Pulmonary physical medicine interventions for elderly patients with muscular dysfunction

Pathophysiology 

The restrictive pulmonary syndrome is characterized by low VC, reduced total lung capacity, tachypnea, shallow breathing, reduced pulmonary compliance, increased elastic work of breathing, and almost always, impaired cough with inadequate generation of peak cough flows (PCFs). The VC is directly related to respiratory muscle strength and pulmonary compliance [9]. The PCFs are dependent on inspiratory, expiratory, and bulbar muscle function.

The four pathophysiologic presentations of restrictive pulmonary syndromes are as follows: (1) primary parenchymal disease, (2) surgical removal of lung tissue, (3) diseases of pleura and chest wall, and (4) reduced generation of respiratory muscle force [10]. Of these, ventilatory impairment is primarily seen with the last three presentations and only the first represents a combination of oxygenation and ventilatory impairment.

Mechanical dysfunction involving the chest wall and/or lungs includes thoracic deformities, thoracic muscle weakness, obesity, hypopharyngeal collapse during sleep with obstructive apneas [11], and any complicating conditions that decrease lung or chest wall expansion, including intercurrent pulmonary infiltrations or pleural disease. Severe CO2 retention alone has been demonstrated to independently decrease muscle strength [12]. Pulmonary deterioration is exacerbated by acute respiratory tract infections, which can lead to repeated pneumonias and lung scarring. Subsequently, patients with restrictive pulmonary syndromes can worsen with age or disease progression.

In contrast to individuals with intrinsic pulmonary disease or COPD, who tend to have regional ventilation-perfusion disturbances, individuals with mechanical and/or restrictive conditions tend to have global alveolar hypoventilation. Symptoms may be minimal because the gradual resetting of respiratory control centers accommodates to chronic hypercapnia [11]. Hypercapnia is likely when the VC falls to less than 55% of predicted normal levels [9]. Hypoxia, hypercapnia, and decrease in VC are exacerbated when intrinsic lung disease, kyphoscoliosis, sleep-disordered breathing, or obesity are also present, complicating respiratory muscle weakness from any cause. Both dynamic and static pulmonary compliance can be diminished [13]. The shallow breathing pattern with loss of the ability to take occasional deep inspirations (sighs) contributes to loss of compliance.

The VC gives an indication of maximum inspiratory and expiratory pressures and MVV [10]. Maximum inspiratory and expiratory pressures generated at the mouth correlate best with inspiratory and expiratory muscle strength. The MVV measures respiratory muscle endurance. VC is easy to measure, objective, and reproducible. The rate of loss of VC is most dramatic for patients with neuromuscular diseases, such as amyotrophic lateral sclerosis or Duchenne muscular dystrophy [14]. Other patients susceptible to late-onset ventilatory failure include poliomyelitis survivors who lose VC at a rate of 1.8% per year [15], [16]. This occurs because of the senescent dropping-out of aging anterior horn cells, fatigue, and/or recrudescence of disease on residual respiratory muscle strength, lung compliance and pulmonary function. This can be observed as worsening hypercapnia even in usually mild, generalized neuromuscular conditions such as Charcot-Marie-Tooth disease, facioscapulohumeral muscular dystrophy, and myotonic dystrophy. Diminished pulmonary volumes usually increase spontaneously with recovery in patients with Guillain-Barré syndrome (Table 1).

Table 1. Conditions associated with muscular dysfunction and secondary restrictive pulmonary syndromes among elderly patients

	Becker MD	Traumatic and nontraumatic spinal cord injury
	Limb-girdle MD	Spinal muscular atrophies
	Facioscapulohumeral MD	Amyotrophic lateral sclerosis and other motor neuron diseases
	Congenital MD	Poliomyelitis
	Autosomal recessive, myotonic MD	Hereditary sensory motor neuropathies
	Generalized nondystrophic myopathies	Phrenic nerve neuropathies
	Metabolic myopathies	Guillain-Barré syndrome
	Inflammatory myopathies	Botulism, Lambert-Eaton syndrome, and other neuromuscular junction diseases
	Mixed connective tissue disease myopathies

Abbreviation: MD, muscular dysfunction.

Individuals with CNS disorders can develop restrictive pulmonary disease caused by muscle weakness and benefit from pulmonary physical medicine interventions. Similar to neuromuscular diseases, the degree of diminished pulmonary volumes can vary greatly among patients with CNS disorders such as multiple sclerosis and spinal cord injury [17]. Although restriction in pulmonary function is generally defined by a reduction in all lung volumes, spinal cord–injured patients with tetraplegia and thoracic-level paraplegia often have increased residual volume at the expense of decreased expiratory reserve volume. In these patients lung volumes and ventilatory capacity can also be very different when measured with the patient in sitting, recumbent, or side-lying positions. This is because the strength of the diaphragm relative to the weak abdominal wall tends to allow abdominal contents to sag, thus decreasing diaphragm excursion and VC in the sitting position. An abdominal binder may be useful to increase diaphragmatic excursion and VC for spinal cord–injured patients during seated position. Like polio survivors, these patients are susceptible to late-onset ventilatory failure, developing decades after acute injury [15]. In addition, there is a loss of pulmonary compliance, which can be exacerbated by chest wall spasticity and fibrotic changes in intercostal muscles [18].

In Parkinson disease clinical studies show a predominantly restrictive pattern, but with a concomitant obstructive pattern. The restrictive pattern is characteristic of neuromuscular diseases in general, with FEV1/forced VC greater than 80% of predicted normal and diminished VC, MVV, and maximal respiratory pressures. Suggested theories explaining the mechanisms include incoordination and inadequate force of the muscles of respiration, muscle rigidity, and diminished compliance [13], [19], [20], [21], [22]. Theories for an observed upper airway, peripheral, and central obstruction include the following: intrinsic loss of elastic recoil, airway resistance from involuntary movements of striated upper airway muscles, abnormal parasympathetic tone, decreased mobility of the cervical spine with kyphoscoliosis, or the presence of an underlying chronic obstructive disease. In clinical studies in which dopaminergic agents and thalotomy resulted in neurologic improvement, resolution of the obstructive pattern was not seen [20], [21], [22], [23], [24].

Anticholinergic agents used for Parkinson disease permit bronchodilation and have reportedly benefited patients with respiratory dysfunction. In small-scale clinical studies levodopa (l-dopa) resulted in some improvements in pulmonary function but not in the normalization of flow volume loops or peak expiratory flows [25], [26]. Reports of dyskinetic activity of the respiratory muscles were seen with high doses of l-dopa. Subsequent reduction of the dose or the use of antidopaminergic agents possibly relieved the drug-induced respiratory distress. In addition, there have been case reports of adverse effects of ergot derivatives causing pleuropulmonary fibrosis for these patients [5], [27], [28], [29], [30], [31].

In a study of elderly nursing facility residents with uncomplicated medical histories the patients' mean VC was less than 40% of predicted normal levels. This was attributed to the effects of relative inactivity. In many cases the restrictive pulmonary syndrome was sufficiently severe to warrant the use of noninvasive ventilatory support. With peak expiratory musculature and severely diminished PCFs it is not surprising that one of the most common causes of morbidity and mortality in elderly individuals in nursing facilities is pneumonia. The effects of medications, such as calcium channel blockers, aminoglycosides, corticosteroids, benzodiazepines, and other sedatives for the geriatric population can reduce the ventilatory response to hypercapnia permitting the development of microscopic atelectasis and loss of pulmonary compliance. These effects are compounded by multiple medication therapy. Malnutrition, acidosis, electrolyte disturbances, cachexia, infection, fatigue, supplemental oxygen administration, and muscle disuse or overuse can also worsen ventilatory insufficiency and increase hypercapnia.

Patients with expiratory muscle weakness have difficulty clearing secretions especially following general anesthesia and during upper respiratory tract infections (URIs). Chronic mucus plugging can lead to ventilation-perfusion imbalance, chronic microatelectasis, frequent pneumonias, pulmonary scarring, further loss of lung compliance, cor pulmonale, and eventually, cardiopulmonary arrest. Risk is heightened in the presence of weak oropharyngeal musculature. Mucus plugs can also cause sudden hypoxia and respiratory failure. With proper treatment using the techniques described in this article intubation can be avoided, obstructing mucus plugs prevented or quickly cleared, and the risk of life-threatening pneumonias minimized for many weak and elderly individuals.

Evaluation 

Symptoms of hypercapnia include fatigue, daytime somnolence, and, for patients able to ambulate, dyspnea [11]. There is often a history of frequent hospitalization for respiratory impairment. Patients who are able to walk chiefly complain of exertional dyspnea; however, headaches, fatigue, sleep disturbances, hypersomnolence, and difficulty with concentration are also common complaints [11]. For wheelchair users symptoms may be minimal except during intercurrent respiratory infections that cause profuse airway secretion. Rather than dyspnea, anxiety and the inability to fall asleep are the typical complaints of wheelchair users hours before cardiopulmonary arrest. Other symptoms can include difficulty controlling airway secretions and drooling caused by chronic fatigue, nausea and retching, headache, impairment of intellectual function, nightmares, depression, and weight loss [11].

In acute ventilatory compromise, the patient is observed for increased rate, decreased depth, or irregularity of breathing. Purely diaphragmatic breathing or asymmetric movements of the abdomen or thorax are often present. Signs of ventilatory insufficiency may include the following: inability to count to more than 15 with one breath, reduced capacity for blowing and coughing, nasal alae flaring, use of auxiliary respiratory musculature, peribuccale or generalized cyanosis with or without polycythemia, flushing or pallor, hypertension, drooling and difficulty controlling airway secretions, dysphagia, regurgitation of fluids through the nose, nasality of speech, cor pulmonale, confusion, and fluid retention. Signs, particularly those of cor pulmonale, are present only in advanced stages and do not occur among those properly managed patients with predominantly ventilatory impairment [11].

Bulbar function impacts on the ability to clear secretions and to maintain ventilation through noninvasive means. Objective measures to evaluate for bulbar function include maximum insufflation capacity (MIC), and PCF. These evaluations can be performed to obtain baseline values prior to the development of respiratory symptoms, to monitor progress, and to determine the feasibility of noninvasive ventilation.

When pulmonary function testing demonstrates a predominantly restrictive pulmonary syndrome regular evaluation of VC with a portable spirometer is recommended to monitor patient progress and response to treatment. The VC is measured in the sitting position, supine position, and with other positional changes or while using thoracolumbar orthoses when applicable. This is because lung volumes and ventilatory capacity can be very different when measured with the patient in sitting, recumbent, or side-lying positions, particularly for patients with kyphoscoliosis, non-Duchenne myopathies [11], spinal cord injury, or in patients who are postpoliomyelitis. For example, for individuals following spinal cord injuries with subsequent restrictive pulmonary syndromes, the strength of the diaphragm relative to the weak abdominal wall tends to allow abdominal contents to sag, thus decreasing diaphragm excursion and VC in the sitting position.

The MIC is the maximum volume of air that can be held with a closed glottis. It is obtained by the air stacking of mechanical insufflations delivered by manual resuscitator or volume-cycled ventilator and is a function of pulmonary compliance and the strength of oropharyngeal and laryngeal muscles. MIC is useful for assessing bulbar function and the potential for assisting ventilation by noninvasive means as opposed to tracheostomy. The MIC is greater than the VC when there is any glottic function. Weak oral muscles can be splinted during these insufflations by delivering the air via a Bennett lip seal (Puritan-Bennett, Boulder, CO) held firmly over the mouth (Fig. 1). An MIC of at least 500 mL is necessary to achieve useful exsufflation flows during attempts at manually assisted coughing [32]. Assisted PCFs exceeding 160 L/minute are the minimum needed to cough out any airway debris [33], [34]. This is necessary to prevent mucus plugging, atelectasis, and pneumonia during URIs. In patients with intact bulbar musculature the MIC should approach the predicted inspiratory capacity.

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Fig. 1. A 69-year-old man requiring continuous mouthpiece intermittent positive pressure ventilation (IPPV) for 37 years after having had acute poliomyelitis in 1955. He used lip-seal retention (shown) for nocturnal mouthpiece IPPV until dying of leukemia in 1995. The lip seal can also be used for air stacking for patients with weak buccal musculature.

PCFs are measured by having the patient cough through a peak flow meter. If PCFs are less than 300 L/minute then the patient is taught assisted coughing. First the patient air stacks consecutively delivered volumes of air from a manual resuscitator or volume-cycled ventilator to maximum lung volumes. Once the lung is fully insufflated the patient coughs through a peak flow meter as someone applies an abdominal thrust to further augment flows. PCFs of 160 L/minute are the minimum needed to eliminate airway secretions [33]; this is the best indicator for tracheostomy tube removal, irrespective of remaining pulmonary function [34]. The ability to achieve assisted PCF greater than 160 L/minute is the primary indication for decanulation of any patient with a tracheostomy tube whether the patient has any measurable VC or not. Likewise, an inability to achieve assisted PCFs of 160 L/minute and aspiration of airway secretions such that baseline SpO2 decreases to less than 95% are the prime indications for tracheotomy [34], [35], [36].

Any patient with symptoms of nocturnal hypoventilation and VC less than predicted normal levels undergoes SpO2 and end-tidal CO2 monitoring during sleep. The capnograph, for end-tidal CO2 monitoring, and oximeter must be capable of collating and printing the data [11], [37]. Symptomatic patients with normal VC for whom the diagnosis is unclear require polysomnography for possible sleep-disordered breathing. These studies are most conveniently performed on an ambulatory basis.

Management 

For the management of patients with primarily ventilatory impairment the fundamental goals include maintenance of normal ventilation 24 hours a day, maintenance of pulmonary compliance, and maximizing PCF to clear airway secretions, particularly during URIs. Early diagnosis and introduction of these goals are important. Counseling is needed to explain the importance of these three goals and the respiratory muscle aids that can accomplish them. In addition, supplemental oxygen therapy should be used only during episodes of acute pulmonary disease when partial pressure of arterial oxygen (PaO2) does not exceed 60 torr in the presence of normal ventilation [11]. Patients are educated to avoid sedatives, obesity, heavy meals, extremes of temperature, humidity, excessive fatigue, crowded areas, or exposure to respiratory tract pathogens. Appropriate influenza and bacterial vaccinations are encouraged and early medical attention is given to URIs. The value of pursuing personal goals and encouraging self-directed activities and decision making and maximizing the level of functioning and daily activities are emphasized.

Maintenance of pulmonary compliance 

Just as articular range-of-motion therapy is important to prevent joint contractures caused by immobility, regular maximal lung expansion is necessary to maintain pulmonary compliance and MIC for patients with diminished VC. Air stacking should be performed two or three times a day to volumes that approach the predicted inspiratory capacity [38]. In addition to air stacking of mechanical insufflations [39], glossopharyngeal breathing (GPB) [40], [41] can often be used for lung expansion therapy. The consecutively delivered volumes of air for air stacking are provided by manual resuscitator or portable volume cycled ventilator. The earlier and more aggressively this is introduced the better perhaps the ultimate effect on dynamic and possibly static lung compliance. This is important because decreased pulmonary compliance increases the work of breathing and exacerbates hypercapnia.

GPB is taught to patients with less than 1000 mL of VC and adequate oropharyngeal muscle strength for functional swallowing and speech. GPB is the use of the glottis and pharyngeal muscles to capture and project boluses of air into the lungs. One breath consists of 6 to 30 boluses (gulps) of 30 to 200 mL each. Effective GPB permits patients with little or no VC to autonomously sustain alveolar ventilation throughout waking hours [42]. It also normalizes speech production and permits the patient to take a deeper “breath” for shouting and coughing. Progress with GPB should be monitored by regularly measuring the volume of air per gulp and the number of gulps per breath.

Inspiratory muscle aid 

Patients with ventilatory impairment require various regimens of inspiratory muscle assistance. Symptomatic patients with supine VC less than 30% of predicted normal capacity usually require at least nocturnal ventilatory support [11]. Weaker patients can use noninvasive IPPV around-the-clock rather than undergo tracheotomy for ventilatory support, provided that assisted PCFs exceed 160 L/minute. Although invasive IPPV (ie, tracheostomy IPPV) can greatly extend survival for patients with ventilatory failure caused by neuromuscular and CNS disorders [43], morbidity and mortality outcomes are not as favorable as by management with strictly noninvasive approaches [44]. Noninvasive ventilatory support is offered to patients with PCFs greater than 160 L/minute and intact [35]. Tracheostomy buttons are useful to optimize air passage through the upper airway for autonomous breathing and during transition from tracheostomy to noninvasive IPPV [45].

Noninvasive IPPV can be provided by mouthpiece [14], [37] (Fig. 2), nasal interface [11], [46], [47] (Fig. 3), or oronasal interface (Fig. 4). For all three methods, custom-molded interfaces can enhance comfort and efficacy (see Fig. 3) [48]. These interfaces may also be useful in the management of simple sleep-disordered breathing. Mouthpiece IPPV can also facilitate ventilator weaning [15], [45].

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Fig. 2. Patient with intrinsic lung disease 24 years following thermal damage to lungs in chemical explosion extubated to mouthpiece intermittent positive pressure ventilation, on which he became continuously dependent for more than 1 year.

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Fig. 3. Patient with chronic alveolar hypoventilation using custom-molded acrylic nasal interface for nocturnal nasal intermittent positive pressure ventilation.

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Fig. 4. A 65-year-old man with chronic alveolar hypoventilation since age 16 associated with Milroy disease (congenital absence of lympathics). He underwent tracheotomy in 1992 after failing 6 months of ventilator-weaning attempts. He was decanulated 2 months later to continuous noninvasive intermittent positive pressure ventilation (IPPV), which he has been using for the last 9 years. He is seen here using an oronasal interface for nocturnal IPPV.

The intermittent abdominal pressure ventilator (IAPV) consists of an inflatable bladder in an abdominal belt worn under the user's clothing. The bladder is cyclically inflated by a positive pressure ventilator. This pushes the abdominal contents up against the diaphragm and ventilates the patient. The IAPV generally augments the patient's tidal volume by 300 to 600 mL, but much greater volumes are often possible [49]. The IAPV is not effective in the presence of scoliosis or extremes of body weight. It is effective only at greater than 30° from the horizontal position and is best in the sitting position at 75° to 85°. It is the method of choice for daytime ventilatory support for most wheelchair-dependent patients with less than 1 hour of autonomous breathing tolerance because it is cosmetic, practical, and ideal for concurrent GPB [49].

Assisted coughing 

When maximum PCFs or assisted PCFs are less than 270 L/minute the patient is at high risk of developing pneumonia during otherwise benign URIs. He or she is then trained in and equipped for manually and mechanically assisted coughing to clear airway secretions [32], [50], [51], [52]. Manually assisted coughing involves the delivery of a maximal inspiration or insufflation. An assistant then delivers a manual thrust to the anterior chest wall and epigastrium as the patient initiates his or her expulsive effort (Fig. 5). Mechanically assisted expulsion of airway secretions, or mechanical insufflation-exsufflation (Cough-Assist, JH Emerson Co, Cambridge, MA) is less labor intensive and often more effective. Mechanical insufflation-exsufflation involves the delivery of a maximum lung insufflation at 35 to 60 cm H2O of pressure followed by a forced exsufflation to −35 to −60 cm H2O. This provides 10 L/second of expulsive flow [50], [51], [52]. An abdominal thrust is applied concurrent with the exsufflation to combine manually and mechanically assisted coughing. Mechanically assisted coughing is instrumental in avoiding pneumonias and hospitalizations for patients otherwise too weak to cough effectively [53], [54].

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Fig. 5. Manually assisted cough applied to a patient with myotonic dystrophy.

Oximetry feedback 

Oximetry feedback can assist the patient with ventilatory impairment in maintaining more normal daytime ventilation. The patient should be instructed to keep his or her SpO2 at 95% or greater throughout daytime hours by supplementing his or her breathing with mouthpiece IPPV [14], [15], [16]. Mouthpiece or nasal IPPV is used to reset respiratory control centers and maintain normal arterial blood gases [11], [46], [47], [55], [56]. The oximeter can effectively gauge ventilation, provided that supplemental oxygen therapy is avoided. Continuous SpO2 monitoring is also particularly useful during URIs when sudden desaturations, usually caused by acute airway mucus plugging, and a decrease in SpO2 baseline to less than 95% indicate atelectasis or pneumonia. As soon as plugging is signaled by acute desaturations, the caregivers provide assisted coughing to the patient until the airway is clear and SpO2 returns to normal. In this way pneumonia and respiratory failure are avoided [53], [54].

Respiratory muscle exercise 

Respiratory muscle exercise training has been shown to increase inspiratory muscle endurance, both with patients with COPD and for patients with neuromuscular and CNS disorders. This increased inspiratory muscle endurance has not been demonstrated to translate into reduced morbidity or mortality, probably because it does little to increase cough flows. [39], [57].

Perioperative considerations 

Elderly individuals have decreased respiratory reserve with decreased VC, PCFs, and endurance. Decreased respiratory reserve along with a weak cough and possible obesity, malnutrition, sleep-disordered breathing, and concomitant medical conditions can hinder recovery from general anesthesia. In addition, these conditions can result in a high risk for failure to wean from the ventilator and to maintain extubation. In patients with muscular weakness caused by neuromuscular diseases or CNS disorders [53], [54], it is likely that respiratory morbidity and mortality can be avoided by training these high-risk patients in the use of noninvasive respiratory muscle aids before surgical interventions. In this way they can be extubated and the use of noninvasive respiratory muscle aids can be instituted immediately on extubation to maintain normal alveolar ventilation and keep airways clear.