# Henry's law and O2 concentration in alveoli blood

Can Henry's law be applied to find $\ce{[O2]}$ in alveoli blood?
This kind of question appeared in an another forum and I've been struggling to find a definitive answer. My initial thought was 'no', because Zumdahl's Chemical Principles book says that

Henry's law is obeyed most accurately for dilute solutions of gases that do not dissociate or react with the solvent. $\ce{O2}$ will bind to the haemoglobin in the blood. Given this reaction in the solvent, $\ce{O2_{(g)}}$ in blood does not follow Henry's law.

However, a quick google search turned up multiple sources that use Henry's law directly to find the dissolved oxygen concentration (which is about $2\%$ of total oxygen):

What I failed to understand is why the dissolved oxygen is linearly proportional to the partial pressure while the oxygen dissociation curve is not. Is there something I'm missing?