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Non-invasive continuous estimation of blood flow changes in human patellar bone
Jan Näslund1, Jonas Pettersson, Thomas Lundeberg
1Department of Physiology and Pharmacology, Karolinska Institutet, 171 77, Stockholm, Sweden. j.naslund@mailbox.calypso.net
Medical & Biological Engineering & Computing
|August 29, 2006
Summary
A new photoplethysmographic (PPG) technique successfully assesses pulsatile blood flow in bone tissue. This non-invasive method uses near-infrared and green light to monitor blood flow in the patellar bone and overlying skin.
Area of Science:
- Biomedical Engineering
- Medical Devices
- Physiology
Background:
- Assessing bone tissue blood flow is crucial for understanding bone health and healing.
- Existing methods for evaluating bone vascularization are often invasive or indirect.
- Photoplethysmography (PPG) is a non-invasive optical technique typically used for peripheral circulation assessment.
Purpose of the Study:
- To develop and validate a novel photoplethysmographic (PPG) technique for assessing pulsatile blood flow specifically within bone tissue.
- To differentiate between blood flow signals originating from bone versus overlying skin tissue.
- To establish the feasibility of using PPG for non-invasive monitoring of bone vascularization.
Main Methods:
- A custom PPG probe utilizing near-infrared (804 nm) and green (560 nm) light sources was applied over the patella.
- The pulsatile (AC) component of the PPG signals from both wavelengths was analyzed.
- Experimental occlusions (arterial and superficial skin) were performed to differentiate signal origins.
- A physical model study was conducted to elucidate the nature of the PPG AC component.
Main Results:
- Arterial occlusion led to the complete disappearance of PPG signals at both wavelengths, indicating systemic blood flow dependence.
- Local pressure occlusion of superficial skin blood flow selectively eliminated the PPG signal at 560 nm, isolating the bone signal.
- The physical model confirmed that the PPG AC component reflects pulsatile blood flow within a rigid structure.
- The PPG technique demonstrated the ability to monitor pulsatile blood flow in the patellar bone.
Conclusions:
- The developed PPG technique is capable of assessing pulsatile blood flow within bone tissue.
- The dual-wavelength approach allows for differentiation between bone and skin blood flow signals.
- This non-invasive PPG method holds promise for future clinical applications in evaluating bone vascularization.
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