works of breathing ( main lec) Flashcards
(31 cards)
Mechanics Of Respiration:
Inspiration occurs when the alveolar pressure — atmospheric pressure, and may be due to:
- lowering alveolar pressure below atmospheric pressure → — pressure respiration
- raising atmospheric pressure above alveolar → — pressure respiration
Expiration occurs when the alveolar pressure — atmospheric pressure
<
-ve
+ve
>
Elastic Recoil of the Lungs:
-The tendency of elastic lung tissue to recoil from the chest wall results in a —pressure.
-At FVC, the mean intrapleural pressure ~
— cmH20 sub-atmospheric
-The intrapleural pressure is normally estimated by an — balloon catheter
-This is more accurate in measuring changes rather than absolute pressure, due to interference from the — of the heart
- sub-atmospheric intrapleural
- 4-5
- osophegeal balloon
- weight
INTRAPULMONARY PRESSURE, (INTRA-ALVEOLAR PRESSURE):
In quite breathing =
– atmospheric pressure i.e. — mm Hg.
During inspiration: — mm Hg.
During expiration: – mm Hg.
Factors affecting : intrapulmonary pressure.
- valsalva manoeuvre (— mm Hg)
Muller’s manoeuvre (— mm Hg)
0
760
759
761
+100
-80
forces of respiration :
— muscles provide the force necessary to overcome,
a. — of the lungs and chest wall
b. —
i. Caused by — of lung tissue and thoracic cage → — resistance
ii. To air flow in the conducting airways → — resistance
Resistance To Breathing
1. Elastic Resistance ~ — %
2. Non-elastic resistance ~ — %
i. Airflow ~ — %
ii. Viscous ~ — %
inspiratory
elastic recoil
frictional resistance
deformation
tissue
airway
65
35
80
20
pressure volume loop :
1- Triangle APAE
Represents the amount of — work to overcome the — [elastic forces] of the chest
2- Area ACBPA represents amount of — to overcome
— during —
3- Triangle APAD represents amount of — to overcome – during —
4- The insp area [area w/in the — ] represents total — due to —
mechanical work
complaince
work
Raw
inspiration
work
Raw
expiration
hyseresis
total WOB
Raw
check graph its easier
compliance diagram of lungs:
Definition: The ability of the lungs to – is expressed using a measure known as the — .
Lung compliance is the — change per unit — change.
It is represented as
C = —
The Pressure-Volume Loop:
Since compliance is determined by ΔV/ΔP, the P-V loop provides useful information on the — of a a patients compliance.
There are 2 different curves according to different phases of respiration.
The curves are called :
— compliance curve
—- compliance curve
The total work of breathing of the cycle is the area contained in the — .
expand
lung complaince
volume
pressure
ΔV/ΔP
characterstic
inspiratory
expiratory
loop
increased compliance as —-
decreased complance as —
( pls check the graph in slide 9 )
- A — is drawn from the beginning point dividing the expiratory and inspiratory limb. A shift of the slope towards the pressure axis indicates a — in compliance whereas shift towards the volume axis indicates an — in compliance.
empheysma , surfacant therpay
ARDS , CHF , atelectasis
slope
decrease
increase
( pls check slide 9 for graph )
P-V Loop Demonstrating Airway Resistance:
As airway resistance increases, the loop will become — . An increase in expiratory resistance is — commonly seen.
wider
more
compliance types:
1- Static Compliance:
It is the relationship between — change of lung and the — change, i.e. airway - intrapleural pressure change, measured under known static conditions ( – airflow)
Reflects the — of the lung and chest wall.
-Given by CST = — Vt/ ( — Pressure - — End — Pressure)
The normal value for a 70 kg adult ~ — ml/cmH20
The value decreases as lung volume — , due to the limitations of the — components of the lung/chest wall system.
Measures purely the —
volume
transpulomanry pressure
zero
elastic resistance
correct Vt ( platue - postive end expiratory pressure)
200 ml
increases
non eleastic
elastic resistance
Measurement Of Static Compliance:
-The patient takes a breath from a — and holds it until the transpulmonary pressure difference becomes —
-This is repeated with different — to produce a pressure/volume — , where
Compliance = the slope of the — curve
-The patient is inflated with known volumes of gas and the transpulmonary pressure change determined at — . This is taken as the — balloon gradient.
Factors Affecting Static Compliance:
1. — volume - the bigger the lungs the — the compliance.
2. — Volume: pulmonary venous congestion from any cause will — the compliance
3. — :
4. Restriction Of Chest — : Causes only — changes in compliance
5. Recent — History
6. —
spirometere
stable
tidal volume
curve
pressure/volume
equilibrium
mouth -esophegal ballon
lung volume
larger
pulomnary blood
decreases
age
expansion
temporary
ventialtory
disease
Dynamic Compliance:
Airflow is — at the point of flow reversal during the normal respiratory cycle. Measurements of lung compliance made using these points reflect dynamic compliance.
-Given by CDYN = — Vt/ ( — Pressure- — )
-In normal lungs at low and moderate frequencies, dynamic and static lung compliance are about the — value
-However, at higher frequencies in normal lungs, and at normal frequencies in abnormal lungs, dynamic compliance is — than static compliance. This is due to — filling of alveoli in the time available.
Measures both — and airway (—) resistance
zero
corrected ( plaute - PEEP )
same
less
imcomplete
elastic and non elastic
Measurement of Dynamic Compliance:
-Taken from the slope of the transpulmonary pressure/volume loops recorded during —
Using a differential pressure — , from an oesophageal balloon to the airway.
Pneumotachograph: the pneumotachograph measures — however, this may be — integrated over time to give volume
Thus, the pressure difference at the no flow points of the P/V loop can be established.
Factors Affecting Dynamic Compliance:
1- — dynamic lung compliance is seen especially with — airways resistance, eg. asthma, chronic bronchitis and emphysema
2-Emphysema — static lung compliance but — dynamic compliance as the respiratory frequency — , as slower alveoli fail to– .
tidal ventilation
transducer
instantaoues flow
electronically
decreased
increased
increases
decreases
increases
fill
Low Compliance:
The volume change per unit pressure change is — . The lungs are — and are resistant to —
The patient has – lung volumes and — minute ventilation.
Clinical conditions that decrease lung compliance
1- static compliance as atelectasis , ARDS , tension penumothorax m obesity , retianed secretions
2- dynamic: brnochospasm , kinking ET tube , airway obstruction
High Compliance
Volume change is — per unit pressure change.
In extreme high compliance situations the —- is incomplete due to lack of — of the lungs.
Usually seen in conditions that increase the patients —. Patients have — lung defect, airflow obstruction, incomplete — and poor —
—- is one such condition where there is destruction of lung tissues, enlargement of terminal and respiratory bronchioles leading to air trapping and consequent impairment in gaseous exchange.
low
stiff
expansion
low
low
large
exhalation
elastic recoild
FRC
obsrrucitve
exhalation
gas exchnage
emphseyma
elastance:
Elastance, is the — of compliance, i.e. the pressure change that is required to elicit a unit volume change. This is a measure of the — of a system to — .
Elastance = —- = Pressure change / Volume change
Elastance is a measure of the work that has to be exerted by the msucles of — to expand the lungs. An increased elastance needs to be counteracted by an increased — of the muscles of inspiration, leading to an increased work of breathing (work of breathing is the physical work that have to be carried out by the muscles of respiration to overcome the — the respiratory system and the — of the airways).
recipirocl
resistance
expand
1/compliance
inspiration
power
elastic and non elastic resistance
Factors Affecting Elastance of the Respiratory System…
1- The elastance of the whole respiratory system depends on the elastance of the — and that of the — .
2- Since the chest wall and the lungs have a serial relationship, in forming the respiratory system, the elastance of the whole respiratory system can be calculated by the — of the — of the chest wall and the lungs. Since the elastance in each of the lungs and the chest wall is approximately – cmH2O, the elastance of the respiratory system is approximately — cmH2O.
3-Changes in the elastance (and therefore the compliance) of the chest wall are uncommon. In contrast, the elastance of the lungs is affected by many respiratory diseases. Thus, variations in the elastance of the respiratory system are mainly due to alterations of the elastance of the — , which is governed by two main factors:
- — forces of the lung tissue
- Forces Exerted by — at the Air-Alveolar Interface
chest wall and lungs
addition of elstance
5
10
lungs
elastic recoil forces
surface tension
factors affecting elastic resistance
1. — forces of the lung tissue
The — forming the pulmonary interstitium resist — and exhibit the property of returning to its original length, when stretched .
This accounts for approximately — to — of the elastic resistance of the lungs and holds the responsibility of generating the recoil forces necessary to increase the — pressure during expiration, which is a — process.
elastic recoil force
elastin fibres
stretchinf
one fourth to one third
intra alveolar pressure
passive
factors affectinf elastic resistance:
Forces Exerted by — at the Air-Alveolar Interface :
- This is responsible for the remaining — to — of the elastance of the lungs.
Since the alveoli are — structures, having a thin lining of fluid, which comes into contact with air, the net surface tension force acts —.
- Laplace’s Law
-to prevent the alveoli from — , a — should be acting across the — wall. This pressure, for a single alveolus, is equal to 2 X surface tension / radius of an alveolus (2T/r).
Smaller alveoli have — tendency to collapse
surface tensio
two thirds to three fourths
gobular structures
inwards
collapsing
transmural pressure
alveolar walls
collaps
greater
( so basically high radius = low pressure to collaps )
factors affecting elastic resistance:
Surfactant and Reduction in Surface Tension:
Reduction in the surface tension would lead to a reduction in the — that is required to keep the alveoli—- . Thus, this decreases the power that needs to be generated by the muscles of — and hence, the work of breathing.
The surface tension in the lungs is reduced by a chemical agent, known as — composed of a — - Di-Palmitoyl Phosphatidyl Choline, secreted by the
—- cells in the lungs
transpulmonary pressure
expanded
inspiration
surfactant
phospholid
type ii alveolar cells
recap of anatomy
Most alveoli occur in clusters called —
Adjacent alveoli are NOT completely — structures—connected by — (allows — of pressure)
They share adjacent walls, so they are “—- ,” that is, they depend on the — (inflation) of neighboring alveoli to help them inflate
Alveolar wall inter dependance:
Alveoli are surrounded by other — and interconnected by — tissue.
If alveolus starts to collapse, surrounding alveoli are — and they apply — forces on the collapsing alveolus, thereby help to keep it — , this is called — .
Loss of alveolar walls results in :
Loss of — for —
Loss of — (greater tendency to — = local regions of — )
alveolar sacs
independent
aveolar pores
equilibrium
interdependent
expasnion
alevoili
conective tissue
stretch
expanding forces
alveolar interdependance
surface area
diffuison
interdependance
collaps
atelectasis
Resistance (Non-elastic component):
Non-Elastic Resistance to Breathing
This is composed of,
a. — flow resistance ~ 80%
b. — resistance, or — resistance ~ 20%
1- Airway Resistance
Definition: It is the — that is required to overcome the resistance to — flow through the airways during — .
Normal value for a healthy adult ~ — cmH20/l/s
airway flow
pulmonary tissue
visvous
pressure
gas flow
repsiration
0.5-1.5
types of flow pattern:
1- Laminar Flow
-Below critical flows, gas proceeds through a — tube as a series of — that slide over one another. Fully developed flow has a — profile with a velocity of — at the cylinder wall and a maximum velocity at the — of the advancing “cone.”
-Peripheral cylinders tend to be — , and the central cylinder moves — . The advancing conical front means that some fresh gas reaches the end of the tube — the tube has been completely filled with fresh gas.
Clinical implication: Significant alveolar ventilation can occur even when the tidal volume ( Vt) is — than anatomic dead space. This phenomenon, noted by Rohrer in 1915, is important in —-frequency ventilation.
striaght
concentric cylinders
parabolic
zero
centre
stationary
fastest
before
less
high
types of flow pattern:
2-Turbulent Flow
— flow rates, particularly through — or — shaped tubes, disrupt the orderly flow of laminar gas.
Turbulent flow usually presents with a — front, so fresh gas will not reach the end of the tube until the amount of gas entering the tube is almost — to the volume of the tube. Thus, turbulent flow effectively purges the contents of a tube.
high
branched or irregulalry
square
equal
types of flow pattern:
Four conditions that will change laminar flow to turbulent flow are
1) — gas flows,
2) — angles within the tube,
3) — in the tube,
4) change in the tube’s — .
During turbulent flow, resistance — in proportion to the flow rate. Turbulent flow occurs when there is a net — flow, but there are many — currents (little circulations that occur).
Turbulent flow of air is observed in the — airways where the radius is — and the airflow is more rapid.
high
sharp
branching
diametre
increases
forward
local eddy current
upper
larger
Reynolds Number:
The Reynolds number is used as an — to determine whether flow is – or —. It is a — number that is defined as:
Re = 2rvd/η,
where r is radius, v is velocity, d is density, and η
is viscosity.
< — - Laminar.
> — - Turbulent.
2000 – 4000 – Both
According to this equation, turbulent flow is likely if the tube has a — radius, a – velocity, a — density, or a – viscosity
index
laminar or turbulent
unitless
<2000
>4000
large
high
high
low
