A Quantitative Study of the Pulmonary Vascular Bed and Pulmonary Weight: Body Weight Ratio in Chickens Exposed to Relative Normoxia and Chronic Hypobaric Hypoxia

The number of pulmonary blood vessels of different diameter range and the lung weight: body weight ratio were calculated in broiler chickens, as potential markers of adaptation to hypobaric hypoxia. Cobb500 broilers were housed at 460 and 2638 meters above sea level. Four week-old birds were assigned to the following groups: 1) non-pulmonary-hypertensive chickens reared under normoxia and 2) 3), non-pulmonary-hypertensive chickens and pulmonary-hypertensive chickens maintained under natural conditions of hypobaric hypoxia, respectively. The number of blood vessels per area was calculated in representative lung tissue samples of chickens from each group. The blood vessel diameter ranges included for quantitative assessments were ≥50-100, >100-200 μm, using 100 magnifications, and >200-300 and >300-500 μm, under 40 magnifications. Although for the diameter ranges >100-200, >200-300 and >300-500 μm no statistically significant differences were found in the number of vessels/area (P>0.05) among different groups, pulmonary-hypertensive chickens reared under hypoxia showed numerically higher values when compared with non-pulmonary-hypertensive chickens reared under hypoxia or normoxia. For the ≥50-100 μm range, pulmonary-hypertensive and non-pulmonary-hypertensive chickens reared under hypoxia had a significantly lower number of blood vessels (P0.05). It is possible that the time under hypoxia was not long enough to permit compensatory lung growth which could allow for neo-formation of respiratory or blood capillary in the lungs.