In addition to lung volume restriction, individuals with chronic
tetraplegia exhibit reduced airway caliber and
bronchodilator responsiveness similar to persons with
asthma. In
asthma, airflow obstruction is closely linked to airway
inflammation. Conversely, little is known regarding the airway inflammatory response in
tetraplegia. To compare levels of
biomarkers of
inflammation in exhaled breath condensate (EBC) and serum in subjects with chronic
tetraplegia, mild
asthma, and able-bodied controls.Prospective, observational pilot study. Thirty-four subjects participated:
tetraplegia (n = 12),
asthma (n = 12), controls (n = 10).
Biomarkers in EBC [8-
isoprostane (8-IP),
leukotriene B4 (LT-B4),
prostaglandin E2 (PG-E2),
tumor necrosis factor alpha (TNF-α),
interleukin 6 (IL-6)] and serum (8-IP, LT-B4, TNF-α, IL-6) were determined using commercially available EIA kits (Cayman Chemical Company, Ann Arbor, MI). Separate, one-way ANOVA with Bonferroni's post-hoc analyses were performed to determine group differences in demographic and dependent variables [EBC and serum
biomarkers, fractional exhaled
nitric oxide (FeNO), pulmonary function parameters, and specific airway conductance (sGaw)]. The
tetraplegia group had significantly elevated 8-IP levels in EBC compared to the
asthma (68 ± 38 versus 21 ± 13 pg ml(-1); p < 0.001) and control groups (22 ± 13 pg ml(-1); p < 0.01), respectively. FeNO levels were significantly elevated in the
asthma compared to the control group (26 ± 18 versus 11 ± 4 ppb; p < 0.05), and trended higher than levels in the
tetraplegia group (15 ± 6; p = 0.08). Levels of serum
biomarkers did not differ significantly among groups. Through analysis of EBC, levels of 8-IP were significantly elevated compared to levels found in individuals with mild
asthma and healthy controls. Further studies are needed to extend upon these preliminary findings that suggest the presence of airway
inflammation in subjects with chronic
tetraplegia, and how this relates to pulmonary dysfunction in this population.