Failure

Acute Respiratory Failure

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Acute Respiratory Failure, Respiratory Failure

  • Types
  • Hypoventilatory Respiratory Failure or Hypercapnic Respiratory Failure (Bellows Failure)
  1. Defining features
    1. High PaCO2 >50 mmHg (not due to respiratory compensation for Metabolic Alkalosis)
    2. Normal A-a Gradient
  2. Causes: Compromised lung mechanics
    1. Upper airway obstruction
      1. Infection (Epiglottitis, Bacterial Tracheitis, croup)
      2. Adenotonsillar Hypertrophy
      3. Neck Mass
      4. ThyroidGoiter
      5. Obstructive Sleep Apnea
      6. Vocal Cord Paralysis (bilateral)
      7. Laryngeal Foreign Body
    2. Pulmonary muscle Fatigue (Skeletal muscle Fatigues at >40% of maximum load)
      1. Obesity
      2. Ascites
      3. Pleural Effusion
      4. Supine position
      5. Kyphoscoliosis
      6. Ankylosing Spondylitis
      7. Hypercarbia (fever, Sepsis, burns)
      8. Inefficient breathing (flat diaphragm, high Residual Volume)
        1. Asthma
        2. Emphysema
    3. Unstable chest wall
      1. Pneumothorax
      2. Flail Chest or multiple Rib Fractures
      3. Diaphragmatic Rupture
  3. Causes: Neuromuscular
    1. Drug Overdose or depressant drugs
      1. Opioids
      2. Benzodiazepines
      3. Barbiturates
      4. Procedural Anesthesia (e.g. Propofol)
      5. Phencyclidine (PCP)
    2. Toxins (or other medication adverse effects)
      1. Aminoglycosides
      2. Arsenic
      3. Strychnine
      4. Botulism
    3. Electrolyte and endocrine abnormalities
      1. Hyponatremia
      2. Hypocalcemia
      3. Hypokalemia
      4. Hyperkalemia
      5. Hypomagnesemia
      6. Severe Hypophosphatemia
      7. Hypothyoidism
    4. Brainstem injury
    5. Severe global CNS injury
      1. Head Trauma
      2. Intracranial Hemorrhage
      3. CNS Infection (Meningitis, Encephalitis, Brain Abscess, West Nile Encephalitis, Poliomyelitis)
      4. Central Sleep Apnea
      5. Central Alveolar Hypoventilation Syndrome (CHS)
    6. Nerve dysfunction
      1. Spinal cord injury
      2. Polyneuritis (e.g. Guillain-Barre Syndrome)
      3. Amyotrophic Lateral Sclerosis
      4. Multiple Sclerosis
      5. Nerve Agent Exposure (e.g. Organophosphates)
      6. Phrenic nerve injury
        1. Example: Phrenic Nerve Injury from Birth Trauma
    7. Muscular dysfunction
      1. Muscular Dystrophy
      2. Myasthenia Gravis
      3. Polymyositis
      4. Tetanus
  • Types
  • Ventilation-perfusion mismatch (venous admixture)
  • Types
  • Hypoxemic Respiratory Failure (or physiologic right to left shunting)
  1. Defining features
    1. Low PaCO2
    2. Low PaO2 <50-60 mmHg on room air
    3. A-a Gradient may be increased
    4. May not improve with Supplemental Oxygen
  2. Causes
    1. Cardiac pulmonary edema (high pressure edema)
      1. Left Ventricular Failure
      2. Acute Myocardial Ischemia (left ventricle)
      3. Malignant Hypertension
      4. Mitral Regurgitation or stenosis
    2. Lung Conditions
      1. Lobar Pneumonia
      2. Atelectasis
      3. Pulmonary Contusion
      4. Alveolar Hemorrhage
      5. Bronchospasm
      6. Cystic Fibrosis
      7. Acute Respiratory Distress Syndrome (ARDS)
        1. Increased permeability (low pressure edema)
  • Signs
  1. General appearance
    1. Altered Mental Status
    2. Diaphoresis
  2. Increased work of breathing
    1. Accessory muscle use
    2. Intercostal retractions
    3. Tachypnea
    4. Paradoxical breathing patterns
      1. Abdominal wall moves inward with inspiration as respiratory Fatigue occurs
  3. Cardiovascular changes
    1. Mucous membrane and nail bed Cyanosis
    2. Tachycardia
    3. Hypertension
  • Differential Diagnosis
  1. See Causes above
  2. See Dyspnea Causes
  3. See Tachypnea Causes
  4. See Hypoxia
  1. Hypoxemic Respiratory Failure (Inadequate oxygenation)
    1. Reflected by Arterial Blood GasPaO2 and Oxygen Saturation
    2. Concepts
      1. Increase oxygen delivered to the lung (esp. FIO2) or
      2. Increase mean airway pressure (or Positive End-Expiratory Pressure)
    3. Interventions
      1. Continuous Positive Airways Pressure (CPAP)
  2. Hypercarbic Respiratory Failure (Inadequate ventilation)
    1. Reflected by Arterial Blood GasPaCO2 and pH
    2. Concepts (increase minute ventilation)
      1. Increase Tidal Volume (TV) or
      2. Increase Respiratory Rate (RR)
    3. Interventions
      1. Bilevel Positive Airway Pressure (BiPap)
  3. References
    1. Mallemat and Runde in Herbert (2015) EM:Rap 15(2): 7-8
  • References
  1. (2016) Fundamental Critical Care Support, p. 46-60
  2. Davies (1986) Acute Respiratory Failure, Cyberlog
  3. Presberg in Noble (2001) Primary Care, p. 705-16