Phenotypic characterization of CO2-requiring strains of Streptococcus bovis from koalas.

We examined phenotypic characteristics of six mannitol-fermenting strains of Streptococcus bovis, including two unusual CO2-requiring strains isolated from koala feces. These strains did not grow in air, but grew in air supplemented with CO2 and under reduced oxygen conditions. All six strains had the same biochemical characteristics, except that the CO2-requiring strains did not produce beta-N-acetylglucosaminidase.     

Accuracy of mini peak flow meters in indicating changes in lung function in children with asthma.

OBJECTIVE--To assess whether mini flow meters used to measure peak expiratory flow can track changes in lung function and indicate clinically important changes. DESIGN--Comparison of measurements with a spirometer and different brands of mini flow meter; the meters were allocated to subjects haphazardly. SUBJECTS--12 boys with asthma aged 11 to 17 attending boarding school. MAIN OUTCOME MEASURES--Peak expiratory flow measured twice daily for three months with a spirometer and at least one of four brands of mini flow meter. RESULTS--The relation between changes in lung function measured with the spirometer and those measured with the mini flow meters was generally poor. In all, 26 episodes (range 1-3 in an individual child) of clinically important deterioration in lung function were detected from the records obtained with the spirometer. One mini flow meter detected six of 19 episodes, one detected six of 15, one detected six of 18, and one detected three of 21. CONCLUSIONS--Not only are the absolute values of peak expiratory flow obtained with mini flow meters inaccurate but the clinical message may also be incorrect. These findings do not imply that home monitoring of peak expiratory flow has no place in the management of childhood asthma but that the values obtained should be interpreted cautiously.     

Interpretation of interrupter resistance after histamine-induced constriction in the dog

The interrupter method for measuring respiratory system resistance involves interrupting flow at the airway opening and measuring the resultant changes in pressure. We have recently shown (J. Appl. Physiol. 65: 408-414, 1988) that in open-chest mongrel dogs, under control conditions, the initial rapid pressure change (delta Pinit) reflects conducting airway resistance and the subsequent gradual pressure change (delta Pdif) reflects stress recovery of the tissues. We questioned whether the same interpretation would apply after induced constriction. Accordingly, we performed interruption experiments on anesthetized, paralyzed, tracheostomized, open-chest mongrel dogs during passive expiration, measuring pressure at the trachea and in three different alveolar regions with alveolar capsules. We recorded measurements before and after the administration of increasing concentrations of histamine aerosol (0.1-30.0 mg/ml). We found a significant increase in the heterogeneity of alveolar pressures during the relaxed expiration with increasing concentrations of histamine. Despite the introduction of significant mechanical heterogeneities, delta Pinit still reflected the pressure drop as the result of the resistance of the conducting airways. delta Pdif, however, reflected a combination of the stress recovery of the tissues and pendelluft.