Predictors of loud snoring in persons with spinal cord injury.

BACKGROUND: Predictors of loud snoring were examined in a cohort of 197 persons with chronic spinal cord injury (SCI) recruited by advertisement and from a Veterans Affairs Medical Center SCI Service. METHODS: Data were collected on age, marital status, antispasticity medications, duration of injury, level and completeness of injury, stature, and weight. Body mass index (BMI) was calculated for all participants. A health questionnaire was used to collect data on snoring and respiratory history. Habitual snorers were defined as those who reported loud snoring more than 1 night per week. RESULTS: The mean age (+/- SD) was 51.2 +/- 14.8 years, and 84 of 197 (42.6%) were habitual snorers. The most obese research subjects, regardless of antispasticity medication use, were more likely to report snoring, but the risk of snoring was greatest among subjects who were obese and used antispasticity medication. Subjects who used antispasticity medication and had a BMI above the median (> or = 25.3 kg/m2) had a 7-fold risk of reporting snoring compared with subjects below the median who did not use antispasticity medication (P = .001). The greatest risk occurred in those who used diazepam alone or baclofen and diazepam together and had a BMI at or above the median. Subjects who used these medications and had a BMI below the median did not have a significantly increased risk. Neurological motor completeness, level of injury, age, and years since injury were not significant predictors of snoring. CONCLUSION: Because snoring is a marker for obstructive sleep apnea (OSA), the data suggest that in obese individuals with SCI, the use of antispasticity medications may be a risk factor for OSA.

Prevention of human diaphragm atrophy with short periods of electrical stimulation.

We determined whether prolonged complete inactivation of the human diaphragm results in atrophy and whether this could be prevented by brief periods of electrical phrenic nerve stimulation. We studied a subject with high spinal cord injury who required removal of his left phrenic nerve pacemaker (PNP) and the reinstitution of positive-pressure ventilation for 8 mo. During this time, the right phrenic nerve was stimulated 30 min per day. Thickness of each diaphragm (tdi) was determined by ultrasonography. Maximal tidal volume (VT) was measured during stimulation of each diaphragm separately. After left PNP reimplantation, VT and tdi were measured just before the resumption of electrical stimulation and serially for 33 wk. On the previously nonfunctioning side, there were substantial changes in VT (from 220 to 600 ml) and tdi (from 0.18 to 0.34 cm). On the side that had been stimulated, neither VT nor tdi changed appreciably (VT from 770 to 900 ml; tdi from 0.25 to 0.28 cm). We conclude that prolonged inactivation of the diaphragm causes atrophy which may be prevented by brief periods of daily phrenic nerve stimulation.

Breathlessness and exercise in spinal cord injury.

After spinal cord injury (SCI), breathlessness during daily activities is common. In 308 individuals with SCI, the authors measured pulmonary function and administered a survey regarding health status, participation in wheelchair athletics, and breathlessness during different activities. The following questions were included: A. Are you troubled by shortness of breath when hurrying on the level or going up a slight hill?; B. Do you have to go slower than people of your own age on the level because of breathlessness?; C. Do you ever have to stop for breath when going at your own pace on the level?; and D. Do you ever have to stop for breath after going about 100 yards on the level? The analysis was restricted to 183 subjects with neurologically motor complete or incomplete SCI who, to get around, used hand-propelled wheelchairs more than 50% of the time. Of these, 56 (31%) reported breathlessness during some types of activities. Subjects with neurologically motor complete cervical or high thoracic SCI (T-6 and above) were more likely to report breathlessness than others (39% compared with 25%, p = .039). Among wheelchair athletes, the prevalence of breathlessness was 8/49 (16%) versus 48/134 (36%) for non-athletes (p = .011). Adjusting for smoking, neurological level, and history of obstructive lung disease, non-athletes were 2.3 times more likely to report breathlessness than athletes were (p = .049 to .075, depending on regression model). This relationship persisted when adjusted for percent predicted forced expiratory volume (FEV1) and maximal expiratory and inspiratory pressures. Therefore in SCI, wheelchair athletes are less likely to report breathlessness than non-athletes, but the mechanism does not appear to be improvement in respiratory muscle performance or pulmonary function.

Breathlessness in spinal cord injury depends on injury level.

Little is known about the prevalence and predictors of breathlessness in individuals with neurologically complete chronic spinal cord injury (SCI). Between December 1992 and September 1993, we mailed a respiratory questionnaire to 1,147 community-based individuals with chronic SCI. The questionnaire included four questions about the presence of breathlessness during activities related to moving about. Of the 485 who replied (42 percent response rate), analysis was limited to adult males with neurologically complete motor injuries who reported using a hand-propelled wheelchair more than 50 percent of the time to get around. Of 130 subjects (33 tetraplegics, 53 high thoracic SCI, 44 lower injury levels), the patients with tetraplegia reported breathlessness more frequently (range for the four questions, 21-33%) than those with high thoracic (range, 9-15%) or lower injury levels (range, 2-11%). For each of the four questions there was a significant trend (p < 0.05) for subjects with higher levels of injury to report the greatest prevalence of breathlessness (tetraplegia > high thoracic > lower). The frequency of breathlessness was greatest in those with neurologically complete cervical injuries, an effect that was independent of obesity, smoking, age, and years since SCI. The mechanisms of breathlessness in SCI are unclear but elucidation might lead to strategies for providing relief.

Maximal expiratory pressures in spinal cord injury using two mouthpieces.

STUDY OBJECTIVE: A technique for assessing expiratory muscle strength is the measurement of maximal expiratory pressure (PEmax). Previous studies have shown that a tube-style mouthpiece yields greater PEmax values than a flange-style mouthpiece because the latter technique is limited by the strength of the buccal muscles. In individuals with weak muscles of exhalation, this limitation may not apply because the strength of their buccal muscles may exceed that of the respiratory muscles. DESIGN: A tube-style mouthpiece and flange-style mouthpiece were used to measure PEmax. The order of the mouthpiece used in testing was alternated between subjects and the greatest values obtained after three efforts were compared. SETTING: Department of Veterans Affairs Medical Center. PARTICIPANTS: Fifty subjects with chronic spinal cord injury without acute medical illnesses recruited from veterans and the community. RESULTS: The mean difference between PEmax(tube) and PEmax(flange) was 20.7+/-26.4 cm H2O (p = 0.0001). Differences were negligible in those with the weakest muscles of exhalation but were substantial even in some quadriplegic subjects. CONCLUSION: Even in individuals with neuromuscular disorders, errors in assessment of expiratory strength occur when a flange-style mouthpiece is used, and we recommend that this technique be abandoned in the measurement of PEmax.

Assessment of stature in spinal cord injury.

Assessment of stature has been a neglected part of the medical assessment of individuals with spinal cord injury (SCI). In past studies of pulmonary function in SCI, it has not been stated how stature was assessed in order to calculate predicted pulmonary function. As part of a study of respiratory function in SCI, we examined the accuracy of self-report of stature and whether upper extremity measurements could be used to predict stature in 88 individuals with SCI. Although armspan and four other upper extremity measurements were significant predictors of length, recalled height was the best predictor. On average, for any value of armspan, an individual with complete SCI was 2.3 cm shorter than an individual with incomplete SCI. Individuals with complete SCI also had greater differences between recalled height and measured length compared with individuals with incomplete SCI, and this difference was not due to age or years since injury. It is likely that differences in bone demineralization account for the differences in length comparing individuals with complete and incomplete SCI. The 95 percent confidence intervals for predicted values of length based on armspan or recalled height were too wide for accurate calculation of predicted pulmonary function. In order to classify accurately the extent of pulmonary function abnormality, we suggest that measurements of supine length be made part of the medical assessment of individuals with SCI.

Spirometry--acceptability and reproducibility in spinal cord injured subjects.

The American Thoracic Society (ATS) has formulated guidelines for spirometry. We hypothesized that individuals with SCI (SCI), as a result of weak respiratory muscles, would exhibit poor test acceptability and reproducibility. Seventy-eight SCI subjects (39 with complete SCI) answered a respiratory questionnaire and performed spirometry. Of those with complete SCI, the proportion of subjects which met ATS criteria decreased with higher levels of injury. Poor test performance was not associated with age, respiratory symptoms or muscle fatigue. The most common reason for failing to meet ATS criteria for acceptability was excessive back extrapolated volumes (EBEV). Individuals with efforts that were acceptable except for EBEV and/or for exhalation of less than six seconds had values for forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) that were reproducible. If ATS criteria for acceptable spirometry were used in studying subjects with SCI, individuals producing otherwise reproducible values for FVC and FEV1 would be excluded. We found reproducibility similar to what has been reported in other cohorts and conclude that longitudinal study of respiratory function in SCI is feasible.