1. Are the loops similar between attempts?
   1. YES: Skip to next
   2. NO: See first page's comment if ATS reproducibility criteria was met
2. Roughly speaking, do the loops appear obstructive or restrictive?

Source

1. Required:
   1. BDR >10%

1. Calculation
   1. $ BDR = \frac{FEV1_{postBD} - FEV1_{preBD}}{FEV1_{predicted}}$

Important NOTE:

1. Calculation is not
   1. $ BDR = \frac{FEV1_{postBD} - FEV1_{preBD}}{FEV1_{preBD}}$
2. Does NOT require
   1. $\Delta FEV1_{volume} >200 mL$

Source, pg 17

1. Check spiro
   1. Is $FVC \cdot z_{score} \leq -1.65$ (e.g. < 5th percentile)?
      1. Yes: get lung volumes
      2. No: no restriction
2. Check lung volumes
   1. Is $TLC \cdot z_{score} \leq -1.65$ (e.g. < 5th percentile)?

• IF not performed, skip to below
• IFF TLC < 80% or < LLN:

VC: ↓ in restriction, ↓ in air trapping RV & FRC: ↑ with air trapping RV & FRC: ↓ with restriction ERV: ↓ in obesity

FRC is the primary thing calculated in lung volume calculations.

Boyle’s Law

• $P_1V_1 = P_2V_2$
• $\implies V_{tg} = 970\frac{\Delta V}{\Delta P}$

$ FRC = ERV + RV $

$TLC = VC + RV $

• Helium is used because He doesn’t cross the alveolar-capillary membrane
  • $ C_1V_1 = C_2(V_1+V_2)$
  • $\implies V_2 = V1(\frac{C_1}{C_2}-1)$
  • limitations since inhalation done only for a few minutes, would get into poorly ventilated lungs, so will underestimate FRC

Method for calculation is similar to Helium method.