Berlowitz et al. 2005;
USA
Downs & Black = 19
Longitudinal
N = 30

Population: 25 males and 5 females with acute tetraplegia; mean age 33.7 (range 18 – 69 yrs).
Methodology: Measured the incidence of sleep disordered breathing (SDB), and identified the relationship between SDB and previously postulated predictors
Outcome Measures: Apnea-Hyopnea Index; Incidence of sleep disordered breathing (SDB); overall respiratory function

1. At 2 weeks, 60% had SDB; at 4 weeks, 62%; at 13 weeks, 62%; at 26 weeks, 83%; at 52 weeks, 62%.
2. After 12 mos. 13 subjects showed a biphasic change in abdominal and neck girth.
3. All participants had reduced respiratory function compared with normative population values.

Biering-Sorensen & Biering-Sorensen 2001;

Denmark

Downs & Black = 16

Cross-sectional with AB controls

N SCI = 408

N controls = 339

Population: 331 males and 77 females; mean age 42.5 + 14.1 (range 17 – 86 yrs); mean YPI 12.1 + 6.3 (rnage 2.5 – 45.1 yrs); age and gender matched AB controls

Methodology: Comparison of oxygen desaturation

Outcome Measures: Nordic Sleep Questionnaire

1. Subjects with SCI snored more often (p < 0.00001), louder (p = 0.013), for more years (p = 0.011), and started at younger ages (p < 0.00001) compared to AB controls. 

Tamplin et al. 2011;

Australia

Downs & Black = 13

Cross-sectional with AB controls 

N SCI = 6

N control = 6

Population: 6 individuals with SCI; motor-complete C5-C7 tetraplegia; YPI > 1 yr; 4 males, 2 females; age 28-62. 6 AB age-matched controls

Methodology: Participants directly through phonatory exercises, standardized reading passages, and familiar songs

Outcome Measures: Maximal inspiratory and expiratory flow rates, timed lung volumes, surface electromyographic activity from accessory respiratory muscles, sound pressure levels during vocal tasks, Voice Handicap Index, Perceptual Voice Profile, ventilator function, upper airway function

1. Participants with tetraplegia had smaller lung capacities (p=0.028), reduced respiratory pressures (p=0.028), and significantly greater vocal impairment (p=0.046)
2. Significantly higher peak amplitude from participants with tetraplegia during loud and soft speech compared to control
3. Control participants had wider dynamic range (median 18dBA) compared to participants with tetraplegia (median 15dBA)
4. Control able to sustain vowel for longer (median 16.4s) than participants with SCI (15.2s)

Bach & Wang 1994;
USA
Downs & Black = 12
Longitudinal
N = 10

Population: 9 males and 1 female with tetraplegia; mean age 41+ 12.3 (34 – 77 yrs); mean YPI 7.7 + 5.8 (6mos-19 yrs).
Methodology: Comparison of oxygen desaturation
Outcome Measures: Oxygen desaturation, assessed through pulse oximetry

1. At baseline, 6 subjects had desaturation below 90%. At follow-up, 5 subjects had an increased number of transient nocturnal oxygen desaturations.

Cahan et al. 1993;

Australia

Downs & Black = 12

Cross-sectional with AB controls

N SCI = 16

N controls = 12

Population: All males with tetraplegia; mean age 49 + 15 (range 23 – 64 yrs); mean YPI 14 + 10 (1 – 32 yrs); age and gender matched AB controls

Methodology: Comparison of oxygen desaturation

Outcome Measures: Pulse oximetry

1. 6 patients with tetraplegia had ↓ in oxygen saturation levels below the normative range, indicative of SDB.

Loveridge et al. 1992;
Canada

Downs & Black = 11
Longitudinal
N = 6

Population: All males with acute SCI; mean age 30 + 11; for persons with tetraplegia; mean age 32.6 (21 – 50 yrs); mean time post-injury 38.6months
Methodology: Comparison of lung function and breathing patterns
Outcome Measures: Lung function parameters including, force vital capacity, inspiratory capacity, residual volume, forced expiratory capacity, functional residual capacity, and maximum inspiratory mouth pressure; Breathing pattern indicators including, Inspiratory time, tidal volume, and expiratory time; assessed in both sitting and supine positions, at 2, 6, and >12 months post-injury

1. Seating position resulted in greater stress on the respiratory system and breathing patterns in the group with tetraplegia compared to the AB control group.
2. Over time, breathing patterns of the group with tetraplegia improved and were comparable to those of the AB control group.

Wicks & Menter 1986;
USA
Downs & Black =11
Longitudinal
N = 134

Population: 118 males and 16 females with tetraplegia
Methodology: Review of patients’ medical records over 10 yrs in order to determine the number of patients who could be weaned off mechanical ventilation and to assess their long-term survival rate
Outcome Measures: Medical records between 1974 – 1983; mortality rates, Ventilation status

1. Individuals over 50 yrs of age had less successful weaning attempts and higher mortality rates than younger individuals despite similar levels of injury.

Ovechkin et al. 2010;

USA

Downs & Black = 11

Cross-sectional with AB controls

N SCI = 18

N control = 14

Population: 15 males and 3 females with SCI (8 motor-complete, 10 motor-incomplete with SCI ranging from C3 to L2); 9 male and 5 female AB controls

Methodology: Comparison of respiratory muscle control between SCI subjects and AB controls through PFT (standard spirometry)

Outcome Measures: Pulmonary function test (PFT); respiratory motor control assessment (RMCA) by surface electromyographic recording (sEMG)

1. Similarity index values relating individuals with SCI and the control group were developed.
2. Values for inspiratory (0.92±0.03) and expiratory (0.93±0.04) tasks were consistent with the control group.
3. Altered multi-muscle patterns in the SCI group produced values that trended lower 0.84±0.11 for inspiratory tasks, and significantly lower for expiratory tasks (0.59±0.22).