You would find hemoglobin that is relatively oxygen-poor in the venous blood returning from the tissues in a healthy resting person. This is because hemoglobin releases oxygen to the tissues where the partial pressure of oxygen (PO2) is lower, typically around 40 mmHg, resulting in about 75% hemoglobin saturation with oxygen in venous blood, compared to nearly 100% saturation in arterial blood leaving the lungs

. More specifically:

• In the lungs, hemoglobin is almost fully saturated with oxygen (close to 100%) due to the high PO2 (~100 mmHg) in alveolar air

• As blood passes through systemic tissues, oxygen diffuses from hemoglobin to the cells where PO2 is lower (around 40 mmHg), causing hemoglobin to release oxygen and become less saturated (about 75% saturation), thus relatively oxygen-poor hemoglobin is found in venous blood returning to the heart

• This deoxygenated or partially oxygenated hemoglobin is called deoxyhemoglobin and is essential for delivering oxygen to meet tissue metabolic demands

Therefore, in a healthy resting person, relatively oxygen-poor hemoglobin is found primarily in the venous blood after it has delivered oxygen to peripheral tissues.