Assessment of sleep studies in myotonic dystrophy.

Myotonic dystrophy (MD) is the commonest adult muscular dystrophy and is associated with respiratory muscle weakness. The role of screening sleep studies is unclear in MD. We prospectively evaluated polysomnography/overnight oximetry in a group of MD patients and related this to the daytime respiratory function in an attempt to evaluate the usefulness of screening sleep studies. Twenty-five patients with type I MD [15 males; mean age (SD) 40.0 (10.9) years] who had at least one symptom suggestive of nocturnal hypoventilation were included in the study. We performed spirometry, maximal inspiratory and expiratory mouth pressures, sniff nasal inspiratory pressure, arterial blood gases and polysomnography or overnight oximetry. Excessive tiredness and sleepiness were the most common presenting symptoms. Prevalence of sleep related breathing disorder (SRBD) was 36%. FVC was found to be normal in 33% of subjects with significant SRBD. Mouth pressures were reduced more than FVC, even in patients with normal overnight oxygen saturation. Of all the daytime measures, FVC correlated best with arterial carbon dioxide tension (r = -0.7). Sleep studies were useful to identify a small group of myotonic dystrophy patients (12%, three out of 25 in our series) with SRBD that would have been missed with routine daytime assessments. Targeted sleep monitoring in patients who are older, with multiple symptoms suggestive of SRBD, especially if they are overweight seems to be the best way to utilize the existing resources. Home unattended oximetry was well tolerated and offers a practical screening tool in this challenging patient group where excess daytime sleepiness is often due to causes other than SRBD.

Long-term continuous positive airway pressure (CPAP) outcomes from a sleep service using limited sleep studies and daycase CPAP titration in the management of obstructive sleep apnoea/hypopnoea syndrome.

BACKGROUND: Detailed polysomnography (PSG) and overnight continuous positive airway pressure (CPAP) titration as the basis for investigation and treatment of obstructive sleep apnoea/hypopnoea syndrome (OSAHS) incurs high costs from inpatient stays and technician attendance, even when split night studies are employed. Responding to rapidly increasing demand, from 1996 the sleep service at Glasgow Royal Infirmary adopted limited sleep studies and daycase CPAP titration as first line management. Here we describe the outcomes of this service between 1996 and 1999. METHODS: Data were collected from prospective records made at follow up by sleep technicians and by casenote review. RESULTS: Results were available for 158 subjects (97.5%) of 162 commenced on CPAP during this period. One hundred and forty-eight (91%) were diagnosed by limited sleep studies and 80 (50%) were diagnosed at home. The median follow up was 23 months (interquartile range (IQR), 13-35). Median use of CPAP in those continuing therapy was 5.3 hours/night (IQR, 3.1 to 6.5) and 77% were still using CPAP at three years. Only initial low CPAP compliance (< 2 hours/night) significantly predicted early CPAP cessation. In those still on CPAP in 1999, the mean drop in Epworth Sleepiness Scale score was 4.6 points (95% confidence intervals, 3.2 to 6.0). CONCLUSION: These data from the CPAP population at Glasgow Royal Infirmary provide information on longterm outcomes using a diagnostic protocol based on limited sleep studies and daycase CPAP titration.

Predicting resting energy expenditure in patients with musculoskeletal deformities.

UNLABELLED: The aim of this study was to assess the validity of the commonly used equations (Harris-Benedict (HB), Schofield (S) and equations based on midarm circumference (MAC) and midarm muscle circumference (MAMC) in predicting resting energy expenditure (REE) in a population of patients with musculoskeletal deformities. 20 kyphoscoliotic patients (15 female (F); 5 male (M); mean age 59.6 years) and 10 controls (7 F; 3M; 59.8 years) were studied. REE measured by indirect calorimetry (IC) with a ventilated canopy system (Deltatrac metabolic monitor) was not significantly different between patients and controls (Mean (SD) REE (MJ/24 h): PATIENTS: 5.48 (1.1); controls: 5.28(0.8)). In patients with deformities the Schofield equation gave values which were closest to measured REE (mean difference and limits of agreement IC vs S: 0.098 MJ/24 h; -0.822 and 1.018). The Harris-Benedict equation using height (Ht) and armspan (AS) in lieu of height also gave acceptable results (IC vs HB (Ht): 0.34; -0.638 and 1.318; IC vs HB (AS): 0.255; -0.683 and 1.253). Equations based on MAC and MAMC compared poorly (IC vs MAC equation: 0.398; -1.530 and 2.326; IC vs MAMC equation 0.687; -0.911 and 2.285). On regression analysis the equation REE = 0.295 (MAMC) + 0.0483 (AS) -0.0324 (age) -6.25 predicted REE best in the patient population (r(2) = 0.861).

Resting energy expenditure and nutritional state of patients with increased oxygen cost of breathing due to emphysema, scoliosis and thoracoplasty.

BACKGROUND: Weight loss is a well recognised feature of patients with emphysematous chronic obstructive pulmonary disease (COPD). It has been suggested that this weight loss could be due to a hypermetabolic state resulting from the increased oxygen cost of breathing (OCB). To clarify the relation between resting energy expenditure (REE), nutritional state, and OCB these indices were measured in patients with respiratory impairment and an increased OCB due to COPD, scoliosis, and thoracoplasty. METHODS: Eighteen patients (six COPD, six scoliosis, six thoracoplasty) of mean (SD) age 59.9 (8.6) years (8M, 10F) and six controls (45.5 (9.9) years; 2M, 4F) were studied. OCB was estimated by the addition of dead space to the breathing circuit and REE was measured by indirect calorimetry using a ventilated canopy system. Height, arm span, weight, triceps skin fold thickness (TSF), mid-arm muscle circumference (MAMC), forced expiratory volume in one second (FEV1), and vital capacity (VC) were measured in all study subjects. RESULTS: OCB was elevated in all patient groups (mean 7.0 ml/l) compared with controls (1.9 ml/l). All patients with COPD, four with scoliosis, three with thoracoplasty, and none of the controls were < 90% ideal body weight. Mean (SD) measured REE as % predicted (Harris-Benedict equation) was 103.8 (7.6) in patients with COPD, 105.5 (10.9) in those with scoliosis, 106.3 (6.9) in the thoracoplasty patients, and 103.3 (3.4) in controls. One patient with COPD, two with scoliosis, two with thoracoplasty, but no controls were hypermetabolic (REE > 110% predicted). In all groups there was a negative relation between OCB and lung function (OCB v FEV1 r = -0.83 in COPD, -0.62 in scoliosis, -0.67 in thoracoplasty, and -0.76 in controls). There was no correlation between REE and OCB or MAMC. CONCLUSIONS: In patients with respiratory disease OCB (augmented ventilation) is related to lung function but not to REE. This is evidence against the hypothesis that hypermetabolism due to increased oxygen cost of breathing at rest is the sole or major cause of malnutrition in patients with lung disease.