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Breath rate
14 /min
Tidal volume
83 mL
O₂ in blood
95.7%
CO₂ in blood
4.7%
How to use: Air comes down the trachea and splits into the two bronchi,
one for each lung. Inside, the airflow ends at millions of microscopic alveoli —
tiny air sacs wrapped in capillaries. Oxygen (red) diffuses from the sacs into the blood,
while carbon dioxide (teal) diffuses back out to be exhaled. Speed up or slow down the
breathing, then deepen it and watch the alveoli stretch.
Notice: oxygen moves from where there's more of it (the air in the
alveolus) to where there's less (the blood) — that's diffusion down the concentration
gradient. Deep slow breaths move more air per minute than fast shallow ones, because the
tidal volume grows. And with every exhale, the same alveoli that just loaded
oxygen into the blood now dump carbon dioxide back into the air.