S Sl le ee ep p--r re el la at te ed d r re es sp pi ir ra at to or ry y d di is st tu ur rb ba an nc ce es s i in n p pa at ti ie en nt ts s w wi it th h D Du uc ch he en nn ne e m mu us sc cu ul la ar r d dy ys st tr ro op ph hy y Four patients (67%) showed symptoms that suggest sleep-related respiratory disturbances. At night, the apnoea-hypopnoea index (AHI) was 11±6. The patients with more symptoms during the daytime had the highest AHI scores. Most of the apnoeas (85%) were central, particularly during rapid eye movement (REM) sleep. Sleep architecture was well-preserved. Arterial desaturation (>5% below baseline) occurred during 25±23% of total time. AHI correlated with daytime PaO 2 , and AHI in REM sleep correlated with age. A stepwise multivariate analysis showed that PaO 2 and, to some extent, the degree of airflow obstruction were significantly correlated with AHI.We conclude that sleep-related respiratory disturbances are frequently present in patients with Duchenne muscular dystrophy. Therefore, physicians should look for symptoms related to sleep-related respiratory disturbances in these patients. Furthermore, sleep-related respiratory disturbances should be strongly suspected in older Duchenne muscular dystrophy patients, particularly if diurnal arterial hypoxaemia is concurrently present.

Twenty consecutive patients (16 women and 4 men), with a mean age of 40 years, who were diagnosed and treated for myasthenia gravis were enrolled in a prospective investigation aimed at determining the amount of respiratory disturbance occurring during sleep while they received treatment. Patients were clinically evaluated to determine body mass index, presence of upper airway anatomical abnormalities, level of functional capacity and activity scored from 1 to 5, and presence of sleep-related complaints. They underwent daytime pulmonary function tests, determination of maximal static inspiratory pressure, measurement of transdiaphragmatic pressure, and measurement of arterial blood gas levels. Polygraphic monitoring during sleep, evaluating respiration and oxygen saturation, was also performed. Results indicated that in the studied population, all subjects had evidence of daytime diaphragmatic weakness as demonstrated by transdiaphragmatic pressure measurements, independent of the degree of autonomy and functional capacity and activity level reached. Older patients with moderately increased body mass index, abnormal total lung capacity, and abnormal daytime blood gas concentrations were the primary candidates for development of diaphragmatic sleep apneas and hypopneas, and oxygen desaturation of less than 90% during sleep. However, these clear indicators were not found in all subjects with sleep-related disordered breathing. Rapid-eye-movement sleep was the time of highest breathing vulnerability during sleep. Sleep-related complaints may also help identify subjects at risk for abnormal breathing during sleep, even when daytime functional activity is judged normal.

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The present experiment was designed to study the importance of strength and muscle mass as factors limiting maximal oxygen uptake (VO2max) in wheelchair subjects. Thirteen paraplegic subjects [mean age 29.8 (8.7) years] were studied during continuous incremental exercises until exhaustion on an arm-cranking ergometer (AC), a wheelchair ergometer (WE) and motor-driven treadmill (TM). Lean arm volume (LAV) was estimated using an anthropometric method based upon the measurement of various circumferences of the arm and forearm. Maximal strength (MVF) was measured while pushing on the rim of the wheelchair for three positions of the hand on the rim (-30 degrees, 0 degrees and +30 degrees). The results indicate that paraplegic subjects reached a similar VO2max [1.23 (0.34) 1 x min(-1), 1.25 (0.38) 1 x min(-1), 1.22 (0.18) 1 x min(-1) for AC, TM and WE, respectively] and VO2max/body mass [19.7 (5.2) ml x min(-1) x kg(-1), 19.5 (6.14) ml x min(-1) x kg(-1), 19.18 (4.27) ml x min(-1) x kg(-1) for AC, TM and WE, respectively on the three ergometers. Maximal heart rate f((c) (max)) during the last minute of AC (173 (17) beats x min(-1)], TM [168 (14) beats x min(-1)], and WE [165 (16) beats x min(-1)], were correlated, but f((c) (max)) was significantly higher for AC than for TM (P < 0.03). There were significant correlations between MVF and LAV (P < 0.001) and between the MVF data obtained at different angles of the hand on the rim [311.9 (90.1) N, 313.2 (81.2) N, 257.1 (71) N, at -30 degrees, 0 degrees and +30 degrees, respectively]. There was no correlation between VO2max and LAV or MVF. The relatively low values of f((c) (max)) suggest that VO2max was, at least in part, limited by local aerobic factors instead of central cardiovascular factors. On the other hand, the lack of a significant correlation between VO2max and MVF or muscle mass was not in favour of muscle strength being the main factor limiting VO2max in our subjects.