Montana Anesthesia Services

Alternatives to Finger Pulse Oximetry for Oxygenation Monitoring

Finger pulse oximetry is a standard method of monitoring oxygenation due to its ease of use, widespread availability, and non-invasive nature. However, in certain clinical settings, finger pulse oximetry may be inaccurate, inappropriate, or insufficient. Compromised peripheral perfusion can lead to inaccurate readings, whether due to peripheral vascular disease, shock, hypothermia, or vasoconstriction1–3. In other clinical settings, the fingertip may be unavailable due to trauma or amputation, among other factors. Finally, providers may simply require more information than a finger pulse oximeter can provide. It is also important to note that patient-specific factors such as skin pigmentation and nail polish can affect pulse oximetry readings4. Therefore, clinicians must be aware of alternatives approaches to oxygenation monitoring other than traditional finger pulse oximetry.

When the finger cannot provide clear information on the patient’s oxygenation status, clinicians have a wide range of alternative superficial sites available to them for pulse oximetry. These include the toe, earlobe, and forehead5. Other sites have recently been explored for use in hypoperfusion. The nasal septum2, ear canal6, and penile shaft7 have been demonstrated to be viable alternatives in preliminary studies.

When exploring alternative sites for probe placement, it is important to be aware of the different technologies available. Pulse oximeters typically function by emitting a beam of light that passes through tissue and toward a sensor on the other side (called transmission pulse oximetry). However, certain devices can function through a technique called reflectance pulse oximetry. In this method, a sensor is placed adjacent to the device’s light source, allowing the oximeter to measure beams of light that are reflected rather than transmitted through tissue8. Transmission pulse oximetry works well for thin structures like the fingertip or earlobes. Unfortunately, these sites are vulnerable to inaccurate readings in hypoperfusing states. In this case, reflectance pulse oximetry can be used on more central sites that are too thick for transmission pulse oximetry like the wrist, upper arm9, chest, or forehead.

Another technology which can be used to measure oxygenation is Near Infrared Spectroscopy (NIRS), which measures the oxygen saturation of hemoglobin in the specific tissue region in which the NIRS probes are placed. NIRS has been used most extensively in cardiac surgery for perioperative monitoring of cerebral oxygenation but continues to gain traction in other fields10. Unlike traditional pulse oximetry, NIRS provides information about local tissue oxygenation rather than a global measure of oxygenation; it also measures both venous and arterial oxygenation simultaneously, leading to lower readings than are seen in pulse oximetry.

Clinicians may also consider invasive alternatives to finger pulse oximetry for measuring oxygenation. Arterial blood gas (ABG) analysis provides a reliable assessment of oxygenation and may be helpful in confirming the accuracy of finger pulse oximetry. Mixed venous oxygen saturation and central venous oxygen saturation also allow for invasive monitoring of oxygenation11,12; they are particularly useful in gaining an insight into tissue oxygen delivery and consumption.

Altogether, clinicians have a wide range of alternatives to finger pulse oximetry for monitoring oxygenation. By considering alternative probe sites, embracing new technologies, and integrating data from multiple sources, it is possible to gain a confident assessment of oxygenation status for many patients.


1. Pathania YS. Alternatives for erroneous finger probe pulse oximetry in systemic sclerosis patients during COVID-19 pandemic. Rheumatol Int. 2021;41(12):2243-2244. doi:10.1007/s00296-021-05032-w

2. Oh Y, Kim DK, Ryu DK, Choi JW. Evaluation of pulse oximeter at the nasal septum during general anesthesia: comparison with finger oximeter. J Anesth. Published online March 19, 2024. doi:10.1007/s00540-024-03317-5

3. Falconer RJ, Robinson BJ. Comparison of pulse oximeters: accuracy at low arterial pressure in volunteers. Br J Anaesth. 1990;65(4):552-557. doi:10.1093/bja/65.4.552

4. Sjoding MW, Dickson RP, Iwashyna TJ, Gay SE, Valley TS. Racial Bias in Pulse Oximetry Measurement. N Engl J Med. 2020;383(25):2477-2478. doi:10.1056/NEJMc2029240

5. Clayton DG, Webb RK, Ralston AC, Duthie D, Runciman WB. Pulse oximeter probes. A comparison between finger, nose, ear and forehead probes under conditions of poor perfusion. Anaesthesia. 1991;46(4):260-265. doi:10.1111/j.1365-2044.1991.tb11492.x

6. Budidha K, Kyriacou PA. In vivo investigation of ear canal pulse oximetry during hypothermia. J Clin Monit Comput. 2018;32(1):97-107. doi:10.1007/s10877-017-9975-4

7. Şenaylı YA, Keskin G, Akın M, et al. A prospective study for an alternative probe site for pulse oximetry measurement in male patients with severe burn trauma: penile shaf. Turk J Med Sci. 2023;53(2):504-510. doi:10.55730/1300-0144.5610

8. Leppänen T, Kainulainen S, Korkalainen H, et al. Pulse Oximetry: The Working Principle, Signal Formation, and Applications. Adv Exp Med Biol. 2022;1384:205-218. doi:10.1007/978-3-031-06413-5_12

9. Braun F, Bonnier G, Theurillat P, et al. Influence of Measurement Location on Reflectance Pulse Oximetry in Sleep Apnea Patients: Wrist vs. Upper Arm. Annu Int Conf IEEE Eng Med Biol Soc IEEE Eng Med Biol Soc Annu Int Conf. 2021;2021:1297-1300. doi:10.1109/EMBC46164.2021.9630185

10. Ali J, Cody J, Maldonado Y, Ramakrishna H. Near-Infrared Spectroscopy (NIRS) for Cerebral and Tissue Oximetry: Analysis of Evolving Applications. J Cardiothorac Vasc Anesth. 2022;36(8 Pt A):2758-2766. doi:10.1053/j.jvca.2021.07.015

11. Shepherd SJ, Pearse RM. Role of central and mixed venous oxygen saturation measurement in perioperative care. Anesthesiology. 2009;111(3):649-656. doi:10.1097/ALN.0b013e3181af59aa

12. Lee CP, Bora V. Anesthesia Monitoring of Mixed Venous Saturation. In: StatPearls. StatPearls Publishing; 2024. Accessed May 8, 2024.