The effect of pulmonary emphysema on diaphragm capillary
geometry.
Poole, David C., and Odile Mathieu-Costello.
Departments of Kinesiology and Anatomy/Physiology, Kansas State
University, Manhattan, KS 66506-5602 and Department of Medicine,
University of California, San Diego, 9500 Gilman Drive, La Jolla, CA.
92093-0623
APStracts 3:0468A, 1996.
In emphysema, the diaphragm shortens by losing sarcomeres. We
hypothesized that unless capillaries undergo a similar shortening,
capillary geometry must be altered. Without quantifying this
geometry, capillary length and surface area per fiber volume, which
are critical measures of the structural potential for blood-tissue
exchange, cannot be resolved. Five months following intratracheal
elastase (E) or saline (C) instillation, diaphragms from male Syrian
Golden hamsters were glutaraldehyde perfusion-fixed in situ at
reference lung positions (residual volume, RV; functional residual
capacity, FRC; total lung capacity, TLC) to provide diaphragms fixed
over a range of sarcomere lengths. Subsequently, diaphragms were
processed for electron microscopy and analyzed morphometrically.
Emphysema increased lung volume changes from -20 to +25 cmH2O airway
pressure (i.e., passive vital capacity) and excised lung volume (both
P<0.001). In each region of the costal diaphragm (i.e.,
ventral, medial, dorsal), sarcomere number was reduced (all
P<0.05). Capillary-to-fiber ratio increased (C, 2.2+0.1; E,
2.8+0.1, P<0.01) and fibers hypertrophied (C, 815+35; E,
987+67 [mu][mu]2, P<0.05; both values at 2.5 [mu]m sarcomere
length, l). Capillary geometry was markedly altered by the loss of
sarcomeres in series. Specifically, the additional capillary length
derived from capillary tortuosity and branching was increased by 183%
at 2.5 [mu]m l compared with C values (C, 359+43; E, 1020+158 mm-2,
P<0.01). This significantly increased total capillary length
(C, 3115+173; E, 3851+219 mm-2 at 2.5 [mu]m, P<0.05) and
surface area (C, 456+13; E, 519+24 cm-1, P<0.05) per fiber
volume. Thus, emphysema substantially alters diaphragm capillary
geometry and augments the capillary length and surface area available
for blood-tissue exchange.
Received 4 March 1996; accepted in final form 11 September 1996.
APS Manuscript Number A217-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996