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Thomas K. Aldrich, MD; Sean P. Stoy, MD; Pragya Gupta, MD
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From the Pulmonary Medicine Division, Montefiore Medical Center and Albert Einstein College of Medicine.

CORRESPONDENCE TO: Thomas K. Aldrich, MD, Pulmonary Medicine Division, Montefiore Medical Center, 111 E 210th St, Bronx, NY 10467; e-mail: taldrich@montefiore.org


CONFLICT OF INTEREST: T. K. A. is the author of a US patent application (61992292, “Pulseless oximeter and uses thereof to estimate arterial oxygen saturation noninvasively in patients with weak pulses,” May 13, 2014) for the technology described in this manuscript, submitted by Albert Einstein College of Medicine. None declared (S. P. S., P. G.).

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;148(6):e190-e191. doi:10.1378/chest.15-2099
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To the Editor:

We appreciate the interest of Drs Asahina and Miyasaka in our article and our technique.1 Our method was described in more detail at the 2014 Health and Bio Technology Summit in New York.2 It is indeed different from the technique based on artificial pulses generated by oscillating inflation of occluding cuffs that is described by Asahina et al3 and explored in more detail by Schoevers et al.4 We use momentary arterial (and specifically not venous) occlusion and release, rather than cuff occlusion, and, to estimate arterial oxygenation, we take a ratio of directly measured changes in attenuance of each wavelength that occur immediately after release, rather than measuring a ratio of alternating current/direct current ratios, making pulsations unnecessary.

We believe that a crucial element of the technique is that changes in blood content of the digit during measurement should be exclusively arterial. Consequently, simple cuff occlusion is unsuitable because of the resulting venous and tissue pulsation artifacts alluded to by Drs Asahina and Miyasaka. An alternative might be to use rapid two-stage cuff occlusion, the first above arterial pressure and the second below arterial but above venous pressure; the blood content change between the two stages should be arterial alone, and measurement would be of changing attenuance ratios, as we describe,1 between the two occlusions.

We fully agree that pulseless oximetry would provide an important level of safety above and beyond intermittent blood gas monitoring for patients with cardiopulmonary bypass, extracorporeal membrane oxygenation, left ventricular assist devices, and any other pulseless or near-pulseless condition with preserved digital perfusion. Perhaps the most valuable use would be in ambulatory patients with left ventricular assist devices, for whom arterial puncture for blood gas monitoring is particularly unappealing.

References

Aldrich TK, Gupta P, Stoy SP, Carlese A, Goldstein DJ. Pulseless oximetry: a preliminary evaluation. Chest. 2015;148(6):1484-1488.
 
Aldrich TK. Pulseless oximetry. Health & Bio Technology Summit website. http://www.hbtsummit.com/wordpress/pdfs/Einstein-Aldrich.pdf. Published November 6, 2014. Accessed September 16, 2015.
 
Asahina T, Takii Y, Nishikoori T, Ozaki M. Novel concept of measuring percutaneous oxygen saturation monitor during cardio-pulmonary bypass. Anesthesiology. 2003;99:A557.
 
Schoevers J, Scheffer C, Dippenaar R. Low-oxygen-saturation quantification in human arterial and venous circulation. IEEE Trans Biomed Eng. 2009;56(3):846-854. [CrossRef] [PubMed]
 

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References

Aldrich TK, Gupta P, Stoy SP, Carlese A, Goldstein DJ. Pulseless oximetry: a preliminary evaluation. Chest. 2015;148(6):1484-1488.
 
Aldrich TK. Pulseless oximetry. Health & Bio Technology Summit website. http://www.hbtsummit.com/wordpress/pdfs/Einstein-Aldrich.pdf. Published November 6, 2014. Accessed September 16, 2015.
 
Asahina T, Takii Y, Nishikoori T, Ozaki M. Novel concept of measuring percutaneous oxygen saturation monitor during cardio-pulmonary bypass. Anesthesiology. 2003;99:A557.
 
Schoevers J, Scheffer C, Dippenaar R. Low-oxygen-saturation quantification in human arterial and venous circulation. IEEE Trans Biomed Eng. 2009;56(3):846-854. [CrossRef] [PubMed]
 
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