Patient Populations

Obstructive diseases (Asthma, COPD)

  • May need the lower end of tidal volumes (5-6 mL/kg)
  • Need longer expiratory period, therefore need higher I:E ratio (1:2 or higher)
  • Are more prone to air trapping and Auto PEEP, therefore may need lower PEEP setting
  • May do better with SIMV if tachypneic to prevent full volume breaths
  • May need bronchodilators
  • May need higher pressures to deliver breaths if using PC

Restrictive diseases (ILD, pulmonary fibrosis, obesity, chest wall injuries)

  • Decreased respiratory compliance
  • May have higher peak pressures
  • Need higher FiO2 and PEEP

Head Injuries

  • Hyperventilation is usually contraindicated
  • Maintain EtCO2 at low end of normal (35-40 mmHg)
  • PEEP can increase ICP, but may only be significant with much higher settings (>15 cmH2O)

RV failure (Massive PE, pulmonary HTN)

  • Lower PEEP, higher FiO2 to maintain oxygenation
  • Higher PEEP → higher intrathoracic pressure → increased pulmonary vascular pressures → worsening RV failure

Full term pregnancy

  • These patients have around a 40% higher minute ventilation starting during the first trimester. These patients may need a higher VT.
  • May need to be sitting up higher or tilted on their side
  • Adjust minute ventilation to maintain a PaCO2 of 30-32 mmHg to replicate normal physiology of a baseline respiratory alkalosis
    • Maternal hypercapnia >40 mmHg causes fetal respiratory acidosis

Acute Lung Injury (ALI) & Acute Respiratory Distress Syndrome (ARDS)

  • May be caused by the actual illness/injury itself, fluid administration or barotrauma
  • Characterized by an inflammatory response (inflammation, pulmonary edema)
  • This causes separation of alveoli and alveolar capillaries
  • Also associated with pulmonary hypertension
  • Must be differentiated from pneumonia, CHF
  • Needs higher FiO2, PEEP, and lung protective tidal volume (4-6 mL/kg)