Non-invasive continuous estimation of blood flow changes in human patellar bone.
A photoplethysmographic (PPG) technique to assess blood flow in bone tissue has been developed and tested. The signal detected by the PPG consists of a constant-level (DC) component-which is related to the relative vascularization of the tissue-and a pulsatile (AC) component-which is synchronous with the pumping action of the heart. The PPG probe was applied on the skin over the patella. The probe uses near-infrared (804 nm) and green (560 nm) light sources and the AC component of the PPG signals of the two wavelengths was used to monitor pulsatile blood flow in the patellar bone and the overlying skin, respectively. Twenty healthy subjects were studied and arterial occlusion resulted in elimination of PPG signals at both wavelengths, whereas occlusion of skin blood flow by local surface pressure eliminated only the PPG signal at 560 nm. In a parallel study on a physical model with a rigid tube we showed that the AC component of the PPG signal originates from pulsations of blood flow in a rigid structure and not necessarily from volume pulsations. We conclude that pulsatile blood flow in the patellar bone can be assessed with the present PPG technique.
Näslund
Jan
J
Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden. j.naslund@mailbox.calypso.net
Pettersson
Jonas
J
Lundeberg
Thomas
T
Linnarsson
Dag
D
Lindberg
Lars-Göran
LG
D000328:Adult; D006801:Humans; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D010329:Patella / Q000098:blood supply*; D017156:Photoplethysmography / Q000379:methods; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D012815:Signal Processing, Computer-Assisted