CO2 arterial-alveolar difference in the course of cystic fibrosis

Battistini, A.; Waring, W.W.

Il Fracastoro 63(3): 642-648


ISSN/ISBN: 0015-9271
PMID: 5517034
Document Number: 5052
Arterial-alveolar difference for co, (aAPco2) is obtained by subtracting alveolar Pco, (PAco2) from arterial Pco, (Paco,). Large differences reflect abnormal relationships between ventilation and blood flow within the lung. Arterial Pco2, as determined by a rebreathing technique, and the immediately previously recorded end-tidal Pco, (PAco2) were used to calculate the aAPco2. The test was performed in II normal children, in 29 children with cystic fibrosis (CF) and in zo children with chronic lung disease of various types other than CF. The CF group has significantly higher values (mean=10,9 mmHg) than either no:mal (mean=5,1 mmHg) or those with other types of pulmonary disease (mean=6 2 mmHg). This means that in CF there is a largo number of alveoli that are hyperventilated in relation to their blood flow. The increase in aAPco, is usually produced by decrements of PAco, rather than by increments of Paco,. This and serial studies of aAPco, in the same subject suggest a sequence of patterns produced by worsening disease. The initial pattern is an abnormal aAPco, produced by low Paco, and normal arterial Pco2. The, second is an elevated arterial Pco, with persistent low or normal alveolar Pco2. Later stages are persistent elevations of arterial Pco, and rising alveolar Pco, with the aAPco, remaining increased.

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CO2 arterial-alveolar difference in the course of cystic fibrosis