09 PFT - Boards and Beyond

  • PFT in context
  • in real life: deconditioning common cause, out of shape
  • cardiac: HF, coronary diseases

  • obstruction: more at neck, air can't get out
  • restriction: can't expand

PFT

  • most air blown out in 1st second
  • FEV1: forced expiratory volume in 1 second
  • FVC: forced vital capacity, total

  • restrictive: normal slope and shape. No problem with mechanics of getting air out. Can't draw enough air in. FVC lower
  • obstructive: slope slower. Shape different

  • restrictive: lower FEV1. Can't draw as much air in in first place, so can't exhale as much out
  • obstructive: very low. Obstruction to outflow. Can't get out
  • Both has lower FEV1, decrease in obstructive much lower

  • falls in both
  • restrictive: can't draw as much in
  • obstructive: can't get out

  • restrictive: normal or may even rise

  • Obstructive: volume higher because air trapping, starts at higher point at 0
  • Restrictive: can't get air in. Starts at lower point

  • PEF: peak expiratory flow, fall in obstructive lung disease

  • Obstructive: PEF much lower, gentle gradual down slope instead of rapid (obstruction, changes shape)
  • Restrictive: looks like normal curve just smaller

Work of breathing

  • amount of energy body expends to move air

  • bronchoconstriction: moves curve up
  • bronco dilator: curve moves down

  • more work to inflate a completed deflated lung than to inflate partially deflated lung
  • top: very low respiratory rate, alveoli completely deflate/inflate with each breath
  • bottom: high respiratory rate, alveoli start with some air, not as much work to inflate

  • restrictive: at all rate, more work required, same shape = same respiratory rate as normal. Working harder to breath overall, but rate unchaged
  • obstructive: different shape, min point shifted to left. Increased resistance to airflow, breath at lower, long breaths to avoid turbulent flow