Diaphragmatic Dysfunction - Causes and Management

Introduction:

The diaphragm is a dome-shaped muscular-fibrous membrane that separates the thoracic and abdominal cavities, and it is the primary muscle of respiration. Diaphragmatic dysfunctions may be asymptomatic and may be associated with decreased exercise tolerance, dyspnea, respiratory failure, disturbances during sleep, and death.

What Are the Causes of Diaphragmatic Dysfunction?

The causes of diaphragm dysfunction are classified into anatomic, neurologic, neuromuscular junction, and myopathic disorders.

Anatomic Defects:

Anatomic defects can again be grouped based on congenital and acquired defects.

• Acquired Defects:

Defects that are penetrating injuries, blunt traumatic rupture, and iatrogenic injury during surgery or other invasive procedures.

• Congenital Defects:

Bochdalek hernia (developmental defect in the posterolateral diaphragm, allowing herniation of abdominal contents into the thorax causing mechanical compression of the developing lung parenchyma and causing lung hypoplasia)

• Morgagni Hernia: Rare congenital diaphragmatic defects that lead to bowel obstruction.

• Eventration of the diaphragm and diaphragmatic agenesis.

Neurologic Defects:

• Spinal cord disorders: Disorders include injury to the cervical spinal cord, poliomyelitis, syringomyelia, and anterior horn cell disease.

• Cervical spondylosis.

• Brainstem stroke.

• Phrenic nerve injury due to surgery, radiation, or a tumor.

• Heavy metal toxicity due to lead and arsenic.

• Diabetic neuropathy.

• Alcoholic neuropathy.

• Cervical chiropractic manipulation (cervical spine or neck manipulation in patients complaining of neck, upper back, or shoulder pain).

• It includes viral and post-viral neuropathy (polio, herpes zoster, West Nile virus, human immunodeficiency virus).

• Multiple sclerosis (disorder in which the immune system attacks protecting the covering of nerves).

• Amyotrophic lateral sclerosis (nervous system disease that weakens the muscle and impacts physical function).

• Connective-tissue disease (e.g.:systemic lupus erythematosus [SLE], rheumatoid arthritis).

Myopathic Causes:

• Malnutrition - Malnutrition refers to insufficient nutrients in the body.

• Limb- Girdle dystrophy (refers to a group of diseases that causes weakness and wasting of muscles in the arms and legs).

• Atrophy - Disuse atrophy due to mechanical ventilation.

• Electrolyte Disturbances - Hypokalemia, hypocalcemia, hypophosphatemia.

• Acid Maltase Deficiency - A group of diseases that interferes with the processing of food for energy production).

• Systemic Lupus Erythematosus (SLE) - Anautoimmune disease where the immune system attacks its own healthy tissues.

• Dermatomyositis - Inflammatory disease marked by muscle weakness and skin rashes.

• Mixed Connective Tissue Disorder - Has signs and symptoms of polymyositis, primary lupus, and scleroderma.

• Amyloidosis - Build-up of amyloid proteins in the heart, liver and kidney, and other organs.

• Myasthenia Gravis - Weakness and rapid fatigue of muscles under voluntary control.

• Muscular Disorders - Myotonic dystrophies, Duchenne muscular dystrophy (an inherited disorder of progressive muscular weakness), metabolic myopathies (disorder in which lack of certain enzymes involved in muscle contraction).

What Is the Pathophysiology of Diaphragmatic Disorders?

Disorders of Neuromuscular:

During normal respiration, the brainstem transfers action potentials to the third through fifth cervical spine levels, giving off dorsal ramifications that join to form the phrenic nerves bilaterally. The phrenic nerves then traverse the neck and thorax and enter the diaphragm. The impulse of respiratory stimulus from the brain to the diaphragm can be compromised by interruption of the phrenic nerve at any point along this course.

Traumatic injury to the head or brainstem prevents nerve signals from reaching the phrenic nerve. Therefore, injuries that affect the brain and brainstem are more severe with poor survival chances. Other causes of central nervous system damage that affect the brainstem include stroke, poliomyelitis, and multiple sclerosis.

What Are the Phrenic Nerve Disorders in Diaphragmatic Dysfunctions?

Injury to the phrenic nerve can affect transmitting signals from the brainstem to the diaphragm. Various clinical entities that can affect the phrenic nerve are,

• Trauma.

• Cardiac or thoracic surgery.

• Radiation therapy.

• Demyelinating diseases.

• Chiropractic cervical spine manipulation.

• Uremia.

• Lead neuropathy.

• Post-infectious neuropathies.

What Are the Diseases of Neuromuscular Junction Involved in Diaphragmatic Disorders?

Certain neuromuscular junction diseases affect or inhibit the production of neurotransmitters at the phrenic- diaphragmatic synapses. These include-

• Botulism - Rare poisoning caused by toxins produced by Clostridium botulinum bacteria.

• Myasthenia Gravis - It refers to the weakness and fatigue of voluntary muscles.

• Lambert Eaton Syndrome - It is a condition in which the immune system attacks the immune system.

• Disorders of Neuromuscular System - Poisoning due to organophosphates.

What are the Muscular diseases involved in diaphragmatic dysfunction?

Certain muscular diseases involved in diaphragmatic dysfunction are:

• Muscular dystrophies (refers to a group of genetic disorders that cause progressive weakness and loss of muscles).

• Glucocorticoid myopathy (the most common type of drug-induced myopathy in which the glycolytic muscle fibers are affected).

• Malnutrition (refers to insufficient nutrients in the body).

• Statin myopathy (refers to the myopathy that is induced due to statins medications (used in the treatment of heart-related diseases).

• Thyroid disorders.

• Disuse atrophy in mechanically ventilated patients.

These diseases affect the diaphragm, causing decreased muscle strength, decreasing the ability to generate diaphragmatic pressure gradients, and producing less negative inspiratory pressure.

• Disorders of Anatomy:

Anatomic disorders of the diaphragm are typically classified into congenital and acquired.

• Congenital Hernia:

Congenital diaphragmatic hernias occur when the diaphragm muscle does not develop normally, displacing the abdominal components into the thorax.

Congenital diaphragmatic hernias are classified based on the position of the defect. For example, Bochdalek hernias are present on the posterolateral defects of the diaphragm that fail in the development of pleuroperitoneal folds or absent migration of diaphragmatic musculature. These hernias represent between 80 % and 90 % of congenital diaphragmatic hernias.

Morgagni hernias affect the anterior portion of the diaphragm. On the other hand, congenital diaphragmatic hernias involve the central part of the diaphragm, which occurs very rarely.

• Acquired Hernia:

Trauma is the leading cause of acquired diaphragmatic disorder hernia and can be caused by blunt or penetrating injury. In addition, vehicle accidents or direct impacts cause blunt injury. Left-sided rupture commonly occurs in 65 to 75 % of blunt trauma cases.

Up to 65 % of diaphragmatic ruptures result from penetrating injury from stab or gunshot wounds.

What Is the Prognosis of Diaphragmatic Disorders?

• Patients with diaphragmatic disorders due to transient neuropathies such as Guillain - Barre syndrome or post-viral neuropathy and patients with iatrogenic phrenic nerve injury due to cardiac or thyroid surgery generally have a favorable prognosis with complete functional recovery in 69 % of patients within two years.

• Ventilator-induced diaphragm dysfunction in intensive care units indicates an unfavorable prognosis due to weakness of the diaphragm from defective contractility and reduced muscle mass, structural damage, and muscle fiber remodeling.

• Persons with high levels of cervical spine fractures generally have a poorer prognosis than with transient neuropathies.

• Trauma at the level of cervical spine C1 to C2 results in complete diaphragmatic paralysis.

• Trauma to C3 and C4 leads to substantial loss of diaphragm function.

• Trauma to C4 and C5 results in the requirement of ventilatory support.

• In the case of degenerative myopathies or neurologic disorders, respiratory muscle weakness progresses to respiratory failure.

• Patients with amyotrophic lateral sclerosis are marked based on the respiratory muscle strength level of prognosis.

• In congenital diaphragmatic hernias, the prognosis of post-surgical survival rates is 60 to 80 %. Despite the surgical improvements, complications still affect 20 to 40 % of the treated children over the years.

• These complications include both surgical (recurrence, stenosis, strictures, recurrent fistulae, postoperative adhesions, and obstruction), pulmonary problems (obstructive and restrictive pulmonary dysfunction, chronic lung disease), and gastrointestinal problems (gastroesophageal reflux, impaired intestinal motility, dysphagia), and failure to thrive.

What Are the Clinical Presentations of Traumatic Rupture?

The initial phase of traumatic rupture manifests with:

• Respiratory distress.

• Abdominal pain.

• Cardiac dysfunction.

• Intra abdominal and intrathoracic injuries.

In the latent phase, the symptoms include:

• Gastrointestinal complaints.

• Pain in the left shoulder.

• Dyspnea (shortness of breath).

• Orthopnea (discomfort in breathing while lying down flat, most common in heart and lung conditions).

• Pain in the left upper quadrant of the chest.

The gastrointestinal obstructive phase manifests with:

• Nausea.

• Abdominal pain.

• Vomiting.

• Prostration.

• Respiratory distress.

How to Manage Diaphragmatic Dysfunctions?

Medical Care:

• Patients with severe bilateral diaphragmatic dysfunction require ventilatory support.

• In concomitant chronic respiratory or cardiac disease, transient ventilatory support is required.

• Pulmonary rehabilitation shows improved diaphragmatic contractility in patients suffering from diaphragmatic dysfunction.

• Suppose a patient does not respond to nasal or oral positive pressure ventilation. In that case, alternative therapies such as negative-pressure cuirass ventilation or jacket ventilator or airtight bodysuit (e.g., pulmo wrap), or positive pressure pulmo belt can be used.

• In the case of amyotrophic lateral sclerosis, tracheotomy with permanent ventilation is recommended.

• Diaphragmatic pacing is indicated in patients with reconditioning with cervical hypoventilation or cervical spine injuries. These patients require tracheostomies because pacer-induced breathing is not synchronized with the upper airway. High stimulating frequencies and a prolonged pacing period may result in irreversible muscle dysfunction.

Surgical Care:

• Surgery is indicated in case of anatomic defects in the diaphragm. The type depends on congenital or acquired anatomic defects.

• Transabdominal primary surgical repair is carried out to manage congenital diaphragmatic defects.

• Thoracoscopic application of the hemidiaphragm is recommended in case of acquired diaphragmatic defects (traumatic rupture, late-onset congenital diaphragmatic defect). Plication results in improved lung function and exercise endurance and less dyspnea. Plication improves ventilation to well-perfused lungs and improves gas exchange.

Conclusion:

Patients with progressing diseases should be continuously monitored to develop nocturnal desaturations. In addition, patients should follow dietary and lifestyle modifications to maintain a better prognosis. An interprofessional team approach well manages positive outcomes. Treating the underlying cause and a clear approach leads to better diagnosis and management.