Cholinergic bronchomotor tone and airway caliber in tetraplegic patients

Study design: Case - control study. Objectives: To evaluate the resting airway caliber in subjects with tetraplegia; to de. ne the participation of cholinergic innervation in this condition; and to determine if baclofen modifies this pattern. Setting: A rehabilitation hospital, Brasilia, Brazil. Methods: We studied 18 tetraplegic patients, with complete motor loss between C4 and C8, and 18 healthy control subjects by measuring airway conductance, before and after inhaled ipratropium bromide. Results: At baseline, the pulmonary function parameters revealed mild-to-moderate restrictive impairment in tetraplegic patients as defined by decreases in total lung capacity and predicted percent of slow vital capacity. The average baseline specific airway conductance (sGaw) was less in tetraplegic patients (0.25 +/- 0.11) than in the control group (0.41 +/- 0.101/s/cm H2O) (P < 0.0001). All patients had improved postbronchodilator sGaw >= 40% compared with only four of the 18 controls (P <= 0.001). The average increase for tetraplegic patients was 235% (+/- 93) versus 25% (+/- 24) for controls ( Po0.0001). Analysis of variance for repeated measurements showed significant difference in sGaw between the control and spinal cord injury (SCI) groups (P < 0.0001) following bronchodilator challenge, but found no difference for total gas volume. No difference for mean basal sGaw and bronchodilator challenge was encountered comparing tetraplegic patients using baclofen to those not using it. Conclusions: Cervical SCI patients have a reduced baseline conductance compared to controls. Marked improvement occurs after an inhaled anticholinergic drug. This behavior was not affected by the use of baclofen. The study adds support to the hypothesis of an increased cholinergic bronchomotor tone in tetraplegic patients.