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

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.

Use of near‐infrared systems for investigations of hemodynamics in human in vivo bone tissue: A systematic review

“…Twenty‐one studies were identified using near infrared spectroscopy (NIRS) and 10 studies were identified using photoplethysmography (PPG) non‐invasively on in vivo bone tissue . Fifty‐seven studies were identified using laser Doppler flowmetry (LDF) in vivo of which 56 were intra‐operative.…”

“…We identified 10 PPG studies from two research groups investigating the patella and tibia . These studies utilized bespoke PPG systems making use of an isobestic 804 nm NIR wavelength to measure the amplitude of pulsatile flow in bone tissue based on attenuation changes in reflected signal.…”

“…Other applications of NIRS and PPG systems applied to healthy populations included hemodynamic measurements taken during positional changes such as leg extension, or head up/down tilt to demonstrate oxygen saturation and blood volume changes . Four studies examined the effects of positive and negative external pressure changes using lower body pressure chambers on the amplitude of PPG pulsatile flow and oxygen saturation . In the case of Larsson et al, the use of hyperbaric chambers and variable respired oxygen levels were also used to observe their effects on bone hemodynamics at the patella .…”

“…Four studies examined the effects of positive and negative external pressure changes using lower body pressure chambers on the amplitude of PPG pulsatile flow and oxygen saturation . In the case of Larsson et al, the use of hyperbaric chambers and variable respired oxygen levels were also used to observe their effects on bone hemodynamics at the patella . These studies concluded that the use of pressure alterations may have applications for therapy by mimicking weight‐bearing physiology in a microgravity environment, or for potential therapeutic applications involving vascular mechanisms in bone.…”