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Pulseless oximetry: A preliminary evaluation.
Chest. 2015 Jul 23;
Authors: Aldrich TK, Gupta P, Stoy S, Carlese A, Goldstein DJ
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 LVAD patients.
Methods: The technique involves 5-10 second occlusions of radial and ulnar arteries on one hand. A fingertip is transilluminated alternately with LEDs emitting 660nm (red,R) and 905nm (infrared,IR). During the ∼1 second after release of occlusion, changing absorbance of each wavelength is measured and their 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 gold standard. We also studied seven pulseless LVAD patients (two studied twice) at clinically-determined oxygenation.
Results: Normal subject data showed close correlation of SpO2 with R/IR, [SpO2 =111-(26.7 x R/IR), R2=0.975]. For LVAD patients, 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.
Clinical Implications: 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.
PMID: 26204107 [PubMed - as supplied by publisher]