TY - JOUR

T1 - Blood flow index using near-infrared spectroscopy and indocyanine green as a minimally invasive tool to assess respiratory muscle blood flow in humans

AU - Guenette, Jordan A

AU - Henderson, William R

AU - Dominelli, Paolo B

AU - Querido, Jordan S

AU - Brasher, Penelope M

AU - Griesdale, Donald E G

AU - Boushel, Robert Christopher

AU - Sheel, A William

PY - 2011

Y1 - 2011

N2 - Near-infrared spectroscopy (NIRS) in combination with indocyanine green (ICG) dye has recently been used to measure respiratory muscle blood flow (RMBF) in humans. This method is based on the Fick principle and is determined by measuring ICG in the respiratory muscles using transcutaneous NIRS in relation to the [ICG] in arterial blood as measured using photodensitometry. This method is invasive since it requires arterial cannulation, repeated blood withdrawals, and reinfusions. A less invasive alternative is to calculate a relative measure of blood flow known as the blood flow index (BFI), which is based solely on the NIRS ICG curve, thus negating the need for arterial cannulation. Accordingly, the purpose of this study was to determine whether BFI can be used to measure RMBF at rest and during voluntary isocapnic hyperpnea at 25, 40, 55, and 70% of maximal voluntary ventilation in seven healthy humans. BFI was calculated as the change in maximal [ICG] divided by the rise time of the NIRS-derived ICG curve. Intercostal and sternocleidomastoid muscle BFI were correlated with simultaneously measured work of breathing and electromyography (EMG) data from the same muscles. BFI showed strong relationships with the work of breathing and EMG for both respiratory muscles. The coefficients of determination (R(2)) comparing BFI vs. the work of breathing for the intercostal and sternocleidomastoid muscles were 0.887 (P <0.001) and 0.863 (P <0.001), respectively, whereas the R(2) for BFI vs. EMG for the intercostal and sternocleidomastoid muscles were 0.879 (P <0.001) and 0.930 (P <0.001), respectively. These data suggest that the BFI closely reflects RMBF in conscious humans across a wide range of ventilations and provides a less invasive and less technically demanding alternative to measuring RMBF.

AB - Near-infrared spectroscopy (NIRS) in combination with indocyanine green (ICG) dye has recently been used to measure respiratory muscle blood flow (RMBF) in humans. This method is based on the Fick principle and is determined by measuring ICG in the respiratory muscles using transcutaneous NIRS in relation to the [ICG] in arterial blood as measured using photodensitometry. This method is invasive since it requires arterial cannulation, repeated blood withdrawals, and reinfusions. A less invasive alternative is to calculate a relative measure of blood flow known as the blood flow index (BFI), which is based solely on the NIRS ICG curve, thus negating the need for arterial cannulation. Accordingly, the purpose of this study was to determine whether BFI can be used to measure RMBF at rest and during voluntary isocapnic hyperpnea at 25, 40, 55, and 70% of maximal voluntary ventilation in seven healthy humans. BFI was calculated as the change in maximal [ICG] divided by the rise time of the NIRS-derived ICG curve. Intercostal and sternocleidomastoid muscle BFI were correlated with simultaneously measured work of breathing and electromyography (EMG) data from the same muscles. BFI showed strong relationships with the work of breathing and EMG for both respiratory muscles. The coefficients of determination (R(2)) comparing BFI vs. the work of breathing for the intercostal and sternocleidomastoid muscles were 0.887 (P <0.001) and 0.863 (P <0.001), respectively, whereas the R(2) for BFI vs. EMG for the intercostal and sternocleidomastoid muscles were 0.879 (P <0.001) and 0.930 (P <0.001), respectively. These data suggest that the BFI closely reflects RMBF in conscious humans across a wide range of ventilations and provides a less invasive and less technically demanding alternative to measuring RMBF.

KW - Adult

KW - Electromyography

KW - Female

KW - Humans

KW - Indocyanine Green

KW - Male

KW - Prospective Studies

KW - Regional Blood Flow

KW - Respiration

KW - Respiratory Muscles

KW - Spectroscopy, Near-Infrared

U2 - 10.1152/ajpregu.00739.2010

DO - 10.1152/ajpregu.00739.2010

M3 - Journal article

C2 - 21289237

VL - 300

SP - R984-92

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0363-6119

IS - 4

ER -