Compliance and Positioning

• Supine Position:

  • Reduced lung compliance
  • Reduced tidal volume (VT ) - abdominals move up and push underside of diaphragm so it doesn't descend the same
  • Reduced Functional Residual Capacity - caused by reduced tidal volume
  • Reduced vital capacity (VC) - caused by reduced tidal volume
  • Increased pulmonary congestion - some fluid leak out of capillary and sits in area around alveoli
  • Reduced chest wall compliance
  • Raised intra-abdominal pressure
  • Altered diaphragm mechanics
• Other Negative Effects of Supine:

  • Decrease in expiratory flow rate
  • Increase in work of breathing
  • Decrease in Functional residual capacity contributes to closure of dependent airways (atelectasis)
  • Decrease in arterial oxygenation (PaO2 )