Reaction of the chick to one atmosphere of oxygen

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Abstract
The white Leghorn chick between the ages of 2 and 7 weeks is markedly resistant to the toxic effects of 1 atm O2. Continuous exposure for as long as 4 weeks caused neither deaths, obvious morbidity, or signs of pulmonary damage on gross autopsy. Nevertheless the hyperoxia had some adverse effects, primarily reducing the growth rate to 75–25% of normal, reducing feed intake per unit body weight to 75% of normal, slowing respiratory rate by 31%, decreasing erythrocytes, hemoglobin, and hematocrit by 9– 12%, and causing some reversible histological changes in the lungs. Arterial O2 tensions were elevated over 300 mm Hg, but arterial Pco2 and blood pH were unaffected. No residual effects were noted upon return to air breathing. The anatomical peculiarities of the avian lung may play some role in the chicks resistance to hyperoxia, but it is also possible that it is a function of age similar to the tolerance shown by the young rat but not the adult. oxygen toxicity; chick respiratory system; artificial atmospheres; avian physiology; sealed systems Submitted on February 8, 1965