**Respiratory Muscle Aids in the Management of Neuromuscular Respiratory Impairment to Prevent Respiratory Failure and Need for Tracheostomy**

A. J. Hon and J. R. Bach *Department of Physical Medicine and Rehabilitation, UMDNJ-New Jersey Medical School USA* 

### **1. Introduction**

234 Neuromuscular Disorders

Wong, B. (2006). Management of the child with weakness. *Seminars in Pediatric Neurology*,

Respiratory impairment results from primary disease of the lungs / airways or from impairment of the respiratory muscles. The proper identification of the respiratory impairment allows for proper management to decrease morbidity and mortality. Patients with neuromuscular impairment typically have hypoventilation or ventilator insufficiency/failure resulting in hypercapnia, hypoxia and an ineffective cough. In contrast, lung and airway diseases are characterized by hypoxia with eucapnia or hypocapnia, which often occur during an exacerbation resulting in acute respiratory failure (ARF). Often physicians evaluate and treat both as respiratory insufficiency/failure.

Historically and even currently, when neuromuscular patients develop respiratory failure the traditional paradigm has been resorting to tracheostomy, resulting in increasing weakness of inspiratory muscles and loss of ventilator free breathing ability. In contrast, we and others with neuromuscular patient populations, successfully use a new management paradigm including noninvasive interfaces for intermittent positive pressure ventilation (NIV) in place of tracheostomy (TIV) to maintain not only life but also quality of life (Bach, 2010). It has been noted previously that patient populations prefer NIV over TIV both overall and specifically with regards to comfort, convenience, speech, swallowing, cosmesis, and safety (Bach, 1993).

NIV can provide from intermittent up to continuous ventilatory support for patients with advanced neuromuscular disease who have normal lung tissue but respiratory muscle weakness. These concepts and techniques can be used for any patient with respiratory muscle weakness, for example high level traumatic spinal cord injury and polio patients (Bach, 1991; Bach & Alba, 1990; Bach et al., 1989). Even in patients with severely dysfunctional expiratory muscles with little to no vital capacity or maximum expiratory pressures, noninvasive pressure aids can provide effective cough flows. The inability to cough up secretions, due to an ineffective cough, often results in mucous plugging of the airways, but when using noninvasive ventilatory muscle aids, a cough can be augmented for effective and sufficient secretion removal.

Respiratory Muscle Aids in the Management of Neuromuscular

should be delivered simultaneously to the opening of the glottis.

useful information. Most conveniently they can be performed in the home.

approach or attain the MIC independently.

NIV and should be reevaluated in 3 to 6 months.

**4. Lung expansion therapy** 

spans of bi-level PAP is ineffective or at the least, suboptimal.

Respiratory Impairment to Prevent Respiratory Failure and Need for Tracheostomy 237

Spirometry is also used for monitoring the maximum insufflation capacity (MIC), that is, the ability to "air stack". The ability to air stack is holding with the glottis a maximal volume by holding consecutively delivered volumes of air delivered from a manual resuscitator or volume cycling ventilator. Interfaces that can be used for air stacking include a simple mouthpiece or when the lips are too weak for this, a nasal interface or lipseal. In patients who have learned glossopharyngeal breathing (GPB) techniques, this enables them to

Cough Peak Flow (CPF), measured with a peak flow meter, is an indicator of the patient's cough effectiveness. A CPF of 160 L/m is the minimum needed for sufficiently effective coughing and airway clearance to reliably permit safe extubation (Bach & Saporito, 1996). This is also the best indicator for tracheostomy removal, regardless of pulmonary function, that is, the status of the inspiratory and expiratory muscles. Patients with a VC of less than 1,500 mL should have an assisted CPF measured using a maximal lung volume by air stacking and an abdominal thrust for a manually assisted cough. The abdominal thrust

In patients without significant intrinsic lung disease, arterial blood gas sampling is unnecessary. Many patients (25%) tend to hyperventilate due to discomfort or anxiety from the procedure (Currie et al., 1986), so accurate results can be difficult to obtain. Oximetry monitoring and capnography, which is the measurement of end tidal pCO2, provide more

Patients with questionable symptoms, multiple hourly nocturnal oxyhemoglobin desaturations to below 95%, and elevated nocturnal PaCO2 should undergo a trial of nocturnal NIV. If the questionably symptomatic patient finds nocturnal NIV to be more burdensome than the symptoms of ventilatory insufficiency, the patient can discontinue

In symptomatic patients with a normal VC, no carbon dioxide retention and no clear pattern of oxyhemoglobin desaturation, a polysomnogram is warranted to evaluate for sleep disordered breathing (Williams et al., 1991). Patients with obesity-hypoventilation also should be treated with NIV or pressure or volume control ventilation and not CPAP. Neuromuscular disease NMD patients with decreased VC have no indication for undergoing polysomnography as the device is programmed to interpret each apnea and hypopnea as having a central nervous system or obstructive etiology rather than being due to inspiratory muscle weakness. Treatment of asymptomatic NMD patients based solely on polysomnographic abnormalities with continuous positive airway pressure (CPAP) or low

Lung expansion therapy often results in increasing VC, increasing CPF, maintaining or increasing pulmonary compliance, decreasing atelectasis and facilitating introduction of NIV. Various devices and techniques have been developed to prolong survival without tracheotomy through maintaining pulmonary compliance, and augmenting inspiratory and expiratory muscle function. For example, researchers have found that Duchenne muscular dystrophy patients requiring up to continuous ventilator dependence as NIV, can avoid

Inspiratory and expiratory muscle aids, including devices and manual assisted techniques, result in intermittent pressure changes to assist inspiratory and expiratory muscles in their natural function. Noninvasive inspiratory and expiratory muscle aids are used to maintain lung and chest wall compliance, maintain normal alveolar ventilation, and to maximize cough peak flows (CPF) thus preventing episodes of acute respiratory failure, especially during intercurrent chest infections. This allows for decreased hospitalizations and prolongs survival without tracheostomy for patients with Duchenne muscular dystrophy (DMD), Spinal Muscular Atrophy including type 1 (SMA), amyotrophic lateral sclerosis (ALS), and others.
