1. Near-infrared (IR) spectroscopy is based on the relative transparency of skin, skull and brain to the light in the near-IR region (700-1100 nm) and on the oxygen-dependent tissue absorption changes of haemoglobin. 2. We evaluated the most relevant factors (reproducibility, venous return, age and sex) that might affect reliability of near-IR spectroscopy to test CO2 cerebrovascular reactivity. 3. Thirty-four healthy volunteers were enrolled in the study. The protocol consisted of a 3-min baseline, a 3-min hypercapnia (5% CO2 in air) and a 2-min recovery. Transcranial Doppler sonography measurements were simultaneously performed. The CO2 reactivity test was repeated on 27 subjects after 1 h to assess reproducibility. CO2 reactivity was also evaluated at different body positions (supine, 35 degrees Trendelenburg and 35 degrees reverse Trendelenburg), and over a gradual increase of the inspired CO2. 4. Changes in near-IR spectroscopy and transcranial Doppler sonography parameters were significantly correlated with variations of end-tidal CO2 (P < 0.005). A significant correlation between the reactivity indexes of near-IR spectroscopy parameters and flow velocity was also found (P < 0.01). A high reproducibility was also found for deoxyhaemoglobin (r(i) = 0.76), oxyhaemoglobin (r(i) = 0.68) and flow velocity (r(i) = 0.60) reactivity indexes. No significant differences between the reactivity indexes of different body positions were found (P > 0.05). The reactivity index of oxyhaemoglobin and deoxyhaemoglobin decreased (P < 0.05) and increased (P < 0.01) with age respectively. 5. We found that near-IR spectroscopy is a reliable and reproducible method for the evaluation of cerebrovascular reactivity and might be considered, after appropriate validation, for the assessment of patients with cerebrovascular disease.

Evaluation of potential factors affecting the measurement of cerebrovascular reactivity by near-infrared spectroscopy

QUARESIMA, VALENTINA;CAROLEI, ANTONIO;FERRARI, Marco
1998

Abstract

1. Near-infrared (IR) spectroscopy is based on the relative transparency of skin, skull and brain to the light in the near-IR region (700-1100 nm) and on the oxygen-dependent tissue absorption changes of haemoglobin. 2. We evaluated the most relevant factors (reproducibility, venous return, age and sex) that might affect reliability of near-IR spectroscopy to test CO2 cerebrovascular reactivity. 3. Thirty-four healthy volunteers were enrolled in the study. The protocol consisted of a 3-min baseline, a 3-min hypercapnia (5% CO2 in air) and a 2-min recovery. Transcranial Doppler sonography measurements were simultaneously performed. The CO2 reactivity test was repeated on 27 subjects after 1 h to assess reproducibility. CO2 reactivity was also evaluated at different body positions (supine, 35 degrees Trendelenburg and 35 degrees reverse Trendelenburg), and over a gradual increase of the inspired CO2. 4. Changes in near-IR spectroscopy and transcranial Doppler sonography parameters were significantly correlated with variations of end-tidal CO2 (P < 0.005). A significant correlation between the reactivity indexes of near-IR spectroscopy parameters and flow velocity was also found (P < 0.01). A high reproducibility was also found for deoxyhaemoglobin (r(i) = 0.76), oxyhaemoglobin (r(i) = 0.68) and flow velocity (r(i) = 0.60) reactivity indexes. No significant differences between the reactivity indexes of different body positions were found (P > 0.05). The reactivity index of oxyhaemoglobin and deoxyhaemoglobin decreased (P < 0.05) and increased (P < 0.01) with age respectively. 5. We found that near-IR spectroscopy is a reliable and reproducible method for the evaluation of cerebrovascular reactivity and might be considered, after appropriate validation, for the assessment of patients with cerebrovascular disease.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11697/11736
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