Effects of extrathoracic airway obstruction on intrathoracic pressure and pulmonary artery pressure in exercising horses.
OBJECTIVE
To determine whether dorsal displacement of the soft palate (DDSP) results in pulmonary artery hypertension and leads to increases in transmural pulmonary artery pressure (TPAP); to determine whether pulmonary hypertension can be prevented by prior administration of furosemide; and to determine whether tracheostomy reduces pulmonary hypertension.


METHODS
7 healthy horses.


METHODS
Horses were subjected to 3 conditions (control conditions, conditions after induction of DDSP, and conditions after tracheostomy). Horses were evaluated during exercise after being given saline (0.9% NaCl) solution or furosemide.


RESULTS
Controlling for drug, horse, and speed of treadmill, DDSP-induced increase in intrathoracic pressure was associated with a significant increase in minimum (36 mm Hg), mean (82 mm Hg), and maximum (141 mm Hg) pulmonary artery pressure, compared with values for control horses (30, 75, and 132 mm Hg, respectively). Increases in pulmonary artery pressure did not induce concomitant increases in TPAP. Tracheostomy led to a significant reduction of minimum (53 mm Hg), and mean (79 mm Hg) TPAP pressure, compared with values for control horses (56 and 83 mm Hg, respectively). When adjusted for horse, speed of treadmill, and type of obstruction, all aspects of the pulmonary artery and TPAP curves were significantly decreased after administration of furosemide, compared with those for horses given saline (0.9% NaCl) solution.


CONCLUSIONS
DDSP was associated with increases in pulmonary artery pressure but not with increases in TPAP.


CONCLUSIONS
Expiratory obstructions such as DDSP are likely to result in pulmonary hypertension during strenuous exercise, but may not have a role in the pathogenesis of exercise-induced pulmonary hemorrhage.
Hackett
R P
RP
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Ducharme
N G
NG
Ainsworth
D M
DM
Erickson
B K
BK
Erb
H N
HN
Soderholm
L V
LV
Thorson
L M
LM
D000402:Airway Obstruction / Q000662:veterinary*; D000818:Animals; D004232:Diuretics / Q000627:therapeutic use; D005080:Exercise Test / Q000662:veterinary; D005260:Female; D005665:Furosemide / Q000627:therapeutic use; D006470:Hemorrhage / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary*; D006734:Horse Diseases / Q000188:drug therapy / Q000517:prevention & control*; D006736:Horses; D006976:Hypertension, Pulmonary / Q000517:prevention & control; D008171:Lung Diseases / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary*; D008297:Male; D010160:Palate, Soft; D010805:Physical Conditioning, Animal; D011651:Pulmonary Artery; D011669:Pulmonary Wedge Pressure / Q000187:drug effects; D014139:Tracheostomy / Q000662:veterinary
D004232:Diuretics; D005665:Furosemide