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:– 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

– 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

techniques2. Manual/mechanically assisted cough techniques3. Nocturnal ventilation4. Daytime ventilation5. 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 non-

invasive 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 non-invasive 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