BIOM30002 Lecture Notes - Lecture 3: Contracture, Pressure Ulcer, Atelectasis
Some variability in course
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Ambulation lost anywhere between 8-14 years
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Gradual decline in upper limb function: difficulty bringing hands to mouth by 16-18 years
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Weakness first proximally and moves distally as disease progresses
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Death average approx. 25 years
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Death is usually from respiratory failure. Intercostals fail
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Cardiac death in about 10%: cardiomyopathy or arrhythmias. Because dystrophin expressed in
heart as well
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In frame mutations cause partially functional/less dystrophin. Milder, presents later. Degree of
progressive weakness is less
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Commonly 5-15 years
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Occasionally as late as 3rd or 4th decade
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Onset after age 5 years
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Progressive limb-girdle weakness
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Calf pain and myalgias common
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Able to walk after 15 years
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Respiratory failure after 4th decade
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Cardiomyopathy is MORE common than in DMD: greater strain on heart caused by greater
exercise and activity
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Natural History of Becker MD
Duchenne muscular dystrophy
Weakness of intercostal muscles > diaphragm
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In the early years, vital capacity increases with age and growth
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In the early teens, vital capacity plateaus and then declines steadily (5-10%/year)
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Respiratory failure typically occurs in the late teens or early 20s
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Results in some sleep disorders
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Respiratory deficit
Muscle weakness causes restrictive lung disease
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In all neuromuscular disorders, respiratory muscle function is worst in sleep: decreased
respiratory muscle tone and central drive
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This sleep-disordered breathing (SDB) is worst in REM sleep
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Fatigability, poor exercise tolerance, poor school performance
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Symptoms relate to increased CO2 retention, not hypoxia
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Does not cause shortness of breath or cough
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May manifest with sleepiness, headache, etc.: because not exchanging O2 well in sleep
(hypoventilating).
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Progresses to nocturnal and then also to daytime hypoventilation
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Early recognition enables appropriate treatment
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Treatable so try and identify it early
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Sleep-disordered breathing
Increased resistance to airflow due to partial or complete obstruction at any level
(trachea, bronchi, terminal or respiratory bronchioles)
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Lung function tests show decreased maximal airflow rates during forced expiration,
usually measured by forced expiratory volume in 1 sec (FEV1)
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Asthma
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Obstructive lung disease
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Reduced expansion of lung parenchyma and decreased total lung capacity
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Lung function tests show a reduced total lung capacity (TLC) and an expiratory flow rate
that is normal or reduced proportionately to TLC
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Chest wall disorders, e.g. neuromuscular diseases, severe obesity, kyphoscoliosis
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Chronic interstitial and infiltrative diseases, e.g. pneumoconioses and interstitial
fibrosis (fibrosis in the lungs)
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Restrictive defects occur in two general conditions:
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Restrictive lung disease
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Typical forms of lung disease
Progresses to nocturnal and then also daytime hypoventilation
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Advanced Duchene muscular dystrophy: respiratory deficit
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Document Summary
Gradual decline in upper limb function: difficulty bringing hands to mouth by 16-18 years. Weakness first proximally and moves distally as disease progresses. Cardiac death in about 10%: cardiomyopathy or arrhythmias. Occasionally as late as 3rd or 4th decade. Cardiomyopathy is more common than in dmd: greater strain on heart caused by greater exercise and activity. In the early years, vital capacity increases with age and growth. In the early teens, vital capacity plateaus and then declines steadily (5-10%/year) Respiratory failure typically occurs in the late teens or early 20s. In all neuromuscular disorders, respiratory muscle function is worst in sleep: decreased respiratory muscle tone and central drive. This sleep-disordered breathing (sdb) is worst in rem sleep. : because not exchanging o2 well in sleep (hypoventilating). Symptoms relate to increased co2 retention, not hypoxia. Does not cause shortness of breath or cough. Progresses to nocturnal and then also to daytime hypoventilation.
