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

Impairments that occur due to SCI;

1. Reduced lung volumes and flow rates (Due to respiratory muscle weakness/ paralysis, reduced expiratory volume due to denervation of abdominal muscles responsible for forced exhalation, reduced inhalation volume due to denervation of the diaphragm and intercostal muscles responsible for chest expansion)
2. Reduced total lung capacity
3. Impaired cough (The cough reflex is preserved but, the weakness of abdominal muscles responsible for forced expiration impairs effective coughing techniques which result in secretion retention)

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.

Medical Management

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References

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