Maximal exercise performance-impairing effects of simulated blast overpressure in sheep.
Lung contusion has been identified as a primary blast injury. These experiments addressed a fundamental and overt endpoint of primary blast injury, incapacitation (performance decrement). Respiration, hemodynamics, and blood gases were measured in sheep undergoing incremental exercise challenge before and 1 h after simulated blast exposure of the thorax. Pathologic examination of lung tissue was performed after exposure and exercise testing. Blast overpressure was simulated in the laboratory using a compressed air-driven shock tube. Three levels of lung injury (Levels 1-3, 'Trivial', 'Slight', and 'Moderate' injury, respectively) were examined for effects on maximal oxygen consumption (VO[2max]), an index of cardiorespiratory fitness. Resting hemodynamics and blood gases were relatively normal an hour after exposure, immediately before exercise. However, Levels 1-3 lung injury were associated with average 4.8, 29.9 and 49.3% VO(2max). decreases, respectively. These performance decrements for Levels 2 and 3 were significantly different from respective controls (non-exposed). Exercise caused significant hemoconcentration in sheep under control conditions, before exposure (resting 9.5 +/- 0.9, end-exercise 11.8 +/- 0.9 g/100 ml). Blast exposure resulted in average decreases of 4.9 +/- 3.4, 12.8 +/- 4.0, and 12.6 +/- 3.3% in exercise-induced hemoconcentration for Levels 1-3 injury, respectively. Normal exercise-induced hemodynamic increases were also attenuated after exposure. Levels 2 and 3 injury resulted in average 22.6 +/- 2.9 and 18.5 +/- 11.2% stroke volume decreases, and also 22.3 +/- 8.4 and 29.0 +/- 14.2% cardiac output decreases, respectively, during exercise. While blast lung pathology and pulmonary function changes could account for post-blast performance decrements, these experiments suggest that in sheep, early after exposure, diminished hemoconcentration and cardiac disfunction may also contribute to decreased exercise performance.
Januszkiewicz
A J
AJ
Walter Reed Army Institute of Research, Department of Respiratory Research, Washington, D.C. 20307-5100, USA.
Mundie
T G
TG
Dodd
K T
KT
D000399:Air Pressure; D000818:Animals; D001753:Blast Injuries / Q000503:physiopathology*; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology; D005107:Explosions; D005260:Female; D006339:Heart Rate / Q000502:physiology; D008168:Lung / Q000503:physiopathology; D055370:Lung Injury; D009622:Noise / Q000009:adverse effects*; D010101:Oxygen Consumption / Q000502:physiology*; D010805:Physical Conditioning, Animal; D015203:Reproducibility of Results; D012119:Respiration / Q000502:physiology; D012756:Sheep; D013314:Stress, Mechanical; D013318:Stroke Volume / Q000502:physiology; D013898:Thoracic Injuries / Q000209:etiology; D013909:Thorax / Q000473:pathology