Why would patients with copd be given low flow concentration (1-2l/min) supplemental oxygen?

Low blood oxygen: At the advanced stages of copd, the lungs do not perform their function well, oxygen has a harder time crossing into the blood stream. At this point, the body is not getting enough energy, the blood oxygen level is low. Raising the amount of inhaled oxygen offsets the problem, and prolongs life. Oxygen is used at the lowest amount that would achieve the goal.

All they need...: Patients with COPD need to have a certain level of oxygen in their blood to decrease their morbidity and mortality rate. Most patients only need 1-2 liters of oxygen to achieve this level.