Pulmonary Function Tests - Pulmonary

Snapshot
- A 23-year-old man presents to the emergency department with weakness. He states his legs were weak yesterday but now he is also having trouble breathing. He recently recovered from a diarrheal illness. The patient's forced vital capacity is significantly reduced and he is subsequently intubated (Guillain Barre syndrome).

Pulmonary Function Tests

Metrics	Definition	Obstructive	Restrictive
Elasticity	Ease of recoil after lungs have expanded	↓	↑
Compliance	Ease of alveoli expansion	↑	↓
Volumes
Minute volume	Volume of air expired in 1 minute	=/↓	↓
Residual volume (RV)	Air left in lung after max expiration	↑	↓
Total lung capacity (TLC)	All the air in the lung = vital capacity + residual volume	↑	↓
Tidal volume	Volume of air breathed in and out for a normal breath	↓	↓
Vital capacity	Total volume exhaled after full inspiration.	↓	↓
Spirometry
Forced expiratory volume (FEV1) normal = 4L	Volume expelled in one second	↓	=/↓
Forced vital capacity (FVC) normal = 5L	Entire volume that can be expelled	=/↓	↓
(FEV1)/FVC normal = 80%	Considered best screen, values of less than 50% correlate with postoperative pulmonary complications.	↓	=/↑