Respiratory Care in Neuromuscular Disease

1. Respiratory Care in Neuromuscular Disease Cori Daines, MD Pediatric Pulmonary MedicineUniversity of Arizona

2. Neuromuscular Disease • Duchenne’s muscular dystrophy • Becker’s muscular dystrophy • Limb-Girdle muscular dystrophy • Spinal muscular atrophy • Myotonic dystrophy

3. Neuromuscular Disease • Genetically inherited • Muscle weakness • Extremities • Trunk/spine • Respiratory • Swallowing • Cardiac

4. Neuromuscular disease Controller failure Chest wall compromise Muscle weakness Hypotonia Hypertonia

5. Respiratory Control Maintain homeostasis Oxygen Carbon dioxide Hydrogen ion concentration (pH) Optimize mechanical efficiency Complex functions Vocalization Cough Exercise Adaptation to disease

6. Respiratory Muscles Diaphragm Intercostals Accessory muscles (shoulder girdle) Pharynx Larynx Abdominal wall Perineum

7. Physiologic impact Ventilatory impairment Oxygenation impairment [(A-a)DO2 ] Sleep disordered breathing Maintenance of lung volume Growth of the lung in children Lung clearance impairment Lung inflammation from aspiration Nocturnal vs diurnal dysfunction varies

8. Prevention Assuming that there is no primary lung disease most NMD patients can have normal lungs “An ounce of prevention is worth a pound of cure” 4 E’s = “Expansion, Evacuation, Evasion and Evaluation” i.e. expand the lungs, clear the airways, and avoid aspiration and infection Evaluate how the patient progresses acutely and over the long term

9. Minimize work of breathing Normally 15% of energy = WOB In NMD this can be exceeded Decreased use of energy in movement Increased work of breathing due to inefficient system and/or stiff/obstructed lungs Increased WOB will lead to chronic hypercapnea and compensatory alkalosis

10. Expansion Weakness leads to Poor inspiration Atelectasis and decreased compliance due to fluid accumulation and microatelectasis Chest wall/Shoulder girdle contracture Kyphoscoliosis (except DMD) Loss of MIP correlates with loss of lung volume and MIP < 30 are predictive of increases in CO2

11. Duchenne MD: FVC vs Age Bach et al. Arch Phys Med Rehabil 1981; 62:328

12. Expansion Reduced: TLC, VC, FRC, ERV Balance between chest wall and diaphragm Affects optimal position (Upright better with weak diaphragm) Rate of loss of function affects degree of breathing intolerance: Rapid is worse

13. Evacuation Optimal humidity and warmth to maintain ciliary function Cough Sense Close glottis Pressurize pulmonary gas by tensing abdomen and perineum (200 cm H2O) Explosively open airway Continue cough to lower lung volume Cough peak flow transients are 6 to 12 liters per second; i.e. 360 to 720 L/min

14. Pulmonary clearance failure Disrupted cilia due to drying and inflammation Low tidal volume (< 20 ml/kg) Poor glottic closure Poor abdominal compression CPF < 2.7 L/sec = 160L/min predict failure of extubation in adults (i.e. < 2 L/min/kg) Poor coordination Inablility to continue to low lung volume

15. Evacuation Chest physiotherapy Stacking with voluntary cough Stacking with augmented cough Mechanical insufflation-exsufflationTracheostomy

16. EVASION: Avoid pulmonary damage Growth failure Poor expansion Poor nutrition Aspiration Foreign body (tracheostomy) Poor clearance with inflammatory processes

17. Evasion: Aspiration A tension exists between natural, pleasure giving aspects of feeding and danger of aspiration and inadequate nutrition Often this leads to an illogical approach; i.e. pt has to fail oral feeds to go to alternative as opposed to succeed with oral feedings to move off of supportive modalities (NG,GT etc) Progresses early in SMA/Brainstem dysfunction and later in DMD Oral hygiene important even if NPO

18. Evaluation History and physical including QOL and sleep questionnaire Chest film Lung volumes MIP/MEP Sniff MIP Inspiratory flow reserve Maximum insufflation capacity Cough peak flows

19. Patient status changes with viral respiratory infections Increased secretions Decreased muscle strength Surfactant dysfunction in LRI Transient increase in need for support We commonly evaluate patients when they have recovered from an illness or are stable

20. Dr. Bach: Outpatient Protocol Patients at risk During chest colds w/ assisted PCF below 270 LPM Patients prescribed Oximeter and MIE device Patients trained in Air stacking insufflated volumes via mouth and nasal interfaces Manually assisted coughing Mechanical in-exsufflation at [+35 to +50] to [-35 to -50] cm H2O

21. Outpatient Protocol Patients given 1-hour access to Portable volume ventilator Cough Assist MIE (J. H. Emerson Co., Cambridge, MA) Various mouthpieces and nasal interfaces Patients and care providers are instructed SaO2 <95% indicates hypoventilation or airway mucus accumulation that must be cleared to prevent atelectasis and pneumonia Use SaO2 monitoring whenever fatigued, short of breath, or ill Use noninvasive IPPV and manually and mechanically assisted coughing as needed to maintain normal SaO2 at all times

22. Outpatient Protocol Patients with elevated EtCO2 or daytime SaO2 <95% Undergo nocturnal SaO2 monitoring When symptomatic or nocturnal SaO2 mean <94% A trial of nocturnal nasal IPPV is provided People continue to use nocturnal nasal IPPV when they felt less fatigue and nocturnal mean SaO2 increases. Most young patients use noninvasive IPPV for the first time to assist lung ventilation during chest infections.

23. Respiratory muscle aids: Indications Failure to maintain a healthy lung with growth and optimal ventilatory function i.e. failing the 3 E’s Prevention is key Optimize support in relation to the needs of the patient

24. Using what the patient has Daytime spontaneous respiration with nocturnal support for control, airway obstruction, recruitment of lung volume Glossopharyngeal breathing during the daytime with nocturnal ventilation Optimizing cough and lung volume with stacking maneuvers

25. Glossopharyngeal breathing

26. Maximal insufflation capacity Breath stacking Measured unassisted with spontaneous breathes or GPB breaths Commonly 1.5x the VC Can be augmented with interface and manual resuscitator bag Maintain lung volume and compliance and chest wall compliance

27. Inspiratory muscle aids Rocking bed and abdominal belt Disadvantage is no expansion of lung; i.e. frc to less than frc Negative pressure ventilators Disadvantages are OSAS and aspiration Non-invasive IPPV Tracheostomy and IPPV

28. Nocturnal support Used prior to need for 24/7 support Improves daytime PaO2, PaCO2 Reduces respiratory muscle work at night and rests the muscles Reverses cor pulmonale perhaps in addition to O2 by improving lung volume

29. Nocturnal support Increases MIP and lung volume Improves compliance and FRC during the daytime Can be used even in patients with severe breathing intolerance CCHS or Quadraparesis with daytime diaphragmatic pacing GPB during daytime Can be transitioned to 24/7 with illnesses

30. NIPPV: Interfaces Full face mask Nasal mask Custom mask Mouthpiece / Lipseal Leakage and dental issues Sipper mouthpiece

31. NIPPV: Nasal mask / Prongs 2-3 x preferred compared to mouthpiece Problems: Leak, esp mouth Nasal bridge pressure with mask Gum erosion or compression with mask Nasal erosion with prongs Chin strap may be needed

32. NIPPV: Full face mask Decreased leak Decreased Cough Talking Eating Nocturnal use with daytime nasal mask

33. NIPPV: Sipper / Mouthpiece Daytime use Allows facial freedom Flexed mouthpiece +/- custom orthodontics Intermittently used to augment breathing Continuously used

34. NIPPV: Sipper / Mouthpiece Large VT set on ventilator or High insp flow if pressure controlled Allows stacking maneuvers Head/neck control for intermittent use Use of flexed mouthpiece with a back pressure of 2-3 cmH2O can reduce low pressure/disconnect alarms

35. Complications of NIPPV Facial and orthodontic changes Aerophagia (PIP > 25 cmH2O) Nasal drying/congestion = humidify Volutrauma - air leak

36. Tracheostomy Controversial Current view in rehab circles is that with proper care a tracheostomy is never needed Our experience is that tracheostomy may have a role Patient preference Upper airway dysfunction Severe central airway obstruction by secretions

37. Ventilators

38. Ventilators Pressure cycled vs Volume cycled Pressure cycled are often triggered by flow sensing reducing work of breathing Flow sensing is also important in pts with high respiratory rates = infants/toddlers

39. Ventilators Leak can vary with sleep, position, and effort which is problematic with volume cycled ventilators Variable airway resistance and/or pulmonary or chest wall compliance better with volume settings Pressure cycling limits ability to stack

40. Ventilator triggering and rate Small/weak or brainstem/CNS pts may not trigger well Spontaneous-timed modes are useful with a backup rate higher than spontaneous when initiating ventilation in infants/young children Back-up rates lower than spontaneous once comfortable

41. Ventilation goals Healthy lungs with good volumes and no atelectasis Rate on the low side and Vt or PIP on the high side PaCO2 = 35 ± 5 mmHg Room air Patient comfort Ability to trigger vent Ability to deliver needed volume/flow in time No auto-PEEP No auto-cycling / Ventilator-Patient dysynchrony Primary lung disease may change this approach

42. BiPAP settings S/T mode / High span IPAP/EPAP If OSAS is main issue low span is appropriate IPAP range 15-18 May need higher with high UA resistance, non-compliant lungs, obesity/non-compliant chest wall May need to be lower with high spont rates EPAP range 2-4 Depending upon circuit may need 4 cmH2O to avoid rebreathing High EPAP is rarely needed

43. Other issues Inspiratory time I:E of 1:2 Ti of 0.5 min (infant) and 1.0 (>infant) Insp flow rate necessary to achieve pressure comfortably Trigger sensitivity set to reduce WOB, but not autocycle Pressure support may improve comfort with spontaneous breaths Ultimately creates an S/T mode depending upon settings

44. LTV system - Pulmonetics

45. LTV system - Pulmonetics

46. LTV system

47. LTV: Features

49. Control mode ventilation Limited respiratory control / Inability to trigger breaths

50. Assist Control Mode Can trigger breaths, but needs support with each breath