Evaluation of Breathing Pattern and Dyspnea in Subjects With Tetraplegia

Breathlessness is an extremely common and uncomfortable symptom that is reported in more than two-thirds of persons with tetraplegia. This disordered pulmonary function is due to respiratory muscle paralysis or to sympathetic denervation results in a restrictive impairment and airway hyperreactivity, respectively. These restrictive and obstructive dysfunctions have been associated with the symptom of breathlessness. However, mechanisms contributing to dyspnea in persons who have tetraplegia are not well understood. It has been demonstrated that persons with tetraplegia have an increased prevalence of breathlessness and may have an altered breathing pattern. The purpose of this study is to determine the breathing pattern at rest and measure the changes in breathing after a bronchodilator treatment (a medicine commonly used to treat asthma that relaxes and opens up airways). The determination of breathing pattern is done by measuring the movements in the chest wall while breathing. This design will elucidate differences in breathing patterns between those with tetraplegia and controls, as well as demonstrate the effect of bronchodilatation on motor drive and timing. Knowledge of the intraindividual variability and mean values of the components of the breathing pattern will improve our understanding of breathlessness in these individuals.

The goal of this study is to evaluate mechanisms of dyspnea in tetraplegia. This goal will be accomplished by completing the following specific objectives:

1. To noninvasively assess dyspnea, motor drive, and respiratory timing during prolonged periods of resting breathing.
2. To determine if relationships exist between these breathing pattern components and dyspnea.
3. To determine if the relationships among respiratory timing, drive, and dyspnea are altered by a bronchodilator and over its duration of action.

These specific objectives will be used to test the hypotheses that:

1. During prolonged periods of resting breathing, respiratory timing will be altered and motor drive will be increased and less variable than in able-bodied controls.
2. There will be a positive association between motor drive and dyspnea.
3. Improving respiratory mechanics by bronchodilator administration will reduce drive, normalize timing and lessen dyspnea over the duration of action of the drug.

Completion of the proposed studies will expand our existing knowledge of ventilatory control in persons with tetraplegia and relate these changes to dyspnea, a common and distressing clinical problem in these individuals. These studies will also provide a better characterization of breathing patterns and their intrasubject variability in persons with tetraplegia. Currently, the only information regarding breathing patterns in tetraplegia are of limited duration (15-30 minutes). If this pilot study reveals significant relationships between motor drive, timing, and dyspnea, compiling "normative" data for breathing patterns from large numbers of individuals with tetraplegia may be useful in evaluating dyspnea in different clinical settings.

Eligibility Criteria:
Inclusion Criteria:

1. Subjects who have cervical spinal cord injury
2. Complaints of dyspnea
3. Healthy non-paralyzed controls

Exclusion Criteria:

1. Active pulmonary infection
2. Current history of chronic pulmonary disease or asthma
3. Current smoker (\> 0.5 ppd)
4. Age \< 18 or \> 60 years
5. Duration of spinal cord injury \< 1 year
6. Unable to sit upright in a chair or wheelchair for a full day
7. Persons taking anticholinergic (e.g., ditropan) or gaba (e.g., baclofen) agents