Mechanics of Breathing, Pressures & Work Flashcards
1
Q
FIO2
A
fraction of inspired oxygen
2
Q
FRC
A
Functional Residual Capacity
3
Q
Patm
A
atmospheric pressure
4
Q
Ptp
A
transmural pulmonary pressure
5
Q
Ppl
A
intrapleural pressure
6
Q
Palv
A
intrapulmonary/intra-alveolar pressure
7
Q
PTM
A
pressure at the mouth
8
Q
RAW
A
airway resistance
9
Q
RR
A
respiratory rate
10
Q
RV
A
residual volume
11
Q
TLC
A
Total Lung Capacity
12
Q
Respiratory system slide
A
complete
13
Q
Tidal Volume definition and is at rest
A
volume of each breath
500mL at rest
14
Q
Dalton’s Law
A
when two or more gases which do not chemically react are present in the same container (lungs) the total pressure is the sum of the partial pressure of each gas
15
Q
Dalton’s Law problem
A
complete
16
Q
Boyle’s Law
A
pressure exerted by gas (CO2) in a closed container (lungs) is inversely proportional to the volume of gas in the container
occurs at a constant temperature
P is inversely proportional to V
17
Q
Charles’s Law
A
V is proportional to T
18
Q
Henry’s Law
A
Applies to gases dissolved in liquids
The number of molecules of a gas dissolving in the liquid is proportional to the partial pressure at the surface of the gas = solubility
19
Q
Inspiration:
- intercostal muscles —– and —– the ribs
- diaphragm moves —-
- Scalene muscles inserted into ribs —- and —–, ——— the upper ribs and ——- the sternum ——- in —— action, which —— the anterior-posterior diameter of the thoracic cavity
- sloping lower ribs rise and move out = ———- action and increases the ——— diameter of the chest wall
A
- elevate and evert
- downward
- 1 & 2, raising, pushes, forward, pump, increases
- bucket handle, transverse
20
Q
What percentage increase in volume when the diaphragm contracts?
A
75%
21
Q
At the end of inspiration, pressures are equal.
True or False?
A
True
22
Q
Expiration occurs due to
A
elastic recoil of the lungs and the chest wall
23
Q
Forced contraction (eg: ——-) requires
A
- coughing/sneezing
- contraction of the abdominal walls, which push the diaphragm upward
24
Q
During forced expiration, intrapleural pressures may rise to
A
+8kPa
60mmHg
25
Intrapleural pressure equilibrates with the atmosphere.
True or False?
False
26
Why does intrapleural pressure not equilibrate with the atmosphere?
As the pleural space is closed and fluid filled, it is slightly sub-atmospheric due to the recoil of the chest and lungs away from each other - stops the lungs from collapsing.
27
Ptp: Transmural Pulmonary Pressure is
The distending pressure on the pleural space, which is transmitted to the alveoli to increase their volume, lower the pressure and generate airflow inwards.
28
Under physiological conditions (quiet breathing):
Ptp: Transmural Pulmonary Pressure is always positive or negative?
Positive
29
Under physiological conditions (quiet breathing):
Ppl: Intrapleural Pressure is always positive or negative?
Negative
30
Under physiological conditions (quiet breathing):
Palv: intrapulmonary/alveolar pressure is always positive/negative?
Moves from slightly negative to slightly positive as we breathe, it is always higher than the intrapleural pressure because of the recoil of the lungs; it is 0 at the end of inspiration and expiration, so there is no airflow
31
For a given lung volume, the Ptp; the transmural pulmonary pressure is less than the elastic recoil pressure of the lung.
equal and opposite to the elastic recoil pressure of the lung.
32
What "sucks the lungs out and sucks the lungs back in"?
transmural pulmonary pressure
Ptp
ensures the lungs don't collapse
33
During inspiration, atmospheric pressure in relation to alveolar pressure
greater
hence air flows in
34
At the end of expiration, atmospheric pressure in relation to alveolar pressure
equal, FRC, no air flow, outward and inward recoil of lungs are equal
35
FRC: Functional Residual Capacity
- volume of air left in the lungs at the end of a normal breath
- at FRC respiratory muscles are relaxed and the lungs and the chest wall recoil in opposite directions and inward and outward recoil are exactly balanced
36
Volume of FRC is determined by the
elastic properties of the lungs and the chest wall
37
Pulmonary Fibrosis affecting FRC
- lungs are stiff and small
- increase in elastic recoil
- decrease in FRC
38
Emphysema affecting FRC
- loss of alveolar tissue, break down of alveolar sacs
- decrease in elastic recoil
- increase in FRC
39
Impedance
Frictional Airway Resistance and Elastic Resistance to the stretching of the lungs and chest wall
40
inspiratory muscles contract to overcome the ------ offered by the lungs and chest wall.
impedance
41
Lung compliance refers to
the ability of the lungs to stretch and recoil during ventilation
42
CL =
change in lung volume/unit change in distending pressure
43
The distending pressure is
the pressure difference across the lung = alveolar-intrapleural pressure
44
Static pressure-Volume loop
45
A dynamic pressure volume loop is obtained from
continuous measurements of intrapleural pressure and volume during a normal breathing cycle
46
How can we find dynamic compliance from a dynamic pressure-volume loop?
At the end of inspiration airflow is 0
At the end of expiration alveolar pressure is 0
The slope of the line joining these points is the dynamic compliance
47
In lung diseases (stiff lungs) dynamic compliance is similar to static compliance.
True or False?
False
- in healthy lungs are similar
- different in stiff lungs
48
In lung diseases (stiff lungs) dynamic compliance is similar to static compliance.
True or False?
False
- in healthy lungs are similar
- different in stiff lungs
49
What is hysteresis?
- frictional resistance changes, hence compliance curves are different for inspiration and expiration.
50
Is the lung more or less compliant at higher volumes?
Less compliant
51
altered lung compliance in lung disease
52
altered lung compliance in lung disease
insert
53
altered lung compliance in disease
enter
54
Laminar and Turbulent Flow
during quiet breathing there is laminar air flow in airways
gas particles move parallel to the walls of bronchi
center layers move faster than outer ones creating a cone shaped front
turbulent flow occurs at higher linear velocities in wide airways and near branch points
Turbulent flow occurs in the trachea during exercise
55
laminar and turbulent airflow diagram
56
RAW: Airway Resistance
- originates from friction between air and mucosa
- affects ventilation and has to be overcome along with elastic recoil and inflate the lung
- pressure difference between the alveoli and mouth divided by the flow rate
- inversely proportional to the 4th power of the radius
- inversely proportional to the viscosity of fluid
57
How can RAW be indirectly assessed?
From Forced Expiratory Measures (FEV1,FVC, FEV1/FVC)
58
airflow equation
(mouth-alveolar pressure)/RAW
59
Halving radius of airway increases laminar flow (airway resistance) by
16x
60
Which areas offer the most resistance during respiration?
Nose, pharynx and trachea
61
Mouth breathing (eg: during exercise) increases or decreases resistance?
Decreases
62
Disease that affects peripheral, smaller airways effect on RAW?
Increases airway resistance
63
Tone of bronchial smooth muscle and epithelium as a factor affecting laminar flow
parasympathetic nerve supply affects bronchomotor tone (Ach and M3 receptors)
Beta adrenergic receptors activated, cause relaxation (broncho)
64
mmHg is the millimeters of mercury and is used for
blood pressure
65
SI unit of pressure is, which is equal to
1 pascal = 1Newton per m^2
66
cmH2O used for
Intrapleural Pressure
Central Venous Pressure
67
Inspiration and Expiration are active processes.
True or False?
False
Expiration is a passive process
68
inspiratory muscles diagram
69
Q =
flow rate =
Q = (piPr^4)/8nl
flow rate = (pi*pressure*radius^4)/ (8*fluid viscosity*length of tubing)
70
Nitric Oxide causes bronchodilation or bronchoconstriction?
Bronchodilation
71
Resting bronchomotor tone during bronchoconstriction:
- radius
- resistance
- airflow
- radius decreases
- resistance increases
- airflow decreases
72
Resting bronchomotor tone during bronchodilation:
- radius
- resistance
- airflow
- increases
- decreases
- increases
73
Acute Asthma affecting RAW:
- bronchonstriction
- mucosal oedema
- mucus hypersecretion
- mucus pluggin
74
COPD affecting RAW:
- bronchoconstriction
- chronic mucosal hypertrophy
75
Surface Tension in lungs are caused by
explain
name
air-fluid interface in alveoli
cohesive forces between molecules at the surface of an alveolus creates a tension that causes the alveolus to shrink
Alveoli and small airways are inherently unstable and can collapse during expiration = atelectasis
76
Surface tension of alveolus changes with (2)
age
disease
77
Pulmonary Surfactant is
a mixture of phospholipids (phosphatidylcholine and proteins)
78
Where is pulmonary surfactant found?
Floats on the surface of alveolar fluid
79
Pulmonary surfactant are produced by
Type 2 pneumocytes
80
How does pulmonary surfactant reduce surface tension?
Hydrophilic and Hydrophobic ends repel each other and interfere with liquid molecule attraction, which lowers surface tension.
81
Why is pulmonary surfactant important? (5)
- increases lung compliance by reducing surface forces
- promotes alveolar stability
- prevents alveolar collapse as small alveoli do not get smaller and large alveoli don't get bigger
- reduces surface tension which reduces hydrostatic pressure in tissue outside capillaries and hence keeps lungs dry
- important defense against infection
82
How does pulmonary surfactant help keep the lungs dry?
- surface tension will suck fluid from the capillaries into the alveoli
- reduction of the surface tension reduces the hydrostatic pressure in tissue outside capillaries and keeps the lungs dry
83
Lack of surfactant in premature babies (<28 weeks) causes
neonatal respiratory distress syndrome
84
lung volume and capacity
