(------non nbme physio q------) - sallu004

[ArchivalUser]

If patient has pio2=90, Pao2=60, pco2=30. He was given 100% O2 for 10mins and his pao2 is 85.

Most likely diagnosis?

1. Hypoventilation

2. Shunt

3. Fibrosis

4. Pneumothorax

[ArchivalUser]

4...

In these patients, administration of 100% oxygen promotes resolution by speeding the absorption of gas from the pleural cavity into the pulmonary vasculature.

[ArchivalUser]

3.., diffusion impairement, supplemental oxygen will increase pressure gradient across the alveolar memb. My confusion here is Pio2, looks less than regular room air and A-a gradient is around 17mmhg.

[ArchivalUser]

PAO2 = PiO2 – PCO2, 90 – 30 = 60.

P(A – a)o2 difference = 60 – 60 = 0.

If A – a difference < 10 ..... hypoventilation.
> 10 ..... diffusion impairment eg..fibrosis
pulmonary shunt.
If we give 100% O2 to hypoventilation and diffusion impairment pt there is increase in pao2 but for shunt there is no increase in pao2.

If u see above patient has A - a difference < 10 and improvement in pao2 after administering 100% O2.

Hence answer is A.

This Q is from Kaplan physio lecture video. Here pco2 is 30 which is contrary to hypoventilation where it should be >40. Please somebody clarify. Thank u.