Correct!
5. Shift of the oxygen dissociation curve to the left
The normal PaO2 is about 95 and the normal venous partial pressure of oxygen, PvO2, is about 40. If you look at the at these pressures in figure 1 you can see that the difference in oxygen saturation, and therefore, the amount of oxygen delivered is much less when the oxygen dissociation curve is shifted to the left. This means that the carboxyhemoglobin is less able to release oxygen Figure 1). .
Figure 1. Oxygen dissociation curve with no carboxyhemoglobin and 60% carboxyhemoglobin.
The shift to the left occurs because when only one of the four binding sites for oxygen on hemoglobin is occupied by CO there is a confirmational change in the hemoglobin molecule making it more difficult for the remaining 3 oxygen binding sites to release oxygen. All the other mechanisms do occur but most experts favor the left shift of the oxyhemoglobin dissociation curve as the major mechanism lead to hypoxia.
Which of the following are true regarding CO poisoning? (click on the correct answer to be directed to the fifth of seven pages)