Effect of capillaroscopic patterns on the pulse oximetry measurements in systemic sclerosis patients

• SpO2 cannot be measured in all fingers of SSc patients.
• Mean SpO2 values were not different between the groups of capillaroscopy patterns.
• SpO2 differences can be equal or more than 4% among fıngers of SSc patients.
• Highest SpO2 values measured among the fingers may be more suitable in clinical practice.

Nailfold capillaroscopy is a simple method for determining microvascular damage in systemic sclerosis (SSc). The pulse oximeter is a noninvasive tool that is used to estimate a patient's arterial blood oxygen saturation. The aim of this study was to investigate the effect of capillaroscopic patterns on pulse oximetry measurements in SSc patients. The nailfolds from 2nd to 5th fingers in both hands were examined in all subjects by using capillaroscopy. Patients were categorized according to their capillaroscopy findings in 3 groups as having early, active or late patterns. Oxygen saturation (SpO2) measurements were performed from 2nd to 5th fingers in both hands with a finger probe. We studied 53 SSc patients (F/M: 48/5). According to capillaroscopy findings 18 patients were classified as having early pattern (34.0%), 19 active pattern (35.8%), and 15 late pattern (28.3%). Only 1 (1.9%) patient had normal capillaroscopy findings. SpO2 could not be measured in 47 (11.0%) fingers and in 20 (37.7%) SSc patients. There were 20 (37.7%) patients with a ≥ 4% difference between the minimum and maximum SpO2 measurements among fingers. There were no difference between the groups of SSc patients defined by capillaroscopy findings in terms of mean maximal SpO2 or mean minimal SpO2 measured from fingers (p NS, for all). Assessment of SpO2 values in patients with SSc is challenging. We did not detect any effect of capillaroscopic patterns on mean SpO2 values. On the other hand ≥ 4% difference between minimum and maximum SpO2 values measured from fingers of a patient may be considered as an indirect sign of microvascular damage. Assessment of the highest measured SpO2 values among the fingers of a patient may be more suitable in practice.