Guidelines for the measurement of respiratory function. Recommendations of the British Thoracic Society and the Association of Respiratory Technicians and Physiologists. Respir Med. 1994; 88:(3)165-194

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

Davidson AC, Banham S, Elliott M BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults. Thorax. 2016; 71:ii1-ii35

Fluck RR, Schroeder C, Frani G, Kropf B, Engbretson B. Does ambient light affect the accuracy of pulse oximetry?. Respir Care. 2003; 48:(7)677-680

Haynes JM. The ear as an alternative site for a pulse oximeter finger clip sensor. Respir Care. 2007; 52:(6)727-729

Johnson CL, Anderson MA, Hill PD. Comparison of pulse oximetry measures in a healthy population. Medsurg Nurs. 2012; 21:(2)70-75

Jubran A. Pulse oximetry. Crit Care. 2015; 19:(1)

Luks AM, Swenson ER. Pulse oximetry for monitoring patients with COVID-19 at home. Potential pitfalls and practical guidance. Ann Am Thorac Soc. 2020; 17:(9)1040-1046

P179 Patient safety alert: a prospective study on 100 patients highlighting inaccuracy of pulse oximeter finger probes used on ear lobes. 2018.

Mannheimer PD. The light–tissue interaction of pulse oximetry. Anesth Analg. 2007; S10-17

Milner QJW, Mathews GR. An assessment of the accuracy of pulse oximeters. Anaesthesia. 2012; 67:(4)396-401

NHS Improvement. Patient Safety Alert. Risk of harm from inappropriate placement of pulse oximeter probes. 2018. (accessed 26 May 2021)

Nitzan M, Romem A, Koppel R. Pulse oximetry: fundamentals and technology update. Med Devices (Auckl). 2014; 7:231-9

O'Driscoll BR, Howard LS, Earis J, Mak V BTS guideline for oxygen use in adults in healthcare and emergency settings. Thorax. 2017; 72:ii1-ii90

Royal College of Physicians. National Early Warning Score (NEWS) 2. Royal College of Physicians. 2017. (accessed 26 May 2021)

Shenoy N, Luchtel R, Gulani P. Considerations for target oxygen saturation in COVID-19 patients: are we under-shooting?. BMC Med. 2020; 18:(1)

Placement of finger oximeter on the ear: comparison with oxygen saturation values taken from the finger

10 June 2021
11 min read
Volume 30 · Issue 11


Pulse oximetry is widely used to assess oxygen saturation (SpO2) in order to guide patient care and monitor the response to treatment. However, inappropriate oximeter probe placement has been shown to affect the measured oximetry values in healthy and normoxic outpatients. This study evaluated how treatment decisions might be impacted by SpO2 values obtained using a finger probe placed on the pinna of the ear in a cohort of 46 patients receiving non-invasive ventilation compared with values obtained from a probe on the finger and the results of arterial blood gas (ABG) (SaO2) analysis. Bland-Altman analysis was performed to evaluate agreement between the methods. Finger probe saturation was not statistically different from SaO2, with a mean difference of -0.66% (P>0.05). Saturation from the ear was significantly different (-4.29%; P<0.001). Subgroup analysis in hypoxic patients (SaO2<90%) showed a significant difference between ABG SaO2, and finger and ear SpO2. The study provides evidence that placement of a finger probe on the ear is unsafe clinical practice, potentially leading to patient mismanagement.

Pulse oximetry is an indirect, non-invasive, accurate and safe method of measuring oxygen saturations (SpO2). It is widely used in a range of outpatient and inpatient settings to record clinical observations, which includes calculation of the patient's National Early Warning Score 2 (NEWS 2) (Royal College of Physicians, 2017). A number of treatment protocols are guided by the results of oxygen saturation measurements, for example during assessment for, and response to, interventions such as oxygen therapy (O'Driscoll et al, 2017) and non-invasive ventilation (NIV) (Davidson et al, 2016). More recently, pulse oximetry has been used to monitor the condition of patients with COVID-19 both in hospital (Shenoy et al, 2020) and home settings (Luks, 2020).

Pulse oximeters are designed to record SpO2 by measuring the absorption of specific wavelengths of light by oxygenated haemoglobin (HbO2) versus that in deoxygenated haemoglobin (Hb). Oximeter probes contain light-emitting diodes (LEDs) that project light of two wavelengths—red (660 nm) and infrared (940 nm)—from one side of the probe towards a photodetector on the opposite side. Pulsatile arterial blood during systole delivers oxyhaemoglobin (HbO2) to the tissue, which results in the absorption of more infrared light and so less light will reach the photodetector. The level of oxygen saturation of the blood therefore determines the degree of light absorption. The result is processed and a digital readout of the oxygen saturation results is shown on the oximeter screen, represented as SpO2.

Register now to continue reading

Thank you for visiting British Journal of Nursing and reading some of our peer-reviewed resources for nurses. To read more, please register today. You’ll enjoy the following great benefits:

What's included

  • Limited access to clinical or professional articles

  • Unlimited access to the latest news, blogs and video content