Respiratory Physiology: The Respiratory Cycle Flashcards
1
Q
Abbreviations:
Q (or Q with a dot over it)
A
Blood flow
2
Q
Abbreviations:
V=?
A
Volume of gas
3
Q
Abbreviations:
V with a dot over it (Vdot)=?
A
Airflow or volume per unit time
4
Q
Abbreviations:
F=?
A
-Fractional concentration of gas (again you specify which gas)
-No units
-Example FO2=partial pressure of oxygen
(100% Oxygen = 1.0, 21% = .21)
5
Q
Modifiers:
A=?
A
- Alveolar gas
- Conventional use: PAO2
6
Q
Modifiers:
a?
A
- Arterial gas
- Conventional use: PaO2
7
Q
Modifiers:
v?
A
venous blood
8
Q
Modifiers:
E?
A
- Expired gas
- Can indicate that the volume in question was measured during expiration
9
Q
Modifiers:
I?
A
- Inspired gas
- FIO2: Fraction of inspired oxygen
10
Q
Muscles of Inspiration
-The diaphragm-Innervated by?
A
The phrenic nerve-C3,4,5 keeps the diaphragm alive
11
Q
Muscles of Inspiration
-The diaphragm-What happens when it contracts?
A
- When the diaphragm contracts, it flattens or moves down into the abdomen
- As a result, the volume in the thorax is increased
12
Q
Muscles of inspiration
-External Intercostal Muscles-Location? Which way do they run?
A
- The External intercostal muscles are located in between the ribs
- They slope down and forward-“Hands in pockets”
13
Q
Muscles of inspiration
-External Intercostal Muscles-What happens when they contract?
A
- When the external intercostal muscles contract, they raise the ribs
- As a result, the anteroposterior diameter of the thorax is increased
- the “bucket handle motion”
14
Q
Muscles of inspiration
-Additional muscles that participate in inspiration under certain circumstances (e.g. exercise)
A
- Scalene
- Sternomastoids
- Some muscles in head and neck
15
Q
Muscles of inspiration
- Additional muscles that participate in inspiration under certain circumstances (e.g. exercise)
- Scalene-function?
A
Raise 1st and 2nd ribs
16
Q
Muscles of inspiration
- Additional muscles that participate in inspiration under certain circumstances (e.g. exercise)
- Sternomastoids-function?
A
Raise sternum
17
Q
Events in inspiration
-Step 1?
A
- Contraction of the inspiratory muscles
- Increase in thoracic volume
NOTE: Under normal conditions, the lungs and the muscles/ribs are NOT physically connected to one another
18
Q
Events in Inspiration
-Pleurae
A
- Parietal pleura (outer layer) and visceral pleura (inner layer) with fluid/surfactant in between
- Fluid effectively connects the pleurae together
19
Q
Intrapleural pressure
- Pressure generated from?
- How does this pressure compare to atmospheric pressure?
A
- Because of their anatomy and physical characteristics, the lungs and the chest wall are constantly trying to pull away from each other (even at rest)
- Intrapleural pressure is less than atmospheric pressure
20
Q
Conventions in respiratory physiology
-Talks about units and such
A
- Because the pressures we are dealing with are relatively small, they are measured in cm H2O (not mmHg)
- We also normalize atmospheric pressure to 0cm H2O (so a barometric pressure of 760 mmHg = 0 cmH2O)
- If you are in a place with a different barometric pressure, it is still 0 cmH2O
21
Q
Value of intrapleural pressure at rest?
A
-5 cmH2O
22
Q
Events in inspiration
-As the thorax volume increases, what happens to intrapleural pressure?
A
-As the thorax volume increases, the intrapleural pressure will DECREASE to about -8 cmH2O
23
Q
Events in inspiration
-Because of the coupling of the lungs and chest wall?
A
The lungs will expand as the thorax expands
24
Q
Events in inspiration
-As the lungs increase in size, what happens to alveolar pressure (pressure within the alveoli)?
A
-As the lungs increase in size, alveolar pressure DECREASES
25
How do alveolar pressure and atmospheric pressure compare at rest?
They are both 0 cmH2O
26
- What happens to alveolar pressure during a normal inspiration?
- What causes this change?
- During a normal inspiration, alveolar pressure will go decrease to -1 cmH2O
- This change is caused by the increase in alveolar size
27
Which way does air flow when alveolar pressure drops below atmospheric pressure?
Air flows INTO the lungs (inhale) when alveolar pressure is LESS than atmospheric pressure
28
The Respiratory Cycle
| -Typical graph shows changes in?
- A typical graph shows the change in volume, the alveolar pressure, the intrapleural pressure, and the airflow
- By convention, inspiratory volume is down (don't worry about why)
29
The Respiratory Cycle
- As inspiration proceeds, what happens to intrapleural pressure?
- Graphs!
As intrapleural pressure proceeds, intrapleural pressure will reach its lowest point at the end of inspiration (in a normal breath, about -8 cmH2O)
30
The Respiratory Cycle
| -As inspiration proceeds-what happens to airflow into the lungs as alveolar pressure returns back to 0 cmH2O?
Airflow into the lungs will DECREASE
31
The Respiratory Cycle
- As inspiration proceeds-Tidal volume?
- Tidal volume in a typical breath?
- The amount of air inhaled in a given breath
- Abbreviated VsubT
- In a typical breath, tidal volume = 500mL
32
Expiratory muscles
| -3 groups?
- Abdominal muscles
- Internal intercostals
- Accessory muscles of expiration
33
Expiratory muscles
| -Abdominal muscles-action?
Push into the abdomen to displace the diaphragm upwards
34
Expiratory muscles
- Internal Intercostals
- orientation relative to external intercostals?
- action?
- Oriented at (more or less) a right angle to the external intercostals
- Decrease the AP diameter of the thorax
35
Expiratory muscles
- Accessory muscles of expiration-IMPORTANT:
- In a normal breath, we don't have to use these muscles because?
- In a normal breath, we don't have to use these muscles because expiration is PASSIVE
- The lungs "want" to be smaller (like a balloon)
36
Events in expiration
- As the inspiratory muscles relax, what happens to the volume of the thorax?
- What happens to the diaphragm and rib cage?
- As the inspiratory muscles relax, the volume of the thorax decreases
- The diaphragm and rib cage return to their starting positions
37
Events in Expiration
| -As the volume decreases, what happens to intrapleural pressure?
As the volume decreases, the intrapleural pressure returns to its starting point-increases (-8)-->(-5)
38
Events in Expiration
-What happens to alveolar pressure? What is this cause by? When does it reach its peak and what is the normal value for this peak?
- Alveolar pressure INCREASES in expiration due to action of the rib cage
- Reaches a peak of about +1 cmH2O at mid-expiration
39
The respiratory cycle-Expiration
| -There is now a pressure gradient that forces?
Air out of the lungs-Volume in lungs decreases
40
As expiration proceeds and the volume of air in the lungs decreases, what happens to alveolar pressure?
- Alveolar pressure begins to go back to 0
| - Eventually, all the air that entered during inspiration is exhaled
41
Be able to draw the respiratory cycle
| -Include magnitude (Y axis)
DRAW OUT
42
Compare and contrast intrapleural and alveolar pressures
| -Intrapleural pressure at rest?
-5 cmH2O
43
What happens to intrapleual pressure with inspiration?
Intrapleural pressure becomes more negative with inspiration
44
Intrapleural pressure-when does it reach its peak negative value?
End-inspiration
45
What happens to intrapleural pressure in normal expiration?
Stays negative
46
When does intrapleural pressure reach its peak positive value?
End-expiration
47
Compare and contrast intrapleural and alveolar pressures
| -Alveolar pressure at rest?
0 cmH2O at rest
48
What happens to alveolar pressure with inspiration?
Becomes negative
49
When does alveolar pressure reach its peak negative value?
MID-inspiration
50
What happens to alveolar pressure in ANY type (normal or otherwise) of expiration?
Becomes positive
51
When does alveolar pressure reach its peak positive value?
MID-expiration
52
WHY?
- Does the intrapleural pressure not return to resting value until the end of the respiratory cycle?
- Can also approach from standpoint of alveolar pressure-Why did the alveolar pressure return to 0 at the end of each phase?
kw efkje s
53
Ventilation
- minute ventilation
- definition?
- how is it calulated?
- How much air is inhaled every minute
| - V(dot)=tidal volume x frequency
54
Alveolar ventilation
- How much air ACTUALLY gets to the alveoli
| - The first 16 generations of airway don't have any alveoli-considered anatomic dead space
55
Anatomic dead space-definition?
Volume of air that remains in the conducting airways
56
Abbreviations:
| P=?
- Partial pressure of a gas-you must specify which gas you are referring to
- Units are mmHg
- Examples-PO2, PCO2
57
Anatomic dead space
- Dead space-blood can't get oxygen there
| - Anatomic-were not designed to exchange oxygen
58
The anatomic dead space of a patient can be estimated by knowing the patients weight
-If a patient weighs 150 lbs how much dead space do they have?
150 mL of dead space
59
Minute Alveolar Ventilation
| How is it calculated?
Subtracting the anatomic dead space volume from the tidal volume
Valv=tidal volume-dead space volume
V(dot)ALV= Valv x f
60
Minute alveolar ventilation
| -example-150 lb person who breathes in 500 mL with each breath
Valv=Tidal volume-dead space volume
Valv=500-150
Valv=350
61
Alveolar ventilation=?
tidal volume - dead space volume
62
Minute ventilation=?
Tidal volume x breathing rate
63
Minute alveolar ventilation=?
VALV x breathing rate
64
Minute alveolar ventilation
- example-150 lb person who breathes in 500 mL with each breath-->Valv=350 mL of every breath gets to alveoli
- Minute alveolar ventilation-Patient is breathing 12 breaths per minute V(dot)ALV=?
350 x 12 =4200 mL/min
65
alveolar ventilation
VT-Vdeadspace
66
Minute ventilation
VT x f
67
Minute alveolar ventlation
Valv x f
