Compression of the photoprobe is effective in reducing Hb signals of the frontal skin in near infrared spectrophotometic cerebral tissue oximetry

摘要

Abstract: The cutaneous hemoglobin of the forehead can contribute to near infrared spectrophotometric cerebral tissue oximetry in both light scattering and absorption. Wide distance between the light source and detector was theoretically proved to increase substantial signal from cerebral tissue, however increase in signal to noise ratio was practically undesirable. The tight compression of the probe onto the head expels the subcutaneous blood, which is supposed to improve cerebral signal detection. The spectrophotometric effect of probe compression with a head band was examined by NIRS monitor having temporal resolution of 10 Hz which provided detailed information in tissue hemoglobin signals including pulsatile fluctuations. The measurement for healthy volunteers was done in both supine and sitting positions. The oxygenated Hb and total Hb levels significantly decreased with probe compression in supine position. Compared with pre-compression state, the amplitude of Oxy-Hb pulsation was reduced to 61.0 $POM 10.0 (mean $POM SD)% in sitting position, and 53.3 $POM 68% in supine position (p $LS 0.01). The postischemic hyperemia was also observed in every measurement. The results indicate that cutaneous blood in the scalp significantly contributes pulsatile Hb signals in cerebral NIRS, and probe compression is a good measure to reduce scalpel effect especially in supine position.!8