MCQ Question 692 Figure 12.1 shows two blood oxygen dissociation curves. ‘A’ represents the oxygen partial pressure in normal alveoli, ‘H’ the lowered alveolar oxygen pressure in hypoxic lungs due to high altitude or pulmonary disease and ‘V’ the mixed systemic venous oxygen pressure in the person suffering from hypoxia. In this diagram: a. If (i) is a normal person’s curve, then (ii) is the hypoxic person’s curve, rather than vice
versa. b. The blood in curve (i) has a higher red cell level of 2,3-diphosphoglycerate (2,3-DPG). c. The O2 saturation of blood leaving the hypoxic lungs is lower with curve (ii) than with
curve (i). d. The oxygen extracted by the tissues equals oxygen uptake in the lungs for both curves
in both people, other things being equal. e. The curve labelled (i) is more suitable for fetal conditions than the curve labelled (ii).