Respiratory 2 Flashcards
(109 cards)
1
Q
what is pleural space?
A
a relative vacuum
2
Q
what is pleural pressure
A
the negative pressure in the pleural space because lung recoil inwards and chest wall recoils outwards
3
Q
when are the inward and outward forces equal in the pleural space
A
at FRC
4
Q
transpulmonary pressure=
A
alveolar pressure - pleural pressure
5
Q
how much transpulmonary pressure does the first breath of a neonate generate?
A
40-80cmH20
6
Q
Alveolar Pressure
A
is the air pressure in alveoli, its normally = 0cmH20
7
Q
what is the major driving force for air flow into the lungs? during normal quiet inspiration
A
alveolar pressure
8
Q
Pleural Pressures resting=
A
resting -5cmH20
9
Q
Pleural Pressures inspriation=
A
-8cmH20
10
Q
alveolar pressure resting=
A
0cmH20
11
Q
alveolar pressure inspiration=
A
-1cmH20
12
Q
alveolar pressure expiration=
A
+1cmH20
13
Q
at rest what is alveolar pressure equal to? (before inspiration begins)
A
alveolar pressure equal atmospheric pressure and is said to be zero (no flow)
14
Q
how to we measure pleural pressure
A
by a balloon catheter in the esophagus
15
Q
what is FRC
A
functional residual capacity- is lung volume at the end of passive expiration
16
Q
why is pleural pressure negative?
A
the elastic recoil of lungs trying to collapse and the chest wall trying to expand, creates a negative pressure in the intrapleural space.
17
Q
breathing cycle during inspiration
A
inspiratory muscles contract causing the volume of the thorax to increase.
as lung volume increases, alveolar pressure decreases to less than atmospheric pressure (becomes more negative -1cmH20)
the pressure gradient between the atmospheric and alveoli now causes air to flow into the lungs, air flow will continue until the pressure gradient dissipates.
18
Q
during inspiration what happens to pleural pressure
A
it becomes more negative than it was at rest (-5 to -8 cmH20)
19
Q
what is FRC at peak of inspiration
A
lungs volume is the FRC plus one TV
20
Q
during expiration what happens to alveolar pressure
A
alveolar pressure becomes greater (becomes positive +1cmH20) than atmospheric pressure
21
Q
during expiration
A
intra pleural pressure returns to its resting value during a normal passive expiration.
22
Q
what happens during forced expiration
A
intra pleural pressure actually becomes positive. this positive intrapleural pressure compresses the airways and makes expiration more difficult.
23
Q
during expiration and COPD patients. What do we teach them?
A
airway resistance is increased, patient learn to expire slowly with “PURSED LIPS” to prevent the airway collapse that may occur with forced expiration.
24
Q
during expiration what happens to FRC
A
lung volume returns to FRC
25
what does lung compliance show?
it shows "distensibility" of lungs and chest wall
26
what is lung compliance inversely related to?
| 2 things
it is inversely related to elastane which depends on the amount of elastic tissue
is inversely related to stiffness
27
lung compliance is the slope of the ?
pressure volume curve
28
compliance=
change in volume of lung for each unit change in pressure. pressure refers to transpulmonary pressure
29
at high expanding pressure what is compliance?
at high expanding pressure, compliance is lowest, the lungs are least distensible, and the curve flattens
30
in middle range of pressure what is compliance
compliance is greatest and the lungs are most distensible
31
At FRC what is the collapsing force of the lungs and expanding force of the chest wall considered?
equal and opposite. it is at equilibrium
32
as a result of the two opposing forces of the collapsing lungs and expanding chest what is intrapleural pressure
Negative (sub atmospheric)
33
Name the condition of air being introduced into the pleural space
pneumothorax
34
pneumothorax-
intra pleural pressure becomes equal to atmospheric pressure - the lung will collapse (its natural tendency) and chest wall will spring outward (its natural tendency)
35
changes in lung compliance with emphysema
lung compliance is increased and the tendency of the lung to collapse is decreased.
36
why do patients with emphysema becomes barrel-shaped.
the tendency of the lungs to collapse is less than the tendency of chest wall to expand. the lung-chest wall system will seek a new HIGHER FRC so that the two opposing forces can be balanced the patient then becomes barrel shaped- the patient has increase elastance due to less rubber bands-
37
Fibrosis and lung compliance?
lung compliance is decreased and the tendency of lungs to collapse is increased
38
in fibrosis what happens to FRC
the tendency of the lungs to collapse is greater than the tendency of the chest wall to expand. the lung chest wall system will seek a new lower FRC so that the two opposing forces can be balanced.
39
name the 4 causes of decreased Lung compliance
high expanding pressures
increase Pulmonary venous pressure
fibrosis (deposition of collagen)
lack of surfactant.
40
name the two causes of increase lung compliance
emphysema (destruction of elastic fibers)
| old age
41
tell me about collapsing pressure and small alveoli
have high collapsing pressure and are more difficult to keep open In the absence of surfactant the small alveoli have a tendency to collapse (atelectasis)
42
tell me about collapsing pressure and larger alveoli
have low collapsing pressure and are easy to keep open
43
p=?
2T/r
p= collapsing pressure on alveolus (or pressure required to keep alveolus open)
T=surface tension
R=radius of alveolus
44
what type of cells secrete surfactant
type 2 alveolar cells
45
what is surfactant composed of?
composed of phospholipid, proteins, and calcium
46
What week gestation does synthesis of surfactant start at?
| when is it almost always present?
24 weeks
week 35
47
what is the mechanism of action for surfactant
lines the alveoli- surface tension reducer- disrupting the intermolecular forces(hydrogen bond) between the water molecules of liquid-act like detergent.
this reduction in surface tension prevents small alveoli from collapsing and increases compliance, decrease work of inspiration allowing the lungs to inflate much more easily
48
neonatal respiratory distress syndrome
Occurs in premature infants because of lack of surfactant. The infant shows atelectasis (lung collapse), difficulty reinflatting the lungs( as a result of decreased compliance) and hypoxemia because of decreased V/Q
49
Treatment for Neonatal respiratory distress syndrome
Treatment
Maternal steroid shots before birth. This speeds up formation of surfactant in the fetus.
Artificial surfactant to infants by inhalation
50
slide 27 ground glass appearance of the lung
These findings correlate clinically with moderate to severe retractions and oxygen dependence in premature infants with RDS.
51
Q=
Change P=
R=
air flow
pressure gradient
airway resistance
52
Q=
change P/R
53
R=
n=
l=
r=
resistance
viscosity of the inspired gas
length of airway
radius of airway
54
Notice the powerful inverse fourth-power relationship between resistance and size ( radius) of airways.
If airway radius decreases by a factor of 4, then resistance will increase by a factor of 256(44) and air flow will decrease by a factor of 256
55
Contraction and relaxation of bronchial smooth muscles
| Parasympathetic stimulation
irritants, slow reacting substance of anaphylaxis-A (asthma) constrict the airways, decrease the radius and increase the resistance to airflow
56
Contraction and relaxation of bronchial smooth muscles
| Sympathetic stimulation
and sympathetic agonist dilate the airways , increase radius and decrease resistance to airflow via B2 receptor
57
Low lung volumes
are associated with less radial traction and increased airway resistance
58
High lung volumes
are associated with greater radial traction and decrease airway resistance. In asthma, pt “learn” to breath at higher lung volumes to offset the high airway resistance associated with their disease.
59
Site of airway resistance
| where is the major site of airway resistance
the medium sized bronchi
60
do the smallest airways offer the highest resistance???
no they do not because of their parrallel arrangement
61
when do respiratory muscles work?
during normal quiet condition, respiratory muscles work only during inspiration and not during expiration
62
Tidal Volume:
is the volume inspired or expired with each normal breath
63
Inspiratory Reserve Volume
is the volume that can be inspired over and above the tidal volume. It is used during exercise
64
Expiratory Reserve Volume
is the volume that can be expired after the expiration of tidal volume
65
what type of pulmonary volume is seen with exercise
inspiratory reserve volume
66
Residual Volume
is the volume that remains in the lungs after a maximum expiration. It cannot be measured by spirometry
67
pulmonary volumes are recorded by
spirometer
68
residual volume is measured by
helium dilution method
69
```
Vital Capacity (VC)
is the sum of?
```
TV, IRV, and ERV
| everything but residual volume
70
Inspiratory Capacity=
TV+IRV
71
Functional Residual Capacity
ERV+ Residual Volume
Volume remaining in the lungs after a tidal volume is expired
Acts as RESERVIOR for O2 during airways obstruction or apnea
Prevents large SWINGS of PO2 by acting as buffer
72
Total Lung Capacity
Is the sum of all four volumes.
| It is the volume in lungs after a maximum inspiration
73
what reduces FRC (4)
Supine position
Obesity
Pregnancy
Anesthesia
74
Implication: PREOXYGENATION / DENITORGENATION
before anesthetic induction is very important providing reservoir of O2, as this “fills” the FRC with 100% O2, allowing more time (upto10 min.) for airways manipulation, breath holding episodes etc.
75
FRC Increases by:
PEEP , CPAP
| Increase airway resistant – asthma
76
Forced vital capacity (FVC)
tell me about the ratio?
Is the volume of air that can be forcibly expired as hard and as rapid possible, after taking maximum inspiration
Is normally 80% of the forced vital capacity (FVC)
FEV1/FVC ratio = 4/5= 0.80 (80%)
77
FORCED EXPIRATORY VOLUME IN 1ST SECOND ( FEV1)
Is the volume of air that can be expired in the first second of a forced maximal expiration as hard and as rapid possible
78
what two conditions are FEV1 low in?
both obstructive and restrictive diseases (trouble is blowing air out )
79
what do you find for FEV1 and FVC with obstructive lung diseases?
In obstructive lung diseases such as asthma and COPD, FEV1 is reduced more than FVC so that FEV1/FVC is decreased (hallmark)
80
what do you find for FEV1/FVC for restrictive lung diseases?
In restrictive lung disease such as pulmonary fibrosis, pneumothorax, scoliosis, myasthenia gravis or ALS, both FEV1 and FVC are reduced and FEV1/FVC is either normal or is increased
81
Forced expiratory flow (FEF 25-75) or Midmaximal expiratory flow
what does it access?
Is best of accessing small airway disease
82
obstructive lung disease
what is the FEV1/FVC ratio?
increases resistance to flow. resulting in air trapping in the lung.
emptying impaired leads to high RV low VC
FEV1/FVC ratio decreases (hallmark sign)
83
4 types of obstructive lung disease
bronchiectasis
chronic bronchitis
emphysema
asthma
84
Restricted lung disease- LUNG VOLUMES?
causes decreased all lung volumes. decrease vital capacity decrease TLC. PFT, FEV1/FVC ratio >80%
85
restrictive lung disease poor breathing mechanics
extra pulmonary
Poor muscular effort: polio, M gravis
Poor apparatus: scoliosis
86
restrictive lung disease Poor lung expansion
pulmonary
Lungs are restricted; cannot expand
Defective alveolar filling: pneumonia, ARDS, pulmonary edema
Interstitial fibrosis: causes increased recoil (compliance), thereby limiting alveolar expansion. Complications include cor pulmonale. Can be seen in diffuse interstitial pulmonary fibrosis and bleomycin toxicity. Symptoms include gradual progressive dyspnea and cough
87
PCWP
is an indirect measure of ‘left atrial pressure’
Normally ~ 10mmHg
Measure by Right Sided Heart Catheterization
88
when is pwp used?
CHF to study pressure changes in left atrium
89
hypovolemic shock
decrease wedge decreased BP
90
failing heart
decreased BP increased Wedge
91
right atrium pressure
<5
92
right ventricle pressure
<25/<5
93
left atrium pressure
<12
94
left ventricle pressure
<150/10
95
pulmonary trunk pressure
<25/10
96
aorta pressure
<150/90
97
wedge pressure
<12
98
Pressure pulmonary circulation
Are much lower in pulmonary circulation (15mmHg) than in the systemic circulation (100mmHg)
99
compliance pulmonary circulation
is much higher
100
resistance pulmonary circulation
is much lower
101
cardiac output of the right ventricle
Is pulmonary blood flow
| Is equal to CO of the left ventricle
102
what does alveolar hypoxia cause
vasoconstriction
103
explain vasoconstriction during hypoxia
This diverts blood away from poorly ventilated, hypoxic regions towards well-ventilated regions of lung leads to decrease shunting of blood (protective)
104
SVR=
MAP-CVP/Cardiac output x80
105
normal svr
900-1200
106
fetal pulmonary vascular resistance is very high due to hypoxic vasoconstriction which leads to?
decreased blood flow
107
oxygenation with first breath decreases pulmonary vascular resistance
increases blood flow
108
global hypoxia breathing in thin air at high altitude leads to vasoconstriction of entire lungs leads to
pulmonary HTN leads to RVF
109
PVR=
Pul Art-Pul L atrium/ cardiac outputx80
