dyspnea (shortness of breath {SOB})

Introduction

The sensation of shortness of breath, difficulty breathing, labored breathing. Alternatively, the uncomfortable awareness of breathing.

Classification

Severity grading: (New York Heart Association Classification)

• 0. No dyspnea except with strenuous exercise
• 1. Slight dyspnea while walking uphill or rapidly on a flat surface.
• 2. Dyspnea while walking on a flat surface; unable to keep up with peers, having to stop to catch breath
• 3. Dyspnea on walking 100 yards or after a few minutes & having to stop to catch breath
• 4. Dyspnea with minimal exertion, i.e. dressing or undressing
• 5. Dyspnea at rest.

Etiology

• heart disease, heart failure
  • increased pulmonary capillary pressure
  • left atrial hypertension
  • increased airway resistance
  • decreased lung compliance
  • myocardial ischemia, myocardial infarction
  • HFrEF & HFpEF
• obstructive airway disease
  • upper airway obstruction
    • foreign body aspiration
  • bronchitis
  • asthma
  • chronic obstructive pulmonary disease
• restrictive lung disease/pulmonary parenchymal disease
  • pneumonia
  • pneumoconiosis
  • sarcoidosis
• pulmonary vascular disease
  • pulmonary embolism
  • pulmonary hemorrhage
  • chronic thromboembolic pulmonary hypertension (CTEPH)
• pleural effusion
• chest wall or respiratory muscle disorder
  • severe kyphoscoliosis
  • paralysis of diaphragm
  • respiratory muscle weakness
    • amyotrophic lateral sclerosis (ALS)
• other
  • anemia
  • pregnancy
  • drugs
  • infection
  • psychogenic
  • deconditioning
  • obesity
  • esophageal reflux disease
  • advanced cancer (>50-60%, up to 74% with lung cancer)
    • prevalence increases during the last 6 weeks of life

Pathology

• generally the result of increased work of breathing
• other mechanisms
  • abnormal activation of respiratory centers
  • voluntary hyperventilation
  • Cheyne-Stokes respirations
  • stimulation of pressure receptors in pulmonary vasculature or right atrium (pulmonary embolus)
• underlying factors
  • hypoxia
  • hypercarbia

History

• rate of onset, orthopnea, paroxysmal nocturnal dyspnea, effect of physical exertion, history of myocardial infarction, history of syncope, prior episodes of dyspnea, aggravating or relieving factors, edema, weight gain, cough, sputum, fever, nausea, HIV risk factors, history of asthma, occupational exposure

Clinical manifestations

• response to dyspnea is both physiologic & psychologic
  • tachycardia, tachynea
  • pain, anxiety, fear
• heart disease (heart failure)
  • dyspnea on exertion
  • orthopnea
  • paroxysmal nocturnal dyspnea
  • dyspnea at rest
  • S3 (best predictor of heart failure), S4
  • murmurs
  • cardiomegaly
  • jugular venous distention
    • predicts heart failure, but less so than S3
  • hepatomegaly
  • peripheral edema
    • predicts heart failure, but less so than S3
• obstructive airway disease
  • upper airway obstruction
    • acute dyspnea with difficulty inhaling
    • inspiratory stridor
    • monophonic wheeze
    • retraction of supraclavicular fossa
  • asthma
    • acute intermittent dyspnea
    • expiratory wheezes
  • chronic obstructive pulmonary disease
    • slowly progressive exertional dyspnea
• pulmonary parenchymal disease
  • exertional dyspnea early
  • tachypnea
  • inspiratory rales
• pulmonary embolism
  • multiple discrete episodes of dyspnea with recurrent pumonary embolism
  • may be progressive dyspnea without abrupt worsening
  • tachypnea
  • deep venous thrombosis may or may not be present
• chest wall or respiratory muscle disorder
  • severe kyphoscoliosis
    • must be severe before respiratory function is compromised
  • paralysis of diaphragm
    • appears normal standing
    • severe orthopnea

Laboratory

• complete blood count
• serum TSH
• basic metabolic panel
• serum BNP useful in distinguishing cardiac from pulmonary source of dyspnea (high serum BNP suggests cardiac source)*

* a serum BNP not likely useful in a patient with a normal echocardiogram

Diagnostic procedures

• peak flow rate
• pulmonary function tests
  • spirometry, lung volumes, DLCO
  • flow volume loop may distinguish intrathoracic from extrathoracic airway obstruction
    • useful for evaluating dyspnea in elderly with kyphosis
• fiberoptic exam of upper airway if suspecting upper airway obstruction
  • fiberoptic bronchoscopy if suspected foreign body aspiration
• arterial blood gas
• electrocardiogram
  • atrial fibrillation predicts heart failure
  • ST segment & T wave changes predict heart failure
  • Q wave predicts heart failure
• exercise tolerance testing
  • especially useful in assessment of exertional dyspnea
• H2FPEF risk score if diastolic heart failure suspected
• other tests depend on specific etiology

Radiology

• lateral neck films if suspecting upper airway obstruction
• chest X-ray
  • pulmonary edema (LR of heart failure = 11)
  • cardiomegaly (LR of heart failure = 7)
  • pleural effusion (LR of heart failure = 5)
• high-resolution computed tomography (CT) if suspecting:
  • interstitial lung disease
  • malignant infiltrate
  • bronchiectasis
  • emphysema
• CT angiography (spiral CT) detects pulmonary emboli
• point-of-care ultrasonography can improve diagnostic accuracy in unexplained acute dyspnea

Management

• specific measures for specific etiologies
  • corticosteroids particularly useful for bronchospasm
  • diuretics may be useful for hypervolemia
  • oxygen of benefit if hypoxemic, otherwise not
    • fans are of benefit for reducing dyspnea in non-hypoxic patients
  • systemic opiates for refractory dyspnea in palliative care
• general measures
  • exercise training program
    • improves physical well-being, endurance & breathlessness without improving lung function or gas exchange
  • breathing techniques reduce sense of respiratory effort
    • purse-lipped breathing
    • diaphragmatic breathing
  • cool air moving across the face from a fan or open window stimulates the maxillary nerve (cranial nerve V-2) which has a central inhibitory effect on the sensation of breathlessness
  • supplemental oxygen
    • benefit in patients with significant dyspnea & only mild hypoxia
    • not beneficial in the absence of hypoxia
    • high-flow oxygen relieves dyspnea in palliative care patients
  • low-dose opiates reduce sense of breathlessness
    • oral
    • nebulized/aerosolized morphine
      • adjunct for patients already receiving oral opiate
      • may be combined with bronchodilator (albuterol)
      • no better than nebulized saline
  • low-dose benzodiazepines & opiates, alone or in combination, are safe
  • anxiolytic agents are generally not effective
  • haloperidol reduces sense of breathlessness
  • theophylline use to improve diaphragmatic contractility is controversial
  • respiratory muscle training of little value
• pneumonectomy (bilateral)

More general terms

• sign/symptom

More specific terms

• exertional dyspnea; dyspnea on exertion (DOE)
• orthopnea
• paroxysmal nocturnal dyspnea (PND)
• platypnea
• trepopnea

Additional terms

• respiratory distress syndrome (RDS)
• respiratory urgency