09 PFT

Dyspnea

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• 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

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• 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

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• Obstructive: volume higher because air trapping, starts at higher point at 0

• Restrictive: can't get air in. Starts at lower point

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• 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

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• 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