Pulmonary Rehabilitation in Neuromuscular Diseases- An Overview

Introduction

Respiratory issues contribute significantly to neuromuscular disease, causing morbidity and mortality. Patients with neuromuscular diseases (NMD) may develop restricted pulmonary sickness patterns due to respiratory muscle degeneration; as breathing muscles deteriorate, patients with neuromuscular disorders (NMD) often have restrictive pulmonary disease patterns.

Regular lung volume and maximal respiratory pressure measurements are needed to determine muscle strength. Muscular weakness causes respiratory issues, alveolar hypoventilation, and hypercapnia.

Hypercapnia can include morning headaches, nightmares, afternoon drowsiness, and attention deficits. Reduced alveolar ventilation and coughing are common respiratory issues in NMD patients. Given these factors, pulmonary function must be carefully assessed to guarantee adequate support for the inspiratory and expiratory muscles, preserving normal respiratory function.

What Are the Characteristics of Respiratory Dysfunction in Individuals With Neuromuscular Disorders (NMD)?

• Hypercapnia- Respiratory muscles are affected in NMD individuals with progressive muscle weakness, as the condition can gradually worsen, leading to hypercapnia. The aging process, in general, can worsen muscle weakness, and hypercapnia is also a symptom of aging, even with a non-progressive version of the disease.

• Muscular Strain- The respiratory muscle workload increases in the presence of any respiratory difficulties in these patients, which might result in decompensation of the respiratory muscles. The sudden pH drop can cause severe respiratory failure without support. The main component of NMD's respiratory treatment is managing the symptoms of respiratory muscle exhaustion.

For an individual with advanced respiratory muscle weakness, weaning off ventilatory assistance after the cure of respiratory problems might be challenging due to recurrent respiratory muscle exhaustion. In this circumstance, a patient would require recurrent intubations, supported ventilation, and possibly a tracheostomy tube for long-term support. After the intubation tube is removed from such patients, it would be preferable to provide non-invasive ventilatory assistance through a nasal mask or mouthpiece instead of completely weaning them; the respiratory muscle decompensation by giving ventilatory support non-invasively.

• Airway Secretions- Normal people can cough out their increased airway secretions caused by a respiratory tract infection and seldom experience subsequent consequences like pneumonia. On the other hand, because their coughs are ineffective, patients with NMD frequently develop improper inflation of the lung's alveoli and pneumonia. The chance of decreased coughing ability to expel secretions increases with the degree of expiratory muscle weakness.

• Respiratory Efficiency- Additionally, decreased adherence to breathing mechanisms that result in contracture of the chest wall and lung parenchyma impacts the inspiratory phase of coughing. Removing respiratory secretions for patients with limited lung expansion caused by lung tissue contracture is more challenging. When assistance is required for coughing, this may lead to other issues. A precise patient assessment is needed to provide the ventilation support required to efficiently clear airway secretions.

What Symptoms Do Patients With NMD Experience?

As inspiratory muscle weakness advances, NMD patients suffer hypoventilation symptoms such as:-

• Sleeping disturbance.

• Morning headache.

• Daytime somnolence (a state of sleepiness or an intense desire to fall asleep.)

• Nightmare.

• Hypercapnia-related anxiety.

What Is the Concept of Intermittent Positive Pressure Breathing (IPPV)?

Non-invasive ventilation is typically used to treat hypercapnia (when the blood contains excessive carbon dioxide) and accompanying symptoms. Intermittent positive pressure breathing (IPPV) is a common non-invasive aid. If the patient has sufficient bulbar muscular power, these interventions can help patients with weak respiratory muscles.

• The use of non-invasive IPPV improves the quality of life of tracheostomized ventilator users by tracheostomy without causing hypercapnia.

• Non-invasive mechanical ventilators can be either body ventilators or positive pressure ventilators that provide air straight to the trachea. Body ventilators were previously the first-line technique for long-term assisted ventilation.

• Non-invasive IPPV employs pressure-limited and volume-limited portable ventilators. Volume-limited ventilators give a fixed amount of air regardless of mouth or nose leakage, and the ventilator's gauge measures maximum airway pressure depending on air volume, interface leakage, and lung elasticity. It is appropriate for people with obstructive pattern respiratory illnesses such as sleep apnea, but it cannot treat persistent alveolar hypoventilation caused by weakening respiratory muscles.

• Pressure-limited ventilators cannot stack air to maintain pulmonary compliance or provide adequate air to patients with atelectasis or endotracheal secretions. Patients with NMD should use volume-limited ventilators for non-invasive mechanical ventilation.

The Benefits of Non-invasive IPPV Are:

• Patients with non-invasive IPPV had fewer respiratory issues, lower hospital admission rates, and shorter hospital stays.

• The pathophysiology of non-invasive ventilators demonstrates that they can increase maximum inspiratory pressure and VC in individuals with persistent alveolar hypoventilation.

• Non-invasive breathing without a tracheostomy necessitates the preservation of the bulbar muscle.

The Drawbacks of Non-invasive IPPV Are:

• The non-invasive ventilators cannot be used for all patients with ventilatory failure.

• Acquiring impairment and severe bulbar muscle palsy are common.

• Patients acquiring deficiencies cannot use aided coughing or airway secretion removal equipment.

Which Are the Various Invasive Methods?

Mechanical ventilation should be initiated to alleviate respiratory distress. Intubation and tracheostomy tubes can be emotionally draining for patients and carers. Supportive ventilation should be offered in these circumstances to prevent respiratory muscle exhaustion.

• The patient is initially administered with a mouthpiece or nasal mask to relieve respiratory distress symptoms, as patients accept the mechanical ventilator more easily.

• Patients with bulbar muscular palsy and bulbar dominant ALS have difficulty raising intrapleural pressure while coughing with the glottis closed.

• Airway secretions cannot be cleared without a device, resulting in repeated saliva aspiration, a major cause of aspiration pneumonia; for such a patient, tracheostomy and invasive ventilation are unavoidable.

GPB/Frog Respiration: The tongue and pharyngeal muscles gulp air into the lung during GPB.

Which Is the Respiratory Secretion-Eliminating Method?

• Expiratory Muscle Aid: Endotracheal secretions are eliminated using either a technique or a mechanical device called an expiratory muscle aid. Coughing correctly is necessary for clearing endotracheal secretions and removing a mucus obstruction. The PCF of normal, healthy individuals is greater than 6 to 12 L/sec. Deep inspiration and adequate intrapleural pressure are required for normal coughing to occur. Insufflating additional pre-cough volume is necessary to induce coughing in a patient with a decreased VC. A PCF greater than 160 L/min should be maintained to eliminate endotracheal secretions efficiently. There are diverse methods and devices for managing airway secretions; however, this session will focus on the methods that are especially useful in NMDs.

• Supportive Wheezing: Coughing is necessary to eliminate tracheal secretions, and its impairment can lead to respiratory complications such as pneumonia. In the long run, ineffective coughing may be the leading cause of death in MND patients with inspiratory and expiratory muscle paralysis or bulbar muscle palsy. Therefore, NMD and respiratory muscle dysfunction patients should receive a coughing aid. Manually assisted coughing is the most prevalent form of assisted coughing. After inhaling deeply, the patient is instructed to cough as vigorously as possible while an abdominal thrust is performed simultaneously. Although adequate air intake should precede coughing, many NMD patients find it challenging to inhale sufficient air due to their weakened respiratory muscles. Before attempting the abdominal thrust, it is necessary to provide additional insufflation through a manual resuscitation bag for patients with inspiratory muscle insufficiency.

• Cough Assist/Mechanical Insufflator: Patients can easily clear airway secretions without undergoing tracheostomy by deploying Cough Assist through an oronasal mask. For individuals with a tracheostomy tube, it can be a more effective method for draining secretions than manual suction by catheter, as it is an essential device for users of non-invasive mechanical ventilators with very limited coughing capacity. In addition, postoperatively, it can eliminate bronchial secretions without causing wound site discomfort due to expiratory muscle contraction.

Conclusion

As per other rehabilitative treatment programs, pulmonary rehabilitation can reduce a patient's respiratory symptoms, prevent complications, and improve their quality of life. NMD patients with ALS, myopathy, or spinal muscular atrophy typically need more pulmonary rehabilitation yet have been overlooked because of their illness. An awareness of the disease's etiology and early patient assessment can reduce respiratory effects with ventilatory and coughing assistance. Lower respiratory issues may lower NMD mortality. Long-term use of non-invasive devices can improve a patient's quality of life and medical condition. As a result, non-invasive respiratory aids that reflect respiratory pathophysiology help NMD patients live longer and better.