Bone and Soft Tissue Blood Flow during Normobaric and Hyperbaric Oxygen Breathing in Healthy Divers

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.