Effects of theophylline on pulmonary function in patients with traumatic tetraplegia.

BACKGROUND/OBJECTIVES: To assess the effects of theophylline on pulmonary function in patients with chronic traumatic tetraplegia, we conducted a double-blind placebo-controlled crossover study in 10 patients. METHODS: The patients (age: 41 +/- 3 years; time from injury: 16 +/- 3 years; neurological levels: C3 to C7-T1) were randomized to receive oral theophylline or placebo for 6 weeks. After 2 months of washout, the patients received the medication not taken in the first trial for an additional 6 weeks. We measured lung volumes, expiratory flow rates, maximal inspiratory pressure (MIP), and maximal expiratory pressure (MEP) at both baseline and at the end of each treatment arm. Theophylline blood serum assays were measured during the first week of the treatment and on the day of respiratory measurements. RESULTS: Mean theophylline level on the day of treatment completion was 12.6 +/- 1.4 microg/mL. In analyzing the data from the group of 10 patients, the percent changes from baseline in total lung capacity, forced vital capacity, forced expiratory volume at 1 second, MIP, and MEP did not differ significantly between the two treatment arms (P > 0.05 in all). CONCLUSION: These data show that in this small group of 10 subjects with chronic tetraplegia, administration of oral theophylline did not improve pulmonary function.

Hypocapnia is associated with increased upper airway expiratory resistance during sleep.

We hypothesized that hypocapnia is responsible for increased expiratory resistance during NREM sleep. Hypocapnia was induced by hypoxic hyperventilation in 21 subjects (aged 29.4 ± 7.8 yrs, 10 women, BMI 24.4 ± 4.3 kg/m(2)). Isocapnic hypoxia was induced in 12 subjects of whom, 6 underwent hypocapnic hypoxia in the same night. Upper airway resistance (R(UA)) was measured at the linear pressure-flow relationship during inspiration and expiration. Inspiratory flow limitation (IFL) was defined as the dissociation in pressure-flow relationship. (1) Expiratory R(UA) increased during hypocapnic but not isocapnic hypoxia relative to control (11.0 ± 5.6 vs. 8.2 ± 3.6 cm H(2)O/L/s; p < 0.05, and 11.45.0 vs. 10.94.4 cm H(2)O/L/s; p = NS, respectively). (2) No gender difference was found in R(UA) (p = NS). (3) Increased expiratory R(UA) correlated with the IFL change during hypocapnic but not isocapnic hypoxia. (4) No changes were noted in inspiratory R(UA) or IFL. Expiratory R(UA) increased during hypocapnia and was associated with IFL, indicating upper airway narrowing. Gender does not influence the upper airway response to hypocapnic hypoxia.