spirometry and peak flow

asthma symptoms

Wheeze, breathlessness, night-time cough

COPD symptoms

Productive cough, breathlessness, frequent infections

FEV1 def

Forced Expiratory Volume in 1 second

FEV1 for healthy lungs

~80% of air expelled in 1 second

FVC def

• Forced Vital Capacity

• Total volume of air forcibly exhaled after full inhalation

FEV₁/FVC Ratio

Used to diagnose obstructive lung diseases

FEV₁/FVC Ratio below 70%

suggests COPD

Tidal Volume (TV)

Normal breath in and out (~500 mL)

Inspiratory Capacity (IC)

max volume of air a person can inhale after a normal, resting expiration

Expiratory Reserve Volume (ERV)

Extra air that can be exhaled after a normal breath out

Vital Capacity (VC)

greatest volume of air that can be expelled from the lungs after taking the deepest possible breath

normal breathing

• ~12 breaths per min

• ~500mL tidal volume

increased rate/depth

• ~20 breaths per min

• ~1750mL tidal volume

tidal volume calc

IC - IRV

vital capacity calc

IC + ERV

breathing rate calc

60 / time per breath

FEV₁/FVC % calc

(FEV₁ ÷ FVC) × 100

why is reversibility testing used

to differentiate asthma from COPD

reversibility testing method

• Perform baseline spirometry.

• Administer short-acting bronchodilator (e.g., salbutamol).

• Repeat spirometry.

Improved FEV₁/FVC from rev testing

likely asthma

Peak expiratory flow (PEF)

a person's maximum speed of expiration (L/min)

good control based on peak flow monitoring

≥80% of predicted value

peak flow diary

• Tracks morning/evening readings.

• Diurnal variation (day-night difference) indicates asthma.

• Reduced variation and rising scores = improved control.

What FeNO level is an indication of Asthma?

> 50 ppb