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Home / Equine Research Bank / J Appl Physiol (1985) / Stress failure of pulmonary capillaries in racehorses with e...
Journal of applied physiology (Bethesda, Md. : 1985)1993; 75(3); 1097-1109; doi: 10.1152/jappl.1993.75.3.1097

Stress failure of pulmonary capillaries in racehorses with exercise-induced pulmonary hemorrhage.

Abstract: Bleeding into the lungs in thoroughbreds is extremely common; there is evidence that it occurs in essentially all horses in training. However, the mechanism is unknown. We tested the hypothesis that exercise-induced pulmonary hemorrhage (EIPH) is caused by stress failure of pulmonary capillaries. Three thoroughbreds with known EIPH were galloped on a treadmill, and after the horses were killed with intravenous barbiturate the lungs were removed, inflated, and fixed for electron microscopy. Ultrastructural studies showed evidence of stress failure of pulmonary capillaries, including disruptions of the capillary endothelial and alveolar epithelial layers, extensive collections of red blood cells in the alveolar wall interstitium, proteinaceous fluid and red blood cells in the alveolar spaces, interstitial edema, and fluid-filled protrusions of the endothelium into the capillary lumen. The appearances were consistent with the ultrastructural changes we have previously described in rabbit lungs at high capillary transmural pressures. Actual breaks in the endothelium and epithelium were rather difficult to find, and they were frequently associated with platelets and leukocytes that appeared to be plugging the breaks. The paucity of breaks was ascribed to their reversibility when the pressure was lowered and to the fact that 60-70 min elapsed between the gallop and the beginning of lung fixation. Capillary wall stress was calculated from pulmonary vascular pressures measured in a companion study (Jones et al. FASEB J. 6: A2020, 1992) and from measurements of the thickness of the blood-gas barrier and the radius of curvature of the capillaries. The value was as high as 8 x 10(5) dyn/cm2 (8 x 10(4) N/m2), which exceeds the breaking stress of most soft tissues. We conclude that stress failure of pulmonary capillaries is the mechanism of EIPH.
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Publication Date: 1993-09-01 PubMed ID: 8226517DOI: 10.1152/jappl.1993.75.3.1097Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research investigates why bleeding into lungs occurs in thoroughbred horses during exercise, concluding that this experience, known as exercise-induced pulmonary hemorrhage (EIPH), is caused by stress failure in the lungs’ capillaries.

Research Methodology

  • The research involved three thoroughbred horses known to have EIPH.
  • The horses were made to gallop on a treadmill and then euthanized intravenously with barbiturate.
  • Their lungs were then removed, inflated, and prepared for electron microscopy, a technique that provides increased resolution for detailed examination.

Research Findings

  • The researchers conducted an ultrastructural study providing extensive insights into the cell structure and organization.
  • The results showed evidence of stress failure in the capillaries of the horses’ lungs.
  • Findings included disruptions in capillary endothelial and alveolar epithelial layers, accumulations of red blood cells in the lung’s wall interstitium, the presence of protein-rich fluid and red blood cells in alveolar spaces, interstitial edema, and the protrusion of fluid-filled endothelia into the capillary lumen.
  • The team noted that the observed changes align with the transformations they previously discovered in rabbit lungs subject to high capillary pressures.

Further Observations & Calculations

  • The researchers had difficulty finding actual breaks in the endothelium and epithelium, which were often associated with platelets and white blood cells that seemed to be clogging these fracture points.
  • The small number of such breaks was attributed to their reversibility when pressure was reduced and to the delay (60-70 mins) between the horses’ gallop and the commencement of lung fixation.
  • The stress on the capillary walls was calculated from the measurements of pulmonary vascular pressures (in a companion study) and the measurements of blood-gas barrier thickness and capillary curvature radius.
  • The recorded value obtained via these calculations exceeded the breaking stress of most soft tissues.

Research Conclusion

  • The team concluded that the EIPH in thoroughbred horses during exercise is caused by stress failure in the pulmonary capillaries.

Cite This Article

APA
West JB, Mathieu-Costello O, Jones JH, Birks EK, Logemann RB, Pascoe JR, Tyler WS. (1993). Stress failure of pulmonary capillaries in racehorses with exercise-induced pulmonary hemorrhage. J Appl Physiol (1985), 75(3), 1097-1109. https://doi.org/10.1152/jappl.1993.75.3.1097

Publication

Journal of applied physiology (Bethesda, Md. : 1985)
ISSN: 8750-7587
NlmUniqueID: 8502536
Country: United States
Language: English
Volume: 75
Issue: 3
Pages: 1097-1109

Researcher Affiliations

West, J B
  • Department of Medicine, School of Medicine, University of California, San Diego, La Jolla 92093-0623.
Mathieu-Costello, O
    Jones, J H
      Birks, E K
        Logemann, R B
          Pascoe, J R
            Tyler, W S

              MeSH Terms

              • Animals
              • Blood-Air Barrier
              • Capillaries / pathology
              • Capillaries / physiopathology
              • Female
              • Hemorrhage / etiology
              • Hemorrhage / physiopathology
              • Hemorrhage / veterinary
              • Horse Diseases / etiology
              • Horse Diseases / pathology
              • Horse Diseases / physiopathology
              • Horses
              • Lung / ultrastructure
              • Lung Diseases / etiology
              • Lung Diseases / physiopathology
              • Lung Diseases / veterinary
              • Male
              • Microscopy, Electron
              • Pilot Projects
              • Pulmonary Circulation
              • Running
              • Stress, Mechanical

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