title: Pulseless Oximetry: A Preliminary Evaluation.
abstract: BACKGROUND
  Pulse oximetry fails when pulsations are weak or absent, common in patients with continuous flow left ventricular assist devices (LVADs). We developed a method to measure arterial oxygenation (Sao2) noninvasively in pulseless patients with LVADs.
  
  
  METHODS
  The technique involves 5- to 10-s occlusions of radial and ulnar arteries on one hand. A fingertip is transilluminated alternately with light-emitting diodes emitting 660 nm (red) and 905 nm (infrared). During the approximately 1 s after release of occlusion, changing attenuance of each wavelength is measured and their red/infrared arterial blood attenuance ratio (R/IR) calculated. We studied five normal subjects breathing hyperoxic, normoxic, or hypoxic gas mixtures to establish a calibration curve, using standard pulse oximetry as the gold standard. We also studied seven pulseless patients with LVADs (two studied twice) at clinically determined oxygenation.
  
  
  RESULTS
  Normal subject data showed close correlation of oxygen saturation by pulse oximetry (Spo2) with R/IR, (Spo2 = 111 - [26.7 × R/IR]; R2 = 0.975). For patients with LVADs, predicted Sao2 (from the calibration curve) tended to underestimate measured Sao2 (from arterial blood) by a clinically insignificant 1.1 ± 1.6 percentage points (mean ± SD), maximum 3.4 percentage points.
  
  
  CONCLUSIONS
  Preliminary results in a small number of patients demonstrate that pulseless oximetry can be used to estimate arterial saturation with acceptable accuracy. A noninvasive oximeter that does not rely on pulsatile flow would be a valuable advance in assessing oxygenation in patients with LVADs, for whom the only current option is arterial puncture, which is painful, risks arterial injury, and only provides a snapshot evaluation of oxygenation.
authors.affiliation: Pulmonary Medicine Division, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY. Electronic address: taldrich@montefiore.org.
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Aldrich
authors.affiliation: Pulmonary Medicine Division, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY.
authors.forename: Pragya
authors.initials: P
authors.lastname: Gupta
authors.affiliation: Pulmonary Medicine Division, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Stoy
authors.affiliation: Critical Care Medicine Division, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY.
authors.forename: Anthony
authors.initials: A
authors.lastname: Carlese
authors.affiliation: Department of Cardiothoracic Surgery, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Goldstein
mesh_terms: D000328:Adult; D000368:Aged; D001243:Assisted Circulation / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006353:Heart-Assist Devices / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000295:instrumentation / Q000379:methods; D010100:Oxygen / Q000097:blood*; D015203:Reproducibility of Results
chemical_list: D010100:Oxygen