respiratory system

hey guys, i'm looking for the explanation of relationship between arterial oxygen saturation and heart rate, i've been searching on google but got stuck in the situation where i have to pay an account for reading journal with the same topic. could anyone explain to me please? thank you.

I had a question on pulmonary collapse and surfactants I know that surfactants reduce the surface tension of the alveoli fluid because by adding the surfactant the hydrophilic molecules are able to move away underneath this surfactant if we apply a force and therefore they aren't that resistant...