Anatomy, Physiology, Investigations Flashcards
(94 cards)
1
Q
Anatomical definitions of: nasopharynx, oropharynx, laryngopharnyx
A
Nasopharynx = posterior to choanae to dorsal aspect soft palate Oropharynx = soft palate to superior border of epiglottis Laryngopharynx = superior border of epiglottis to inferior border of cricoid (C6)
2
Q
role of intrinsic vs extrinsic laryngeal muscles
A
- Intrinsic – function in speech
2. Extrinsic (infrahyoid group) – elevate larynx during swallowing
3
Q
VC abduction vs adduction produces what kind of sound?
A
- When cords adducted, vibration causes high pitched sound
- When cords abduction, lower pitch sounds
4
Q
cell lining of trachea
A
Pseudostratified columnar epithelium, with goblet cells, cilia and basal stem cells
5
Q
right lung vs left lung: # of lobes, and fissures
A
right lung: 3 lobes. horizontal above and oblique fissure below
left lung: 2 lobes with lingula, oblique fissure only
6
Q
aspirated contents most likely to go into which lobe? why?
A
apical segment of RLL
RMB more vertical and larger
7
Q
compare the conducting vs gas exchange zone of the lungs
A
conducting zone: up to terminal bronchioles (dead space). low surface area, high resistance / turbulence
gas exchange zone: generation 16 to alveoli, high surface area, low resistance / turbulence
8
Q
what is the bronchopulmonary segment vs pulmonary lobule?
A
bronchopulmonary segment: portion of lung supplied by each tertiary bronchus
pulmonary lobule: portion of lung ventilated by one bronchiole
9
Q
types of alveolar cells
A
1) type 1 (95% SA): squamous, rapid gas exchange
2) type 2 (5% SA, though more in number): cuboidal, repair alveolar epithelium and secerete surfactant
3) alveolar macrophages
10
Q
normal pulmonary pressure at alveoli
A
10mmHg - keeps alveoli dry
11
Q
what is the respiratory membrane and what is it made of?
A
barrier between alveolar air and blood made of: 1) squamous alveolar cell 2) shared basement membrane 3) squamous endothelial cell of pulmonary capillary
12
Q
surfactant:
- produced by what
- production starts when
A
- type II alveolar cells (present at 20-24 weeks)
- surfactant secretion starts at 30 weeks
13
Q
alveolar development:
- starts when
- when does most of it occur
A
- starts week 24
- true alveoli seen by week 32
- most alveolar development is postnatal (85%)
- exponential until 2yo, and develops until 8yo
14
Q
how many alveoli at birth vs adult?
A
term: 15 mil
adult: 300-600 mil
15
Q
outline process of development of airways
A
embryonic - 3 weeks: bud from primitive foregut
pseudoglandular at 3 – 16 weeks: bronchial tree
cannicular at 16 – 24 weeks: beyond 16 generations (small airways), thinning, surfactant
saccular at 24 – 36 weeks: gas exchange stuff
birth – 3 years: alveoli inc number
3-8yo: inc zize and complexity of alveoli, pores of Kohn
16
Q
central vs peripheral chemoreceptors
- where
- what they respond to
A
Central chemoreceptors
- ventral surface of medulla, surrounded by CSF
- Respond to CSF [H+]: ↑ PaCO2 → ↑ CSF [H+] → ↑ ventilation
Peripheral chemoreceptors
- bifurcation of common carotid arteries in neck, and aortic bodies around arch of aorta
- Respond to ↓ PaO2, ↓ pH, ↑ PaCO2 → ↑ ventilation
17
Q
what is the herring-breuer reflex?
A
excessive inflation triggers pulmonary stretch receptors to feedback via vagus to medulla inspiratory centre, inhibiting further inspiration
18
Q
lung elastance vs compliance
A
Reciprocals of one another:
elastance = amount of pressure takes to expand the lung unit
compliance = amount of lung volume expanded per pressure unit
19
Q
lung physiology: describe resistance
A
amount of pressure required to generate flow of gas across the airways
20
Q
compare elastic vs resistive work of breathing
A
Elastic work (work required to overcome lung and chest wall elastance) = tidal volume Resistive work (work required to overcome airway and tissue resistance) = respiratory rate
21
Q
what is the concept of time constant?
A
time constant = amount of time it takes for alveoli to equilibriate with Patm = compliance x resistance
22
Q
poiseuille’s law for resistance across airways
A
R= (8xlength) / radius^4
23
Q
which is active in quiet breathing: inspiration or expiration? why?
A
inspiration is active - need to contract diaphragm and intercostals to create negative intrapleural and intrathoracic pressure (cf Patm) to get airflow in. Need to overcome:
A) elastic resistance (65%)
B) airway resistance (35%)
24
Q
examples of extrathoracic, intrathoracic and extrapulmonary, and intrapulmonary airway obstructions
A
extrathoracic: croup, choanal atresia etc.
intrathoracic/extrapulmonary: vascular ring, tumour etc.
intrapulmonary (distal to main bronchi): asthma, bronchiolitis
25
what tends to happen with resp sounds as obstructions move from extrathoracic to intrapulmonary?
extrathoracic: more stridor and retractions, less wheeze / grunting
intrapulmonary: more wheeze / grunting, less stridor.
26
essentially, how does surfactant work?
exerts smaller attracting forces for liquid molecules therefore lower surface tension
27
what is the primary component of surfactant?
surfactant is 90% lipid: Dipalmitoyl phosphatidyl choline (DPPC)
28
at which level of airway is resistance highest? why?
highest at 4th-8th generation - bc so many small airways that in total, resistance is low
29
how many ml is normal anatomical dead space?
150ml
30
4 factors affecting alveolar gas exchange
1) pressure gradient of the gases
2) Gas co-efficient = Weight and solubility of gases in water to travel across membrane
3) membrant thickness and SA
4) V/Q matching
*only
31
which is more soluble in water - CO2 or O2?
CO2, so:
A) CO2 diffusion limitation only occurs with severe AC problems
B) even though pressure gradient of oxygen much greater than carbon dioxide, equal amounts of the two gases are exchanged because CO2 is so much more soluble and therefore diffuses quicker
32
what is the normal V/Q ratio?
```
V = 4L/min
Q = 5L/min
```
therefore 0.8 i.e. more blood flow, less ventilation
33
how is most CO2 transported around the body?
90% as carbonic acid:
| CO2 + H2O –> H2CO3 –> HCO3 + H+
34
where in the lungs are V and Q greatest?
LOWER lobes - ventilation 3x more, perfusion 12x more
35
where is V/Q ratio highest and why?
highest at apex because:
V > Q at apex
Q > V at base
36
what happens in pulmonary shunting?
Right to left: blood that enters arterial system without going through ventilated areas of the lung
37
4 pulmonary factors causing hypoxemia vs hypercapnea
hypoxemia: hypoventilation, diffusion limitation, shunting, v/q mismatch
hypercapnoea: hypoventilation and v/qmismatch
38
what can cause pulse oximetry to be falsely high vs low?
falsely high: carboxyhaemoglobinaemia, methhemoglobinaemia
falsely low: hypoperfusion, profound anaemia, venous congestion
39
O2-Hb binding: left vs right shift = what?
left shift = inc affinity = hold on to O2
| right shift = dec affinity = lose O2
40
what causes left shift of the O2-Hb curve? pathological causes?
low CO2
low H
low temp
low 2,3 DPG
pathological: CO poisoning (increases Hb affinity to O2), methaemoglobinaemia, fetal Hb
41
2,3 DPG - what is it?
allosteric effector: produced by RBC in response to stress esp HYPOXIA- helps haem offload O2; particularly binds to deoxygenated haem i.e. in tissues
42
describe the short and long term effect of O2 and O2-haem binding
- Hypoxia > respiratory compensation with hyperventilation -> respiratory alkalosis = initial LEFT shift
- After 2-3 days chronic hypoxia -> increased 2-3 BPG -> right shift
- After 1 week -> EPO production -> polycythaemia
43
describe the Bohr effect
low pH causes right shift
44
in an infant CXR, where are air bronchograms physiological vs pathological?
physiological if seen through cardiac shadow, pathological if peripheral
45
what ribs should the diaphgram cover in a well inspired film?
5th to 7th anterior ribs
46
when might an expiratory film be actually useful?
FB (ball valve effect)
| PTX
47
when does the thymus reach maximal weight, and when does it start to involute?
max in adolescence 12-19yo -> involutes 20-60yo
48
signs of thymus on CXR
o “Sail” shape = thymus is seen as a triangular sail frequently towards the right mediastinum
o Thymic wave = indentation of normal thymus in young children by the ribs resulting in wavy border
o Thymic notch, interrupting cardiac silhouette
49
6 causes of narrow trachea on CXR
i. Croup (most common)
ii. Vascular ring
iii. Foreign body
iv. Tumor
v. Tracheal stenosis
vi. Stricture – E.g. post intubation
50
3 causes of widened trachea on CXR
i. Prolonged intubation
ii. Chronic cough – E.g. CF
iii. Mounier-Kuhn syndrome – congenital tracheomegaly
51
four causes of anterior mediastinal mass
4Ts: teratoma, thymus, thyroid, terrible lymph nodes
52
2 causes of posterior mediastinal mass
neurogenic tumour
| oesophageal disease
53
3 causes of narrowed mediastinum
a. Steroid treatment – thymic atrophy
b. Acute infection – thymic atrophy
c. Absent thymus – DiGeorge syndrome
54
5 causes of opacity on cxr
1. alveolar opacity i.e. infection
2. interstitial opacity e.g. infection, ILD
3. pleural fluid - ?fluid vs pus vs blood
4. mass
5. collapse
55
8 causes of neonatal bilat pulmonary opacity on CXR
i. Idiopathic RDS
ii. Pulmonary hypoplasia
iii. Pulmonary haemorrhage
iv. Cardiac failure
v. GBS pneumonia
vi. Bilateral pleural effusion
vii. Meconium aspiration
viii. Aspiration
56
what can help you determine which is the abnormal hemithorax on cxr?
i. Vascular markings, decreased then abnormal
ii. Expiratory films, side changes least is abnormal
iii. Hemithorax that is small and opaque is abnormal
57
two major parameters for reliability of spirometry
1. duration and shape of expiratory phase: must be at least 1 second, and plateau
2. reproducibility of flow-volume: 3 volume curves must be superimposable
58
5 meds to withhold prior to spirometry, and duration to withold prior to testing
- Salmeterol – cease 48 hours prior
- Nedocromil sodium – cease 48 hours prior
- Theophylline – cease 12-24 hours prior
- Montelukast – cease 24 hours prior
- Salbutamol – cease 8 hours prior
59
direct vs indirect provocation spirometry: compare
Direct = bronchoconstriction via stimulation of airway smooth muscle
• Methacholine
• Histamine
Indirect = bronchoconstriction through intermediate pathways ie release of inflammatory mediators
• Physical exercise
• Inhalation of hypertonic saline, mannitol
60
what is FRC?
functional residual capacity = amount of air left in lungs after expiration
61
what can cause reduced vs increased FRC?
reduced FRC: alveolar interstitial disease, thoracic deformity (reduced chest wall pull outwards)
increased FRC: intrathoracic obstruction > incomplete exhalation
62
# Define the following terms:
- tidal volume (TV)
- Inspiratory reserve volume (IRV)
- Expiratory reserve volume (ERV)
- Residual volume (RV)
- Vital capacity (VC)
- Inspiratory capacity (IC)
- TV = amount of air moved in and out of the lungs / breath
- IRV = amount of air in excess of TV that can be inhaled with maximum effort (measure of compliance)
- ERV = amount of air exhaled by maximum expiratory effort after tidal expiration
- RV = air in lungs after maximum respiratory effort
- VC = air moved in and out of the lungs with maximum inspiration and expiration = ERV + TV + IRV
- IC = air from maximum inspiratory effort after tidal expiration = TV+IRV
63
FEV1:
- what
- normal values
- inc/dec in obstructive / restrictive disease?
- Volume of air blown out in first 1 second of expiration (after maximal inhalation)
- 0.8-1.2
- low in obstructive AND restrictive
64
Forced vital capacity (FVC):
- what
- normal values
- inc/dec in obstructive / restrictive disease?
- max amount of air blown out after full inspiration
- 0.8-1.2
- dec in restrictive disease. normal/small dec in obstructive bc of gas trapping and hyperinflation
65
FEV1/FVC ratio - normal value
>0.7
66
Forced expiratory flow at 25-75% of FVC (FEF25-75):
- normal
- inc/dec in obstructive / restrictive disease?
- >0.65
| - reduced in obstructive
67
what is the most sensitive spirometry measure of small airways disease in small children? why?
FEF25-75: represents flow in smaller conducting airways
68
what is the most useful spirometry measure long-term of disease progression in obstructive airways disease?
FEV1
69
what is the key spirometry outcome measure for CF? what would indicate referral for transplant?
FEV1: FEV1 <30% = 50% 2 year survival – consideration for transplant referral
70
DMD - what FVC % indicates what degree of disordered breathing?
o FVC <60% = REM sleep disordered breathing
o FVC <40% = NREM/REM sleep disordered breathing
o FVC <20% = daytime respiratory failure
71
Obstructive disease vs restrictive disease
FEV
FVC
FEV/FVC
Obstructive: reduced FEV +++, reduced or normal FVC-> ratio reduced
Restrictive: reduced or normal FEV, reduced FVC -> ratio normal/increased
72
define restrictive lung disease by TLC
reduction in functional lung volume - TLC < 80%
73
restrictive lung disease:
| flow volume loop
- Configuration of loop is narrowed because of reduced exhaled volume
- Flow rates are preserved because of elastic recoil of lungs
74
RV in restrictive disease - up or down?
- Pulmonary disease – ↓ RV, normal RV/TLC ratio
| - Neuromuscular weakness/ chest or spine abnormalities – RV normal, ↑ RV/TLC
75
obstructive disease - what kind of change in FEV1 indicates:
- reversibility with bronchodilator response?
- provocation testing?
- change with exercise?
- reversibility with bronchodilator response – +ve if 12 % change in FEV1
- Provocation testing with methacholine, histamine, hypertonic saline -+ve if 15-20% decrease in FEV1
- Assessing change with exercise - +ve if 12% change in FEV1
76
in large airway obstruction, how do upper vs lower airways respond to insp vs exp?
- Upper airway = NARROWS with inspiration, DILATES with expiration
- Lower airway = DILATES with inspiration, COMPRESSED by expiration
77
fixed airway obstruction vs variable: flow-volume loop
fixed - both insp and exp will be reduced
variable extrathoracic- only insp reduced
variable intrathoracic - only exp reduced
78
what does a double hump in the exp curve of the flow-volume loop mean?
obstruction at the thoracic inlet
79
what does a double hump in the exp curve of the flow-volume loop mean?
obstruction at the thoracic inlet
80
what can cause a sawtooth pattern on the flow-volume loop? (give 5 examples)
Neuromuscular disease, laryngeal dyskinesia, tracheobronchomalacia, upper airway burns, OSA
81
what is the difference between the helium dilution method and whole body plethysmography
Plethysmography may be useful if gas trapping/ obstructive disease present (dilutional studies may not show full FRC)
82
what can spirometry not measure?
RV, so therefore not FRC nor TLC
83
3 methods to test lung volumes
1. helium dilution
2. nitrogen washout
3. whole body plethysmography
84
how does gas dilution work to measure lung volume?
known concentration of inert gas
inhale and exhale in closed circuit until equilibrium
then FRC derived from proportional change in gas concentration
85
how to measure lung compliance? how do you do this?
single breath occlusion method:
- Infants airway is briefly occluded at the end- inspiratory part of the tidal breath.
- Induction of the Hering Brauer reflex leads to respiratory system relaxation during the occlusion and immediately after the occlusion is released
- The computer measures the pressure at the time of occlusion and then the flow (converted to volume) to calculate the change in volume/change in pressure
86
what does a positive exhaled positive nitric oxide test mean? useful in?
asthma - indicates esoinophilic inflammation
87
what is the OSA measuring tool on PSG? what would indicate mild, or mod/severe OSA?
apnoea/hypopnoea index
Mild - <10 AH/hour
Moderate/severe - >10AH/hour
88
rules to determine compensation for respiratory acidosis
RULE = for every 10 CO2 rise, HCO3- rises 1 in a pure respiratory acidosis
- If the actual HCO3 is less than this expected value = coexistent metabolic acidosis
RULE = HCO3 rises 3 for every 10 rise in pCO2 in compensated/base excess phase
89
rules to determine compensation for respiratory alkalosis
```
RULE = Every 10 CO2 decreases, HCO3- down by 2.5 in a pure respiratory alkalosis
RULE = HCO3 falls 5 for every 10 fall in pCO2 in compensated/base deficit phase
```
90
acid base imbalance - what works first to compensate: lungs or kidneys
lungs - immediate
91
anion gap:
- how to calculate
- what values are normal
Anion gap = Na+ - (Cl- + HCO3)
| Normal gap is <18, Gap <14 if exclude K+
92
causes of NAGMA: mnemonic
```
C = chloride excess (eg. NaCl)
A = acetazolamide, Addison’s
G = GIT causes – diarrhoea, vomiting, fistula (pancreatic, ureters, biliary, small bowel, ileostomy)
E = extra – RTA
```
93
base excess:
- what is it
- what's normal
- what can it indicate?
- indicator of metabolic component of the acid-base
- normal = 0
- BE <0 means less HCO3 >> metabolic acidosis
- BE>0 means more HCO3 >> metabolic alkalosis
94
rules to determine compensation for metabolic alkalosis
pCO2 increases by 6 for every 10 increase in HCO3
