Scenario/Summary
Adam and his family decided to take a trip to the mountains for the weekend in late February. They had a small cabin and looked forward to a weekend away from the big city. The family had a wonderful time together on Saturday morning hiking in the woods and enjoying nature. However, Saturday afternoon a storm rolled in bringing snow and subfreezing temperatures.
Since the heater in the cabin wasn’t working well, Adam’s mother and sister decided to drive into the nearest town to spend the night. Adam and his father, not being sissies, stayed at the cabin where they started a gas heater to keep them warm.
The next morning Adam’s mother and sister returned to find both Adam and his father unconscious. An ambulance was called and they were both transported to the nearest hospital. Adam had arterial blood gases drawn with the following results:
pH 7.2
PaCO2 31.4,
PaO2 40.7 mmHg
His oxygen saturation was 72%. Adam was diagnosed with carbon monoxide poisoning.
Deliverables
Answer the following questions and save your responses in a Microsoft Word document. Provide a scholarly resource to support your answers.
With respect to hemoglobin loading, please explain the relationship between binding of oxygen (O2) and carbon monoxide (CO) to the hemoglobin molecules.
During the ambulance ride, a pulse oximeter showed 100% O2 saturation. Why is that different from the 72% measured at the hospital?
One course of treatment is a hyperbaric oxygen treatment. How does a hyperbaric chamber work?
Adams blood work shows him to be in an acidosis (normal blood pH is 7.35-7.45). Explain how this will shift the hemoglobin dissociation curve and why.
ANSWER
**1. Relationship between Oxygen (O2) and Carbon Monoxide (CO) Binding to Hemoglobin:**
Hemoglobin (Hb) is the protein in red blood cells responsible for carrying oxygen. It has a high affinity for oxygen, which means it readily binds to oxygen molecules. Carbon monoxide (CO), on the other hand, also binds to hemoglobin but with a much higher affinity than oxygen. This means that when both O2 and CO are present, CO will preferentially bind to hemoglobin over O2.
When CO binds to hemoglobin, it forms carboxyhemoglobin (COHb). The affinity of CO for hemoglobin is approximately 200 times greater than that of oxygen. As a result, CO binds to hemoglobin tightly, reducing the capacity of hemoglobin to carry oxygen. This is why carbon monoxide poisoning can be life-threatening, as it impairs the blood’s ability to transport oxygen to tissues.
**2. Difference in Oxygen Saturation Readings:**
The difference in oxygen saturation readings between the ambulance ride and the hospital is due to the method of measurement and what each reading represents:
– In the ambulance, a pulse oximeter measures oxygen saturation in the arterial blood, specifically oxyhemoglobin (HbO2). An oxygen saturation reading of 100% indicates that nearly all available hemoglobin is carrying oxygen.
– At the hospital, Adam’s blood work showed an oxygen saturation of 72%, which is calculated based on the percentage of oxyhemoglobin (HbO2) compared to the total hemoglobin, including carboxyhemoglobin (COHb). This reading reflects the presence of carboxyhemoglobin, which binds tightly to hemoglobin, reducing the amount available for oxygen binding. Therefore, the 72% reading indicates a dangerous level of COHb and a significant lack of available hemoglobin for oxygen transport.
**3. Hyperbaric Oxygen Treatment:**
Hyperbaric oxygen treatment involves placing the patient in a hyperbaric chamber, where they breathe pure oxygen at elevated pressures. This treatment serves two main purposes:
– It increases the partial pressure of oxygen in the bloodstream, which helps to displace carbon monoxide from hemoglobin. The increased pressure results in a higher oxygen concentration in the blood, making it easier for oxygen to compete with carbon monoxide for binding sites on hemoglobin. This accelerates the removal of CO from the body.
– Hyperbaric oxygen therapy also helps to increase the oxygen supply to tissues that may have been deprived of oxygen due to CO poisoning. It supports tissue recovery and repair.
**4. Acidosis and Hemoglobin Dissociation Curve:**
Acidosis is a condition characterized by a decrease in blood pH (below the normal range of 7.35-7.45), which indicates an increase in hydrogen ion (H+) concentration. When blood becomes more acidic, it causes a rightward shift in the hemoglobin dissociation curve.
This rightward shift of the dissociation curve is a result of the Bohr effect, which describes how changes in blood pH affect hemoglobin’s oxygen-binding affinity. In acidosis, hemoglobin’s affinity for oxygen decreases, meaning it binds to oxygen less tightly. As a result:
– At any given partial pressure of oxygen (PaO2), hemoglobin is less saturated with oxygen. This means that even when the PaO2 is normal, less oxygen will be bound to hemoglobin in the blood, reducing the blood’s oxygen-carrying capacity.
– Tissues will receive less oxygen, exacerbating the effects of CO poisoning, which already impairs oxygen transport.
In summary, Adam’s acidosis shifts the hemoglobin dissociation curve to the right, reducing hemoglobin’s affinity for oxygen and further compromising his oxygen-carrying capacity, making prompt treatment, such as hyperbaric oxygen therapy, essential to reverse the effects of carbon monoxide poisoning.
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