Abstract
Purpose: The study aimed to investigate, using a photoplethysmographic (PPG) technique, how pulsatile blood flow within the patellar bone and skin over the patella reacts to normobaric (NBO) and hyperbaric oxygen breathing (HBO). Methods: Eleven healthy volunteers, breathed air or oxygen. Subjects were blinded to breathing gas. A range of partial pressures of oxygen were administered in 10 minute intervals: 21 kPa, 101 kPa (NBO), 21 kPa, (compression to 280 kPa), 59 kPa, 280 kPa (HBO), 59 kPa, (decompression), and 21 kPa. Changes were measured continuously for each individual. Results: Hyperoxia decreased pulsatile patellar blood flow ~32 resp. 38% and skin blood flow ~36 resp. 42% during the first 2 - 3 minutes of NBO resp. HBO. This decrease was normalized within 5 minutes after exposure. The results were similar when switching from air to NBO (101 kPa) and from air at pressure (59 kPa) to HBO (280 kPa). Conclusions: The study shows that pulsatile patellar skin and bone blood flow, decreases significantly as a reaction to oxygen breathing in healthy subjects. The results suggest that a non-invasive PPG technique could be used to monitor blood flow changes in bone during oxygen treatment.
Highlights
Basic knowledge concerning blood flow regulation in bone tissue is lacking
When switching from air to oxygen breathing during NBO, both the bone blood flow decreased, −32%, as did the skin blood flow −36%
The pattern of change in blood flow during hyperbaric oxygen breathing (HBO) was seen as a decrease in bone blood flow, −38% and in the skin, −42% (Figure 4)
Summary
Basic knowledge concerning blood flow regulation in bone tissue is lacking. Growth, remodelling and repair of. Hyperoxia-mediated vasoconstriction and, as a result, decreased blood flow have been shown to occur in most healthy vascular beds in animals and man [10]. In the latter, this has been demonstrated in the brain, retina, myocardium, and in skeletal muscle. There is a need for different techniques to evaluate the correct dose of oxygen to use to reverse ischemia in these tissues. It was hypothesized that the PPG technique could be applied to detect pulsatile blood flow changes in skin and bone tissue of healthy subjects during their exposure to normobaric and hyperbaric hyperoxia. Whether or not the vascular system in the bone tissue would react in the same way as other vascular beds was not known
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