Duchenne Muscular Dystrophy: Pulmonary Management

1
Duchenne Muscular DystrophyPulmonary Management
2
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

3
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

4
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 lt50 prediceted
• Current use of assisted ventilation

5
Surveillance Non-ambulatory (home measurements)

• See Figure 3, TLN p181

6
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

7
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

8
Interventions

• Specific interventions are dependent on the
  disease phase
• Staged progression
• Volume recruitment/deep lung inflation techniques
• Manual/mechanically assisted cough techniques
• Nocturnal ventilation
• Daytime ventilation
• Tracheostomy

9
Step 1 Volume Recruitment Deep Lung Inflation
Techniques

• By self-inflating manual ventilation bag, or
  mechanical insufflation/exsufflation
• When FVC lt40 predicted

10
Step 2 Manual and Mechanically Assisted Cough
Techniques

• Necessary when
• Respiratory infection present and baseline peak
  cough flow lt 270 L/minute
• Baseline peak cough flow lt 160 L/min or max
  expiratory pressure lt 40cm water
• Baseline FVC lt 40 predicted or lt 1.25 L in older
  teenagers/adults

11
Step 3 Nocturnal Ventilation

• Indicated in patients who have any of
• Signs/symptoms of hypoventilation (patients with
  FVC lt 30 predicted are at especially high risk)
• Baseline SpO2 lt95 and/or blood or end-tidal Co2
  gt45 mm Hg while awake
• An apnoea-hypopnoea index gt10 per hour on
  polysomnography or four or more episodes of SpO2
  lt92 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

12
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
  lt95 and/or blood or end-tidal Co2 gt45mm 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

13
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 patients baseline,
  necessitating frequent direct tracheal suctioning
  via tracheostomy

14
Surgery

• Lung function should be checked before surgery
• DMD patients should never be given inhaled
  anaesthesia or succinylcholine

15
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

16
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