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Pulse Oximetry for Detecting Aspiration in Adults: Review of Evidence

This article discusses the use of pulse oximetry as a tool for detecting aspiration in adults with swallowing impairments. It reviews several studies that have examined the relationship between pulse oximetry readings and aspiration during videofluoroscopy and bedside evaluations. The findings suggest that pulse oximetry may be a valuable addition to the bedside assessment of swallowing function.

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Pulse Oximetry for Detecting Aspiration in Adults: Review of Evidence

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  1. Extravaganza 2007

  2. Who are we? • The Adult Swallowing EBP Group comprises both metropolitan and rural members. • Formed in March 2007, following the division of Adult Swallowing and Communication group into 3 separate groups (Adult swallowing, speech and language). • We are all practicing Speech Pathologists with a particular interest in the management of adult swallowing impairments. • We currently have 15 active members, with 5 more joining in the new year.

  3. Pulse Oximetry

  4. Why pulse oximetry? • We know that bedside evaluations of swallowing are not always sensitive enough to detect aspiration. Many patients who do not overtly aspirate on bedside evaluations have been shown to aspirate on videofluoroscopy (MBS). • e.g. up to 67% of acute stroke patients who aspirate, silently aspirate (as identified on MBS). (Daniels et al, 1998). • e.g. 82% of neurologically impaired patients silently aspirated on MBS (Smith, Logemann et al, 1999). • Many clinicians use pulse oximetry as part of the bedside assessment. Our CAT aimed to review the evidence regarding the use of pulse oximetry in detecting aspiration. • Hypothesis: Aspiration of food into the airways causes bronchoconstriction and leads to oxygen desaturation (Collins and Bakheit, 1997).

  5. What is Pulse Oximetry? • A non-invasive, easy to use method of measuring arterial blood oxygenation (Sp02) in real time. • A valuable tool for bedside monitoring of oxygenation (Sherman 1999).

  6. Principles of Pulse Oximetry • Based on the light absorption characteristics of haemoglobin, which differ depending on whether the haemoglobin has oxygen attached. • Uses a light emitter that shines through a reasonably translucent site with good blood flow. • The pulse oximeter converts the light absorption information into a percentage of oxygen saturation. • Typical adult/paediatric sites are the finger, toe, pinna (top) or lobe of the ear. (Oximetry.org)

  7. Collins & Bakheit (1997): Level III(2) • Used pulse oximetry to measure SpO2 during MBS in 54 stroke patients. • The presence or absence of aspiration was predicted to 81.5% accuracy, using pulse oximetry. Drop of ≥2% was considered clinically significant. • The findings were more sensitive when Sp02 readings 2 minutes after swallow were used in conjunction with readings during the swallow, to account for delay in desaturation after swallow event. • There was lower sensitivity in female patients (prediction rate 67%). • False negatives occurred in patients who were smokers or who had chronic lung disease (they aspirated but did not desaturate).

  8. Sellars, Dunnet & Carter (1998): Level III(2) • Examined SpO2 levels during MBS in 6 patients with neurological impairment • The study had a number of limitations, including:- • Small sample size • ‘Normal’ subjects did not have a VF • Heterogenous patient group • No significant variation in Sp02 among ‘normal’ subjects on swallow. • Following feeding, small but significant drop in Sp02 for dysphagic patient group but not normals. • Found no statistical link between aspiration and Sp02 fluctuations.

  9. Sherman, Nisenboum, Jesberger, Morrow, Jesberger (1999): Level IV • Examined SpO2 during MBS for 46 patients (16 stroke patients, 30 patients with ‘other’ diagnoses) • The study showed a relationship between the degree of oxygen desaturation and the severity of swallowing abnormality. 74% of aspirators were identified using pulse oximetry, however found false positives e.g. some patients ‘not penetrating, not aspirating’ had decline in Sp02 of 4%. • Patients who exhibited aspiration or penetration without clearing had a larger drop in Sp02 than patients who cleared penetration or did not penetrate. • Study did not state what level of Sp02 decline was considered ‘clinically significant’.

  10. Colodny (2000 and 2001): Level III(2) • Examined SpO2 during FEES for 104 patients with dysphagia and measured SpO2 during bedside assessment for 77 healthy controls (controls did not have a FEES). • Aspirators had lower Sp02 levels before, during and after feeding than non-aspirators. • There was a decline in SpO2 during swallowing for dysphagic patients, regardless of aspiration. Normals did not desaturate during feeding, however normals did not have a FEES (therefore, can we draw valid conclusions from this?). • There was no significant difference in Sp02 reduction between aspirator and non-aspirator groups.

  11. Higo, Tayama, Watanabe & Nito (2003): Level III(2) • Measured Sp02 during MBS; 204 subjects. • All subjects at risk of having dysphagia to some extent (included oesophageal disorders and laryngectomees); no true ‘controls’. • Aspirators and non-aspirators both showed SpO2 decline when swallowing on MBS. • Some aspirators did not desaturate. • Pulse oximetry was not statistically significant in detecting aspiration.

  12. Wang, Chang, Chen & Hsiao (2005): Level III(2) • Measured pulse oximetry during MBS; patients and control group. • Range of desaturation for ‘normals’ on swallow was 0–3% SpO2 (20% had 3% decrease; 45% had 2% decrease; 25% had 1% decrease & 10% had no change). • Drop of >3% SpO2 was therefore clinically significant in dysphagic population. Significant proportion of patients with dysphagia showed >3% drop in SpO2, however… • ‘No significant relationship between reduction in SpO2 and aspiration episodes on videofluoroscopy.’

  13. Ramsey, Smithard & Kalra (2006): LevelIII(3) • 189 stroke patients; pulse oximetry measures were taken during MBS. • When Sp02 drop >2% considered significant, study found low sensitivity/specificity and predictive values. • When Sp02 drop of >5% considered significant, study found pulse oximetry was more sensitive (i.e. picked up more aspirators) but specificity and predictive values were reduced (had more false positives). • 43.5% of stroke patients showed some desaturation in the absence of any aspiration or penetration. • No association between penetration/ aspiration (on MBS) and desaturation.

  14. Studies with limitations • Smith, Lee, O’Neill & Connolly (2000): Level IV • Found bedside assessment and pulse oximetry, used together, could predict aspiration and/or penetration BUT couldn’t predict when no aspiration or penetration occurred (i.e. high false positive rate). • Major limitation of study - no control group (therefore did not ascertain standard desaturation in ‘normal’ populations). • Zaidi, Smith, King, Park, O’Neill & Connolly (1995): Level III(2) • Examined saturation levels on liquid swallow separately from bedside assessment. • Fundamentally flawed study; lacked objective assessment of swallow, therefore unable to determine whether aspiration occurred or not. • Cannot draw a valid clinical conclusion from this study. Findings did not contribute to our CAT for this reason

  15. Clinical bottom line…

  16. Discussion… Why do dysphagic patients desaturate when eating (even if they don’t aspirate!)? • Poor breath-swallow coordination (Teramoto, 1996; Colodny, 2001) • Increased pharyngeal transit time and increased apnoeic period (Sellars, 1998) • Anticipatory ‘breath hold’, which then merges into the true swallowing apnoea, ? Due to delayed swallow initiation (Sellars, 1998). • Co-morbid diseases also have an independent effect on oxygen saturation during eating e.g. neuromuscular disease, severe obstructive lung disease (Sherman et al, 1999; Colodny, 2001).

  17. Directions for further research… • Do dysphagic patients desaturate on all physiologic activities or specifically during oral feeding? (Colodny, 2000). • Is there a delay between the hypoxic event and the detection of it on pulse oximetry? Has this influenced the results of research so far? (Collins et al, 1997).

  18. Work in progress… • Dysphagia Rehab Strategies: • Mendelsohn manoeuvre • Effortful swallow • Masako manoeuvre • Shaker technique

  19. References CAP references: • Collins, M. & Bakheit, A. (1997). Does Pulse Oximetry Reliably Detect Aspiration in Dysphagic Stroke Patients? Stroke, 28(9): 1773-1775. • Colodny, N. (2000). Comparison of Dysphagics and Non-dysphagics on Pulse Oximetry during Oral Feeding. Dysphagia, 15: 68-73. • Colodny N., (2001). Effects of Age, Gender, Disease and Multisystem Involvement on Oxygen saturation levels in dysphagic persons. Dysphagia 16: 48-57. • Higo, R., Tayama, N., Watanabe, T., and Nito, T. (2003). Pulse Oximetry monitoring for the evaluation of swallowing function. European Archives of Otolaryngology 260; 124-127. • Rogers, B., Msall, M., and Shucard, D., (1993). Hypoxemia During Oral Feedings in Adults with Dysphagia and Severe Neurological Disabilities. Dysphagia, 8: 43-48. • Sellars, C., Dunnet, C., Carter, R. (1998). A Preliminary comparison of videofluoroscopy of swallow and pulse oximetry in the identification of aspiration in dysphagic patients. Dysphagia, 13, 82-86. • Sherman, B., Nisenboum, J., Jesberger, B., Morrow, C & Jesberger, J. (1999). Assessment of dysphagia with the use of pulse oximetry. Dysphagia, 14: 152-156. • Smith, H., Lee, S., O’Neill, P., & Connolly, M. (2000). The Combination of Bedside Swallowing Assessment and Oxygen Saturation Monitoring of Swallowing in Acute Stroke: A Safe and Humane Screening Tool. Age and Ageing, 29: 495-499. • Wang, T-G., Chang, Y-C., Chen, S-Y., Hsiao, T-Y. (2005). Pulse oximetry does not reliably detect aspiration on videofluoroscopic swallowing study. Arch Phys Med Rehabil, 86:730-4. • Zaidi, N., Smith, H., King, S., Park, C., O’Neill P., & Connolly, M. (1995). Oxygen Desaturation on Swallowing as a Potential Marker of Aspiration in Acute Stroke. Age and Ageing, 24: 267-270. • DJC Ramsey, DG Smithard, L Kalra. 'Can Pulse Oximetry or a Bedside Swallowing Ax be used to detect aspiration after stroke'. (2006). Stroke Journal 37 (12) 2984-2988 Presentation References: • Daniels, S., Bailey, K., Priestly, D., Herrington, L., Weisberg, L., Foundas, M. (1998) Aspiration in patients with Acute Stroke. Arch Phys Med Rehabil 1998;79:14-9 • Smith, C., Logemann, J., Colangelo, L., Rademaker, A., & Pauloski, B. (1999). Incidence and patient characteristics associated with silent aspiration in the acute care setting. Dysphagia. Vol 14: 1-7 • Teramoto, S., Fukuchi, Y & Ouchi, Y. (1996). Oxygen desaturation on swallowing in patients with stroke; what does it mean? Age and Ageing. 25: 333-334 • Websites: Oximetry.org: http://www.oximetry.org/pulseox/principles.htm

  20. Interested in joining? Contact Eva Katalinic or Lisa Howard at Prince of Wales to join, or if you would like a copy of the reference list. Teleconferencing facilities available for rural members wishing to join. Lisa.Howard@sesiahs.health.nsw.gov.au Eva.Katalinic@sesiahs.health.nsw.gov.au Phone: (02) 93828220

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