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SpO2 monitoring in the highly dependent or critically ill infant or child

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Pulse oximetry is a non-invasive technology used to estimate arterial oxygen saturation of haemoglobin by applying light-emitting diodes to an area of the body with good local blood flow. Red and infrared light is shone through the blood-perfused tissue under the sensor and received by an opposing detector probe. The information is transmitted back to a signal-processing unit (monitor) and the calculated estimation of oxygen saturation is displayed (SpO2). Pulse oximetry is used on virtually all patients in the Paediatric Intensive Care and High Dependency Units. Therefore, it is important that the nurse caring for the critically and acutely ill infant/child in these units has a clear understanding of the principles of pulse oximetry and its benefits and limitations in use in order to correctly inform patient management.

This guidance is intended as a resource for staff involved in caring for children in the Paediatric Critical Care unit that require SpO2 monitoring (pulse oximetry). The guideline has been constructed after a literature search and review of sourced journals, textbooks, best practice guidelines, manufacturer guidelines and recommendations, and external nurse expert peer review and opinion. See also recommendations and further information at end of this guideline.


This guideline is intended to support nurses involved in caring for the highly dependent or critically ill infant or child requiring SpO2 monitoring (pulse oximetry) within the Paediatric Critical Care Unit at the Royal Hospital for Children, Glasgow.


All nursing staff involved in the monitoring of SpO2 (pulse oximetry) in the Paediatric Critical Care Unit should be familiar with this nursing procedural guideline.


SpO2 Probe (Examples):

i. Monitor compatible SpO2 probe (disposable adhesive more commonly used)
E.g. Covidien Nellcor OxiMax® MAXN, MAXI or MAXP

Nellcor™ SpO₂ Adhesive Sensors | Medtronic

Fig 1. Fig 2.  Fig 3.


For continuous SpO2 monitoring in PICU:

ii. SpO2 monitor connecting lead/cable (Blue) & Nellcor SpO2 module4  



For continuous SpO2 monitoring during patient transfer/discharge from PICU:

iii. SpO2 monitor connecting lead/cable (Grey) & Phillips MMS module4





Disposible apron
Non-sterile gloves




Gather all necessary equipment & ensure the correct lead used with the correct module.

E.g Blue lead with Nellcor module

      Grey lead with portable MMS  module


See Fig. 4 & 5 above

The Blue lead/cable (M1943NL) must be used with the Nellcor SpO2 module &  Philips Intellivue system for sensor accuracy4

The Grey lead/cable should be used in the Philips MMS  module4 (i.e. for patient transfer)

Using the wrong lead/cable in the wrong module will give inaccurate or false SpO2 readings4

Make sure the probe and monitoring equipment/module is clean and in good working order

In order to minimise the risk of cross infection and ensure that the equipment is suitable for use.

Set-up for new patient to PICU:

Switch on Phillips monitoring system and ensure Nellcor SpO2 module is correctly slotted in to the system.

Plug in SpO2 lead/cable (Blue) into the Nellcor module (Fig. 4) and connect  disposable probe to lead

To ensure monitor performs self calibration and checks prior to patient connection.

To ensure the nurse can see which side the probe is emitting infrared light and thus help determine correct positioning of probe.4

The nurse should wash their hands and don apron and gloves

In order to minimise the risk of cross infection.5

Check correct type and size of probe is selected for the infant or child                    

Using the wrong size probe may lead to the 'penumbra' effect and thus give inaccurate readings.6

Sensor placement & site: (Fig. 1, 2, 3)

Select a suitable area for the probe to be sited ensuring probe is correct type for area and age of child.







The sensor should be positioned to ensure that the LED & photodetector are aligned directly across from one another with 5-10mm of tissue between them. 8



Ensure site selected is clean, dry and free from discolouration.


Using wrong site and/or type of probe may result in inability of the sensor to track the pulse thus giving inaccurate readings.6,7

The site chosen should have a pulsatile vascular bed. For example, a finger, toe, earlobe, palm or foot.2,7,8

The sensor should be placed on the extremity opposite arterial lines and non-invasive blood pressure devices so that pulsatile blood flow is not impeded.7,8

In neonates and infants, the preferred site is the foot or hand (tissue is thinner allowing light to transmit through & probe to pick up reading).

In older children/adults preferred site is the index finger. Ensure light source on sensor is placed on nail side of digit 2,8

This ensures light is transmitted between the emittor/detector, through the digit/area applied and across the arteriolar bed.

If sensor-site (skin) is too thick or thin, pigmented, dirty or coloured - e.g. dark nail polish - appropriate light transmission may be affected and errors in measurement may occur.9,10,11,12

Attach sensor probe as per manufacturers’ instructions.



After a few seconds ensure adequate waveform displayed and that pulse corresponds to that of the infant/child. 



Where possible avoid using tape to secure to secure sensor to skin.



To ensure that the probe is detecting the pulse and calculating the saturation accurately.4

Pulse strength is equal to the fullness of the waveform. This waveform is vital in determining if the saturation recording is reliable.7,8,13

Sensors attached too tightly may cause erroneously low readings. 14

Using additional tape can restrict blood flow to site and cause inaccurate readings.14,15

Additional tape can also cause damage to the sensor and to the patient’s skin.16

Ensure audible pulse and alarm limits are set



To ensure that nursing staff are given early warning of potential problems.

Most saturation monitors have default alarm settings so individual patient adjustment is always required.

Check the sensor probe, placement and skin site regularly (maximum 8 hourly & at least 2 hourly if patient has poor peripheral perfusion).

To ensure probe is still attached correctly and not damaged. 

To ensure that prolonged use does not cause discomfort or pressure damage.

Ensure any change in observations is documented and reported to nurse-incharge

To help ensure that any potential deterioration or problem is quickly identified and managed appropriately.

Ensure all nursing staff in PICU have access to teaching materials on the principles and uses of pulse oximetry.

To ensure that nursing staff are aware of the safe and unsafe limitations of pulse oximetry monitoring.8,12

The SpO2 will be displayed continuously via the monitor and will automatically be recorded on the hour. Each hour the nurse should check and validate (if accurate) the child’s saturation.

The PICU Clinical Information System will record whatever saturation is being monitored/displayed.17

It will not take account of other factors which may lead to an inaccurate recording. For example, if the probe has slipped off or is incorrectly attached, or if the lead/cable is not correct for module.

It is therefore vital that the nurse checks the saturation reading ‘recorded’ and adds comments or events where applicable.


Pulse oximetry is a non-invasive technology used to estimate arterial haemoglobin oxygen saturation (SaO2), by measuring the absorption of light in human tissue beds. The pulse oximeter detects and calculates the absorption of light by functional haemoglobins to produce a measurement, the SpO2.2,4,7,8,13,14,18,19,20,21

Pulse oximetry can be an extremely valuable non-invasive means of monitoring. However, it has limitations in its use and the nurse must be aware of these. Limitations include motion artefact, poor perfusion, irregular heart rhythms, children with cynaotic congenital heart disease, electromagnetic interference, probe positioning, ambient light interference and abnormal haemoglobin states, such as carboxyhaemoglobin or methaemoglobinaemia.8,12,13,18,19,20,21

  1. Collins, CL Andersen, CC (2007) Deceptive simplicity: systemic oxygen delivery and pulse oximetry. Journal of Paediatrics and Child Health, Vol. 43, pp. 510-512.
  2. Ortega, R Hansen, CJ  Elterman, K  Woo, A (2011) Videos in clinical medicine: pulse oximetry. The New England Journal of Medicine, Vol. 363, e33.
  3. Elliot, M Tate, R Page, K (2006) Do clinicians know how to use pulse oximetry? A literature review and clinical implications. Australian Critical Care, Vol. 19 (4), pp 139-144.
  4. Nellcor™ (2011) A technology overview of the Nellcor™ OxiMax Pulse Oximetry System. Covidien, Colorado.  
  5. NHS GG&C (2017) NHS Greater Glasgow Prevention and Control of Infection Manual (2017) NHS Greater Glasgow Control of Infection Committee Policy. NHS Scotland.
  6. Engel, MS  Kochilas, LK (2016)  Pulse oximetry screening: a review of diagnosing critical congenital heart disease in newborns. Medical Devices:Evidence and Research, Vol. 9, pp. 199-203.
  7. DeMeulenaere, S (2007) Pulse oximetry: uses and limitations. The Journal for Nurse Practitioners - JNP, May, pp. 312-317.
  8. Fouzas, S Priftis, KN Anthracopoulos, MB (2011) Pulse oximetry in pediatric practice. Pediatrics, Vol. 128 (4), pp.740-752.
  9. Ballesteros-Peña, S, Fernández-Aedo, I Picón, A Lorrio-Palomino, S (2015)  Influence of nail polish on pulse oximeter readings of oxygen saturation: a systematic review. Emergencias, Vol. 27, pp. 325-331.
  10. Bickler, PE Feiner, JR Severinghaus, JW (2005) Effects of skin pigmentation on pulse oximeter accuracy at low saturation. Anesthesiology, Vol. 102, pp 715-719.
  11. Hinkelbein, J Genzwuerker, HV Sogl, R Fiedler, F (2007) Effect of nail polish on oxygen saturation determined by pulse oximetry in critically ill patients. Resuscitation, Vol. 72, pp 82-91.
  12. Yont, GH  Korhan, EA  Dizer, B (2014) The effect of nail polish on pulse oximetry readings. Intensive and Critical Care Nursing, Vol. 30, pp. 111-115.
  13. Chan, ED  Chan, MM  Chan, Malory M (2013) Pulse oximetry: Understanding its basic principles facilitates appreciation of its limitations. Respiratory Medicine, Vol. 107, pp. 789-799.
  14. Phillips Medical Systems (2003)  Understanding Pulse Oximetry: SpO2 Concepts. Available at:
  15. PA-PSRS (2005) Skin integrity issues associated with pulse oximetry. Pennsylvania Patient Safety Advisory, Vol. 2 (2), June. Available at:
  16. Kumar, R  Bunker, D  Martin, A  Pegg, S (2012) Case report: Thermal injury from a pulse oximeter. ResearchGate, ANZBA-Australian and New Zealand Burns Association.
  17. Lamb, C & iMD-Soft (2009) C.I.S. Basic Help File, Yorkhill NHS Division PICU and HDU Clinical Information System (CIS), pp 12-13. Greater Glasgow & Clyde Health Board, Glasgow
  18. Ross, PA  Newth, CJL  Khemeni, RG (2014) Accuracy of pulse oximetry in children. Pediatrics, Vol. 133, pp. 22-29.
  19. Salyer, J W (2003) Neonatal and pediatric pulse oximetry. Respiratory Care, Vol. 48 (4), pp 386 - 398
  20. Talke, P Stapelfeldt, C (2006) Effect of peripheral vasoconstriction on pulse oximetry. Journal of Clinical Monitoring and Computing, Vol. 20, pp 305-309.
  21. Jubran, A (2015) Pulse oximetry. Critical Care, Vol. 19 (272), pp.1-7.
Editorial Information

Last reviewed: 09 May 2022

Next review: 09 May 2025

Author(s): Jeanette Grady

Version: 5

Approved By: PICU Guidelines Group

Reviewer Name(s): L. Moore, G. Irwin