Hemodynamics of the sternocleidomastoid measured with frequency domain near-infrared spectroscopy towards non-invasive monitoring during mechanical ventilation

Raeef Istfan; Carlos A Gómez; Matthew Applegate; Dmitry Rozenberg; W Darlene Reid; Darren Roblyer

doi:10.1364/BOE.430423

Hemodynamics of the sternocleidomastoid measured with frequency domain near-infrared spectroscopy towards non-invasive monitoring during mechanical ventilation

Biomed Opt Express. 2021 Jun 15;12(7):4147-4162. doi: 10.1364/BOE.430423. eCollection 2021 Jul 1.

Authors

Raeef Istfan¹, Carlos A Gómez¹, Matthew Applegate¹, Dmitry Rozenberg², W Darlene Reid^{3

4

5}, Darren Roblyer¹

Affiliations

¹ Department of Biomedical Engineering, Boston University, Boston, MA 02125, USA.
² Department of Medicine, Respirology and Lung Transplantation, University Health Network, University of Toronto, Toronto, ON, Canada.
³ Department of Physical Therapy, University of Toronto, Toronto ON, Canada.
⁴ Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, ON, Canada.
⁵ KITE - Toronto Rehabilitation Institute, University Health Network, Toronto, ON, Canada.

Abstract

Mechanical ventilation (MV) is used to assist spontaneous breathing in critically ill patients in the intensive care unit (ICU). MV is a cornerstone of critical care medicine but it is now known that inspiratory muscle dysfunction due to injury, disuse, and/or atrophy during MV plays a major role in outcomes for these patients. For example, prolonged MV is strongly correlated with dysfunction of the sternocleidomastoid (SCM), an accessory inspiratory muscle that has been linked to weaning failure from MV. Hemodynamic monitoring of the SCM may provide an important non-invasive and real-time means to monitor MV. In this work, we first conducted multi-layer Monte Carlo simulations to confirm the ability of near infrared light to detect changes in the oxygenation of the SCM over wide ranges of skin tones and adipose layer thicknesses. We then optimized a custom digital frequency domain near-infrared spectroscopy (FD-NIRS) system for continuous 10 Hz measurements of the SCM at 730 nm and 850 nm. A healthy volunteer study was conducted (N=10); subjects performed sets of isometric neck flexions of the SCM. Substantial changes in oxyhemoglobin + oxymyoglobin (oxy[Hb + Mb]), deoxyhemoglobin + deoxymyoglobin (deoxy[Hb + Mb]), and total hemoglobin + myoglobin (total[Hb + Mb]) were observed during sustained and intermittent isometric flexions. There were notable sex differences observed in the magnitude of hemodynamic changes (∼2x larger changes in males for oxy[Hb + Mb] and deoxy[Hb + Mb]). The magnitude of hemodynamic changes when taking into account µ_s' changes during flexions was ∼ 2-2.5x larger as compared to assuming constant scattering (CS), which is a common assumption used for continuous wave (CW) NIRS methods. This study suggests that FD-NIRS provides improved accuracy for hemodynamic monitoring of the SCM compared to CW-NIRS, and that FD-NIRS may provide value for SCM monitoring during MV.