Fig 1.
Visualisation illustrating the underlying concept of a three-optode-receiver-channel spatially resolved continuous wave near-infrared spectroscopy sensor.
Heterodyning dual-wavelength light, visualised here in red, is emitted from (B) three light-emitting optodes in contact with a seal’s skin. Light passes through the underlying tissue before exiting the head, where it is detected by (A) a photodiode in contact with the seal’s skin. Increased distance between the optode and receiver channels provides deeper optical penetration within the underlying tissue.
Fig 2.
Example trace of blubber blood volume and haemoglobin oxygen dynamics during a sequence of dives from a single animal (Ulf).
(A) Blood volume [tHb], haemoglobin oxygenation [Hbdiff], and ΔTSI% dynamics across all the dives in a trial, where the green line represents blood volume, the black line represents haemoglobin oxygenation, and the red line represents TSI. (B) [tHb] and [Hbdiff] dynamics across a single dive marked in blue in (A). Vertical grey lines indicate changes of dive phase, where ‘Descent’ = transit from the surface to the feeding station (feeder), ‘Ascent’ = transit from the feeding station back to the surface, and ‘Surf’ = at the surface. Data can be found here: https://doi.org/10.5061/dryad.k67cg66. [Hbdiff], difference in the concentration of oxy- and deoxyhaemoglobin; [tHb], concentration of total haemoglobin; TSI, tissue saturation index.
Fig 3.
Example trace of blubber blood volume and haemoglobin oxygen dynamics from each of three optode channels during a sequence of dives.
Green lines represent blood volume [tHb], and black lines represent haemoglobin oxygenation [Hbdiff]. Dot and dashed lines represent measurements from the shallowest channel (28 mm), dashed lines represent measurements from the middle channel (33 mm), and solid lines represent measurements from the deepest channel (38 mm). Data can be found here: https://doi.org/10.5061/dryad.k67cg66. [Hbdiff], difference in the concentration of oxy- and deoxyhaemoglobin; [tHb], concentration of total haemoglobin.
Fig 4.
Example trace of cerebral blood volume and haemoglobin oxygen dynamics during a sequence of dives from a single animal (Ulf).
(A) Blood volume [tHb], haemoglobin oxygenation [Hbdiff], and ΔTSI% dynamics across all the dives in a trial, where the green line = blood volume, black line = haemoglobin oxygenation, and red line = TSI. (B) [tHb] and [Hbdiff] dynamics across a single dive marked in blue box in (A). Vertical grey lines indicate changes of dive phase, where ‘Descent’ = transit from the surface to the feeding station (feeder), ‘Ascent’ = transit from the feeding station back to the surface, and ‘Surf’ = at the surface. The box in a dashed red line indicates a period of secondary reoxygenation. The box in a solid red line indicates a mid-surface interval increase in blood volume. All concentrations are expressed as a relative change from a baseline (0 μmol.L−1) taken as the onset of the first dive in a recording session. Data can be found here: https://doi.org/10.5061/dryad.k67cg66. [Hbdiff], difference in the concentration of oxy- and deoxyhaemoglobin; [tHb], concentration of total haemoglobin; TSI, tissue saturation index.
Fig 5.
Example trace of cerebral blood volume and haemoglobin oxygen dynamics from each of three optode channels during a sequence of dives.
Green lines represent blood volume [tHb], and black lines represent haemoglobin oxygenation [Hbdiff]. Dot and dashed lines represent measurements from the shallowest channel (28 mm), dashed lines represent measurements from the middle channel (33 mm), and solid lines represent measurements from the deepest channel (38 mm). Data can be found here: https://doi.org/10.5061/dryad.k67cg66. [Hbdiff], difference in the concentration of oxy- and deoxyhaemoglobin; [tHb], concentration of total haemoglobin.
Fig 6.
Cerebral haemodynamics (‘Haem’) of O2Hb and HHb for two seals during two key phases of a dive.
(A) Mid-surface interval and (B) early in a dive when secondary reoxygenation occurred. Dots represent median concentration change. Error bars represent the interquartile range. Changes are shown as relative changes from CBV minima during a PDSI. Dives by Vebjörn, n = 23. Dives by Ulf, n = 54. Data can be found here: https://doi.org/10.5061/dryad.k67cg66. CBV, cerebral blood volume; HHb, deoxyhaemoglobin; O2Hb, oxyhaemoglobin; PDSI, postdive surface interval.