Mechanical ventilation (main)

Background

• Intubation and ventilation typically required for respiratory failure or airway protection/severe altered mental status

Categories of Respiratory Failure

• Type 1 - Hypoxemia
• Type 2 - Hypercarbia
• Type 3 - Perioperative
• Type 4 - Shock

Patient Positioning

• HOB elevation > 30 degrees
• Reverse trendelenberg at 30 degrees in obese hypoventilaters
• Lateral decubitus for severe unilateral lung disease
  • Good lung to Ground generally
  • Good lung UP in these exceptions:
    • Massive hemoptysis - prevent blood into dependent, good lung
    • Large abscess - pus fills up dependent lung
    • Unilateral emphysema - prevent hyperinflation

See Also

Mechanical Ventilation Pages

• Noninvasive ventilation
• Intubation
  • Rapid sequence intubation
  • Intubation (peds)
• Mechanical ventilation (main)
  • Ventilation modes
  • Initial mechanical ventilation settings
    • Initial mechanical ventilation settings (peds)
  • Adjusting mechanical ventilation settings
    • Deterioration after intubation
    • Lung recruitment maneuver
    • Ventilator high pressures
    • Ventilator associated lung injury
  • Weaning mechanical ventilation
    • Extubation
• Miscellaneous
  • ARDS and EBQ:ARDSnet
  • Airway pressure release ventilation
  • Ideal Body Weight Estimation
  • Sedation

Airway Pages

• Pre-intubation
  • Predicting the difficult airway
  • Bag valve mask ventilation
    • Oropharyngeal airway
    • Supraglottic airway
  • Apneic oxygenation
    • EBQ:ED Preoxygenation
• Induction
  • Critical care quick reference
  • Rapid sequence intubation
  • Delayed sequence intubation
• Intubation
  • Intubation (peds)
  • Direct laryngoscopy
  • Video Laryngoscopy
  • Bougie
  • The difficult airway
  • Advanced airway adjuncts
    • Supraglottic airway
  • Non-traditional intubation
    • Awake intubation
    • Nasal intubation
    • Blind digital intubation
• Surgical airways
  • Surgical cricothyrotomy
  • Needle cricothyrotomy
  • Pediatric jet ventilation
• Post-intubation
  • Mechanical ventilation (main)
  • Deterioration after intubation (DOPE)

Calculators

A-a O₂ Gradient

Alveolar-arterial (A-a) O₂ Gradient

Parameter	Value
Age (years)
FiO₂ (%)
PaCO₂ (mmHg)
PaO₂ (mmHg)
A-a Gradient	mmHg
Expected A-a	mmHg (age-adjusted normal)

Interpretation

Normal A-a gradient ≈ (Age/4) + 4 on room air Elevated A-a gradient suggests: V/Q mismatch, shunt, or diffusion impairment Normal A-a gradient + hypoxia suggests: hypoventilation or low FiO₂

References

Formula: A-a = [FiO₂ × (Patm – PH2O)] – (PaCO₂/0.8) – PaO₂ Kanber GJ, et al. The alveolar-arterial oxygen gradient in young and elderly men during air and oxygen breathing. Am Rev Respir Dis. 1968;97(3):376-381. PMID 5637791.

External Links

• Vent basics resource: https://emcrit.org/wp-content/uploads/2010/05/Managing-Initial-Vent-ED.pdf