Advances in Pulse Oximetry
Samuel Y. Ash, M.D.
Resident, Department of Internal Medicine
University of Washington Medical Center
Disclosures
• No financial disclosures.
• Research presented is unfunded.
Outline
• Background and Technological Review
• Limitations of Traditional Pulse Oximetry
• Next Generation Pulse Oximetry
– Pulse CO-Oximetry
• Applications of Pulse CO-Oximetry
• Conclusions
• Future Areas of Research
Background and Technological Review
• Beer-Lambert Law:
– by knowing the absorptive properties of a
solution or tissue, one can determine the
relative concentrations of the solutes in that
solution or tissue
Background and Technological Review
• Traditional Pulse
Oximetry:
– 940nm
• Near-infrared
• Oxyhemoglobin
– 660nm
• Red
• Deoxyhemoglobin
Image source: Isenhour JL and Slovis CM. Arterial Blood Gas Analysis. J Respir Dis 2008. 29;2: epub.
Limitations of Traditional Pulse Oximetry
• Calibration assumptions
– Measurements in young volunteers
– Use of empirical calibration curves
• Optical interference
– Dyshemoglobinemias
– Bilirubin and intravenous dyes
• Signal artifact
– False signal
– Low signal to noise ratio
Limitations of Traditional Pulse Oximetry
Dyshemoglobinemias
Functional
Non-functional
Oxyhemoglobin
Deoxyhemoglobin
Carboxyhemoglobin
Methemoglobin
Limitations of Traditional Pulse Oximetry
• Carboxyhemoglobin
Image source: http://www.wissensdrang.com/wisbr1.htm
Limitations of Traditional Pulse Oximetry
• Carboxyhemoglobin
Limitations of Traditional Pulse Oximetry
• Carboxyhemoglobin
– endogenous source is breakdown of heme
Dennery 2001
Limitations of Traditional Pulse Oximetry
• Carboxyhemoglobin
– endogenous source is breakdown of heme
Limitations of Traditional Pulse Oximetry
• Carboxyhemoglobin
– Typically associated with exposure to exogenous
carbon monoxide
– Levels in most non-smokers: 1-2%
– Levels in heavy smokers: up to 10-20%
– Increased in cirrhosis by 2%
Image sources: townipproject.wikispaces.com, tobaccofreewny.com, woodstove.net
Limitations of Traditional Pulse Oximetry
Image source: http://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v03/030220r00.HTM
Limitations of Traditional Pulse Oximetry
Limitations of Traditional Pulse Oximetry
• Carboxyhemoglobin
– Absorbs light at 660nm much like
oxyhemoglobin
– Effect on measured oxygen saturation (SpO2)
is to overestimate true oxygen saturation
– Overestimation is approximately proportional
to the carboxyhemoglobin level (COHb)
• SpO2 = SaO2 + %COHb
Limitations of Traditional Pulse Oximetry
• Carboxyhemoglobin
– causes relative hypoxia due to carbon
monoxide’s affinity for hemoglobin
– triggers inflammation through multiple
pathways resulting in cardiac and neurologic
injury
Limitations of Traditional Pulse Oximetry
• Methemoglobin
Image source: http://alexandria.healthlibrary.ca/documents/notes/bom/unit_2/L-03%20HEMOGLOBIN1.xml
Limitations of Traditional Pulse Oximetry
• Methemoglobin
Limitations of Traditional Pulse Oximetry
• Methemoglobin
– Congenital
– Exposure to a number of different agents
• Antibiotics – especially sulfa
• Local anesthetics
• Nitrates
Limitations of Traditional Pulse Oximetry
Limitations of Traditional Pulse Oximetry
Limitations of Traditional Pulse Oximetry
Limitations of Traditional Pulse Oximetry
• Methemoglobin
– Increases both numerator and denominator of
the ratio of relative absorbances
– Drives ratio toward 1 which results in
measured SpO2 of 85%
Pulse CO-Oximetry
• Masimo Rainbow® SET Pulse COOximetry
– Introduced in 2005
– Rainbow: uses 8 wavelengths of light
– SET: Signal Extraction Technology
Pulse CO-Oximetry
• Masimo Radical 7
Pulse CO-Oximetry
Image source: http://www.masimo.co.uk/Rainbow/about.htm
Pulse CO-Oximetry
• Measurements
– Total hemoglobin (SpHb)
– Oxygen content (SpOC)
– Oxygen saturation (SpO2)
– Carboxyhemoglobin (SpCO)
– Methemoglobin (SpMet)
– Photoplethysmographic (Pleth) variability
index (PVI)
– Perfusion index (PI)
– Pulse rate (PR)
Pulse CO-Oximetry
• Measurements
– Total hemoglobin (SpHb)
– Oxygen content (SpOC)
– Oxygen saturation (SpO2)
– Carboxyhemoglobin (SpCO)
– Methemoglobin (SpMet)
– Photoplethysmographic (Pleth) variability
index (PVI)
– Perfusion index (PI)
– Pulse rate (PR)
Pulse CO-Oximetry
• Measurements
– Total hemoglobin (SpHb)
– Oxygen content (SpOC)
– Oxygen saturation (SpO2)
– Carboxyhemoglobin (SpCO)
– Methemoglobin (SpMet)
– Photoplethysmographic (Pleth) variability
index (PVI)
– Perfusion index (PI)
– Pulse rate (PR)
Applications of Pulse CO-Oximetry
• Total hemoglobin – need
– Among the most commonly checked
laboratory values
– Current methods invasive, time consuming
and intermittent
– Blood draws result in significant hospital
acquired anemia
Applications of Pulse CO-Oximetry
• Total hemoglobin – evidence for
– Macket 2007: first clinical validation study
– Macket 2010: pulse co-oximetry based SpHb
is accurate within 1.0 g/dL in health volunteers
undergoing hemodilution
– Causey 2011: appears accurate in general
surgery population
– Frasca 2011: pulse co-oximetry based SpHb
in ICU patients without ongoing bleeding
Applications of Pulse CO-Oximetry
• Total hemoglobin – evidence against
– Lamhaut 2011:
• Small systematic bias
• Significant lack of precision
• Significant number of outliers
– Gayat 2011:
• Moderate systematic bias
• Difficulty obtaining in “sicker” patients
Applications of Pulse CO-Oximetry
• Total hemoglobin – evidence for further
research
– Miller 2011:
• Not accurate enough for all clinical scenarios
• Accuracy appears to improve with time
Applications of Pulse CO-Oximetry
• Total hemoglobin – ongoing work
– Non-invasive measurement of total
hemoglobin in the ICU setting
•
•
•
•
•
Blinded
Prospective
ICU patients receiving blood transfusion
Ongoing subject enrollment
Preliminary results suggest significant lack of
precision in noninvasive measurements due to
outliers*
– *Preliminary data
Applications of Pulse CO-Oximetry
14
12
10
8
non-invasive hemoglobin
invasive hemoglobin
6
4
2
416
330
315
300
285
270
255
240
225
210
195
180
165
150
147
135
120
105
90
75
60
45
30
15
0
-213
0
Applications of Pulse CO-Oximetry
14
12
10
8
non-invasive hemoglobin
invasive hemoglobin
6
4
2
416
330
315
300
285
270
255
240
225
210
195
180
165
150
147
135
120
105
90
75
60
45
30
15
0
-213
0
Applications of Pulse CO-Oximetry
• Carboxyhemoglobin – toxicity
– causes relative hypoxia due to carbon
dioxide’s affinity for hemoglobin
– triggers inflammation through multiple
pathways resulting in cardiac and neurologic
injury
– Symptoms are nonspecific:
• mild headache, nausea, confusion, dizziness
• MI, stroke, death
Applications of Pulse CO-Oximetry
• Carboxyhemoglobin – evidence for
– Case reports of noninvasive measurement
resulting in diagnosis
• Crawford 2008: CO poisoning onboard submarine
• Roth 2009: CO poisoning due to water heater
– Roth 2011: acceptable bias and precision for
screening for CO poisoning in ED
– Suner 2007: acceptable correlation for
screening for CO poisoning in ED
Applications of Pulse CO-Oximetry
• Carboxyhemoglobin – evidence against
– Touger 2010: sensitivity of only 43% for
patients with lab values of COHb greater than
15%
• NB: enrollment was for suspected CO poisoning
Applications of Pulse CO-Oximetry
• Carboxyhemoglobin – transfusion
– Reports of alarming levels of
carboxyhemoglobin in banked blood
– Large volume transfusion may lead to
prolonged increases in COHb levels
Applications of Pulse CO-Oximetry
• Carboxyhemoglobin – ongoing research
– Non-invasive measurement of
carboxyhemoglobin in the ICU setting
•
•
•
•
•
Blinded
Prospective
ICU patients receiving blood transfusion
Ongoing subject enrollment
Inadequate data for preliminary results
Applications of Pulse CO-Oximetry
• Carboxyhemoglobin – DLCO
– ATS/ERS Task Force on Standardization of
Lung Function Testing recommended
adjusting DLCO for total hemoglobin and
COHb
• COHb in particular increases “back pressure”
– Mahoney 2007: noninvasive COHb
measurements may affect categorization of
DLCO impairment
• Retrospective
• No laboratory correlation
Applications of Pulse CO-Oximetry
• Carboxyhemoglobin – DLCO
– Effect of noninvasively assessed carboxyhemoglobin
levels on diffusing capacity measured during
pulmonary function testing
• Prospective
• Spot observation at time of PFT
– Both SpHb and COHb
– Frequent laboratory correlation
• Ongoing subject enrollment
• Preliminary results suggest that lack of
precision in noninvasive measurements limits
utility of device
Conclusions
• Pulse co-oximetry represents a significant
advancement in oximetry technology
• Noninvasive measurement of total
hemoglobin in particular requires further
investigation and validation prior to
widespread use
• Pulse co-oximetry may provide useful
screening information in low risk
populations
Future Areas of Research
• Sensor technology
– Rev E resposable sensor
– Rev G resposable sensor
Future Areas of Research
• Total hemoglobin
– Guidance of blood transfusion in patients with
GI bleed
– Screening for anemia prior to blood donation
• Pleth variability index
– Comparison to pulse variability index monitors
Acknowledgements
• VA Puget Sound Health Care System
– Erik Swenson, M.D.
– Richard Goodman, M.D.
– Robin Boland
– Christopher Click
– Diane Houk
– Barb
– Shelly
Acknowledgements
• UW Internal Medicine Residency
– D. Scott Weigle, M.D.
– Christopher Knight, M.D.
– Tyler Albert, M.D.
• Masimo
– Jolene Hagin, R.N.
– Serop Gharibian
• Family
– Katie Ash Greenzang, M.D.
– Sarah Ash, Ph.D.
References
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Barker and Badal. The Measurement of Dyshemoglobins and Total Hemoglobin by Pulse
Oximetry. Curr Opin Anaesthesiol 21:805-810.
Barker SJ, Tremper KK, Hyatt J: Effects of Methemoglobinemia on Pulse Oximetry and Mixed
Venous Oximetry. Anesthesiology 1989;70:112-117.
Causey MW et al. Validation of noninvasive hemoglobin measurements using the Masimo
Radical-7 SpHb Station. Am J Surg 2011; 201:592-8.
Crawford DM and Hampson NB. Fire and Ice: Diagnosis of Carbon Monoxide Poisoning in a
Remote Environment. Emerg Med J 2008; 25:235-236.
Dennery PA, Seidman DS and Stevenson DK. Neonatal Hyperbilirubinemia. N Engl J Med 2001;
344:581-590.
Ehlers M, Labaze G, Hanakova M, McCloskey D and Wilner G. Alarming Levels of
Carboxyhemoglobin in Banked Blood. J Cardiothorac Vasc Anesth 2009; 23:336-338.
Ernst A and Zibrak JD. Carbon Monoxide Poisoning. N Eng J Med 1998; 339:1603-1608.
Frasca D et al. Accurace of a Continuous Noninvasive Hemoglobin Monitor in Intensive Care Unit
Patients. Crit Care Med 2011; 39(10):1-6.
Gayat E et al. Performance Evaluation of a Noninvasive Hemoglobin Monitoring Device. Ann
Emerg Med 2011; 57:330-333.
Lamhaut L et al. Comparison of the Accuracy of Noninvasive Hemoglobin Monitoring by
Spectrophotometry (SpHb) and HemoCue® with Automated Laboratory Hemoglobin
Measurement. Anesthesiology 2011; 115:548-54.
References
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Macket MR, Allard M, Applegate RL and Rook J. The Accuracy of Noninvasive and Continuous
Total Hemoglobin Measurement by Pulse CO-Oximetry in Human Subjects Undergoing
Hemodilution. Anesth Analg 2010; 111:1424-1167.
Mahoney AM, Stimpson CL, Scott KL and Hampson NB. Noninvasive Measurement of
Carboxyhemoglobin Levels for Adjustment of Diffusion Capacity Measured During Pulmonary
Function Testing. Resp Care 2007; 52:1741-1743.
Miller et al. A Comparison of Three Methods of Hemoglobin Monitoring in Patients Undergoing
Spine Surgery. Anesth Analg 2011; 112:858–863.
Ortega R, Hansen CJ, Elterman K and Woo W. Videos in Clinical Medicine: Pulse Oximetry. N
Eng J Med 2011;364:e33.
Roth et al. Accuracy of Noninvasive Multiwave Pulse Oximetry Compared With
Carboxyhemoglobin from Blood Gas Analysis in Unselected Emergency Department Patients. Ann
Emerg Med 2011; 58:74-79.
Roth et al. Victim of Carbon Monoxide Poisoning Identified by Carbon Monoxide Oximetry. J
Emerg Med 2009; 40:640-642.
Salisbury AC et al. Diagnostic Blood Loss From Phlebotomy and Hospital-Acquired Anemia
During Acute Myocardial Infarction. Arch Int Med 2011; Epub ahead of print.
Scheller MS, Unger RJ, Kelner MJ. Effects of Intravenously Administered Dyes on Pulse
Oximetry Readings. Anesthesiology 1986;65:550-552.
References
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Severinghaus JW. Takuo Aoyagi: Discovery of Pulse Oximetry. Anesth and Analg 2007;105:S1-4.
Sinex JE. Pulse Oximetry: Principles and Limitation;17:59-65.
Suner et al. Non-Invasive Pulse CO-Oximetry Screening in the Emergency Department Identifies
Occult Carbon Monoxide Toxicity. J Emerg Med 2007; 34:441-450.
Touger et al. Performance of the RAD-57 Pulse CO-Oximeter Compared with Standard
Laboratory Carboxyhemoglobin Measurement. Ann Emerg Med 2010; 20(10):1-7.
Tram TT et al. Carboxyhemoglobin and Its Correlation to Disease Severity in Cirrhotics. J Clin
Gastroenterol 2007; 41:211-215.
Ziemann-Gimmel P and Schwartz DE. Increased Carboxyhemoglobin in a Patient with a Large
Retroperitoneal Hematoma. Anesth Analg 2004;99:1800-1802.
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