Question #328

Which of the following best explains why day-to-day variations in barometric pressure have little effect upon the oxygen content of arterial blood? the partial pressure of oxygen is independent of barometric pressure
such changes in barometric pressure have no effect on the forces governing gas diffusion across the alveolar membrane
the saturated vapour pressure of water varies inversely with the barometric pressure, compensating for any effect
the oxygen content of arterial blood depends upon atmospheric, not barometric, pressure
the degree to which haemoglobin is saturated is largely unaffected by such variations in barometric pressure

While oxygen, carbon dioxide and nitrogen represent fixed proportions of the atmospheric gas, barometric (atmospheric) pressure is variable. Partial pressures are therefore indeed dependent on barometric pressure. Since haemoglobin is all but fully saturated with oxygen over the working range of alveolar pO2s, however, such variations have little affect upon the oxygen content of arterial blood.

Any comments or corrections? Please e-mail help@cambridgequestions.co.uk