Hypoxia Shunts and Ventilation Perfusion Mismatch

Discussion of 6 possible causes of hypoxemia, including hypoventilation, diffusion impairments, anatomic shunts, and ventilation-perfusion mismatch.

[@Martina260]

I am so glad to find this site. After I graduated from respiratory I am RRT now, I wish I used this tutorial instead of listening to my teachers and therapists in clinicals. I t is all about the approach... THANK YOU

[@jasonrolfe4009]

You said the FiO2 decreases at altitude, which is incorrect. Possibly what you meant was the partial pressure of oxygen decrease with a decrease in atmospheric pressure. Such as the barometric pressure at sea level is 760mmHg with an FiO2 of 21%, however at the top of Mt. Everest the barometric pressure is about 253mmHg with an FiO2 of 21%. Therefore, you PaO2 would go down because the inspired oxygen pressure goes down not the inspired fraction. That being said, I do like the videos, keep up the good work.

[@HealthEdSolutions]

Thanks for your feedback. We will ask Dr. Wolf and see what he says!

[@Museangel87]

Thank you so much. This video helped me reinforce the hypoxia information I have learned in my pathophysiology course. As a nursing student, I am a visual learner and I am looking forward to watching your other videos. Thank you!

[@Ldemmers]

Amazing!! My Critical Care instructor should use your videos!!

[@madmacabre]

going to replay these videos while Im sleeping in hopes the information will soak into my brain! RT student

[@hylgh]

I wish more people did that in comments instead of just commenting silly stuff with nothing to back it up though!

[@marcoramos2377]

only had to draw it up once with your lecture and its completely brain downloaded! thanks dude!

[@HealthEdSolutions]

Thanks Marco!

[@cooldesi30]

Andrew, I am a M2 at a med school in NY. Your video was very helpful and really made things simple. Thanks and please keep up the great work.

[@lithops7370]

I love all the videos I have watched thus far! You are amazing at being and educator. Your nurse practitioners are very lucky to have you. Thank you for making your videos accessible to everybody!

[@HealthEdSolutions]

Thanks so much for the support!

[@annmariemorgan8518]

This is a very good video, regarding Hypoxia. Unfortunately, in my case I think all the above reasons that he explained that cause Hypoxia, I have experienced symptoms of them all

[@raineywed6896]

This was very helpful in explaining V/Q mismatch. Thanks

[@Spartanchic313]

AWESOME! please keep them coming...on m way to check out your other videos. love the different color notes by the way...helps to organize info!

[@jatheon4316]

The phrase he used was "the amount of oxygen in the air is much lower", which is true. The percentage of O2 in a given breath remains the same, but the amount is reduced - because of decreased air density. Side note: This decreased molecular density at altitude also reduces lift in airplanes - making it harder for them to stay airborne. Happy studying!

[@cynthiahickson9594]

Excellent..loved the simplicity.

[@HealthEdSolutions]

Thanks Cynthia for the kind words! Glad you enjoyed it!

[@hylgh]

These are great! Thanks Andrew!

[@SABERKhann]

You chose a good topic that often cause confusion especially in board but i found it bit bookish worded rather then made it Easy for Students.Stil thumbs up & make'em short as attention span in dry topics is limited. under 10 min is fair

[@Natsac21]

Keep up the good work!

[@aselanissanka3355]

thanks a lot.

[@stefanosdedalos]

Dear Mr. Wolf, I'm a sport science student from Italy. I found your video very useful for preparing my physiology exam and very clear. I have a question: you said that in altitude FiO2 decreases from the 21% at the sea level (point 1). I've studied that in altitude the pressure of the entire air decreases, but the fraction of each gas remains the same. Am I wrong? Thank you.

[@HealthEdSolutions]

Thank you for the feedback! Glad you found it helpful!

[@JohnMaicoPiezasSimm]

this is so informative. I LOVE IT

[@yasmeenkayy6242]

Thank you this was sooo much easier to understand :)

[@HealthEdSolutions]

Thanks Yasmeen! Glad it was helpful!

[@xavisas2041]

amazing

[@Weeefh13]

ASD and VSD cause the blood to move from left side of the heart to right side of the heart due to high pressure on left side.they can cause the blood to move from right to left but it takes time.(eisenmegner syndrome)

[@hamzaatassi1185]

Mr Andrew, How can asthma cause V/Q mismatch ? According to what I know, asthma causes low ventilation. but the O2 that gets into the alveoli is perfused. Is that correct ?

[@jihadmsr]

A 70s man Dx with lung fibrosis is exercising at 1.500ft altitude from sea level. He suffers from hypoxia. What is the most likely cause of his hypoxia? A) Decreased pulmonary diffusion B) V/Q mismatch C) Left-to-right shunt D) Right-to-left shunt I chose A ... is this right?

[@krmarine]

You said that another name for physiologic shunt is VQ mismatch. I though these were different because with a shunt, 100% O2 does not improve the SaO2, but with a VQ mismatch the SaO2 does improve with 100% O2. This is really confusing me. Please help me.

[@melissaresendes2101]

Where would a Pulmonary Embolism fit into this?

[@HealthEdSolutions]

Thanks for the question Melissa. We will ask Dr. Wolf and see what he says!

[@paulhill6233]

What about arteriosclerosis, smoking (CO binds heamoglobin irreversibly), noradrenalin in high concentrations constricts both arteries AND veins, beta blockers lower blood pressure to reduce risk of stroke but reduce oxygen perfusion. CO2 detectors on blood vessels signal the heart to increase output in response to arteriosclerosis thus restoring normal perfusion.

[@paulhill6233]

Didn't mention the most common cause of localized hypoxia, vasocontriction of blood vessels to GI tack, and associated organs, plus kidneys with persistent 'fight or flight' stress. Adrenalin>PGF2>vasoconstriction>hypoxia>activation of HIF's>CANCER.

[@fatboy117]

Hi Dr. Wolf. I really like this videos, it's well explained. But just wondering which of the examples is a more of a Shunt vs Dead Space? Is V/Q mismatches a Dead space ? why? I know the ASD example is a obvious Shunt. but can an Embolism be a shunt as well? Since there is no perfusion .. My boards is coming up this month really need to know the difference.. They all look like shunts to me. =). thanks

[@HealthEdSolutions]

Thanks for the question. We've passed it along to the Health Ed Solutions medical review board.

[@arthurjoseph5666]

According to a different video I watched, and I'm not sure which is correct, the FiO2 is relatively constant when going up into high altitude but the total air pressure is lower giving you a decreased amount of O2. Is that correct or no?

[@HealthEdSolutions]

Thanks for the question. We will ask Dr. Wolf and see what he says!

[@carledin9097]

Thanks for the explanation! One thought popped into my head, though. Should the V/Q-mismatch really be considered to be a cause of hypoxia, in itself? Isn't it just a combination of other causes, such as thickening of the membrane or decreased blood flow?

[@HealthEdSolutions]

Thanks for the question. We will ask Dr. Wolf and see what he says!

[@silvaanimelover8924]

can i have someone who can answer my questions?

[@megangeorge2590]

Andrew, What happends in a hemopneumothorax?

[@HealthEdSolutions]

Thanks for the question. We will ask Dr. Wolf and see what he says!

[@raquelborn]

2:09 is wrong. % of Oxygen doesn't decrease at higher altitudes, the barometric pressure does. "the percentage of oxygen in inspired air is constant at different altitudes, the fall in atmospheric pressure at higher altitude decreases the partial pressure of inspired oxygen and hence the driving pressure for gas exchange in the lungs." (Peacock, 1998, BMJ, "Oxygen at high altitude").

[@jojochannel2557]

By which mechanism does pneumonia cause hypoxia ?

[@HealthEdSolutions]

Thanks for the question Jojo. We will ask Dr. Wolf and see what he says!

[@SrmthfgRockLee]

stargate atlantis mckay hypoxia... rofled my ass off there

[@jasszymiin]

Aren't you speaking of HYPOXEMIA**