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First published online July 20, 2007
Journal of Experimental Biology 210, 2607-2617 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.008078
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Blood oxygen depletion during rest-associated apneas of northern elephant seals (Mirounga angustirostris)

T. K. Stockard1, D. H. Levenson1, L. Berg2, J. R. Fransioli1, E. A. Baranov3 and P. J. Ponganis1,*

1 Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, CA 92093-0204, USA
2 US Naval Medical Center, Balboa Hospital, San Diego, CA 92134, USA
3 Limnological Institute, Siberian Division of Russian Academy of Sciences, Irkutsk, Russia


Figure 1
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  		Fig. 1. Changes in arterial PO2 (A) and O2 content (B) as a function of time into apnea. Points in A and B are individual blood samples from five seals (see Table 2 for labels of individual seals). (A) Equation for exponential rate of PO2 decline: y=58e(–x/2.32)+765e(–x/0.10) +21.8 (r2=0.93, N=82). (B) Equation for linear depletion of O2 content: y=–2.34x+27.2 (r2=0.68, N=82, P<0.0001).

 

Figure 2
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  		Fig. 2. Changes in venous PO2 (A) and O2 content (B) with time into apnea. Individual data points (see Table 2 for labels of seals) from each of the three venous compartments are indicated by color: extradural vein (EDV; red), central veins (CV; green) and pulmonary artery (PA; blue); curve fits indicating compartmental trends are shown in the same respective colors. (A) Equation, from all data pooled (black line), for exponential rate of PO2 decline: y=43.7e(–x/4.30)+15.8 (r2=0.71, N=163). (B) Equation from pooled data (black line) for linear depletion rate of O2 content: y=–2.01x+26.0 (r2=0.54, P<0.0001, N=163).

 

Figure 3
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  		Fig. 3. Comparison of arterial (red) and venous (blue) blood in terms of PO2 (A) and O2 content (B). The venous system is highly saturated; PO2 and O2 content in both the arterial and venous blood become indistinguishable soon into apnea. (Regression equations are the same as in Figs 1 and 2.)

 

Figure 4
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  		Fig. 4. Comparison of arterial and venous blood parameters (PCO2, pH, [Hb] and Hct) during apnea. See Table 2 for labels of individual seals.

 

Figure 5
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  		Fig. 5. Arterial end-of-apnea blood values as a function of apnea duration. Samples were drawn within the last minute of apnea. Dotted lines have been added as a visual aid only, to indicate trends, and do not imply any statistical significance. See Table 2 for labels of individual seals.

 




© The Company of Biologists Ltd 2007