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Gas exchange during exercise in patients with cystic fibrosis (CF) is characterised by an elevated physiological deadspace to tidal volume ratio. While this has been attributed to alveolar ventilation perfusion mismatch, there are other potential causes of the high proportion of wasted ventilation, including factors relating to the volume and the ventilation of the airway deadspace. CF (n = 6, F = 1, FEV1 26-63% pred) and control (n = 6, F = 2) subjects completed steady-state exercise on a cycle ergometer. Gas exchange was measured breath-by-breath and the volume of the airway deadspace (V(Daw)) determined using the equal areas method. Exercise data were interpolated to a CO2 output of 0.7 l/min. V(Daw) was similar in the two groups both at rest and during exercise. However, the airway deadspace ventilation (V(Daw)) (median (inter-quartile range)), patients, 6.8 (5.1-7.1) l/min; controls, 4.9 (3.5-5.6) l/min, P0.05) was significantly greater in the CF group due to a greater respiratory frequency. These results indicate that in CF patients, abnormally increased V(Daw) is an important contributor to the total (physiological) deadspace ventilation. Exercise performance in CF might be enhanced by efforts directed at facilitating an increase in exercise tidal volume and therefore the adoption of a more efficient pattern of breathing.

Atypical mycobacterial disease has been described in a small number of patients with cystic fibrosis. Apart from one uncontrolled study, there is little information regarding atypical mycobacterial skin reactivity in this group of patients. We evaluated delayed cutaneous hypersensitivity to purified extracts of Mycobacterium avium, Mycobacterium intracellular, Mycobacterium kansasii and Mycobacterium bovis in 23 healthy controls and 43 adult and adolescent patients with cystic fibrosis. Fifteen of the cystic fibrosis group were receiving regular corticosteroids. Additionally, direct smear examination and Lowenstein Jensen culture were performed on sputum from the cystic fibrosis group. The prevalence of positive skin reactions was similar in the group with cystic fibrosis (30%) and in the control group (57%). Subgroup analysis showed that those cystic fibrosis patients receiving corticosteroids had a markedly lower prevalence of positive reactions (7%) compared to controls (P less than 0.01). When this subgroup was excluded from analysis, the prevalence of positive skin reactions among patients with cystic fibrosis was 43%. In the prospective sputum bacteriology study, one of the 43 cases grew Mycobacterium avium-intracellulare and had clinical and radiological evidence of this disease. Of note, this patient showed positive skin tests to all four mycobacterial species tested. Our data show no difference in the prevalence rate of positive skin reactions to atypical mycobacterial antigens between a control population and an adult cystic fibrosis population. In addition, the predictive value of skin testing is low in cystic fibrosis due to the high prevalence of cross-reactivity between different mycobacterial species and the high prevalence of anergy among those patients with advanced disease receiving treatment with corticosteroids.

Summary We present a case of CF chronically colonized with Pseudomonas aeruginosa who developed septicaemia with this organism. Steroid therapy, diabetes mellitus or intrapulmonary haemorrhage, singly or in combination, may have contributed to the septicaemia. These factors operateincreasingly in the older CF population. Episodes of septicaemia may be more common than currently appreciated. Therefore, we recommend blood cultures in all febrile CF patients particularly those with complicated disease.

Summary Background Increased concentrations of exhaled nitric oxide (NO) have been detected in inflammatory lung diseases including asthma and have been attributed to increased expression and activity of inducible nitric oxide synthase (iNOS) within the airways. However, previous studies of exhaled NO in patients with bronchiectasis have yielded conflicting results, with reports of both increased and normal NO values. Recent evidence from animal models suggests that chronic airway infection reduces NO production within the lung, despite causing increased iNOS expression. We tested the hypothesis that, in human subjects with bronchiectasis, chronic airway infection reduces NO output from the conducting airways. Methods Using a recently described two-compartment model, we measured separately the contributions of the conducting airways and the alveoli to exhaled NO in nine patients with stable bronchiectasis and eight control subjects before and after inhaled glucocorticoid therapy. Results We found that airway NO output was significantly lower in bronchiectasis than in normal airways whereas NO output from the alveoli was similar to that of control subjects. High-dose inhaled glucocorticoid therapy did not alter airway or alveolar NO production. Conclusions These findings demonstrate that, in patients with bronchiectasis, airway NO output is reduced and that iNOS does not contribute significantly to airway NO production.