Pulmonary rehabilitation after ventilatory failure

Author(s): Philippines Cabahug, MD, Travis Edmiston, MD, and Amira Noles, MD

Originally published:12/02/2013

Last updated:9/21/2018

1. DISEASE/DISORDER:

Definition

Respiratory failure (RF) is a syndrome that results either from an impairment of oxygenation, carbon dioxide elimination (inadequate ventilation) or both.  Respiratory failure will necessitate invasive or noninvasive mechanical ventilation as indicated by a PaCO2 > 50 mm Hg or PaO2 ≤ 50 mm Hg by arterial blood gas (ABG) testing while on room air.

Individuals with spinal cord injuries (SCIs), multiple sclerosis (MS), and neuromuscular disorders (NMDs) are at risk of developing ventilatory failure because of respiratory muscle weakness, reduction of lung and chest wall compliance, reduced vital capacity, and ineffective cough.

Etiology

The ability to sustain alveolar ventilation is determined by the balance between neuromuscular competence (respiratory drive, neuromuscular transmission, muscle strength) and load (resistive, elastic and minute ventilation).

Impairments in neuromuscular competence:  Primary muscle weakness (such as myopathies), neuromuscular junction disorders, such as Myasthenia Gravis (MG), Central or peripheral nervous system disorders, such as SCI, Guillain-Barre Syndrome (GBS), Amyotrophic Lateral Sclerosis (ALS), present with weakness of inspiratory and expiratory muscles that can lead to a partial or total inability to mechanically ventilate resulting in hypoventilation or failure to produce an effective cough.   Respiratory drive is affected in brain stem lesions, sleep disordered breathing and medication overdose.

Excessive load on the ventilatory system:  Obesity, pulmonary embolism, atelectasis, lung infections, sepsis, pleural effusion progressive spinal deformity (e.g. thoracic kyphoscoliosis), and increased intercostal muscle spasticity can decrease chest wall and lung compliance, placing one at risk for RF.

Epidemiology including risk factors and primary prevention

Listed below are some common disease processes as epidemiology varies with each.

  1. Spinal Cord Injury: Respiratory complications are the most common cause of morbidity and mortality in acute SCI, with an incidence of 36% to 83%. Risk factors include level of injury, aspiration, chronicity of disease, prior lung disease amongst many others.1
  2. Multiple Sclerosis: Advanced respiratory support in MS is highly unusual. A study by Pittock et al. found a total of 22 patients requiring mechanical ventilation over a period of 33 years. The median time to death after the start of ventilation was 22 months.2
  3. Amyotrophic Lateral Sclerosis: Respiratory complications are the most common cause of mortality in ALS and the average survival time for diagnosis is 2-5 years. Older individuals >65 and those with severe bulbar involvement have a much poorer respiratory prognosis.  The use of invasive ventilation is rarely pursued in the US (2-6%), but non-invasive ventilation is essential to increasing survival and quality of life outcomes.3
  4. Guillain-Barre Syndrome: Overall mortality is as high as 18%, but most fully recover.  Respiratory failure is the most common complication, affecting 20–30% of patients.  Risk factors include underlying pulmonary health; admission within 7 days of symptom onset; and neck, cranial nerve or bulbar involvement.4
  5. Myasthenia Gravis: Mortality is 4% to 8% and about 15-20% of individuals will require ventilatory support. Predictive factors include neck or bulbar involvement and particularly MuSK positive serology individuals who make up 7%.  85% of MuSK seropositive patients are women.5,6
  6. Polymyositis/Dermatomyositis: Pulmonary complication rate is 40% but respiratory failure or significant dyspnea is uncommon at 5%.7

Patho-anatomy/physiology

Respiratory dysfunction can be categorized into the following areas:

  1. Muscle weakness resulting in decreased ventilatory function.
    • The diaphragm and accessory muscles provide insufficient force or become fatigued and unable to ventilate effectively.
    • In addition, the intercostal and abdominal muscles become flaccid, leading to paradoxical breathing that reduces efficiency of breathing and reduced vital capacity (VC).
  2. Impaired cough and secretion clearance
    • Cough and mobilization of secretions become ineffective with impaired innervation of abdominal and internal intercostal muscles.
    • Neck, cranial nerve and bulbar involvement reduce the ability for the individual to control secretions once mobilized.
  3. Retained secretions and mucus plugging
    • Mucus hypersecretion can result from loss of sympathetic control and unopposed vagal activity. An increase in secretions is also common with tracheostomy placement.
    • The combination of increased bronchial secretions and ineffective cough can lead to airway obstructions, mucus plugs, sudden respiratory distress and potential cardiac arrest.
  4. Atelectasis
    • Occurs secondary to impaired expansion of the lungs.
    • Decreased inflation of the alveoli also leads to decreased surfactant production.
    • Atelectasis worsens as respiratory muscles fatigue, secretions accumulate, and lung compliance decreases.
    • Segments of collapsed lungs no longer participate in gas exchange leading to ventilation/perfusion mismatch.
  5. Bronchospasms
    • Parasympathetic activity is responsible for bronchoconstriction.
    • Loss of sympathetic control and unopposed vagal activity lead to increased airway tone and bronchospasms.

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

  1. Acute
    • Acute RF is the result of respiratory muscle weakness that leads to impaired cough, decreased VC, atelectasis, decreased lung compliances, increased work of breathing and respiratory fatigue.
    • Focus is on respiratory support and treating any reversible causes such as respiratory infection and/or the underlying cause such as with GBS.
  2. Subacute
    • In SCI, there may be partial recovery of respiratory muscle performance attributed to spontaneous recovery of diaphragm innervation, reflex activity of intercostal muscles, and enhanced performance of accessory muscles of the neck.
    • In insidious progression such as ALS, the recovery of respiratory function depends on reversal of the inciting cause such as pneumonia and initiating preventative strategies.
  3. Chronic
    • Pulmonary function may be altered by age, time since injury, underlying pulmonary health, obesity, and maximal inspiratory pressure.
    • Some individuals may experience late onset ventilatory failure as a result of chronic alveolar hypoventilation.
    • Signs and symptoms of progression: tachypnea or dyspnea especially with decreased work loads, daytime somnolence, fluctuating mental alertness, and position-dependent respiratory dysfunction.
    • Possible etiologies: disease progression, cervical myelopathy, post traumatic syringomyelia, progressive scoliosis or kyphosis, sleep apnea, age-related loss of diaphragm motor neurons.
  4. End Stage
    • Diseases of the respiratory system are the leading cause of morbidity, mortality, and hospitalization among patients progressing to a chronic level of respiratory dysfunction. This is particularly associated with those with bulbar symptoms.

Specific secondary or associated conditions and complications

  1. Pneumonia
    • The risk of developing ventilator associated pneumonia increases by 1% to 3% per day of intubation.1
    • Impaired cough, underlying pulmonary health, aspiration and reduced VC increase risk when not requiring invasive ventilatory support.
    • In invasive ventilation, risk factors include presence of tracheostomy, anterior approach to spinal stabilization, and ongoing mechanical ventilation.
  2. Sleep-disordered breathing (SDB)
    • Risk factors include increased neck and waist circumference, body mass index above 30 kg/m, and use of sedating medications.1
  3. Pleural effusions
    • Can occur because of the presence of atelectasis, which further compromises ventilation leaving an area of low pressure within the pleural space that can be filled by fluid.
  4. Mucus plugging
    1. With increased secretions and impaired cough, mucus plugs can lead to sudden respiratory failure and death.

2. ESSENTIALS OF ASSESSMENT

History

A comprehensive history of this population should include the items below.  It is important to assess for early signs of respiratory compromise in order to determine those who are at risk.   This allows for early initiation of treatments and detection of progressing respiratory failure.

  1. Premorbid pulmonary health issues such as chronic obstructive pulmonary disease, cancer, sleep disordered breathing and OSA.
  2. A focused social history including drug, alcohol, and tobacco use.
  3. Any increase in respiratory infection which may point to reduced secretion clearance or dysphagia.
  4. Family history neuromuscular diseases.
  5. A review of medications to assess for any that put the patient at risk for respiratory failure, such as opiates, benzodiazepines, or Beta blockers.
  6. In patients with spinal cord involvement, ASIA classification and level of injury should be established: high cervical and complete injuries are more likely to require intubation and long-term support.
  7. Subjective symptoms such as dyspnea at rest, increasing activity intolerance or functional decline, poor sleep or daytime sleepiness, morning headaches and difficulty with work or concentration.
  8. Changes in voice, trouble chewing or swallowing, or excessive drooling to assess for bulbar dysfunction.

Physical examination

Physical examination should evaluate for respiratory muscle weakness and bulbar dysfunction.  This includes:

Overall muscle tone and bulk

  1. Alignment of the spine looking for scoliosis or kyphosis
  2. Use of accessory muscles for breathing
  3. Observe changes in breathing while supine or slight reverse Trendelenburg
    • Paradoxical abdominal movement with breathing indicates diaphragmatic weakness
    • If breathing becomes more difficult while lying flat, it could also indicate diaphragm weakness in a patient with NMD
    • Breathing may improve in tetraplegia as this places the diaphragm in a more mechanically advantages position and increases VC.8,9
  4. Evaluate and observe for weakness in head control, cranial nerves, speech and vocal clarity, protruding tongue, and oral secretion control to help assess neck and bulbar function.
  5. Muscle examination should include inspection for muscle atrophy and fasciculations in addition to strength evaluation.
  6. Sensory testing and deep tendon reflexes aid in determining upper and lower motor neuron patterns of disorder.
  7. In patients with spinal cord involvement, ASIA classification and level of injury should be established: high cervical, complete injuries are more likely to require intubation.
  8. A single breath test can be performed at bedside to assess vital capacity. To complete this test have the patient take a max inspiratory breath, then begin counting and continue until the patient has to take another breath. Normal is a count up to 50. Severe impairment of vital capacity is a count less than 15.
  9. If available, Pulmonary function test (PFT): to confirm respiratory muscle weakness by a pattern of restriction.
    • Reduced forced expiratory volume in 1 second (FEV1, < 80% of predicted)
    • Reduced forced vital capacity (FVC, < 80% of predicted)
    • Normative FEV1/FVC ratio (>70% of predicted)
    • Reduced total lung capacity (< 80% of predicted)
    • Increased residual volume (RV)
    • Decreased vital capacity (VC, < 10-15 mL/kg of ideal body weight)
    • Negative inspiratory force (NIF) < -20 to -30 cm of water
    • Peak expiratory flow rate or peak cough flow (PCF): < 160 L/min

Functional assessment

Individuals with chronic neurologic disease should be monitored periodically to follow progression of respiratory function closely to determine the need for intervention and when to discuss possible respiratory support. It is important to determine the need for either invasive or non-invasive ventilation early on because emergent intubation can lead to increased complications.

Mangera et al. proposed a pathway for managing those patients with neuromuscular disease who have respiratory failure.9 A summary of tests that can assist with the decision for intervention with ventilation is as follows:

  1. Functional Vital capacity
    • Test both the seated and supine positions.
    • Vital capacity may only be reduced in the supine position early on indicating weakness of the diaphragm.
    • Non-invasive ventilation should be offered in patients with FVC <50% of predicted values or intermittently > 4 hours (more is better) with FVC <75%.3
    • In acute decline in respiratory function, serial vital capacities should be obtained and if there is a downward trend, and if FVC is less than 15 mL/kg, mechanical ventilation should be considered.
  2. Mouth Pressures
    • Assess both inspiratory and expiratory respiratory muscle strength.
    • Mouth pressures should be assessed with vital capacity to determine respiratory function and need for additional respiratory support.
    • When mouth pressure is reduced to less than 60% predicted, a patient will need close follow up and serial measurements and an ABG.
  3. Sniff nasal inspiratory pressure
    • Assessment of inspiratory muscle strength in a clinic setting
    • Does not replace formal testing
    • Low sniff inspiratory pressures indicates inspiratory respiratory muscle weakness
    • Values of <60 cm H2O in women and <70 cm HOH in men are considered the lower limit of normal.10
  4. Arterial Blood gases
    • pO2 less than 50 mm Hg or pCO2 greater than 50 mm Hg is a sign of impending respiratory failure.
  5. Electrodiagnostics
    • Assessment of phrenic nerve function is conducted during the evaluation of inability to wean from the ventilator or as part of the evaluation for potential diaphragmatic pacer placement.
    • This is the gold standard for phrenic nerve function and often includes evaluation of intercostal function

Imaging

  1. Chest x-ray to identify signs that could indicate risk for respiratory failure including:
    • Kyphoscoliosis
    • Emphysema
    • Respiratory infections
    • Pulmonary edema
    • Atelectasis
    • Raised hemidiaphragm which can by caused by a phrenic nerve palsy, and if this is present further testing of the phrenic nerve should be assessed.
  2. Diaphragm Fluoroscopy: Should be obtained when VC is lower than expected for neurologic level of injury and associated comorbidities. Assess for diaphragmatic paralysis in patient with difficulty weaning off the ventilator.
  3. Diaphragm ultrasound: Used to assess diaphragmatic excursion. Advantages over diaphragm fluoroscopy include portability, lack of ionizing radiation, and ability to quantify diaphragmatic motion.
  4. Computed tomography angiography: Preferred choice of imaging to confirm pulmonary embolism.

Supplemental assessment tools

  1. Continuous pulse oximetry.
  2. Capnography or end-tidal carbon dioxide: once initial arterial blood gas is obtained, end-tidal carbon dioxide can be used as an indirect measure of carbon dioxide partial pressure in arterial blood.
  3. Phrenic nerve conduction studies and diaphragmatic needle electromyography: used to establish diagnosis, determine severity, and follow progression of peripheral respiratory muscle dysfunction.
  4. Sleep studies: Patients who suffer from neuromuscular disease and spinal cord disorders suffer from increased frequency of sleep disordered breathing.
  5. Formal Swallow studies: Identify those who have trouble swallowing to identify those at risk for aspiration and/or nutritional deficiencies.

Early predictions of outcomes

Diaphragmatic innervation and diaphragmatic strength measured by VC can be used as early weaning prognostic indicators.

Poorer outcomes are associated with:

  • Level of injury and complete versus incomplete injury in SCI
  • Bulbar involvement
  • Poor diaphragmatic recovery
  • Poor cognitive function
  • Premorbid pulmonary or respiratory disease
  • Ineffective cough
  • Increased secretions or decreased ability to control secretions
  • Rapid progression of non-respiratory muscular weakness

Professional Issues

Regular updated discussions and about a patient’s current medical status, their goals and care preferences are critical.  Patients should be encouraged to speak with their families about the disease natural history and their care wishes.  An advanced directive should be considered, reviewed and updated regularly.

3. REHABILITATION MANAGEMENT AND TREATMENTS

Available or current treatment guidelines

In 2005, the Consortium for Spinal Cord Medicine developed clinical practice guidelines for respiratory management following SCI.1

In 2014, a review of respiratory failure in ALS which provides good evidence for management in those with progressive RF.3

In 2018, a recent review by Chatwin et al. provides information about airway clearance techniques.11

At different disease stages

Reduce atelectasis and improve ventilation prior to ventilatory support

  1. Deep breathing and voluntary coughing
  2. Intermittent positive pressure breathing
  3. Delivers a positive pressure breath when the patient triggers it.
    • It can increase tidal volume
  4. Glossopharyngeal breathing
    • Helps the patient get a deeper breath by gulping rapid mouthfuls of air and forcing it into the lungs.
  5. Intrapulmonary percussive ventilation
    • Delivers a deep breath while mobilizing retained secretions.
    • The vibrations loosen the retained secretions and deliver aerosol to hydrate viscous mucus plugs
  6. EzPAP
    • Positive expiratory pressure system that can be used with nebulizers to improve atelectasis, secretion clearance, and oxygenation.
    • Continuous positive airway pressure and bi-level positive airway pressure
    • Can be used to provide a deep breath, manage secretions, and provide rest periods to non-intubated patients.
    • In ALS, this has been shown to improve survival and quality of life measures in >4 hrs per day. 3
  7. Patients with tetraplegia from SCI are placed in supine or Trendelenburg position.
    • In SCI, the abdominal wall has increased compliance. In the upright position, the abdominal contents fall and diaphragm flattens. By placing the patients in supine or Trendelenburg position, the effects of gravity will move the abdominal contents upwards toward the diaphragm and have a resultant increase in vital capacity and FEV1 in patients with tetraplegia from SCI. 8
    • Of note, patients with neuromuscular disease may have reduced vital capacity in the supine position, relating to diaphragmatic weakness.
  8. Abdominal binder
    • Prevents the drop in vital capacity that normally occurs in the transition from supine to sitting up in patients with tetraplegia.
  9. Respiratory muscle training
    • Goal is to strengthen inspiratory and expiratory musculature that are less affected from the neurological injury.

Airway clearance and secretion mobilization

  1. Endotracheal suctioning
    • Possible complications: hypoxia, hypotension, infection, tracheal mucosal damage, vagal nerve stimulation, increased bronchial mucus production, and patient anxiety and fear of suffocation.
  2. Mechanical insufflator-exsufflator:
    • Clears retained secretions and reduces the risk of respiratory complications and the need for bronchoscopy.
    • Can be applied via tracheostomy, facemask, or mouthpiece.
    • Contraindications include bullous emphysema, susceptibility to pneumothorax and pneumomediastinum, and recent barotrauma.
  3. Mechanical percussion and vibration
    • Devices include vibration vests and beds with automatic turning and vibration settings
    • Tapping on different areas of the chest with a cupped hand to help mobilize secretions
  4. Postural drainage
    • Passive positioning techniques that utilize gravity to help move secretions from the peripheral pulmonary regions to the main airway.
  5. Manually assisted coughing
    • Chest compressions that are specifically coordinated to a patient’s’ breathing that results in a significant increase in expiratory peak airflow and helps move secretions from the lower lung fields.

Medications to help maintain respiratory function1

  1. Bronchodilators
  2. Cromolyn Sodium
  3. Steroids
  4. Antibiotics
  5. Anticoagulation
  6. Vaccinations
  7. Methylxanthines
  8. Anabolic steroids
  9. Mucolytics

Once ventilatory support is needed

Non-invasive Ventilation

Non-invasive ventilation may help to avoid the need for invasive ventilation. Patients with reduced vital capacity can benefit from nocturnal non-invasive ventilation and can be offered in patients with decreased saturation <95% and CO2 >50 cm H20.  The current practices for when to initiate discussion of NIV with individuals with ALS (the best studied of the insidious onset NMDs) is when they have one or more subjective signs or symptoms of respiratory decline and an objective measure of reduced function.  It is controversial of when to initiate NIV in these patients (FVC <50% versus as high as <75%), but benefit has been shown if used for > 4 hours a day and no harm has been shown.3

  1. Types: CPAP, BiPAP, APAP
    • CPAP: (Continuous positive airway pressure) provides constant and unchanging airway pressure.
    • BiPAP: (Bi-level positive airway pressure) provides preset variable support during inspiration and expiration. This is better than CPAP because it keeps the alveoli open by administering a smaller PEEP.
    • APAP: (Automatic positive airway pressure) provides automatically variable positive pressure support during inspiration and expiration depending on airway resistance.

Tolerance to non-invasive ventilatory support is associated with those who do not have severe bulbar symptoms or facial flaccidity.3

Invasive Ventilation

Indications for intubation include increased respiratory rate, increasing oxygen requirements, decreased breath sounds on auscultation, VC less than 15 mL/kg of ideal body weight (IBW), and ABG  values of PaCO2 > 50 mm Hg or PaO2 ≤ 50 mm Hg while on room air.

The decision to implement invasive ventilation in patients with chronic neurologic disease should be made carefully after a discussion with the patient after a detailed goals of care discussion. Invasive ventilation has the potential to prolong survival time 2-5 years in some ALS patients; however this only pursued by 2-6% of patients in the US.3

The choice to move to tracheostomy in the subacute periods in those who have not been successfully weaned from a ventilator is not uncommon.  Advantages of tracheostomy include easier suctioning and facilitates weaning because it provides less dead space and airway resistance compared with intubation. Disadvantages include increased secretions production, infections, and difficulties with communication.

There are several methods to facilitate communication while on mechanical ventilation, such as lip speaking, mouthing, eye blinks, communication board, use of a Passey Muir valve, cuff deflation, use of cuff fenestrated tubes.

Ventilator weaning protocols may vary between different centers.  In summary, ventilator weaning should be initiated once the patient is afebrile, with stable vital signs, clear or improving chest X-ray, VC of at least 10-15 ml/kg ideal body weight, improved ABG values (PaCO2 of 35-45 mm Hg or PaO2  > 75 mm Hg, pH 7.35-7.45).  As this is often a high anxiety situation, the weaning process should be explained fully to the patient and consent to proceed is obtained.

In disease processes such as high-cervical SCI, discontinued invasive ventilation may not be compatible with survival.  In other NMDs such as GBS and MG with respiratory involvement, tracheostomy may be placed during a prolonged recovery period with potential for decannulation.

Emerging/unique Interventions

Electrical stimulation of the phrenic nerve or diaphragm by diaphragmatic pacing

  1. Allow patients with SCI an alternative form of long term respiratory management.
  2. Both open and minimally invasive techniques are in use.12
  3. Patients should have a backup ventilatory machine at all times in the case of device failure.
  4. Candidates include:
    • SCI level above C4
    • Functional phrenic nerve and diaphragm
    • Lack of significant airway or pulmonary disease
  5. This is currently NOT indicated in ALS. In 2015, a multicentric, open-label, randomized controlled trial was stopped due to lack of benefit and increased mortality.12

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

  1. Follow-up should include regular evaluation of lung function, especially in high risk individuals (high tetraplegia, ventilator dependent patients, patients with phrenic/diaphragmatic pacers, concomitant COPD, ALS, etc).
  2. Ensure caregivers have education, skills and available support prior to discharge home. Review with patient and caregiver principles or airway management (tracheal/stoma care, suctioning, tracheostomy tube change), safe swallow techniques, assisted cough, medications, early recognition of signs and symptoms of infection.  Ideally, patient will be able to direct his care in the presence of a new caregiver.
  3. In patients on long term ventilation, review with the patient and caregiver emergency measures in case of ventilator failure, power failure, equipment malfunction etc.  Check that information regarding technical support and community resources is always on hand. Back-up ventilator should be in good working condition.

4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE

Cutting edge concepts and practice

A recent review looking at spinal cord stimulators for cough restoration has shown that the stimulators are able to produce a near maximal cough similar to physiologic performance. Further, subjects with the implantation have reported, “improved sense of well-being, increased ease and independence in removing secretions, reduces stress, and a greater sense of autonomy and mobility.”13

Rehabilitation in the medical or surgical ICU setting (also known as early mobilization) may improve physical function, and reduce the duration of delirium, mechanical ventilation, and ICU length of stay.  A recent Cochrane Review found that here is not currently sufficient although several additional studies are currently ongoing.14

Functional Electrical stimulation to the abdominal muscles can improve respiratory function in patients with spinal cord injury in both the acute and chronic setting. A review article by, McCaughey et al., found that there was a chronic improvement in vital capacity, functional vital capacity, and peak expiratory flow. They also found an acute improvement in cough peak flow.15

5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE

Gaps in the evidence-based knowledge

The “best” ventilator setting is one of the most controversial topics in respiratory treatment in SCI. Some protocols use a high TV of 20 mL/kg of IBW, whereas others use a low TV of 10 mg/kg. A recent randomized controlled trial showed no significant differences in time to wean, incidence of VAP, or occurrence of adverse events among patients with tetraplegia ventilated with a TV of 10 mL/kg versus 20 mL/kg. In addition, ventilation at a high TV was not associated with barotrauma or acute respiratory distress syndrome. 16

REFERENCES

Consortium for Spinal Cord Medicine. Respiratory management following spinal cord injury: a clinical practice guideline for health-care professionals. J Spinal Cord Med. 2005;28(3):259-293.

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  13. Doiron KA, Hoffmann TC, Beller EM. Early intervention (mobilization or active exercise) for critically ill adults in the intensive care unit. Cochrane Database Syst Rev. 2018;3:CD010754.
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Original Version of the Topic

Kareen A. Velez, MD and Stephen L. McKenna, MD. Pulmonary rehabilitation after ventilatory failure. Original Publication Date: 12/02/2013.

Author Disclosure

Philippines Cabahug, MD
Nothing to Disclose

Travis Edmiston, MD
Nothing to Disclose

Amira Noles, MD
Nothing to Disclose

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