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Duchenne Muscular Dystrophy:
Pulmonary Management
Introduction
• Ambulant boys normally have few respiratory difficulties
• Progressive loss of muscle strength leads to risk of respiratory
complications over time:
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–
–
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Ineffective cough
Nocturnal hypoventilation
Sleep disordered breathing
Daytime respiratory failure
• Staged progression: planned/proactive approach to respiratory
care, aiming to prevent/manage these complications
• Team to include a doctor and therapist skill in
initiation/management of
– Non-invasive ventilation and associated interfaces
– Lung-volume recruitment techniques
– Manual and mechanically assisted cough
• Specific guidelines for respiratory care in DMD have also been
published
Surveillance: Ambulatory
• Minimal assessment to include pulmonary
function
– e.g. sitting Forced Vital Capacity (FVC) at least
annually
– Enables familiarity of patient with equipment
– Allows care team to assess maximum respiratory
function achieved
Surveillance: Non-ambulatory
(clinic measurements)
• Main need for pulmonary care is after loss of independent
walking
• [Figure 2, TLN p181]
• Clinic measurements at least every 6 months
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Sitting FVC
Peak cough flow
Oxyhaemoglobin saturation by pulse oximetry
Maximum inspiratory and expiratory pressures
• Awake end-tidal CO2 level should be measured by
capnography, if patient non-ambulatory and has any of
– Suspected hypoventilation
– FVC <50% prediceted
– Current use of assisted ventilation
Surveillance: Non-ambulatory
(home measurements)
• [See Figure 3, TLN p181]
Family Awareness
• Family should be aware of the symptoms of hypoventilation or a
weak cough, which should be reported to medical caregivers
– Prolonged, apparently minor upper respiratory infections (e.g.
recovery from common colds is slow, with colds progressing to chest
congestion and bronchitis often requiring antibiotic therapy)
– More tiredness than is usual
– Shortness of breath, difficulty catching breath or finishing sentences
– Headaches all the time or in the morning
– Sleepiness for no reason
– Trouble sleeping, frequent waking from sleep, nightmares
– Wakes trying to catch breath, or can feel heart pounding
– Trouble paying attention
• Family should keep copies of the latest breathing test results to
show to attending doctors
Prevention of Problems
• Immunisation with 23-valent pneumoccocal polysaccharide
vaccine for patients ≥ 2 years
• Annual immunisation with trivalent inactivated influenza
vaccine for patients ≥ 6 months
• Both can be given to patients on steroids, though immune
response to vaccination may be diminished
• Detailed information on immunisation indications,
contraindications, and schedules can be obtained from
national sources
• It is essential to keep up to date with vaccination policies as
they can change regularly according to new threats
• If chest infection occurs, then in addition to manually and
mechanically assisted cough, antibiotics should be
prescribed early
Interventions
• Specific interventions are dependent on the
disease phase
• Staged progression:
1. Volume recruitment/deep lung inflation
techniques
2. Manual/mechanically assisted cough techniques
3. Nocturnal ventilation
4. Daytime ventilation
5. Tracheostomy
Step 1: Volume Recruitment & Deep
Lung Inflation Techniques
• By self-inflating manual ventilation bag, or
mechanical insufflation/exsufflation
• When FVC <40% predicted
Step 2: Manual and Mechanically
Assisted Cough Techniques
• Necessary when
– Respiratory infection present and baseline peak
cough flow < 270 L/minute
– Baseline peak cough flow < 160 L/min or max
expiratory pressure < 40cm water
– Baseline FVC < 40% predicted or < 1.25 L in older
teenagers/adults
Step 3: Nocturnal Ventilation
• Indicated in patients who have any of
– Signs/symptoms of hypoventilation (patients with FVC
< 30% predicted are at especially high risk)
– Baseline SpO2 <95% and/or blood or end-tidal Co2 >45
mm Hg while awake
– An apnoea-hypopnoea index >10 per hour on
polysomnography or four or more episodes of SpO2
<92% or drops in SpO2 of at least 4% per hour of sleep
• Optimally, use of lung volume recruitment
assisted cough techniques should always precede
initiation of non-invasive ventilation
Step 4: Daytime Ventilation
• In patients already using nocturnally assisted ventilation
daytime ventilation is indicated for
– Self-extension of nocturnal ventilation into waking hours
– Abnormal deglutition due to dyspnoea, which is relieved by
ventilator assistance
– Inability to speak a full sentence without breathlessness and/or
– Symptoms of hypoventilation with baseline SpO2 <95% and/or
blood or end-tidal Co2 >45mm Hg while awake
– Continuous non-invasive assisted ventilation (with mechanically
assisted cough) can facilitate endotracheal extubation for
patients who were intubated during acute illness or
anaesthesia, followed by weaning to nocturnal non-invasive
assisted ventilation if applicable
Step 5: Tracheostomy
• Indications for tracheostomy include
– Patient and clinician preference
– Patient cannot successfully use non-invasive ventilation
– Inability of local medical infrastructure to support noninvasive ventilation
– 3 failures to achieve extubation during critical illness
despite optimum use of non-invasive ventilation and
mechanically assisted cough
– The failure of non-invasive methods of cough assistance to
prevent aspiration of secretions into the lung and drops in
oxygen saturation below 95% or the patient’s baseline,
necessitating frequent direct tracheal suctioning via
tracheostomy
Surgery
• Lung function should be checked before
surgery
• DMD patients should never be given inhaled
anaesthesia or succinylcholine
CAUTION: Supplemental Oxygen
• In later stages of DMD, supplemental oxygen therapy
should be used with caution
– Can apparently improve hypoxaemia while masking
underlying cause (e.g. atelactasis or hypoventilation)
– Might impair central respiratory drive, exacerbating
hypercapnia
• If patient has hypoxaemia due to hypoventilation,
retained respiratory secretions and/or actelectasis,
then manual and mechanically assisted cough and noninvasive ventilatory support are necessary
– Substitution of these methods by oxygen therapy is
dangerous
References & Resources
• The Diagnosis and Management of Duchenne
Muscular Dystrophy, Bushby K et al, Lancet
Neurology 2010 9 (1) 77-93 & Lancet
Neurology 2010 9 (2) 177-189
– Particularly references, p186-188
• The Diagnosis and Management of Duchenne
Muscular Dystrophy: A Guide for Families
• TREAT-NMD website: www.treat-nmd.eu
• CARE-NMD website: www.care-nmd.eu