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Flashcards in Respiratory Deck (84)
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1
Q

What are Primary Symbols in Respiratory Physiology?

C, P, R, S, V, V̇

A
C = Concentration of O2 in the blood (ml)
P = Pressure or partial pressure
R = Respiratory exchange ratio (aka RER, RQ)
S = Saturation of hemoglobin with O2 (%)
V = Volume of gas 
V̇ = Volume of gas as a rate
2
Q

Secondary Symbols in Respiratory Physiology

A, a, B, c, D, E, I, i, L, v, TM, T

A
A = Alveolar		a = Arterial
B = Barometric	c = Capillary
D = Dead space     E = Expired		
T = Tidal                 TM = Transmural
L = Lung		       v = Venous
I = Inspired             i = Ideal
3
Q

What does CaO2 mean?

A

O2 concentration in arterial blood

4
Q

What does CEO2 mean?

A

O2 concentration in expired breath

5
Q

What does PvO2 mean?

A

Partial of O2 in alveolar gas

6
Q

What does PIO2 mean?

A

Partial of O2 in inspired gas

7
Q

What does SaO2 mean?

A

O2 saturation of Hb in arterial blood

8
Q

What is the Difference Between Ventilation and Respiration?

A

Ventilation: moving air into alveoli

Respiration: Gas exchange at the alveolar-capillary level or the tissue-cellular level

9
Q

Define Physiological unit

A

Gas exchange unit
or
Alveolar unit: Bronchioles –> alveolar ducts –> alveoli

10
Q

What Determines the Volume of the Lungs at Rest?

A

-Lung and chest wall coupled interaction –> they move as a unit!

Coupling due to:

1) Intrapleural fluid (cohesion between parietal and visceral pleura)
2) Sealed pleural cavity

11
Q

Describe Intrapleural Pressure relative to atmospheric pressure

A
  • Pressure in pleural cavity that keeps lungs expanded and prevents chest wall from over expanding
  • Intrapleural P is less than atmospheric, but lung pressures are always referred to atmospheric which is called “zero”.
  • Pressures higher than atmospheric are +
  • Pressures lower than atmospheric are -
12
Q

Why don’t lungs collapse?

A
  • Lung elastic forces favor collapse, whereas chest wall elastic forces favor expansion.
  • Antagonistic action of these forces generates negative intrapleural pressure
  • Positive Lung elastic (recoil) forces due to:
    1) collagen and elastic fibers in the interstitial matrix
    2) surface tension forces in alveoli.
  • Negative Chest wall elastic (spring out) forces due to:
    1) tendons and muscles between ribs
13
Q

Describe the Compliance of the Lung and Chest Wall with changes in Lung Volume

A
  • Compliance is amount of stretch something has (Low = stiff) (High = stretchy)
  • Lung and chest wall compliance are basically equal BUT, the compliance of the combined lung and chest wall system is LESS than that of either structure alone
14
Q

What does the functional residual capacity (FRC) point indicate?

A
  • Lung recoil = chest wall recoil

- FRC is the volume of the lung at the end of a normal expiration

15
Q

Describe collapsing forces when lung volumes are lower than FRC

A
  • This happens during forced expiration

- Expanding chest wall force is greater so the lung and chest wall want to expand.

16
Q

Describe collapsing forces when lung volumes are greater than FRC

A
  • This happens during inspiration

- Collapsing lung force is greater so the lung and chest wall want to collapse.

17
Q

What happens if the chest wall is punctured?

A
  • Traumatic Pneumothorax: Lung collapses, chest wall springs away
  • Vs a Spontaneous Pneumothorax, which is a hole in the lung (Not chest wall)
18
Q

What is Atelectasis

A

Absence of gas from all or part of a lung due to a failure of expansion.

19
Q

What is the Compliance index?

A

An index of the effort needed to expand the lungs.

20
Q

What would happen when someone has Increased compliance

A
  • More air will flow for a given change in pressure due to loss of elastic fibers in the lungs –> Emphysema + Asthma
  • No problem inflating lungs, but have extreme difficulty exhaling air since there are less collapsing force
21
Q

What would happen when someone has Decreased compliance

A
  • Decreased compliance due to scarring/fibrosis of the lungs (greater collapsing force) –> Fibrosis
  • Extra work is required to bring in a normal amount of air.
22
Q

Breathing Cycle At Rest

A
  1. With the respiratory muscles at rest, the elastic recoil of the lung and the chest wall are equal but opposite.
  2. Intrapleural pressure is slightly negative
  3. Pressure along the tracheobronchial tree and in the alveoli is equal to atmospheric pressure –> no air flow
23
Q

Breathing Cycle During Inspiration

A
  1. The diaphragm and other respiratory muscles contract.
  2. Decompressing the contents of the thorax, causing intrapleural pressure and alveolar pressures to fall –> little more negative
  3. Air flows into the lungs down the pressure gradient from the mouth to the alveoli.
  4. The lungs and chest expand in volume.
24
Q

Breathing Cycle End Inspiration

A
  1. An equilibrium exists after inspiration ends and before expiration begins.
  2. Alveolar pressure = zero –> no air flow
  3. Intraplural pressure is super negative
  4. Lungs and chest are fully expanded.
25
Q

Breathing Cycle During Expiration

A
  1. The respiratory muscles relax –> increase in intrapleural pressure (less negative)
  2. The rise in intrapleural pressure causes the alveolar pressure to rise by the same amount and become positive (remember that it was zero during the end of inspiration)
  3. Pressure gradient forces air out of lungs from alveoli to the mouth.
  4. Lung and chest volume decrease as air flows out, until a new equilibrium is reached at the functional residual capacity (FRC).
26
Q

Breathing Cycle End Expiration

A
  • The pleural cavity and the alveoli return to the pressure relationship they had at the start of inspiration:
  • Intrapleural pressure is -5 and alveolar pressure is 0.
27
Q

Breathing Cycle Summary

A

-Intrapleural pressure goes from -5 cm H2O at rest to -8 cm H2O at maximum inspiration. All pressures are relative to atmospheric pressure.

Alveolar pressure (airway pressure) goes negative during inspiration (pulling air in) and positive during expiration (pushing air out).

28
Q

Define Surface tension

A
  • Cohesive forces between liquid molecules.

- Surface tension –> is high at air-water interfaces

29
Q

Surface tension in alveoli would be high if it weren’t for _____

A

-Surfactant, which prevents the alveoli from collapsing in on themselves during expiration.

30
Q

Describe Surface Tension and Alveoli and the law of LaPlace

A

-Surface tension generates a pressure that tends to collapse the sphere.

  • Pressure generated is given by the law of LaPlace:
  • Pressure is proportional to surface Tension and inversely proportional to radius): P = 2T/r
31
Q

What does surfactant do?

A

1) It lowers surface tension of alveoli by 15
2) It diminishes the pressure required to inflate the alveoli
- During expiration the alveoli get smaller and surfactant molecules become more concentrated.
- Surfactant prevents the alveoli from collapsing after a full, forceful expiration (atelectasis) –> allows a residual volume of air to remain in the lungs.
- Since the alveoli never fully collapse there is less surface tension to overcome as they are inflated during inspiration.

32
Q

Describe Airway resistance

A

-The impedance of air flow through the tracheal bronchial tree –> Result of friction of gas molecules

  • Smooth muscle in walls of conducting zone –> Changes in diameter = changes in resistance
    1) B2 receptors = dilate
    2) M receptors = constrict
33
Q

What makes up the conducting zone?

A
  • Brings air to respiratory zone
  • Trachea
  • Bronchi
  • Bronchioles
34
Q

What makes up the respiratory zone?

A
  • Participates in gas exchange
  • Respiratory Bronchioles
  • Alveolar ducts
  • Alveolar sacs
35
Q

Where is most of the airway resistance happening?

A
  • Medium to small-sized bronchi (> 2 mm inside diameter)- account for up to 80% of resistance!
  • Less than 20 % due to airways < 2 mm in dia.

-Due to large # of small airways –> Increases cross sectional area!

  • Early detection of small airway disease hard; resistance changes in sm. airways overshadowed by larger airways.
  • During inspiration, flow is turbulent in the trachea = eddies and vortices; requires a higher driving pressure
36
Q

Resistance in the lungs depends on ____

A

-The number of parallel pathways present

37
Q

What is the relationship between resistance and volume in lung

A

-Resistance decreases as lung volume increases

38
Q

What are the four Primary Lung Volumes

A

1) Inspiratory reserve volume (IRV): volume of air inhaled after normal inspiration.
2) Tidal volume (TV): volume of air inhaled or exhaled during normal breathing at rest
3) Expiratory reserve volume (ERV): volume exhaled after normal expiration.
4) Residual volume (RV): lung volume remaining after maximal expiration (Cant get this out)

39
Q

What are the 5 Primary Lung Capacities

A

-Made of two or more Primary Lung Volumes
1) Functional residual capacity FRC = ERV + RV
Volume of air in the lungs at resting end-expiratory level
2) Vital capacity: IRV + VT + ERV. Volume of air that can be exhaled slowly and completely after maximal inspiration.
3) Inspiratory capacity: IRV + VT. Volume of air that can be inhaled from the resting end-expiratory level.
4) Expiratory capacity: ERV + VT. Volume of air that can be exhaled from the resting end-inspiratory level.
5) Total lung capacity: IRV + VT + ERV + RV
Volume of air in the lungs at maximal inspiration.

40
Q

What is Forced Vital Capacity (FVC)?

A

-The total amount of air exhaled during the Forced Expiratory Volume test –> generally smaller than VC

41
Q

What is Forced Expiratory Volume (FEV)?

A
  • How much air a person can exhale during a forced breath. Usually 1 second (FEV1)
  • In normal lung, FEV1 is ≈ 80 % of FVC.
42
Q

FEV1 is a function of what?

A
  • lung size
  • elasticity of lungs
  • airway diameter (airway resistance)
  • FEV1 often expressed a ratio with FVC:
  • corrects for body size
  • termed FEV1/FVC %, or FEV1%
  • FEV1/FVC% can be altered by disease
43
Q

During a forced expiration, intrapleural pressure becomes _____ and the airways are _________

A

-Positive and the airways are compressed

44
Q

What happens when airway diameter is obstructed (Asthma/emphysema/COPD)?

A
  • The reduction in FEV1 is greater than the reduction in FVC.
  • FEV1 is ≈ 42 % of FVC
  • CANT get the air out
45
Q

What happens when airway diameter is restricted (Pulmonary fibrosis)?

A
  • The reduction in FVC is greater than the reduction in FEV1 –> FEV1/FVC is increased.
  • FEV1 is ≈ 90 % of FVC
  • Can get air out REALLY easily
46
Q

What are some examples of what could happen to the Airways in Obstructive Diseases?

A

1) Excessive secretions
2) Thickening of airway wall
3) Destruction of lung connective tissue that surrounds the airways of the lungs (parenchyma)

47
Q

Describe Radial Traction Forces

A
  • Obstructive Diseases cause a loss of Radial Traction Forces
  • The connective tissue that surrounds the airways of the lungs forms a sort of “scaffold” around the airways, keeping them open with a force known as “radial traction”. As inspiration takes place, the traction increases as the fibers that make the parenchyma are stretched

-In Emphysema, there is dynamic airway collapse with forced expiration because the external pressure applied by the muscles of expiration exceeds the internal pressure of the airways (Radial Traction Forces)

48
Q

Describe open lip breathing

A
  • Breathing with mouth open causes premature airway collapse… the pressure outside is the same as the pressure inside, and the parts of the lung that have lower pressure kind of collapse, cuz they lost that “scaffolding” keeping them open.
  • Airways collapse prematurely due to lack of radial traction support. So breathing with lips open, increases airway resistance during forced expiration
49
Q

Describe pursed lips breathing

A

-Making your lips small minimizes premature airway collapse… you build up the pressure in the lungs, so that they don’t implode (pressure in lung is greater than pressure outside so air leaves like is normally should).

  • Increases expiratory pressure (inhibits airway collapse) and removes some of the trapped air
  • Higher airway pressure mini-mizes premature airway collapse (“pinching the garden hose”); flow is thereby improved.
50
Q

Define Forced Expiratory Flow Rate (FEF)

A
  • Average rate of air flow measured in the middle portion (25% - 75%) of total FVC.
  • Correlates well with FEV1 in disease states
  • Better at detecting some pathologies when compared to FEV1
51
Q

What happens to FEF25-75% when diameter is restricted (Pulmonary fibrosis)?

A

??? DONT GET IT
High expiratory flow rates occur despite low lung volumes due to increased elastic recoil pressure and increased radial traction forces on the conducting airways because of the fibrotic pulmonary interstitium.

52
Q

What are the three types of dead spaces?

A
  • anatomic
  • alveolar
  • physiological
53
Q

Describe Anatomic Dead Space

A

Portion of the breath that remains in the conducting airways

  • Estimate: 1 ml VD per lb body weight (can be measured)
  • About 150 mL
54
Q

What is the function of Anatomic Dead Spaces

A
  • Humidification of air stream
  • Removal of dust (alveoli don’t have cilia)
  • Decreases velocity of airflow
  • Does NOT participate in gas exchange
55
Q

Describe Alveolar Dead Space

A
  • Portion of the breath entering alveoli that are not perfused
  • Pulmonary capillaries are not all open at a given time, thus some alveoli are ventilated but not perfused
  • These alveoli don’t participate in gas exchange
  • “Functional” dead space
56
Q

Describe Physiological Dead Space

A

-Total volume of the lungs that does not participate in gas exchange
PDS = anatomic dead space + alveolar dead space

57
Q

What is Tidal volume (VT)?

A

-Volume of air moving in + out of lungs with each breath; at rest, ≈ 500 ml (8-10 ml/kg)

VT = VD + VA

58
Q

What is Alveolar ventilation volume (VA)?

A

-Amount of VT available for gas exchange

VA = VT - VD = 500 - 150 = 350 ml

59
Q

What is Minute Ventilation?

A

Total volume moved into and out of lung per minute:

V̇T = VT x (breaths/min)

V̇T includes ventilation of dead space (stuff going into the trachea and stuff)

60
Q

What is Functional (alveolar) minute ventilation?

A

V̇A = VA x (breaths/min)

Provides a better estimate of gas exchange

61
Q

What are the Normal Values for PO2 and PCO2

A
  • Ambient air: PO2 = 160 mmHg; PCO2 = 0
  • Trachea air: PO2 = 150 mmHg; PCO2 = 0
  • Alveolar air: PAO2 = 100 mmHg (Constant O2 uptake from capillaries); PACO2 = 40 mmHG (Has CO2 from previous breath)
  • Pulmonary Artery –> Mixed venous blood: PVO2 = 40 mmHG PCO2 = 46 mmHG (Relatively high because muscles produce CO2)
  • Pulmonary vein –> Systemic arterial blood: PaO2 = 100 mmHG PaCO2 = 46 mmHG

-Normally Alveolar and systemic arterial PO2 is the same

62
Q

How is PACO2 and V̇A related?

A

PACO2 = 1/ V̇A, if metabolic rate (VCO2) is constant

63
Q

PACO2 (or PaCO2) is thus a good measure of ______.

A

-Ventilation

  • If PaCO2 is high, then patient is likely hypoventilating
  • If PaCO2 is low, then patient is likely hyperventilating
64
Q

How do we sample Alveolar air?

A

Alveolar air can’t be sampled directly. But alveolar air normally equilibrates with pulmonary capillary blood which becomes systemic arterial blood. Thus, PaCO2 = PACO2.

65
Q

Define Hypoventilation

A
  • Ventilation less than metabolic needs
  • decreased PaO2
  • increased PaCO2
  • decreased pHa (Acidic)
66
Q

Define Hyperventilation

A
  • Ventilation in excess of metabolic needs
  • increased PaO2
  • decreased PaCO2
  • increased pHa (Basic)
67
Q

Define Hypoxemia

A
  • Below normal oxygen tension of the blood

- defined as a decrease in arterial PO2

68
Q

Define Hypoxia

A
  • The state of tissue oxygen deficiency

- defined as a decrease in O2delivery to, or utilization by, the tissues.

69
Q

Define Hypercapnia

A
  • too much CO2 in the blood
  • Normally triggers a reflex which increases breathing
  • A failure of this reflex can be fatal
70
Q

Define Hypopnea

A

-Recognizable transient reduction (but not complete cessation) of breathing for 10 seconds or longer

71
Q

Define Hyperpnea

A

-Increased depth of breathing when required to meet metabolic demand of body tissues

72
Q

Describe Lung Ventilation at the apex of the lung

A

Apex:

  • Alveoli have larger volume due to intrapleural pressure that is more negative w/ respect to atmosphere,
  • Alveoli are expanded so compliance is reduced; alveoli can’t expand as well as those in the base.
  • Alveoli at the beginning of inspiration are almost completely inflated, have low compliance.
  • Very little air flows into these alveoli
73
Q

Describe Lung Ventilation at the base of the lung

A

-Lower zones of the lung ventilate better than the upper zones.

Base:

  • alveoli have smaller volume as intrapleural pressure is less negative w/ respect to atmosphere,
  • however, compliance is greater; these alveoli are ventilated better than those in the apex.
  • Alveoli at the beginning of inspiration are small, but are very compliant.
  • Inflation leads to a large change in size and volume.
74
Q

Where is Lung Perfusion best?

A

Lower zones of the lung are perfused better than the upper zones.

75
Q

What does V̇ represent?

A

Ventilation reaching alveoli ( 4.0 L/min)

76
Q

What does Q̇ represent?

A

Perfusion = Blood flow through lung [cardiac output] (5.0 L/min)

77
Q

What does the Ventilation-Perfusion Ratio (V̇/Q̇) represent?

A
  • Ratio of ventilation to blood flow.
  • Average lung V̇/Q̇ = 0.8
  • Used to describe the entire lung: V̇/Q̇ = V̇A/Q̇T
  • V̇/Q̇ ratio depends on location in upright lung.
  • When ventilation exceeds perfusion, V̇/Q̇ >1
  • When perfusion exceeds ventilation, V̇/Q̇ < 1
78
Q

Describe the PaO2 and PaCO2 if V̇/Q̇ is normal

A

PaO2 =100 mmHg

PaCO2 = 40 mmHg

79
Q

Describe the V̇/Q̇ throughout the lung

A
  • Both ventilation and perfusion de-crease from base to apex.
  • Perfusion, how-ever, changes much more rapidly.
  • There is more perfusion at the BASE of the lung because there is more blood there (gets pulled down by gravity) so Q̇ is increased, making the V̇/Q̇ ratio smaller
  • V̇/Q̇ ratio goes from < 1 to > 3 (base to apex)
80
Q

Describe Variation in PaO2 and PaCO2 in the 3 Lung Zones

A
  • Zone 1: PaO2 high and PaCO2 low
  • Zone 2: PaO2 normal and PaCO2 normal
  • Zone 3: PaO2 low and PaCO2 high
81
Q

Describe V̇/Q̇ in the Dead space, High V̇/Q̇, Low V̇/Q̇, and Shunt

A
  • Dead space: V̇/Q̇ = ∞ Ventilation of lung regions that are not perfused
  • High V̇/Q̇: Ventilation is higher than perfusion
  • Low V̇/Q̇: Perfusion is higher than ventilation
  • Shunt: V̇/Q̇ = 0 Perfusion of lung regions that are not ventilated
82
Q

Describe PO2 and CO2 in the Dead space and Shunt

A
  • Dead space: Perfusion of lung regions that are not ventilated. Same pulmonary capillary concentration as mixed venous blood; PaO2= 40 mmHg, PaCO2 = 46 mmHg
  • Shunt: Ventilation of lung regions that are not perfused; “wasted “ ventilation. No gas exchange is possible in dead space. Same concentration as trachea air: PO2 = 150 mmHg; PCO2 = 0
83
Q

Describe the Oxyhemoglobin Dissociation Curve

A

-Affinity for O2 increases as each subsequent O2 molecule is added to Hb.

  • P50 = PO2 at which Hb is 50% saturated
  • An increase in P50 reflects a decrease in affinity of Hb for O2

-Increased PCO2, [H+] and temperature shift the curve to the right, affinity of Hb for O2 is decreased –> Promotes unloading of O2 at tissues

84
Q

IMPORTANT!!!!

What are the receptors in the different parts of the body (cardiac and pulmonary)?

A
B1 = Increases Heart rate
B2 = Lungs, Dilates arterioles (SNS)
Alpha = Vasoconstriction of skin stuff