Author:
Matthew M.Hall
Christopher JamesWatson
Description
Inability to breathe comfortably
- Describes a symptom of many possible underlying diseases
- May or may not correlate with signs of increased work of breathing
- Usually an unconscious activity, dyspnea is the subjective sensation of breathing, from mild discomfort to feelings of suffocation
- Accounts for 3.5% of ED visits
- Caused by difficulties in maintaining homeostasis with respect to gas exchange and acid-base status
- Can reflect an impairment in ventilation, perfusion, metabolic function, or CNS drive
- Mechanisms that control breathing:
- Control centers:
- Brainstem and cerebral cortex affect both automatic and voluntary control of breathing
- Chemo, stretch, and irritant sensors:
- CO2 receptors located centrally and PO2 receptors located peripherally
- Mechanoreceptors lie in respiratory muscles and respond to stretch
- Intrapulmonary mechanoreceptors respond to chemical irritation, engorgement, and stretch
- Effectors of respiratory center output are in the respiratory muscles and respond to central stimulation to move air in and out of the thoracic cavity
- Motor-sensory control of the diaphragm and muscles of respiration are controlled by C3-C8 nerves and T1-T12 nerves
- Derangements of any of these neurosensory pathways produces dyspnea:
- Many etiologies for the sensation of dyspnea are due to the complex nature of mechanisms that control breathing
Etiology
- Upper airway:
- Epiglottitis
- Laryngeal obstruction
- Tracheitis or tracheobronchitis
- Angioedema
- Pulmonary:
- Airway mass
- Asthma
- Bronchitis
- Chest wall trauma
- CHF
- Drug-induced conditions (e.g., crack lung, aspirin overdose)
- Effusion
- Emphysema
- Lung cancer
- Metastatic disease
- Pneumonia
- Pneumothorax
- Pulmonary embolism (PE)
- Pulmonary HTN
- Restrictive lung disease
- Cardiovascular:
- Arrhythmia
- Coronary artery disease
- Intracardiac shunt
- Left ventricular failure
- Myxoma
- Pericardial disease
- Valvular disease
- Neuromuscular:
- CNS disorders
- Myopathy and neuropathy
- Phrenic nerve and diaphragmatic disorders
- Spinal cord disorders
- Head and cervical spine trauma
- Systemic neuromuscular disorders
- Metabolic acidosis:
- Sepsis
- Ketoacidosis (diabetic, alcoholic, starvation)
- Renal failure (volume overload, uremia)
- Profound thiamine deficiency
- Toxic:
- Methemoglobinemia
- Salicylate poisoning
- Cellular asphyxiants:
- Carbon monoxide
- Cyanide
- Hydrogen sulfide
- Sodium azide
- Toxic alcohols
- Abdominal compression:
- Ascites
- Pregnancy
- Massive obesity
- Psychogenic:
- Other:
- Altitude
- Anaphylaxis
- Anemia
Geriatric Considerations |
- Most common diagnoses in elderly patients presenting to the ED with dyspnea:
- Decompensated heart failure
- Infection (pneumonia, UTI)
- COPD/asthma
- PE
|
Pediatric Considerations |
- Common differential diagnosis for age <2 yr:
- Asthma
- Croup
- Congenital anomalies of the airway
- Congenital heart disease
- Foreign-body aspiration
- Nasopharyngeal obstruction
- Shock
|
Pregnancy Prophylaxis |
- Pregnant women have decreased lung capacity and a propensity for anemia
- While supine, the gravid uterus can compress the IVC, leading to dyspnea and hypotension
- There is an increased risk for PE throughout and shortly after pregnancy, as well as for amniotic fluid emboli in the peripartum and postpartum periods
|
Signs and Symptoms
- Difficult, labored, or uncomfortable breathing
- Upper airway:
- Stridor
- Upper-airway obstruction
- Pulmonary:
- Tachypnea
- Accessory muscle use
- Wheezing
- Rales
- Asymmetric breath sounds
- Poor air movement
- Prolonged expiratory phase
- Cardiovascular:
- S3 gallop
- Murmur
- Jugular venous distention
- CNS:
- Altered levels of consciousness
- Decreased muscle strength
- General:
- Diaphoretic/cool vs. hot/dry skin
- Pallor
- Upright patient position
- Clubbing
- Cyanosis
- Edema
- Ketotic breath odor
History
- Previous history of dyspnea
- Time course, abruptness of onset, triggers, and severity
- History of stridor or wheezing
- Exercise (activity) tolerance
- Medications and recent compliance
- Exposure to allergens
- Past medical history
- Associated symptoms:
- Chest pain
- Fever
- Cough
- Hemoptysis
- Bleeding
Physical Exam
- Signs of acute distress:
- Altered mental status
- Cyanosis
- Respiratory rate
- Retractions suggest severe disease
- Listen for abnormal lung sounds:
- Stridor
- Rales
- Wheezing
- Decreased breath sounds
Essential Workup
- Pulse oximetry:
- May be falsely elevated due to increased ventilation or carbon monoxide
- Low SpO2 despite supplemental O2 suggests shunt physiology or methemoglobinemia
- Ensure a good waveform prior to interpreting
- May need to remove nail polish or place on ear
- End-tidal CO2:
- Quickly suggests PaCO2
- Waveform can give clue to etiology
- CXR:
- Obtain P-A and lateral films for most stable patients
- For diagnosis of pulmonary conditions
- Assess heart size and evidence of CHF
- Venous blood gas (VBG):
- Used to assess pH, pO2, pCO2, and HCO3
- VBG is often adequate as compared to arterial blood gas (ABG) and is easier, less painful, and safer to obtain
- Venous pH is approximately 0.03 lower than arterial pH
- Venous pCO2 correlates well to arterial pCO2 for values ≤45 mm Hg
- No correlation between venous and arterial pO2
- Venous HCO3 is approximately 1.41 mEq higher than arterial HCO3
- ABG:
- Often unnecessary due to VBG, but still essential to determine PaCO2 in hypercapnia ≥45 mm Hg or in severe shock
- Calculate arterial-alveolar gradient:
- A-a (at sea level) = 150 - (pO2 - pCO2)/0.8, normal 5-20
Diagnostic Tests & Interpretation
Lab
- CBC:
- Evaluation for anemia
- Neutrophil count helpful in evaluation of infectious processes
- Electrolyte, BUN, creatinine, glucose:
- Consider when specific metabolic derangements are suspected
- B-type natriuretic peptide may be elevated in CHF
- Toxicology screen
- Methemoglobin/carboxyhemoglobin level
- Thyroid function tests
- d-dimer (ELISA):
- Useful for excluding PE if normal, but has relatively poor specificity
- Strategies to reduce overtesting for PE include:
- Use of “age-adjusted” d-dimer (age* 10) for patients >50 yr old
- Use of the PERC rule for low risk patients <50 yr old
Imaging
- CXR for infiltrate, effusion, pneumothorax, or vascular consolidation
- CT pulmonary angiogram for suspected PE (ventilation-perfusion scan may be beneficial if contrast load is contraindicated in a stable patient)
- Soft tissue neck radiograph, CT neck, or fiberoptic visualization for suspected upper airway obstruction
Diagnostic Procedures/Surgery
Differential Diagnosis
- Anticholinergic or adrenergic toxidrome
- Thyroid storm
- Munchausen syndrome
Prehospital
- Place all patients on supplemental oxygen, pulse oximetry, end-tidal CO2, and cardiac monitor
- Initiate therapy for suspected cause of dyspnea when indicated:
- Utilize advanced airways in the face of impending/realized respiratory failure
- Noninvasive positive pressure ventilation can rapidly improve many respiratory conditions
Initial Stabilization/Therapy
- ABCs
- Immediate intubation for impending respiratory arrest:
- Altered mental status
- Unstable vital signs
- Noninvasive positive pressure ventilation in alert patients:
- Contraindications:
- Cardiac instability
- Suspicion of upper airway obstruction
- Decreased mental status
- Upper GI bleeding
ED Treatment/Procedures
- Based on underlying etiology
- Early antibiotics and fluid for infection/sepsis
- Noninvasive positive pressure ventilation and diuretics for CHF
- Bronchodilators and steroids for asthma
- Aspirin, heparin, and lytics/cath lab for MI
- Other treatments as necessary for other etiologies
- Palliative care with opiates is indicated for the relief of dyspnea in terminally ill patients
Disposition
Admission Criteria
- Assisted ventilation
- Hypoxia at rest or with exercise
- A-a gradient >40
- Medical condition requiring hospital therapy
Discharge Criteria
- Adequate oxygenation
- Stable medical illness that can be managed as outpatient
- Adequate ambulatory pulse ox and work of breathing
Issues for Referral
Based on suspected underlying etiology
Follow-up Recommendations
- Patients should be counseled on the short- and long-term benefits of smoking cessation
- The patient should return for any of the following problems:
- No improvement or worsening in 24 hr
- New chest pain, pressure, squeezing, or tightness
- Shaking chills or a fever >102°F
- New or worsening cough or wheezing
- Abdominal pain, vomiting, severe headache
- Dizziness, confusion, or change in behavior
- Any serious change in symptoms, or any new symptoms that are of concern
- BraithwaiteSA, PerinaD. Dyspnea. In: WallsRM, et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed.Philadelphia, PA: Mosby Elsevier; 2018.
- ByrneAL, BennettM, ChatterjiR, et al. Peripheral venous and arterial blood gas analysis in adults: Are they comparable? A systematic review and meta-analysis . Respirology. 2014;19:168-175.
- GoodacreS, BradburnM, CohenJ, et al. Prediction of unsuccessful treatment in patients with severe acute asthma . Emerg Med J. 2014;31(e1):e40-e45.
- ParshallMB, SchwartzsteinRM, AdamsL, et al. An official American Thoracic Society statement: Update on the mechanisms, assessments, and management of dyspnea . Am J Resp Crit Care Med. 2012;185(4):435-452.
- PonikowskiP, VoorsAA, AnkerSD, et al. 2016 ESC guidelines for the diagnosis and treatment of acute and chronic heart failure: the task force for the diagnosis and treatment of acute and chronic heart failure of the European Society of Cardiology (ESK) developed with the special contribution of the heart failure association (HFA) of the ESC . Eur Heart J. 2016;18:891-975.
- RighiniM, Van EsJ, Den ExterPL, et al. Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: The ADJUST-PE study . JAMA. 2014;311(11):1117-1124.
See Also (Topic, Algorithm, Electronic Media Element)
Respiratory Distress