Respiratory Management in Spinal Cord Injury

Original Editor - Eugenie Lamprecht Top Contributors - Ewa Jaraczewska, Eugenie Lamprecht, Lucinda hampton, Jess Bell, Kim Jackson, Naomi O'Reilly, Vidya Acharya, Chelsea Mclene and Kirenga Bamurange Liliane

Introduction

Respiratory dysfunction is one of the most common medical complications, as well as the leading cause in reduced Quality of Life (QoL) and mortality among individuals with Spinal Cord Injuries (SCIs). The SCI level and whether or not the SCI is complete or incomplete is directly associated with the extent of the respiratory dysfunction. A universal classification tool used to assess the level and the completeness is known as the American Spinal Injury Association (ASIA) scale. Cervical and higher thoracic SCIs are more prevalent to develop respiratory complications. This is due to the diaphragm impairment. The diaphragm is accountable for 65% of forced vital capacity and therefore plays a large role in ventilation. Literature indicates that 67% of individuals with SCI, present with respiratory complications in the acute stage, of which higher cervical SCI are far more common.

Pathophysiology

In order to understand how respiratory functioning is affected among individuals with SCI, it is important to understand how normal ventilation occurs. The video below explains the mechanisms of breathing in healthy individuals;

SCI that involves the innervation of the diaphragm, intercostal muscles and the abdominal muscles directly affects the mechanics of breathing. The following table illustrates the level of neurological injury relevant to impairment;

Neurological level	Impairment
C1-3	Full ventilator dependent
C3-4	Periods of unassisted ventilation Diaphragm impaired - ↓ tidal volume & vital capacity
C5	Independent ventilation Initial ventilatory support Diaphragm intact Intercostals and abdominal muscles impaired - ↓ lung volumes and forced expiration for effective secretion clearance
C6-8	Independent ventilation Diaphragm intact Intercostals and abdominal muscles impaired - ↓ lung volumes and forced expiration for effective secretion clearance Uses accessory muscles to generate an effective cough
T1-4	Independent ventilation Diaphragm intact Intercostals intact - normal lung volumes Abdominal muscles impaired - ↓ forced expiration for effective secretion clearance
T5-12	Ventilation near equal or equal to individuals without SCI

Another common complication that occurs among acute quadriplegia is the excessive bronchial mucus production. The cause of this is still uncertain but is thought to be due to reduced vagal activity. This leads to a parasympathetic imbalance which causes;

• Bronchial spasm
• increased vascular congestion, and
• decreased mucociliary activity (related to mechanical ventilation)

After the shock phase, abnormal spinal reflexes may lead to spastic contraction of abdominal muscles. This increases the work of breathing in these individuals and may lead to dyspnea.

It is also important to know that erect positions negatively affects ventilation due to flattened diaphragm and the forward movement of abdominal content which is related to impaired breathing mechanisms. It is therefore important to consider abdominal binders etc to assist with breathing in erect positions.

Possible complications

1. Hypoventilation,
2. Reduced surfactant production,
3. Mucus plugging,
4. Atelectasis,
5. Pneumonia
6. Pulmonary Oedema
7. Pulmonary Embolism
8. Sleep-disordered breathing and sleep apnoea syndrome

Medical Management

The standard medical practice involves early surgical stabilisation of the spine and close monitoring in intensive-care units.

Monitoring

The entire multidisciplinary team is responsible for monitoring the;

• diaphragmatic function
• pulse oximetry and arterial gasometry

Markers that indicate the need for intubation are;

• VC below 15mL/kg
• Maximum inspiratory pressure below -20cmH2O
• Increased pCO2

Ventilation, weaning and extubation

Intubation is important when individuals require respiratory support, which is 100% of cases with complete C5 and above SCIs. Different ventilation methods and settings are used to the specific respiratory needs of the individual.

Evidence supporting the optimal weaning protocols are limited but literature indicates a regime of starting with bidaily trails and 3 to 4 hours rest between and progressing from there onwards. Progressive ventilator-free breathing (PVFB), T-tube with pressure support (PS), and synchronized intermittent mandatory ventilation (SIMV) are the most used methods of weaning. It's important to note however those individuals on SIMV generally take longer to wean successfully.

The decision to extubate has to be made by the entire multidisciplinary team and close monitoring and chest physiotherapy should follow. Requirements before extubation include;

1. No surgical or diagnostic procedures on the day of extubation
2. No sedation
3. Stable vital signs as arterial gas levels
4. Normal fluid balances
5. SATS > 95%, pCO2 < 40-45mmHg
6. FiO2 < 25%, PEEP < 5cmH2O
7. Inspiratory pressure < -20cmH2O
8. VC > 10-15mL/kg of ideal body weight
9. Normal Chest X-rays
10. Few secretions
11. No contra-indications for physiotherapy intervention

Tracheostomy and decannulation

Reasons for tracheostomy include; upper-airway obstruction relieve, preventing upper-airway damage, enable frequent suctioning and enables long-term ventilatory support. Benefits include patient comfort, reduced work of breathing, improved safety, improved oral hygiene, accelerated weaning and lower risk of ventilator-associated pneumonia. Many individuals with SCI that develop respiratory complications or have complete SCI are likely to receive a tracheostomy. When decannulation is considered it is important for the entire multidisciplinary team to assess the airway patency, cough and swallowing effectiveness. As well as oxygen requirements, medical stability, patient co-operation, oxygen dependence and infection markers.

Physiotherapy Management

Respiratory Treatment

Maintenance of lung volume is extremely important to prevent complications listed above. Intermittent positive pressure breathing (IPPB) and in/exsufflation can be used to increase lung volume and flow via mouthpiece, facemask or tracheostomy. Noninvasive ventilation (NIV) may also be used to achieve optimal lung volumes.

References

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