674:Pulse; D012015:Reference Standards; D012039:Regional Blood Flow / Q000502:physiology; D015203:Reproducibility of Results; D013599:Systole / Q000502:physiology