THE INFLUENCE OF DIFFERENT ENVIRONMENTAL TEMPERATURES ON PULMONARY GAS EXCHANGE and BLOOD GAS CHANGES AFTER BIRTH |
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Authors: | RAGNAR TUNELL |
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Affiliation: | The Department of Paediatrics, Karolinska Sjukhuset, Stockholm, Sweden |
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Abstract: | Abstract. Tunell, R. (Department of Paediatrics, Karolinska Sjukhuset, Stockholm, Sweden). The influence of different environmental temperatures on pulmonary gas exchange and blood gas changes after birth. Acta Paediatr Scand, 64:57, 1975.–The oxygen uptake (Vo2) and respiratory exchange ratio (R) was determined during the first 20 min and at one and at 2 hours after birth in 16 healthy full-term newborn infants studied in different environmental temperatures. Arterial blood gases and acid-base balance were determined on repeated blood samples from the abdominal aorta. The infants were grouped in a “warm” group (n= 10) where efforts were made to avoid cooling after birth, and a “cold” group (n=6) where a decrease in rectal temperature to a mean value of 35.4oC at 2 hours occurred. Irrespective of environmental temperature, Vo2 was approximately 10 ml/kg min during the first 8 min after birth, thereafter decreasing to about 6–7 ml/kg min. During the first 8 min the main increase in Pa02 occurred and about 2 ml/kg min of the V0 was accounted for by changes in oxygen stores after birth. At 16–20 min and at 60 min after birth a negative relationship was found between Vo2 and Pao2 During the period 8–120 min after birth a close relationship was found between Vo2 and the degree of muscular activity. Within 4–16 min after birth, R values above 1.0 were regularly found simultaneously with the main decrease in Paco2. In infants kept “cold” a tendency to hyperventilate was found, probably elicited by cold stimuli. The rapid drop in deep body temperature regularly seen after birth could thus not be explained by a limited ability to increase pulmonary gas exchange. A high degree of evaporative heat loss, a relatively low “basal” metabolic rate and a limited response in “non-shivering thermogenesis” seem to be the main reasons for the heat loss after birth. |
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Keywords: | Newborn infants oxygen consumption carbon dioxide production environmental temperature blood gases. |
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