Use of Arterial Oxygen Saturation, Heart Rate, and Blood Pressureas Indirect Objective Physiologic Markers to Predict Aspiration

Steven B. Leder, PhDYale University School of Medicine, New Haven, Connecticut, USA

Abstract. If an indirect bedside variable can reliablypredict whether an objective instrumental dysphagiaevaluation is needed, time and money can be saved with-out compromising patient care. To date, the search for areliable indirect subjective marker of aspiration has notbeen successful. However, research on indirect objectivemarkers of aspiration is alluring. The purpose of the pre-sent study was to investigate changes, if any, in thephysiologic parameters of arterial oxygen saturation(SpO2), heart rate, and blood pressure during simulta-neous objective confirmation of aspiration status withFiberoptic Endoscopic Evaluation of Swallowing(FEESt). Sixty adult subjects were divided into 4 groupsof 15. Group 1 did not require supplemental oxygen anddid not aspirate. Group 2 did not require supplementaloxygen and exhibited aspiration. Group 3 requiredsupplemental oxygen and did not aspirate. Group 4 re-quired supplemental oxygen and exhibited aspiration. Si-multaneous SpO2, heart rate, and blood pressure mea-surements were collected at 1-min intervals, i.e., pre-FEES baseline for 5 min; during FEES; and post-FEESfor 5 min. Results indicated no significant differences inSpO2 levels based on aspiration status or oxygen require-ments for any of the 4 groups. A consistent pattern ofhigher heart rate values during FEES and continuing for5 min post-FEES was observed for all 4 groups. A con-sistent pattern of higher blood pressure values duringFEES and then lower blood pressure values post-FEESwas observed for all 4 groups. It was concluded that theuse of changes in SpO2, heart rate, or blood pressurevalues as indirect objective markers of aspiration was notsupported.

Key words: Aspiration — Fiberoptic endoscopicevaluation of swallowing — Arterial oxygen saturation— Heart rate — Blood pressure — Deglutition — De-glutition disorders.

There is a substantial body of research investigatingwhether a small number of indirect subjective variablescan reliably predict aspiration [1–7]. The reasoning isstraightforward: If a subjective bedside variable can re-liably predict whether an objective instrumental dyspha-gia evaluation is needed, time and money can be savedwithout compromising patient care. Variables investi-gated include voice quality (wet, harsh, breathy, and vol-ume), cough (volitional or reflexive), gag reflex, anddysarthria. However, due to poor inter- and intrastudyagreement on variables [8] and the phenomenon of silentaspiration [9], no single subjective variable with accept-able positive and negative predictive values for aspira-tion has been determined.

Although the search for a single indirectsubjec-tive marker of aspiration has not been successful, re-search focusing on indirectobjectivemarkers of aspira-tion is alluring. Pulse oximetry provides accurate, non-invasive, and uninterrupted data on SpO2 levels [10] and,therefore, has been the most commonly used variablereported in the dysphagia literature to date. However,studies using pulse oximetry, reviewed below, have ei-ther methodology problems or insufficient sample sizesfrom which to draw conclusions.

A number of studies monitored SpO2 duringmeals but with no objective determination of aspirationstatus. Individuals with severe chronic obstructive pul-monary disease exhibited a mean decrease of only 1.8%during mealtime, with SpO2 desaturation occurring morecommonly in patients with lower baseline SpO2 satura-tion [11]. A case study reported that a 25-year-old

Correspondence to:Steven B. Leder, Ph.D., Yale University School ofMedicine, Section of Otolaryngology, Communication Disorders Cen-ter, 20 York St., YPB-468, New Haven, CT 06504, USA.E-mail: Steven.Leder@Yale.edu

Dysphagia 15:201–205 (2000)DOI: 10.1007/s004550000028

© Springer-Verlag New York Inc. 2000

woman with severe kyphoscoliosis exhibited transientepisodes of SpO2 desaturation while eating. The episodesstopped after administering supplemental oxygen deliv-ered by nasal prongs [12]. Acute stroke patients exhib-ited a mean fall in SpO2 of 2.64% after swallowing 10 mlof water, while young healthy subjects and age- and sex-matched hospital controls both exhibited a mean fall inSpO2 of 1.12% after a similar water swallow—only a1.52% difference [13]. A case study [14] that monitoredSpO2 in severely disabled, oral-eating people, (7 subjectswith cerebral palsy and 1 subject with epilepsy) showedthat both feeding and posture changes, such as transitionfrom the supine position to sitting, resulted in mixedfindings, i.e., decreased and increased mean SpO2 val-ues.

Two case studies assessed aspiration status usinga modified barium swallow but monitored SpO2 levelsduring meals at a later time. Individuals in both reportsreceived all nutrition orally. The first case study [15]reported on five children with severe cerebral palsy. Itfound that upright oral feeding resulted in hypoxemiadespite the fact that the modified barium swallowshowed that four children did not aspirate and one childexhibited only trace aspiration. The second case study[16] reported on three adults with severe neurologicaldisabilities (case 1 exhibited a moderate amount of as-piration, case 2 did not aspirate, and case 3 had traceaspiration of only liquids). Episodic hypoxemia associ-ated with specific food consistencies was reported for allsubjects. Because of nonsimultaneous data collectionprocedures for modified barium swallow and SpO2 re-sults, however, no direct association between aspirationand hypoxemia can be made from these two case reports.

Four studies [17–20] reported monitoring SpO2

with pulse oximetry simultaneously with an objectiveassessment of aspiration status, i.e., three with modifiedbarium swallow [17–19] and one with FEES [20]. Con-flicting results were reported. One study [17] on six pa-tients with neurogenic dysphagia found no significantrelationship between changes in SpO2 and aspiration.Another study [18] reported an 81.5% accuracy rate inpredicting aspiration among dysphagic stroke patientswhen the criterion of a 2% drop in SpO2 was used. How-ever, use of a 2% decline was both arbitrary (±2% wasthe margin of error for the equipment) and unsupported(a significant decline in SpO2 was reported to be at least4%) [17]. In the third study [19], the relationship be-tween pharyngeal phase dysphagia and aspiration withSpO2 levels was investigated in 46 adult subjects withsuspected swallowing abnormalities. A significant de-cline in SpO2 was found in subjects who exhibited bothaspiration and laryngeal penetration without clearingwhen compared with subjects who penetrated andcleared or did not penetrate. Possible confounding fac-

tors, however, included sampling errors, such as size andage differences, and data management problems, such ascomparison of group mean baseline SpO2 levels to thelowest single oxygen desaturation level during eatingwith no report of group mean SpO2 desaturation levelsand regression to the mean as a result of computingdifference scores rather than baseline scores [20]. Fi-nally, simultaneous FEES results and SpO2 monitoringwere reported [20] on 181 elderly nursing home patientsreferred for suspected dysphagia. No relationship wasfound between SpO2 levels and laryngeal penetration oraspiration [20].

In order to clarify the conflicting reports in theliterature, there is a need for additional objective swal-lowing evaluations with simultaneous assessment ofSpO2, as well as determination of other potential indirectobjective markers of aspiration [21]. The purpose of thisstudy was to investigate changes, if any, in the physi-ologic parameters of SpO2, heart rate, and blood pressureduring simultaneous objective confirmation of aspirationstatus with FEES [22,23].

Materials and Methods

Subjects

The study was approved by the Human Investigation Committee, YaleUniversity School of Medicine. In a prospective manner, 60 consecu-tive adult subjects referred for dysphagia evaluations were included(Table 1). All patients were in an intensive care unit (cardiothoracic,medical, neurosurgical, or surgical), were not taking nutrition orally,and were cleared medically for a dysphagia evaluation prior to initiat-ing oral feedings. Patients who received supplemental oxygen (groups3 and 4) required it at all times, not just during FEES. The 60 subjectswere divided into 4 groups of 15. Group 1 did not receive supplementaloxygen and did not aspirate. Group 2 did not receive supplementaloxygen and exhibited aspiration. Group 3 received supplemental oxy-gen and did not aspirate. Group 4 received supplemental oxygen andexhibited aspiration.

Procedures

All patients were in monitored intensive care unit beds which allowedfor data collection via hardcopy printout at 1-min intervals (MerlinModel 66 M1092 central monitoring unit, Hewlett Packard, Andover,MA, USA). This permitted real-time simultaneous collection of heartrate, mean arterial blood pressure, i.e., (diastolic pressure × 2) + (sys-tolic pressure) ÷ 3, and SpO2 values during FEES. Whenever possiblethe pulse oximeter probe was placed on a finger on the arm oppositefrom that which blood pressure values were taken.

The standard FEES protocol was followed with slight modifi-cations [22,23]. Equipment consisted of a 3.6-mm-diameter flexiblefiberoptic rhinolaryngoscope (Olympus ENF-P3, Melville, NY, USA),endoscope sheaths (Vision Science, Natick, MA, USA), light source(Olympus CLK-4, Melville, NY, USA), camera (ELMO MN401E,Plainview, NY, USA), and color monitor (Sharp 13GM100, Mahwah,NJ, USA). Briefly, each naris was examined and the scope passed

202 S.B. Leder: Physiologic Markers to Predict Aspiration

through the most patent naris without administration of a topical an-esthetic or vasoconstrictor to the nasal mucosa, thereby eliminating anypotential adverse anesthetic reaction and assuring the endoscopist of asafe physiologic examination [24]. The base of tongue, pharynx, andlarynx were viewed and swallowing was evaluated objectively withapproximately 5-ml food boluses dyed with blue food coloring forcontrast. The first food consistency introduced was puree (custard),followed by liquid (milk) and then a solid bolus (cracker), if indicated.No attempt was made to quantify the amount of aspiration. Aspirationwas defined as the entry of material into the airway below the level ofthe true vocal folds [25].

Prior to the start of FEES, the head of the subject’s bed waselevated maximally and then pre-FEES baseline data collected for 5min. During FEES, each bolus was synchronized with a specific minuteand then aspiration status (aspiration or no aspiration) was recorded.All aspiration status decisions were made by the author with 100%corroboration by another speech-language pathologist experienced inFEES interpretation. After the evaluation, 5 min of post-FEES datawere collected while the subject remained in the same position aspre-FEES and during FEES.

Results

There were no significant differences for age, gender, orduration of FEES testing (Table 1). Nasogastric tubeswere present in 34 of 60 (57%) subjects, and aspirationstatus was not influenced by its presence, i.e., a nasogas-tric tube was present in 16 of 30 (53%) subjects withoutaspiration and in 18 of 30 (60%) subjects with aspiration(Table 1).

Table 2 shows means and standard deviations forheart rate, blood pressure, and SpO2 for each of the 4groups pre-, during, and post-FEES. Student’st-tests forcorrelated samples were used to analyze the data. Therewere no significant differences in SpO2 levels based oneither aspiration status or oxygen requirements pre-, dur-ing, or post-FEES for any of the 4 groups.

A consistent pattern of higher heart rate valuesduring FEES and continuing for 5 minutes post-FEESwas observed for all 4 groups. Specifically, significantlyhigher heart rate values were observed between pre- and

during FEES for groups 2, 3, and 4, with group 1 exhib-iting higher but nonsignificant values. Heart rate re-mained elevated for groups 2, 3, and 4 post-FEES butwas not significantly different when compared with dur-ing-FEES values.

A consistent pattern of higher blood pressure val-ues during FEES and then lower blood pressure valuespost-FEES was observed for all 4 groups. Specifically,significantly higher blood pressure values were observedbetween pre- and during FEES for groups 1, 2, and 4,with group 3 exhibiting higher but nonsignificant values.Blood pressure dropped significantly for groups 1, 2,and 3 post-FEES, with a nonsignificant reduction forgroup 4.

Discussion

The presence of aspiration did not significantly changeSpO2 values. This was true whether or not supplementaloxygen was required. Therefore, the use of SpO2 as anindirect objective clinical marker of aspiration was notsupported by the present data.

Examination of the data in Table 2 shows that nogroup mean SpO2 level fluctuated greater than 0.07%.Inspection of individual subject data indicated that onlysubject No. 46 in group 4 (receiving supplemental oxy-gen and with aspiration) exhibited a change in SpO2 ofgreater than 4%, i.e., 97.2% pre-FEES, 94.3% duringFEES, and 93.0% post-FEES, for a maximum change of4.2%. In studies that investigated simultaneous SpO2 andaspiration, it was shown that the association betweenaspiration and change in SpO2 was highly variable, thatis, it was not uncommon for subjects to exhibit specificinstances of decreased SpO2 of 4% or greater regardlessof aspiration status [17,20]. In fact, simply changing pos-ture from supine to sitting resulted in both significantincreases and decreases in SpO2 values of 5% or less[14,26]. Therefore, any event that can potentially causeapnea, e.g., posture, swallowing, or coughing, is likely toinfluence SpO2 levels.

Table 1. Age and gender characteristics, nasogastric tube status, and mean duration of FEES testing for the 4 experimental groups and for all60 subjects

Group 1a Group 2b Group 3c Group 4d Total

Mean age (yrs:mos) 65:05 66:06 62:06 69:08 66:06Age range 37:02–89:11 24:01–94:11 35:11–82:08 46:11–90:06 24:01–94:11Gender (M/F) 8/7 8/7 7/8 11/4 34/26Nasogastric tube (Yes/No) 7/8 9/6 9/6 9/6 34/26Mean duration of FEES (minutes) 6.0 6.5 5.3 6.6 6.1N 15 15 15 15 60

aSubjects not receiving supplemental oxygen and without aspiration.bSubjects not receiving supplemental oxygen and with aspiration.cSubjects receiving supplemental oxygen and without aspiration.dSubjects receiving supplemental oxygen and with aspiration.

S.B. Leder: Physiologic Markers to Predict Aspiration 203

Just because a given variable exhibits statisticalsignificance does not mean it has clinical relevance,e.g., a mean desaturation of 1.8% from mean baseline“. . . appears miniscule, despite being a statistically sig-nificant change” [11]. Similarly, although statistical sig-nificance was found between oxygen desaturation andsubjects who exhibited aspiration or laryngeal penetra-tion without clearing, even Sherman et al. [19] stated that“This physiologic change, although statistically signifi-cant, was not clinically important. . .” Although SpO2

has theoretical clinical importance in dysphagia manage-ment, it does not appear to be a clinically relevant indi-rect marker of aspiration status.

In addition to SpO2 values, the pulse/heart ratevariable was able to be compared with that from twoprevious studies [14,20]. They reported that when sub-jects were fed, pulse rate increased from baseline. Thiscorroborated the heart rate data in this study that showedthat eating was a variable that increased heart rate for all4 groups. Another variable in our study that may haveinfluenced both heart rate and blood pressure values dur-ing FEES was transnasal passage of the endoscope fol-lowing 5 minutes of pre-FEES baseline data collection.However, since FEES coincided with feeding, its iso-lated contribution to heart rate and blood pressure valuescould not be determined.

Similar to previous studies, the presence of a na-sogastric tube did not influence aspiration status [27–29]or alter swallowing function, i.e., bolus transit and clear-ance and airway protection [30]. The presence of a na-sogastric tube, therefore, is not a confounding factorwhen performing either an endoscopic or a fluoroscopicswallowing evaluation.

Acknowledgments.Thanks are extended to Julian Espinosa, M.S., for

participating in the data collection phase of this study. This researchwas supported, in part, by the McFadden, Harmon, and Mirikitaniendowments.

References

1. Horner J, Massey EW, Riski JE, Lathrop DL, Chase KN: As-piration following stroke: clinical correlates and outcome.Neu-rology 38:1359–1362, 1988

2. Horner J, Massey EW, Brazer SR: Aspiration in bilateral strokepatients.Neurology 40:1686–1688, 1990

3. Horner J, Brazer SR, Massey EW: Aspiration in bilateral strokepatients: a validation study.Neurology 43:430–433, 1993

4. Linden P, Siebens AA: Dysphagia: predicting laryngeal penetra-tion. Arch Phys Med Rehabil 64:281–284, 1983

5. Linden P, Kuhlemeier KV, Patterson C: The probability of cor-rectly predicting subglottic penetration from clinical observa-tions.Dysphagia 8:170–179, 1993

6. Splaingard ML, Hutchins B, Sulton LD, Chaudhuri G: Aspira-tion in rehabilitation patients: videofluoroscopy vs bedside clini-cal assessment.Arch Phys Med Rehabil 69:637–640, 1988

7. Daniels SK, McAdam CP, Brailey K, Foundas AL: Clinicalassessment of swallowing and prediction of dysphagia severity.Am J Speech Lang Pathol 6(4):17–24, 1997

8. McCullough GH, Wertz RT, Rosenbek JC, Mills RH, Ross KB,Ashford JR. Inter- and intrajudge reliability of a clinical exami-nation of swallowing in adults.Dysphagia 15:58–67, 2000

9. Leder SB: Fiberoptic endoscopic evaluation of dysphagia toidentify silent aspiration.Dysphagia 13:19–21, 1998

10. Severinghaus JW, Kelleher JF: Recent development in pulseoximetry.Anesthesiology 76:1018–1038, 1992

11. Brown SE, Casciari RJ, Light RW: Arterial oxygen saturationduring meals in patients with severe chronic obstructive pulmo-nary disease.South Med J 76:194–198, 1983

12. Chapman KR, Rebuck AS: Dysphagia as a manifestation ofoccult hypoxemia.Chest 99:1030–1032, 1991

13. Zaidi NH, Smith HA, King SC, Park C, O’Neill PA, ConnollyMJ: Oxygen desaturation on swallowing as a potential marker ofaspiration in acute stroke.Age Ageing 24:267–270, 1995

14. Tamura F, Shishikura J, Mukai Y, Kaneko Y: Arterial oxygen

Table 2. Mean (and standard deviation) heart rate, blood pressure, and SpO2 measures pre-FEESa (5 minutes of baseline), during FEES, andpost-FEES (5 minutes for return to baseline) for group 1 (subjects not receiving supplemental oxygen and without aspiration), group 2 (subjects notreceiving supplemental oxygen and with aspiration), group 3 (subjects receiving supplemental oxygen and without aspiration), and group 4 (subjectsreceiving supplemental oxygen and with aspiration)

Heart rate Blood pressure SpO2b

Pre-FEES During Post-FEES Pre-FEES During Post-FEES Pre-FEES During Post-FEES

Group 1 81.2 83.5 83.1 101.1c 104.2 99.1d 97.5 97.5 97.3(20.6) (18.6) (19.1) (19.2) (19.9) (21.2) (1.5) (2.1) (2.3)

Group 2 91.2c 93.5 94.6 78.6d 84.0 81.1c 96.7 96.3 96.0(16.6) (18.0) (18.1) (12.6) (14.3) (14.2) (2.3) (0.9) (2.4)

Group 3 92.8c 95.8 96.7 88.6 92.1 86.5d 97.5 97.3 97.4(21.2) (22.0) (22.5) (14.9) (17.1) (16.8) (2.3) (1.6) (1.9)

Group 4 92.5c 94.4 95.2 85.6c 89.1 84.9 96.1 95.6 95.6(13.3) (14.4) (14.7) (11.4) (13.8) (15.7) (2.2) (3.9) (2.7)

aFEES4 fiberoptic endoscopic evaluation of swallowing.bSpO2 4 arterial oxygen saturation.cp < 0.05.dp < 0.01.

204 S.B. Leder: Physiologic Markers to Predict Aspiration

saturation in severely disabled people: effect of oral feeding inthe sitting position.Dysphagia 14:204–211, 1999

15. Rogers BT, Arvedson J, Msall M, Demerath RR: Hypoxemiaduring oral feeding of children with severe cerebral palsy.DevMed Child Neurol 35:3–10, 1993

16. Rogers BT, Msall M, Shucard D: Hypoxemia during oral feed-ings in adults with dysphagia and severe neurological disabili-ties.Dysphagia 8:43–48, 1993

17. Sellars C, Dunnet C, Carter R: A preliminary comparison ofvideofluoroscopy of swallow and pulse oximetry in the identi-fication of aspiration in dysphagic patients.Dysphagia13:82–86, 1998

18. Collins MJ, Bakheit AMO: Does pulse oximetry reliably detectaspiration in dysphagic patients?Stroke 28:1773–1775, 1997

19. Sherman B, Nisenboum JM, Jesberger BL, Morrow CA, Jes-berger JA: Assessment of dysphagia with the use of pulse ox-imetry. Dysphagia 14:152–156, 1999

20. Colodny N: Comparison of dysphagics and nondysphagics onpulse oximetry during oral feeding.Dysphagia 15:68–73, 2000

21. Sufit R: Oxygen desaturation during swallowing.Dysphagia8:49–50, 1993

22. Langmore SE, Schatz K, Olsen N: Fiberoptic endoscopic ex-amination of swallowing safety: a new procedure.Dysphagia2:216–219, 1988

23. Langmore SE, Schatz K, Olsen N: Endoscopic and videofluo-roscopic evaluations of swallowing and aspiration.Ann OtolRhinol Laryngol 100:678–681, 1991

24. Leder SB, Ross DA, Briskin KB, Sasaki CT: A prospective,double-blind, randomized study on the use of topical anesthetic,vasoconstrictor, and placebo during transnasal flexible fiberop-tic endoscopy.J Speech Hear Res 40:1352–1357, 1997

25. Logeman J: Evaluation and Treatment of Swallowing Disorders,2nd ed. Austin, TX: Pro-Ed, 1998

26. Elizabeth J, Singarayar J, Ellul J, Barer D, Lye M: Arterialoxygen saturation and posture in acute stroke.Age Ageing22:269–272, 1993

27. Leder SB, Tarro JM, Burrell MI: Effect of occlusion of a tra-cheotomy tube on aspiration.Dysphagia 11:254–258, 1996

28. Leder SB, Ross DA, Burrell MI, Sasaki CT: Tracheotomy tubeocclusion status and aspiration in early postsurgical head andneck cancer patients.Dysphagia 13:167–171, 1998

29. Leder SB, Cohn SM, Moller BA: Fiberoptic endoscopic docu-mentation of the high incidence of aspiration following extuba-tion in critically ill trauma patients.Dysphagia 13:208–212,1998

30. Huggins PS, Tuomi SK, Young C: Effects of nasogastric tubeson the young, normal swallowing mechanism.Dysphagia14:157–161, 1999

S.B. Leder: Physiologic Markers to Predict Aspiration 205