Use of Peripheral Perfusion Index Derived From the Pulse Oximetry Signal as a Noninvasive Indicator of Perfusion

Alexandre Pinto Lima, MD, Peter Beelen, RN, Jan Bakker, MD, PhD

Disclosures

Crit Care Med. 2002;30(6) 

In This Article

Methods

Participants

The study was conducted at a university-affiliated teaching hospital. Group 1 consisted of 108 healthy adult volunteers (mean age, 30 ± 9 yrs). Group 2 consisted of 37 critically ill patients (mean age, 70 ± 13 yrs) admitted to the medical/surgical intensive care unit.

Measurements

Group 1. The measurements included capillary refill time, PFI, and arterial oxygen saturation (SpO2). We measured capillary refill time by applying firm pressure to the distal phalanx of the index finger for 5 secs and recording the time for return of the normal color by using a conventional wristwatch. PFI and SpO2 were measured by using the Viridia/56S monitor (Philips Medical Systems). The Viridia system calculates the PFI as the ratio between the pulsatile component and the nonpulsatile component of the light reaching the light-sensitive cell of the pulse oximetry probe.

Group 2. The measurements included PFI, SpO2, ambient temperature, central temperature, great toe temperature, finger temperature, capillary refill time, and hemodynamic variables including heart rate and mean arterial pressure. The central temperature was measured by using either a pulmonary artery catheter or a rectal probe. The peripheral temperature was measured on the ventral face of the great toe with a temperature probe (Philips Medical Systems 21078A). The finger temperature was measured simultaneously with the PFI measurement on the same finger by using a similar probe. The central-to-toe temperature difference was calculated, and a difference up to 7°C was considered normal.[9] The doses of vasoactive drugs were recorded. Poor peripheral perfusion was defined as a capillary refill time >2 secs or a central-to-toe temperature difference ≥7°C.

Protocol

To evaluate the variation of the PFI in healthy volunteers (group 1), measurements were taken in the hospital restaurant before and after their normal lunch after a 5- to 10-min rest. Volunteers were seated and instructed to keep their hands still on the table to avoid motion artifacts and to have the hands at the level of the heart. A questionnaire was used to collect information about history of smoking and vascular disease (diabetes, hypertension). In group 2, two measurements were taken from each patient. The first measurement was taken when peripheral perfusion was abnormal; the second measurement was taken when the peripheral perfusion profile had normalized. Patients with central hypothermia (core temperature <36°C) and limb ischemia attributable to vascular occlusion were excluded.

Statistical Analysis

Data are presented as mean ± SD and medians with the 25th and 75th percentiles unless otherwise indicated. Differences between groups or within groups were assessed by using the Mann-Whitney test for nonparametric data. Pearson’s correlation index was calculated where applicable. We considered p < .05 to be statistically significant. Statistical analyses were conducted with Statistical Package for the Social Sciences version 9.0 (SPSS, Chicago, IL).

Informed Consent

The Institutional Review Board waived the need for written informed consent from the healthy volunteers. Informed consent was obtained from the relatives of the patients.

Comments

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