Effects of age and exercise on physiological dead space during simulated dives at 2.8 ATA Academic Article uri icon

  •  
  • Overview
  •  
  • Research
  •  
  • Identity
  •  
  • Additional Document Info
  •  
  • View All
  •  

abstract

  • Physiological dead space (Vds), end-tidal CO2(Pet CO2 ), and arterial CO2(PaCO2 ) were measured at 1 and 2.8 ATA in a dry hyperbaric chamber in 10 older (58–74 yr) and 10 younger (19–39 yr) air-breathing subjects during rest and two levels of upright exercise on a cycle ergometer. At pressure, Vd(liters btps) increased from 0.34 ± 0.09 (mean ± SD of all subjects for normally distributed data, median ± interquartile range otherwise) to 0.40 ± 0.09 ( P= 0.0060) at rest, 0.35 ± 0.13 to 0.45 ± 0.11 ( P = 0.0003) during light exercise, and 0.38 ± 0.17 to 0.45 ± 0.13 ( P = 0.0497) during heavier exercise. During these conditions, PaCO2 (Torr) increased from 33.8 ± 4.2 to 35.7 ± 4.4 ( P = 0.0059), 35.3 ± 3.2 to 39.4 ± 3.1 ( P < 0.0001), and 29.6 ± 5.6 to 37.4 ± 6.5 ( P < 0.0001), respectively. During exercise, Pet CO2 overestimated PaCO2 , although the absolute difference was less at pressure. Capnography poorly estimated PaCO2 during exercise at 1 and 2.8 ATA because of wide variability. Older subjects had higher Vd at 1 ATA but similar changes in Vd, PaCO2 , and Pet CO2 at pressure. These results are consistent with an effect of increased gas density.

authors

  • Mummery, HJ
  • Stolp, BW
  • deL. Dear, G
  • Doar, PO
  • Natoli, MJ
  • Boso, AE
  • Archibald, Jason
  • Hobbs, GW
  • El-Moalem, HE
  • Moon, RE

publication date

  • February 1, 2003