Resp Week 5 Flashcards
1
Q
what are 7 components of alveoli
A
type 1 alveolar cells
type 2 alveolar cells
fibroblasts
capillaries
pericytes
macrophages
immune cells
2
Q
describe type 1 pneumocytes
A
primary function is gas exchange involving diffusion of CO2 and O2 across an alveolar membrane
3
Q
describe type 2 pneumocytes
A
primary function is to reduce surface tension by producing surfactant, thus increasing compliance
they also prevent mvmt of fluid into alveolus and activates immune system
4
Q
in relation to Law of LaPlace, describe the function of surfactant
A
pressure is inversely proportional to radius meaning that a smaller object is more likely to collapse under pressure, meaning every time alveolar size decreases during expiration, the lung would collapse
surfactant decreases surface tension as the alveolar size decreases, thus preventing it from collapsing
5
Q
what are 3 molecules that compose surfactant
A
phospholipids
neutral lipids
surfactant proteins
6
Q
describe the development of the foetal lung
A
starts w laryngotracheal groove, caudal of the 4th pharyngeal pouch
then, endoderm lining the groove will become pulmonary endothelium and all glands of resp tract
then, muscles and CT originate from surrounding mesenchyme (mesodermal)
then, cilia present at wk 10
then, mucosal glands present at wk 12
then, lung has enough surfactant to support lung function by wk 35
7
Q
describe alveolar macrophages of the alveolar-capillary unit
A
reside in mucous layer
these are responsible for clearance of apoptotic cells and cellular debris
serve an immune function as they are responsible for phagocytosis of foreign substances
8
Q
describe fibroblasts of the alveolar-capillary unit
A
generates and synthesises ‘fibres’ which are a component of the lung interstitial
attracted to sites of injury when detected by type 2 pneumocytes, allowing for the alveolus to be sealed off for repair
9
Q
describe how fibrosis can occur in the lungs
A
injury e.g smoking > type 2 pneumocytes release cytokines > fibroblasts migrate to area of injury > fibroblasts lay down collagen to repair > increased epithelial cell damage > impaired re-epithelialisation > fibrosis
10
Q
describe the pulmonary circulation
A
transport of low O2 blood to lungs via pulmonary arteries
gas exchange at level of capillaries
transport of high O2 blood to heart via pulmonary veins
P. arteries have thinner walls than systemic circ. arteries
P. arteries and P. veins are not located next to each other (P.A travel w airways while P.V and lymphatics travel in septa b/w lobuli)
11
Q
describe hypoxic pulmonary vasoconstriction
A
in contrast to systemic arterioles, which dilate in response to hypoxia, pulmonary pre-capillary arterioles constrict in response to alveolar hypoxia
this diverts blood to better ventilated areas of the lung, hence perfusion and ventilation are synchronised
12
Q
describe bronchial circulation
A
Vasa Privata - private vessels that supply the lung parenchyma e.g smooth muscle, CT, cartilage etc
bronchial arteries originate from thoracic aorta and 3rd right intercostal artery
in 1/3 of instances, bronchial veins drain into the azygos vein and hemi-azygos or intercostal veins
in 2/3 of instances blood from the peripheral bronchial arteries drains into the pulmonary veins
13
Q
what 3 main muscles are involved in respiration
A
diaphragm
external intercostals
internal intercostals
14
Q
what is the role of the diaphragm in respiration
A
contracts/relaxes to expand/reduce thoracic cavity
15
Q
what is the role of external intercostals in respiration
A
contracts to elevate ribs during inspiration
16
Q
what is the role of internal intercostals in respiration
A
contracts to pull ribs down during expiration
17
Q
describe the lymph drainage of the lungs
A
lung lymph > inferior and superior tracheobronchial lymph nodes > paratracheal lymph nodes > broncomediastinal trunks > right lymphatic duct
18
Q
what are 3 types of lymphatic vessels in the lungs
A
pleural (in CT of visceral pleura)
interlobular (in the interlobular septa)
intralobular
19
Q
what is a cough
A
protective reflex to prevent irritants reaching smaller airways
involves forced expiration against a closed glottis
can be due to URTI, COPD, pertussis, GORD
20
Q
outline the cough reflex pathway
A
irritant enters resp tract, contacting resp epithelium
then, innervation of vagal sensory fibres in the pharynx, trachea and bronchi
then, sensory fibres end in nucleus of the solitary tract (NTS) in brainstem
then, central cough generator (CCG) motor neurons
then, ventral resp group (VRG) motor neurons
then, innervation of resp muscles
then, forceful expiration against a closed glottis ie cough
21
Q
what 2 fibres belong to the vagus nerve involved in the cough reflex
A
A8 fibres
C fibres
these are functional nociceptors and mechanoreceptors, which have cell bodies in the jugular and nodose ganglia of vagus nerve
22
Q
the central cough generator stimulates the diaphragm via what
A
motor neurons C3-C5
23
Q
the central cough generator stimulates the intercostal muscles via what
A
motor neurons T1-T11
24
Q
the central cough generator stimulates the intrinsic laryngeal muscles via what
A
vagus nerve
25
the central cough generator stimulates the abdominal muscles via what
motor neurons T6-T12
26
describe the pathophysiology behind cough and sputum production
exposure to irritants > irritation of bronchial lining > inflammation of bronchial epithelium > goblet cells in bronchial epithelium become hyperactive > increased mucus production
27
what 4 causes of sputum
resp infections
GORD
bronchitis
allergies
28
how do resp infections cause sputum
pathogens > inflammation > increased mucus production
29
how does GORD cause sputum
stomach acid reach airways > irritation > inflammation > increased mucus production
30
how does bronchitis cause sputum
long term irritation > chronic inflammation of bronchial tubes > excessive mucus production
31
how do allergies cause sputum
allergens > immune response > inflammation + increased mucus production
32
what are the 4 components of respiration
pulmonary ventilation
diffusion
gas transport
gas exchange
33
describe air flow
high to low pressure
increase lung volume > negative alveolar pressure (relative to atmospheric pressure) > air inflow
relaxation of diaphragm and elastic recoil of lungs > positive alveolar pressure > air outflow
34
what is the formula for compliance
C = change in volume / change in pressure
35
what two factors determine compliance
elastic forces of lung
elastic forces caused by surface tension
36
what is tidal volume
total volume of air inhaled and exhaled per breath
37
what is inspiratory reserve volume
additional air that can be forcibly inhaled
38
what is expiratory reserve volume
additional air that can be forcibly exhaled
39
what is residual volume
air remaining in lungs after maximal exhalation
40
what is functional residual capacity
volume of air remaining in lungs after a normal exhalation
41
what is vital capacity
max amount of air that can be exhaled after a maximal inhalation
42
describe how pressure, volume, flow and resistance are related
volume = flow x resistance
in a given pressure difference, airflow is inversely related to resistance, meaning that a higher resistance results in lower airflow
43
describe changes in pressure during a normal breathing cycle
pleural pressure becomes more negative during inspiration, which causes alveolar pressure to drop below atmospheric pressure, resulting in airflow into lungs
as lungs expand, lung volume increases and the negative pleural pressure reaches its peak
at end of inspiration, alveolar pressure equals atmospheric pressure, stopping airflow
in expiration, pleural pressure becomes less negative, causing alveolar pressure to rise above atmospheric pressure leading to air outflow
44
define work of breathing
energy expenditure required to overcome the resistance and compliance of respiratory system during ventilation
involves respiratory muscles generating force to create necessary pressure gradients for inhalation and exhalation
45
what is transmural pressure
pressure difference across a structure's wall, determining its distension or collapse
in case of lungs, it is critical for maintaining airway patency and integrity of alveolar structures
46
what is transpulmonary pressure
pressure difference b/w alveolar and pleural pressures, maintaining lung expansion
47
describe the pressure volume loop in relation to lung compliance
in a compliant lung, P-V loop demonstrates steep slope, indicating that a small increase in pressure leads to a significant increase in lung volume
in a less compliant lung, slope is flatter meaning more pressure is required to achieve the same volume change
48
what are 3 factors that affect airflow resistance
airway resistance
pulmonary resistance
chest wall resistance
49
describe airway resistance in terms of airflow resistance
resistance encountered by air moving through airways, influenced by airway diameter and the smooth muscle tone in bronchi and bronchioles
50
describe pulmonary resistance in terms of airflow resistance
the overall resistance to airflow within the lungs, incorporating airway resistance, lung tissue elasticity, and the viscoelastic properties of lung parenchyma
51
describe chest wall resistance in terms of airflow resistance
the resistance from the chest wall and diaphragm during breathing, influenced by muscle tone, rib cage stiffness, and the compliance of the thoracic cavity
52
describe the role of surface tension in the elastic recoil of the lung
contributes to the forces that drive lung deflation
cohesive forces b/w water molecules at air-liquid interface in the alveoli create an inward pull, which helps the lungs return to their resting state after expansion
53
describe regional differences in blood flow of lungs
when standing, lower parts of lung blood blow is higher than apex
lung subdivided into 3 zones (zone 1 = apex, zone 2 = middle, zone 3 = base)
zone 1 = lack of blood flow as alveolar pressure is higher than pressure in pulmonary arteries and veins
zone 2 = blood flow occurs in systole but not diastole as arterial pressure and venous pressure is higher than pressure in alveoli
zone 3 = constant supply of blood flow as arterial pressure is higher than pressure in veins and alveoli
54
describe pulmonary vascular resistance
larger at too small lung volumes bc large vessels are not held open by the stretch of filled alveoli
larger at too large lung volumes bc small vessels are compressed by stretch of filled alveoli
55
describe the relationship b/w exercise and pulmonary vascular resistance
during exercise, pulmonary vascular pressure remains constant bc increased blood flow results in decreased pulmonary resistance, to compensate
this is caused by distension of pulmonary capillaries and recruitment of previously collapsed or narrowed capillaries
56
what are the mechanisms by which PVR is modulated
vasoconstriction to increase PVR
vasodilation to decrease PVR
proliferation of smooth muscle cells to increase PVR
antiproliferation of smooth muscle cells to decrease PVR
57
what are 5 factors affecting PVR and what effect do they have
endothelin-1 = increases PVR
histamine = increases PVR
catecholamines = increases PVR
NO = decreases PVR
adenosine = decreases PVR
58
what are 3 factors influencing O2 dissociation
increased H+
increased temp
increased CO2
59
what is the bohr effect
increased H+ and CO2 promotes offloading of O2 in the peripheral tissues (where PCO2 is high) and promotes O2 loading in the lungs (where PCO2 is low)
60
what causes a left shift on the O2-Hb dissociation curve
demonstrates an increased affinity for O2 therefore:
decreased PCO2
decreased H+
decreased temp
61
what causes a right shift on the O2-Hb dissociation curve
demonstrates a decreased affinity for O2 therefore:
increased PCO2
increased H+
increased temp
62
what is the PO2 at the arterial end of capillaries
95mmHg
63
what is the PO2 in the interstitial cells
45mmHg
64
what is the PO2 in the intracellular solutions
23mmHg
65
what is PO2 in the venous end of capillaries
45mmHg
66
what is the PCO2 in the arterial end of capillaries
40mmHg
67
what is the PCO2 in the interstitial cells
45mmHg
68
what is the PCO2 in the intracellular solutions
46mmHg
69
what is PCO2 in the venous end of capillaries
45mmHg
70
by what 3 mechanisms does CO2 transport occur
dissolved state (5-10%)
bicarbonate ion (70%)
carbaminohaemoglobin (20-25%)
71
describe the haldane effect
greater binding of O2 with haemoglobin increases the release (offloading) of CO2, thus CO2 release is promoted when venous blood is arterialised
72
describe fick's law of diffusion
rate of gas transfer is proportional to the product of diffusing capacity across a membrane and the pressure gradient
73
what is diffusing capacity
net rate of gas transfer for a partial pressure gradient of 1mmHg
74
what four categories affect diffusing capacity
diffusion coefficient of gas
changes in effective SA of gas exchange membrane
changes in physical properties of membrane
changes in uptake of gases by RBC
75
what 3 things influence membrane surface area in terms of diffusing capacity
body size (height)
lung volume
ventilation/perfusion
76
what 3 things influence physical properties of membrane in terms of diffusing capacity
pulmonary congestion
interstitial oedema
membrane thickening
77
what 2 things influence changes in uptake of gas by RBC in terms of diffusing capacity
Hb concentration
capillary transit time
78
what are 2 types of V/Q mismatching
intrapulmonary shunt (V/Q = 0)
alveolar dead space (V/Q = infinity)
79
describe intrapulmonary shunt in terms of V/Q
occurs when there is perfusion without ventilation
blood passes through the lungs without being oxygenated, e.g in conditions like atelecstasis (collapsed alveoli)
80
describe alveolar dead space in terms of V/Q
occurs when there is ventilation without perfusion
air reaches the alveoli but no blood flow is available for gas exchange, e.g in pulmonary embolism
81
what are 4 regional ventilation factors that influence V/Q
gravity (pleural pressure gradient)
anatomical expansion (bases of lung are larger)
lung compliance (bases are more compliant)
breathing pattern (changes alveolar recruitment)
82
what are 4 regional perfusion factors that influence V/Q
gravity (hydrostatic gradient)
hypoxic pulmonary vasoconstriction (redirection)
pulmonary vascular structure (branching)
lung volume (changes ventilation volumes)
83
what is the function of the control of alveolar ventilation
PaCO2 and PaO2 are tightly regulated in order to enable efficient oxygenation and gas exchange in the pulmonary circulation
84
how is control of ventilation achieved
via neurogenic regulation
it is mediated by the respiratory centre in the medulla oblongata
85
describe the respiratory control centre
contains 3 main respiratory groups:
dorsal respiratory group
ventral respiratory group
pontine respiratory group
86
describe the function of the dorsal respiratory group
inspiratory neurons responsible for timing of the respiratory cycle (inspiration)
87
describe the function of the ventral respiratory group
neurons that influence both inspiration and expiration
88
describe the function of the pontine respiratory group
includes the pneumotaxic centre, responsible for limiting the depth of breathing, and apneustic centre, to delay the inspiratory off-switch
89
what are the 3 predominate receptor types in the lung
slowly adapting stretch receptors (SASR)
rapidly adapting stretch receptors (RASR)
vagal C-fibre nociceptors
90
what is the function of slowly adapting stretch receptors
predominately in the airways, acts as a lung volume sensor
91
what is the function of rapidly adapting stretch receptors
located in superficial mucosa, stimulated by changes in TV, RR, and lung compliance
92
what is the function of Vagal C-fibre nociceptors
free nerve endings found in bronchi and pulmonary capillaries, stimulated by oxidative stress, inflammation, or inhaled irritants
93
describe the role of central chemoreceptors in the chemical control of respiration
CO2 passes the BBB
then, increase in PCO2 within CSF
then, CO2 forms carbonic acid, which dissociates to form a bicarbonate ion and hydrogen ion
then, pH decreases (peripheral H+ ions do not permeate the BBB)
then, transmission of this message to medullary respiratory neurons
then, change in pulmonary ventilation
94
describe role of peripheral chemoreceptors in the chemical control of respiration
located in aortic arch and carotid body to detect levels of PO2 (mainly), PCO2 and H+
receptors in aortic arch transmit message to medullary respiratory neurons via vagus nerve, and receptors in carotid body transmit message via glossopharyngeal nerve
this then leads to a change in pulmonary ventilation
95
describe J-receptors
located near pulmonary capillaries
respond to capillary pressure changes
stimulation leads to tachypnea
96
describe chest wall reflexes
activated by receptors in chest muscles, joints and skin
prevent overinflation or sudden deflation of the lung
e.g hering-breuer reflex and deflation reflex
97
describe lung reflexes
activated by irritant and stretch receptors in lung tissue
detect harmful particles and chemicals
activate coughing and bronchoconstriction
assist in maintaining overall TV
98
outline the hering-breuer reflex
inflated lung
then, activation of stretch receptors
then, impulse generated
then, inhibition of inspiratory centre
then, expiration reduces lung inflation
99
outline the deflation reflex
extreme lung deflation (eg pneumothorax)
then, activation of compression receptors
then, impulse generated
then, stimulation of inspiratory centre
then, rapid forced inspiration attempts to restore lung volume
100
describe the respiratory regulation of acid-base balance
homeostatic regulation of pH in extracellular fluid
an increase in PCO2 leads to decreased pH, stimulating central chemoreceptors to increase ventilation
respiratory acidosis is caused by hypoventilation, which leads to increased PCO2 and decreased pH
respiratory alkalosis is caused by hyperventilation, which leads to decreased PCO2 and increased pH
101
outline the process of exercise hyperpnea
aerobic exercise
leads to, metabolic acidosis and mechanical stress on muscles
leads to , detection by central and peripheral chemoreceptors and detection by muscle proprioceptors, respectively
leads to, initiation of respiratory control centre
leads to, hyperventilation
leads to, expulsion of CO2 which restores homeostasis
102
what are pulmonary function tests
measurement of various aspects of pulmonary functions e.g lung mechanics, volumes, flows, pressures, pre-op function etc
103
what are 3 examples of pulmonary function tests
spirometry
single breath diffusing capacity of carbon monoxide
subdivisions of lung volume
104
what does spirometry measure
how much and how fast air can be inhaled and exhaled to and from lungs
105
what are two devices used for spirometry
volume displacing devices or flow sensing devices
for volume displacing, blow > displacement is measure and thus flow is calculated
flow sensing, measure flow and integrate that flow to measure volume
106
describe the spirometry procedure
adult patient seated and children patient stand > nose clipped and lips sealed around mouthpiece > instructed to fill lung completely then blast air out until empty > then inhale as fast as possible when empty > repeat 3-8 times > give bronchodilator > repeat experiment 20 mins after bronchodilation
107
what are 5 PFT parameters
forced expiratory volume (FEV1)
forced vital capacity (FVC)
peak expiratory flow (PEF)
mid forced expiratory flow (FEF25-75%)
forced expiratory time (FET)
108
define FEV1
maximum amount of air that can be expelled in one second
109
define FVC
maximum amount of air that can be expired in one breath
110
define PEF
fastest speed at which air can be expired
111
define FEF25-75%
average flow rate between 25 and 75% of FVC
112
define FET
time take for FVC to be completely expired
113
describe obstructive ventilatory defects
causes airflow limitations, thus it is difficult to empty lungs
results in reduced airway calibre and reduced elastic recoil
decreased FEV1, decreased or same FVC, and decreased FEV1/FVC ratio
114
describe restrictive ventilatory defects
issues with compliance of lungs causes reduced lung volumes
results in difficulty to fully expand lungs
decreased or same FEV1, decreased FVC, increased or same FEV1/FVC ratio
115
what are 4 examples of obstructive ventilatory defects
asthma
chronic bronchitis
emphysema
foreign bodies
116
what are 4 examples of restrictive ventilatory defects
congestion
pleural effusion
kyphoscoliosis
fibrosis
117
describe the significance of bronchodilator response in the obstructive pattern
typically, 200ug salbutamol (bronchodilator) is given post spirometry to create a comparison
a 10% of baseline value in FEV1 or FVC indicates reversibility of obstructive defect
particularly important in case of conditions such as asthma that are reversible in nature
118
what are subdivision of lung volumes
otherwise known as static lung volumes
volumes of gas in the lungs at a given time during the respiratory cycle
119
outline the process of lung dilution
patient breathes in known quantity of helium-oxygen mixture, which contains a precise concentration of helium gas
then, inhaled helium mixes w gases present at lungs, eventually reaching equilibrium (ensures uniform distribution of helium within lung airspaces)
then, patient exhales mixture of helium and gases fro their lungs into a spirometer > measures concentration of helium in the exhaled breath
then, by comparing initial and exhaled concentrations of helium, the dilution of helium in the lungs is calculated. this info helps determine lung volume and other pulmonary parameters
120
describe whole body plethysmography
patient seated in cabin w nose clipped and lips sealed > breathe normally to measure inhalation and exhalation
respiratory effort done against closed shutter as pressure in box, volume in box and change in pressure are known thus volume of lungs can be measured
enables measurement of reserve volume and total vital capacity, entities that cannot be measured w spirometry
121
describe static lung compliance
changes in lung volume per unit of pressure in the absence of flow
122
describe single breath diffusing capacity of carbon monoxide
aka transfer factor of carbon monoxide
reflects SA and diffusing properties of alveolar capillary membrane, volume of capillary blood Hb in contact w alveolar gas and rate of binding b/w Hb and carbon monoxide
123
what causes reduced DLCO (diffusion capacity of lungs for CO)
less Hb available for CO binding
anemia
PE
emphysema
124
what causes elevated DLCO (diffusion capacity of lungs for CO)
more Hb available for CO binding
polycythaemia
erythrocytosis
125
outline how CAD can lead to dyspnea
stenosis/occlusion
leads to, myocardial ischemia
leads to, reduced oxygen to myocardium
leads to, damage to heart muscle
leads to, reduced Q
leads to, inadequate circulation of oxygenated blood
leads to, increased workload of breathing
leads to, dyspnea
126
outline how cardiomyopathy can lead to dyspnea
heart muscle enlargement/stiffening
leads to, reduced Q
leads to, inadequate circulation of oxygenated blood
leads to, increase workload of breathing
leads to, dyspnea
127
outline how valvular disease can lead to dyspnea
stenosis/regurgitation
leads to, increased pulmonary pressure putting strain on right heart
leads to, RV becoming weakened due to strain
leads to, inadequate circulation of oxygenated blood
leads to, increased workload of breathing
leads to, dyspnea
128
outline how inflammation of the pericardium can lead to dyspnea
fluid build up
leads to, fluid-reduced contractility
leads to, reduced Q
leads to, inadequate circulation of oxygenated blood
leads to, increase workload of breathing
leads to, dyspnea
129
outline how anaemia can lead to dyspnea
decreased RBC count
leads to, reduced Hb
leads to, reduced oxygen carrying capacity
leads to, insufficient oxygen delivery to tissues and cells
leads to, reduced oxygen availability at lungs
leads to, dyspnea
130
outline how COPD can lead to dyspnea
inflammation leads to narrowed airways
leads to, obstructed flow of air in/out of lungs
leads to, reduced oxygen uptake
leads to, reduced oxygen availability at lungs
leads to, dyspnea
131
outline how asthma can lead to dyspnea
bronchoconstriction
leads to, reduced airway diameter which reduced oxygen intake
leads to, increase workload of breathing
leads to, dyspnea
132
outline how pneumonia can lead to dyspnea
inflammation and fluid buildup in the lungs
leads to, reduced gas exchange capacity
leads to, inadequate circulation of oxygenated blood
leads to, increase workload of breathing
leads to, dyspnea
133
what is your approach to a patient with acute dyspnea
history (speed of onset of dyspnea, associated symptoms, what happened immediately before onset, other medical problems)
exam (vital signs [O2 sat], chest [wheezing, etc], heart, extremities [oedema, cyanosis], mental status)
investigations (ECG, CXR, CBE)
appropriate intervention
133
what is your approach to a patient with chronic dyspnea
history
examination
investigations
assessment
management plan
reassessment
