Near-infrared spiroximetry: noninvasive measurements of venous saturation in piglets and human subjects

Abstract

We present a noninvasive method to measure the venous oxygen saturation (Sv O 2 ) in tissues using near-infrared spectroscopy (NIRS). This method is based on the respiration-induced oscillations of the near-infrared absorption in tissues, and we call it spiroximetry (the prefix spiro means respiration). We have tested this method in three piglets (hind leg) and in eight human subjects (vastus medialis and vastus lateralis muscles). In the piglet study, we compared our NIRS measurements of the Sv O 2 (Sv O 2 -NIRS resp ) with the Sv O 2 of blood samples. Sv O 2 -NIRS resp and Sv O 2 of blood samples agreed well over the whole range of Sv O 2 considered (20-95%). The two measurements showed an average difference of 1.0% and a standard deviation of the difference of 5.8%. In the human study, we found a good agreement between Sv O 2 -NIRS resp and the Sv O 2 values measured with the NIRS venous occlusion method. Finally, in a preliminary test involving muscle exercise, Sv O 2 -NIRS resp showed an expected postexercise decrease from the initial baseline value and a subsequent recovery to baseline. Keywords tissue spectroscopy; frequency-domain; pulse oximetry; hemoglobin saturation THE POSSIBILITY OF USING LIGHT to measure the oxygen saturation of hemoglobin in vivo has been explored since the 1940s (37). The feasibility of optical blood oximetry stems from the oxygenation dependence of the optical spectrum of hemoglobin. This is illustrated in Fig. 1, which shows the absorption spectra of 100 M hemoglobin for oxygen saturation values of 0,20,40, 60, 80, and 100%. The spectra of Fig. 1 were calculated from published values of the molar extinction coefficients of oxyhemoglobin (HbO 2 ) and deoxyhemoglobin (Hb) (43,53).Oxygen saturation of the pulmonary capillary blood in rabbits has been measured by using dynamic invasive techniques (48). Near-infrared light in the wavelength range from 700 to 900 nm results in a sufficient penetration depth for the noninvasive optical monitoring of skeletal muscle, cerebral gray matter, and breast tissue. As a result, near-infrared techniques allow a noninvasive assessment of hemoglobin saturation for a wide range of applications, such as the study of muscle metabolism (7,9,12,29,45), the diagnosis of vascular disorders NIH Public AccessAuthor Manuscript J Appl Physiol (1985). Author manuscript; available in PMC 2013 September 30.Published in final edited form as: J Appl Physiol (1985). 2002 January ; 92(1): 372-384. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript (2,20,32,33,44,49), functional brain imaging (3,10,24,30,35,50), and breast cancer detection (23,28,40,42,46).If near-infrared light is highly sensitive to the oxygen saturation of hemoglobin, then its large penetration depth inside tissues implies that the arterial, venous, and capillary compartments all contribute to the optical signal. The average hemoglobin oxygenation measured with near-infrared spectroscopy (NIRS) (19,34,41 Hb] at the breathing rate are mostly representative of the...

Is mean blood saturation a useful marker of tissue oxygenation?

“…Indeed, the respiratory-induced oscillations of near-infrared absorption in tissues has been presented as a method of measuring venous saturation (14). Franceschini and colleagues (14) emphasize the importance of verifying that [HbO 2 ] and [Hb] oscillate in phase at the respiratory frequency. However, our study has identified oscillations in [HbO 2 ] without changes in [Hb], and this could only occur in the venous compartment if the S mb O 2 was 100%.…”

“…It suggests that the type II swings are likely to arise from endothelial and sympathetic activity (Ͻ0.04 Hz oscillations), whereas the type I swings appear to be derived not only from endothelial and sympathetic activity but also from myogenic and respiratory influences. The effect of respiration is thought to act predominantly on the venous compartment (14) and would therefore alter the arterial-venous volume ratio to induce type I swings, although this would also induce some change in [Hb]. The passive contraction of the venous compartment induced by inspiration could increase the arterial-venous volume ratio and hence increase S mb O 2 .…”

Development of motion resistant instrumentation for ambulatory near-infrared spectroscopy

“…Additional ambulatory monitoring of cerebral blood supply and oxygenation may thus be useful to help diagnose or manage epileptic patients. Ambulatory pulse oximetry monitoring, used in the study of apnea, provides only arterial blood information; information about venous and tissue blood supply and oxygen consumption 11 cannot be measured using pulse oximeters. And some syndromes, for example hemorrhage and hemorrhagic conversion of ischemic stroke, can be effectively monitored only by ambulatory and continuous cerebral monitoring over long-durations.…”

A Method to Calculate Arterial and Venous Saturation from Near Infrared Spectroscopy (Nirs)

“…[5][6][7] Wolf et al 8 describes a method that calculates both SaO 2 and SvO 2 , however in this study, it is not fully clear how the results were validated. SaO 2 validation studies in adults are done in the range from 90% to 100%.…”