Pulmonary Function After Spinal Cord Injury

1
Pulmonary Function After Spinal Cord Injury

• Suzanne L. Groah, MD, MSPH

2
Pulmonary Function After SCI

• Respiratory complications leading cause of
  mortality after SCI
• Pneumonia leading cause of death
• Year 1 - 18.9
• Subsequent years - 12.7

3
Respiratory Problems Post-SCI

• Secretion management
• Loss of muscles necessary for forceful exhalation
• Atelectasis
• Dependence on the diaphragm for inhalation
• Hypoventilation

4
Pulmonary Function After SCI

• Inspiration
• Diaphragm C3-C4-C5 (phrenic N)
• 65 of VC
• Intercostals T1-T11
• Inspiration at low lung volumes
• Accessory muscles
• Scalene C4-C8
• SCM C2-C3/CN XI
• Trapezius C3-C4/CN XI

5
Pulmonary Function After SCI

• Expiration
• Abdominals T6-L1
• Intercostals T1-T11
• Expiration at large lung volumes
• Clavicular portion of pectoralis major
  (tetraplegia)

6
Respiratory Dysfunction After SCI

• Restrictive ventilatory defect
• ? in all lung volumes
• TLC, VC, ERV, FRC
• ? residual volume (paralysis of expiratory
  muscles)

7
Acute Pulmonary Changes in Tetraplegia

• Paradoxical breathing during spinal shock
• Paralyzed abdominal wall moves outward
• Paralyzed intercostals drawn inward with
  inspiration
• Higher diaphragm at end of expiration ? deeper
  breath
• Restrictive pattern early
• VC decreases to 30
• Exacerbated by halo vest
• IC decreases and approximates VC
• ERV decreases to 0
• PIP decreases to (-)30
• PEP decreases to lt ()30

8
Chronic Pulmonary Changes in Tetraplegia

• Chronically
• VC reduced 30-50
• Improvements due to improved strength
• Improvements with abdominal tone/spasticity
• C4-C6 VC may double in first 3 months
• FRC reduced 25
• ERV reduced 75
• PIP to (-)60
• PEP to ()30

9
Pulmonary Function

• VC correlates with FEV1, inspiratory capacity,
  ERV, FRC, RV, TLC
• VC does not correlate with
• Max positive expiratory P
• Max negative inspiratory P
• Peak expiratory flow
• Correlates with ability to wean
• Average cough flow in tetra 220 L/min (300-700)
• Important indicator of ability to decannulate

10
Respiratory Dysfunction After SCI

• C2 and higher
• C3-C4
• C5 and below
• T1-T5
• T6-T12
• L1 and below

• Need ventilation
• Need initial ventilation
• Potential to wean (51-83)
• Breathe independent
• May need initial vent (2/3)
• Passive expiration
• Weak cough
• Quiet respiration affected
• Weak cough
• No impairment

11
Acute Pulmonary Management

• Secure airway
• Provide adequate ventilatory support
• Prevent secretions and atelectasis
• VC q 8h to monitor
• Postural drainage/rotating beds
• Chest PT
• Suctioning

12
Acute Pulmonary Management

• Assisted cough
• Abdominal binder improves PEF 2-7
• Assisted cough improves PEF 15-33
• Electrical stimulation
• Mechanical insufflation-exsufflation
• Rapid shift in pressure produces high expiratory
  flow rate simulating cough
• 40/-40 produces expiratory flow of 10L/sec

13
Mechanical Insufflation-Exsufflation

• Bach
• SCI, MD, PP
• Increase VC, peak cough flow, O2 sat
• Endotracheal suction vs MI-E in SCI
• MI-E less irritating, painful, tiring,
  uncomfortable
• High patient satisfaction
• Anecdotally, less bronchoscopy

14
Acute Pulmonary Management

• IPPB/IPPV
• BiPAP
• I-PAP start as high as tolerated to 40cm H2O
• E-PAP start at 5-8 cm H2O
• CPAP start at 5-8 cm H2O
• Supine positioning
• VC decreases by 42-65 in sitting

15
Acute Pulmonary Management

• Incentive spirometry and resistance
• Glossopharyngeal breathing
• 6-9 gulps
• Bronchoscopy
• Tracheostomy
• Easier to wean from vent

16
Ventilatory Failure

• Acute, often around 4 days post-injury
• Secretions are trigger
• Diaphragm fatigue can take up to 1 week to
  restore glycogen stores

17
Ventilatory Failure

• Indications for intubation
• Inability to handle secretions
• Impending fatigue
• Hypoxemia unresponsive to O2
• RR 35
• PE max lt 20 PI max lt 25
• VC lt 2x predicted or lt 15cc/kg or lt 1-1.5L
• Hypercapnea

18
Ventilation in Acute SCI

• Invasive preferred acutely
• Chronically, non-invasive decreases pneumonia,
  hospitalizations
• High TV
• Start 12-15 cc/kg IBW ? max 25 cc/kg IBW
• Start flow 70 L/min ? max 120 L/min
• Rate 10-12
• PiP not to exceed 40 cm H2O
• Need 10-12 cm H2O to open close alveolus
• Need 4 cm H2O to maintain open alveolus
• Avoid PEEP

19
Ventilation in Acute SCI

• PEEP
• May not stimulate release of surfactant
• Increases mean airway pressure
• Predisposing to barotrauma
• In SCI, mean airway pressure is lower if larger
  TV used
• May be helpful in isolated cases keep an already
  inflated lung inflated

20
Ventilation in Acute SCI

• High TV protocol group cleared atelectasis
  faster than usual care group

21
Weaning Prognosis

• Poor prognosis with
• High neuro injury
• Age gt 50 (25 weaned and high mortality)
• VC lt 1L (1/76 weaned)
• Weaning methods
• PVFB or T-piece

22
Ventilator Weaning in Acute SCI

• Supine position preferred
• With sitting there is inability to take deep
  breath ? rapid shallow breathing ?
  microatelectasis ? ?pulmonary compliance
• Relative placement of diaphragm improves
  length-tension relationship
• VC varies from 42-65, depending on position

23
Ventilator Weaning in Acute SCI

• Central cord syndrome
• Preservation of intercostals
• Paralysis of diaphragm
• Observation of chest movement or diaphragm fluoro
• Mechanical advantage to breathing with HOB
  elevated and without abdominal binder

24
Ventilator Weaning in Acute SCI

• SIMV vs PVFB
• PVFB successful in 68
• SIMV successful in 35
• SIMV requires lower TV
• SIMV does not allow for adequate rest

25
Pulmonary Pearls

• KNOW LEVEL OF INJURY
• Attention to secretions/pulmonary toilet
• Prevention with vaccination and smoking cessation