Respiratory Case Study # 2

Respiratory Case Study # 2

A young man is rescued from a fire and brought to the emergency department (located at sea level). The patient is unconscious, but his vital signs (heart rate, blood pressure, and respiratory rate) are stable. Below are arterial blood gas data, from a sample drawn while he is breathing 100% oxygen.

Parameter / Patient’s value / Normal
PaO2 / 190 mm Hg
PaCO2 / 36 mm Hg
pH / 7.47
Sa O2 / 60%
COHb / 40%

Does Hb bind carbon monoxide?

How does CO affect the oxyhemoglobin dissociation curve?

How does CO affect the loading of O2 onto hemoglobin in the pulmonary capillaries?

How does CO affect the unloading of O2 from hemoglobin in systemic capillaries?

Does CO affect the amount of O2 dissolved in the plasma?

Why was the patient placed on 100% oxygen?

Is the patient’s PaO2 less than, equal to, or higher than expected under the circumstances (breathing 100% oxygen.) Use the alveolar oxygen equation in making your decision:

PAO2 = PI O2 - PaCO2 [ FIO2 + (1-FIO2)/RQ]

Compare the patient’s PaO2 and PAO2. Is there a problem with the diffusion of oxygen from alveoli to pulmonary capillaries?

Considering the conditions from which the patient was rescued, what is the likely explanation for his elevated A-a gradient?

Would you expect pulmonary arterioles to be dilated or constricted? Why?

How is it possible for the patient to be unconscious yet have stable vital signs?

Considering the response properties of peripheral and central chemoreceptors, why isn’t this patient exhibiting signs of labored breathing?

What is an appropriate treatment for this patient? How urgently is this treatment needed?