How is the size of a planet related to the thickness of its atmosphere

The bigger the planet the bigger the gravitational pull of the planet , which is also stipulated in Newton Law of gravity. The bigger the planet, therefore, the bigger the atmosphere it would have. This is because its gravity is able to overcome the kinetic energy of the gas molecules (especially when heated by rays from a star they are orbiting) that would allow the gas atoms/molecules to escape into space. This is also why the large planets are all gas giants such as Jupiter.

hypoxemia refers to a below usual concentration of oxygen in the blood, mainly in the arteries. hypoxemia is an indication of an issue associated with circulation or breathing and may lead to various symptoms like shortness of breath.  

the condition is identified by determining the level of oxygen in the blood sample obtained from an artery. it can also be predicted by determining the oxygen saturation of the blood with the application of a pulse oximeter.  

the normal arterial oxygen is about 75 to 100 mm hg. the values underneath 60 mm hg is generally considered with the requirement for supplemental oxygen. the normal pulse oximeter readings generally range between 95 to 100 percent. the values under 90 percent are regarded as low.  

in the given case, the oxygen saturation is measured at 93 percent, hence, there is no need to administer oxygen, that is, one should withhold oxygen.