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Week 7 Case Study: Carbon Monoxide Poisoning
BIO255: Anatomy & Physiology III w/Lab
, 2
1. With respect to hemoglobin loading, please explain the relationship between the
binding of oxygen (O2) and carbon monoxide (CO) to the hemoglobin molecules.
The hemoglobin molecule has four binding sites for oxygen molecules: the iron atoms in
the four heme groups. Thus, each Hb tetramer can bind four oxygen molecules. From the
molecular weight of Hb, one can calculate that 1 g of Hb can combine with 1.39 ml of
oxygen. Meanwhile, carbon monoxide is dangerous for several reasons. When CO binds
to one of the binding sites on hemoglobin, the increased affinity of the other binding sites
for oxygen leads to a left shift of the oxygen dissociation curve. Thus, it interferes with
the unloading of oxygen in the tissues. Carbon monoxide prevents the loading of oxygen
due to competition for the same binding sites, thereby showcasing how they relate. This
shift prevents oxygen unloading in peripheral tissue, and therefore the oxygen
concentration of the tissue is much lower than normal. Thus, in the presence of carbon
monoxide, a person can experience severe tissue hypoxia while maintaining a normal
PaO2. For instance, patients with Carbon-monoxide poisoning experience headaches,
malaise, altered mental status, shortness of breath, seizures, or cherry red lips.
2. During the ambulance ride, a pulse oximeter showed 100% O2 saturation. Why
is that different from the 72% measured at the hospital?
The pulse oximeter uses a cold light source that shines a light through the fingertip,
making the tip appear red. By analyzing the light source that passes through the finger,
the device can determine the percentage of oxygen in the red blood cell. Thereby, in
cases of carbon monoxide poisoning, it shows 100% Oxygen saturation because the
device cannot distinguish between the color of carboxyhemoglobin and oxyhemoglobin.
Week 7 Case Study: Carbon Monoxide Poisoning
BIO255: Anatomy & Physiology III w/Lab
, 2
1. With respect to hemoglobin loading, please explain the relationship between the
binding of oxygen (O2) and carbon monoxide (CO) to the hemoglobin molecules.
The hemoglobin molecule has four binding sites for oxygen molecules: the iron atoms in
the four heme groups. Thus, each Hb tetramer can bind four oxygen molecules. From the
molecular weight of Hb, one can calculate that 1 g of Hb can combine with 1.39 ml of
oxygen. Meanwhile, carbon monoxide is dangerous for several reasons. When CO binds
to one of the binding sites on hemoglobin, the increased affinity of the other binding sites
for oxygen leads to a left shift of the oxygen dissociation curve. Thus, it interferes with
the unloading of oxygen in the tissues. Carbon monoxide prevents the loading of oxygen
due to competition for the same binding sites, thereby showcasing how they relate. This
shift prevents oxygen unloading in peripheral tissue, and therefore the oxygen
concentration of the tissue is much lower than normal. Thus, in the presence of carbon
monoxide, a person can experience severe tissue hypoxia while maintaining a normal
PaO2. For instance, patients with Carbon-monoxide poisoning experience headaches,
malaise, altered mental status, shortness of breath, seizures, or cherry red lips.
2. During the ambulance ride, a pulse oximeter showed 100% O2 saturation. Why
is that different from the 72% measured at the hospital?
The pulse oximeter uses a cold light source that shines a light through the fingertip,
making the tip appear red. By analyzing the light source that passes through the finger,
the device can determine the percentage of oxygen in the red blood cell. Thereby, in
cases of carbon monoxide poisoning, it shows 100% Oxygen saturation because the
device cannot distinguish between the color of carboxyhemoglobin and oxyhemoglobin.
