Exam 3 - Lecture 1 Flashcards by Meagan Sadler

What is the partial pressure of nitrogen after gas exchange?

Around 569mmHg

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How do we find the % of nitrogen in expired lung air?

569 divided by 760 = ~75%

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What is % of nitrogen in the atmosphere?

79-80%

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Why is nitrogen % lower in lungs?

Due to the dilution of water vapor, that’s why 75% is more accurate for expired lung air.

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What are the units for nitrogen (or any gas) concentration?

No units, just 75%.

The units cancel each other out in the division.

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Does 75% nitrogen reflect alveolar gas or fresh inspired gas?

Alveolar

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The transition between dead space and alveolar gas isn’t a hard boundary, there’s a _____. This is especially true for _____ test.

Gradual mix zone; Fowlers test

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For a fowlers test, its reading what gas?

EXPIRED gas of nitrogen with nitrogen meter

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What are the unit the capnograph in fowlers test measures?

Either mmHg or just %.

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What are the sources needed for fowlers test?

Patient, nitrogen meter, 100% O2

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How much do you tell patient to breathe in during fowlers test?

1L instead of 500mL

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The nitrogen detected during the fowlers test comes ONLY from

the lungs

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During fowlers test, on the last portion of inspired breath, is the air that ends up in ______, and it should have how much nitrogen in it?

Anatomical dead space; ZERO nitrogen

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The first portion of expiration of breath during fowlers test should have _____ nitrogen

zero

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during fowlers test, as you continue to expire more, the air from the deeper portions will begin to have ____

nitrogen

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How does fowlers test assess for anatomical deadspace?

During a fowlers test, you inspire 100% O2. Any nitrogen that comes during expiration, will had to have come from lungs, after you expire anatomical deadspace (which should have zero nitrogen).

Therefore, the amount of volume you expire before nitrogen is detected, is your anatomical deadspace.

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What’s the specific spot on graph of fowlers test we should focus on to determine amount of anatomical deadspace?

midpoint of transitional phase, should be 150mL

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What is it called when nitrogen begins to level out on graph of fowlers test?

Alveolar plateau

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What is a cheap and easy way to determine anatomical dead space?

Fowler’s test

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What is alveolar plateau dependent upon?

How deep the inspiratory breath was.

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What is the nitrogen washout test?

Hook the patient up to 100% O2 and a nitrogen meter.

Assess how many breaths it takes them to breathe out all of their nitrogen. The results can determine pathophysiology depending upon how many breaths it took.

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During nitrogen washout test, what is the percentage of nitrogen in the first breath?

80%

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What should the % of nitrogen be on the 8th breath during nitrogen washout test?

~15%

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When is the greatest reduction in nitrogen concentration during nitrogen washout test?

after the first breath

What % do they halt the nitrogen washout test?

once it reaches ~2.5%

In a healthy 20 year old patient, the nitrogen washout test should take ______

way under 7 minutes Then said a healthy person should take half the amount of time... 3.5 minutes?

A normal healthy patient should get to 2.5% by ____ breaths.

Per the "unhealthy" patient chart, how many breaths did it take them to get to 2.5%? What else is noted about the chart?

60. It's inconsistent and scattered due to air being directed into different places with each breath.

What are the 2 main reasons it takes a person with COPD longer to complete nitrogen washout test?

So much more air in their lungs already + difficult to expire = longer to dilute

What size are the breaths on flow volume loops according to Schmidt?

"Very large breaths" lol (VC)

What is the measured flow rate (units) in flow-volume loops?

L/s on the Y-axis

What is the x-axis on flow-volume loop?

lung volume

What is the flow volume loop displaying?

How fast you breathe in and out at certain lung capacities throughout the between TLC and RV

What's the max flow rate of air on the flow-volume loop?

10L/s

What part of inspiration has the fastest flow rate?

halfway point of inspiration

What part of expiration has the fastest flow rate?

faster at the beginning, then tapers off

The left side (beginning) of expiration is effort ______

dependent

The right side is effort _____. (end of expiration)

effort independent

Giving effort towards the end of expiration does or does not result in increased speed?

Does NOT

Generally speaking, the more unhealthy you are, the ____ you get air out of the lung

slower

What muscles contract and what forces relax during forceful exhalation?

Diaphragm relaxes Abdominal muscles and internal intercostal muscles contract

Where are the internal intercostal muscles per lecture, and how do they promote forceful exhalation?

In between the ribs INSIDE the ribcage, and they contract to bring ribs together and increase intrapleural pressure.

When someone has terrible COPD, they are almost entirely dependent upon __________

Intercostal muscles

What is the issue with bad COPD and being put under anesthesia?

You take away the accessory muscles that compensate for lack of elastic recoil and their exhalation times are very long. Will have to give them more time for expiration on ventilator, longer than inspiratory time.

What is the expiratory flow function curve measuring?

Using vital capacity, measures difference of lung volume between TLC and RV

On the expiratory flow function curve, What disease is considered a left shift and why?

Obstructive disease (COPD), has increased lung volume, decreased speed, and the shape is also a little curved because of the effort to push the air out

On the expiratory flow function curve, what is a right shift and why?

Restrictive disease, due to less lung volume and decreased airflow speed, but a slightly faster airflow speed than obstructive. Decreased RV,with a similar curve to normal lungs but is more rounded at top of inspiration/expiration.

On the expiratory flow function curve, what is one thing that both restrictive and obstructive disease have in common?

both have decreased air flow speed, but restrictive > obstructive

What is the RV of restrictive disease on the expiratory flow function curve?

around 1L

What is the RV of obstructive disease on the expiratory flow function curve?

almost 5L

What does restrictive disease have "more" of in the lungs?

more springs for increased ER

What is FVC?

Forced vital capacity, and almost always referred to EXPIRED air of the flow volume loop.

X-axis on the expiratory flow function curves actually goes to

Smaller the vital capacity, ________ ___ __________

worse the disease

The delta P is ____ in the lung during passive expiration

35 (alveoli pressure of +35, outside lungs 0)

As the expiration of air goes up the respiratory tree, what happens to delta p?

Gets lower and lower

Why does the Delta P get even lower as it gets to the higher respiratory zones?

due to cartilage

What's the "vulnerable point" in the respiratory tree?

Right before the cartilage begin, as this part as the lowest delta p with a lower pressure than the alveoli but the same external pressure. It's vulnerable to collapse. more detail on another slide

What is the reason there is a vulnerable spot in the respiratory tree?

If alveoli (airway) pressure is low pushing air up, but pleural pressure is high from forced expiration, this is what can cause the small airway to collapse before the cartilage.