Effect of Change in Position of Finger on SpO2 Value by Pulse Oximetry: A Cross Sectional Study

Background: Pulse oximetry is widely used in patients of respiratory diseases for monitoring the oxygen saturation in blood. First commercial pulse oximetry was used in 1975. Although there have been many improvements in its design since then, still there are a few limitations. The limitations of pulse oximetry include mechanical artefacts accuracy, electromagnetic interference, calibration, delay, pulse dependencevolume and rhythm, abnormal haemoglobins, other absorbents, pulsatile veins, pigmentation. Objective: Despite so many studies on the pulse oximetry, there still isn’t any study on pulse oximetry which focused changes in the readings of pulse oximeter with respect to position of finger in relation to the sensor. So in this study we tried to analyse the effect of anatomical plane of finger on O₂ saturation as measured by pulse oximetry. Material and Method: This study was done on 400 patients and included both healthy and unhealthy patients. Portable pulse oximeter was used in the study. Pulse oximetry was done on the subjects with finger in supine, prone and lateral position in respect to the probe, while the patient was in sitting position with a waiting period of 1 min between each reading. Results: The study shows no significant difference (p value > 0.05) between Spo₂ value obtained from any position of finger in relation to the sensor while applying the pulse oximeter. Conclusion: Pulse oximetry is a very safe, non-invasive and inexpensive way of continuous O₂ saturation monitoring in critical patients. Mal-positioning of sensors can be potentially dangerous as it may give erroneous high or low readings. The ways to prevent mal-positioning of the sensor are good design of pulse oximeter and ensuring that it is properly visible to the clinician.