Breath isoprene during acute respiratory exacerbation in cystic fibrosis

Patients with cystic fibrosis (CP) experience a combination of chronic syst emic oxidative stress, generation of free radicals in the lungs due to a hy perimmune response and a diminished ability to scavenge free radicals secon dary to malabsorption and increased consumption, The authors asked the ques tion, "Does breath isoprene content reflect systemic oxidative stress?" The study involved 12 CF patients and 12 matched healthy controls. The pati ents were sampled during acute respiratory exacerbation (increased respirat ory symptoms, reduction in forced expiratory volume (FEV1) of >10%, and a d ecision to treat with intravenous antibiotics) and after two weeks of antib iotic treatment. Blood samples were examined for markers of oxidative stres s. Breath samples were analysed for isoprene content. Malondialdehyde (MDA), erythrocyte membrane polyunsaturated fatty acids, pr otein sulphydryls and protein carbonyls all showed evidence of increased ox idative stress which was moderated by antibiotic treatment. Breath isoprene production rate was significantly lower in patients during exacerbation th an in controls with a mean difference of -39 (95% confidence interval (CT) -11-57) pmol.min.kg(-1) and increased to normal values following treatment (mean change 63 (95% CI 42-84) pmol.min.kg(-1)). In conclusion, breath isoprene cannot be considered a reliable marker of ox idative stress.