Respiratory #2-4 Flashcards

Question

What occurs with airway narrowing?

Answer 1

- More infolded epithelium - Airway recoil becomes outwards (instead of inwards) - Alveolar SEPTA → aiway walls can transmit negative pressure from the pleural space into the lungs to pull airways open - Some airways have cartilage which prevents narrowing

Answer 2

Remove excess fluid to keep alveolar compartements relatively dry

Answer 3

Through bronchial circulation → Small shunt of blood that is not oxygenated Bronchial also helps to heat (conservation of heat) and humidify the inspired air (add water vapour) → add on the way in, take back on the way out (take back the heat which makes water vapour condense)

Answer 4

Functional unit of the peripheral lung Holes allow air drift from 1 alveoli to another = Collateral ventilation → increase in number with age

Answer 5

The taller the person, the greater the total surface area of the lungs → not very strong correlation Other determinants that relate to height that increase surface area

Answer 6

Pulmonary = 25/8 → mean = 15 Systemic = 120/80 → mean = 100

Answer 7

Part of the type 2 alveolar cells that produce surfactant

Answer 8

Thin, flat cover most of the surface Responsible for gas exchange - important to permeability barrier function of alveolar membrane

Answer 9

- Thinner walled than left ventricle - Suited to increase in volume - Unsuited to increase in pressure acutely - Adapts to pressure chronically by hypertrophy

Answer 10

- Increased by increased filtration pressure - Increased by altered pores sizes - Increased by reduced plasma oncotic pressure

Answer 11

S-curve At extreme volumes → more pressure

Answer 12

TLC = empty lungs → max insp. = FRC + IC FRC = empty lungs → quiet exp. IC = quiet exp. → max insp. RV = empty lungs → max exp. ERV = max exp. → quiet exp. Vt = quiet exp. → quiet insp. IRV = quiet insp. → max insp. VC = max exp. → max insp. = ERV + Vt + IRV = TLC - RV

Answer 13

Plethysmograph as a device measures flow → in respect to time → gives volume Measures lung volume changes, changes in the chest wall volume

Answer 14

VC is defined by max and min lung volume (TLC - RV) Determinants of TLC = inspiratory muscle force (neuromusclar diseases) against chest wall and lung recoil forces (emphysema, lung fibrosis) Determinants of RV = Expiratory muscle force (neuromusclar diseases) against outward recoil of forces of chest wall and airways resistances (obstructive airway diseases, aging)

Answer 15

Inspiration → negative side → pleural pressure = esophageal pressure Expiratory → positive side → pleural pressure doesn't quite follow the E.P. line as it can't go as positive

Answer 16

With Boyle's law: PV = kT PV = (P + ∆P)(V - ∆V) where P = Patm and V = thoracic gas volume at point of occulsion of the airway opening Patm*Vtg = (Patm + ∆P)(Vtg - ∆V) → Vtg = Patm(∆V/∆P)

Answer 17

P-V curve not the same for insp. and exp. - During inspiration, higher pressure for same volume than during expiration - During inspiration, as get close to max inspiration → V(y)/P(x) curve flattens at the top - Linear relationship over good range Hysteresis = when pathway up and down are not the same

Answer 18

S-shaped At very low volumes → chest wall outward recoil predominates (Plungs ~ 0, Pw ~ -40 cm H2O) At very high volumes → The recoil of the lungs predominate (Plungs ~ + 40 cm H2O, Pw ~ + 10 cm H2O)

Answer 19

It becomes negative as the diaphragm is higher up (max ~ -20 cm H2O), ~ 0 cm H2O at 40% of VC trans-diaphragmatic pressure also becomes negative, ~ 0 cm H2O at 27% of VC (thoracic - abdominal)

Answer 20

At low transpulmonary pressure → alveolar ducts are narrow, interalveolar wall infolded Pao = 10 cm H2O, alveolar duct is widened, collagen and elastin fiber system stretched *Collagen and elastin in inter-alveolar septum controbutes to mechanical properties Pressure responsible for inflation of lungs = Pleural pressure - alveaolar space pressure

Answer 21

Air-liquid surface tension *Seen as lungs inflate a lot easier in saline solution because there is no air-liquid surface

Answer 22

Reduces surface tension within lungs from 70 dyn/cm → <10 dye/cm - Polar head (interacts with liquid), non-polar tail - Principal component = dipalmitoyl-3-sn-phosphatidylcholine - Surfactant proteins B and C → important for integration in the surface layer - When surface increase, surfactant is recruited from reservoir, when decrease surfactant is squeezed out - Small aggregates of surfactant are recycled via endocytosis inside the AT2 cells and re-cycled Disrupted that cause leaking of plasma proteins into alveolar compartement disrupt surfactant's function, also damaged by high O2 tensions

Answer 23

The smaller (greater surface tension) one will recoil and poor into the larger one Because they all have the same tension T, but different radius P = 2T/r Surfactant reduces T to a greater extent in smaller alveoli

Answer 24

A → activates macrophages → elicit uterine contractions + cause pro-inflammatory reactions SPB → organizes into tubular structures that are much more efficient at reducing surface tension (specific deficiency in surfactant B → respiratory distress) SPC → enhances function of surfactant phospholipids SPD → important in host defense

Answer 25

- Lack of surfactant → respiratory distress syndrome (surfactant administration works, only natural surfactant and need presence of SPB and SPC for speading in vivo) - Inadequately developped alveolar spaces - Oxygen toxicity + mechanical ventilation → bronchopulmonary dysplasia (arrested dev. of the airways and all tissues)

Answer 26

Emphysema = loss of recoil → higher TLC, faster increase in volume of lungs with less increase in pressure (steeper slope) Fibrosis = increased recoil → lower TLC, more increase in pressure needed for same increase in volume

Answer 27

*See the lung as 1 single big compartement from mouth to alveoli PL = Pao - Ppl = Pfr + Pel = Vt/Cl + RawV' Pfr = Pao + Pa = pressure drop across the airways = pressure needed to overcome flow resistance Pel = Pa - Ppl = press difference between alveoli and pleural space (el for elastance on alveoli) Raw = airway resistance = Pfr/V' (V' = flow) Pel = C(L)/V(T)

Answer 28

Flow = insp → +, exp → - Volume = increase during insp. decreases during exp. Pfr = same as flow Pel = same as volume P total = offset from Pel curve because of Pfr P L = P total = Pel + Pfr = Pao - Ppl

Answer 29

Single compartement model: P lungs = transpulmonary pressure = Res*Flow + Elastance(1/compliance)*Volume

Answer 30

Happens as the lungs don't exactly behave as a homogenous unit V = V0 e^(-T/τ) where τ = R*C Different τ → different rates of filling and emptying - Stiff compartements (lower C) will empty faster - Lower resistance will lead to faster filling and emptying *2 alveoli that empty at different rates will join in a common airway and travel at the same speed from that point on

Answer 31

For healthy subjects → constant ratio between dynamic and static compliance ~ 100% to quite high frequencies Asthmatic subjects → dynamic compliance falls with increase frequency of breathing (static stays cste) → Heterogenous airway narrowing meaning that in the time avaliable alveoli don't fill equally/inadequate filling of some airways (can be helped by collateral channels) *Dynamic compliance = difference between transpumonary pressure in inpiration and expiration vs static compliance = pressure at different volumes*

Answer 32

Prevents areas of lung collapsing when airways are obstructed → alveoli at the end of an airways that is obstructed can still get air and participate in ventilation through other airways - Increases with age and disease

Answer 33

Closer to TLC, resistance is at its lowest → as lung volume decrease, resistance increases exponentially (mostly after FRC) because airways narrow at lower lung volumes, elastic recoil will pull inwards (no negative pleural pressure to pull outwards) *Resistive cost higher at lower lung volumes Airways collapse before reaching RV That's why its not advantageous to try to breathe close to RV → takes much more energy

Answer 34

In a fluid system → W = P*V = force over a certain length Total work = Elastic work + Dynamic work Dynamic work = needed to overcome resistance of airways Elastic work = work against elastic recoil of the lungs → helped by outward recoil of the chest wall = space between static pressure-volume curve of lungs and of the chest-wall

Answer 35

Released during allergic reaction → broncho-constrictor When given to subject → breathing frequency increases → FRC rises gradually → hyperinflation (lungs being pushed to higher volume) *Increase the work of breathing (elastic work part) Volume of rib cage increases, Volume of the abdomen (not actual volume, but displacement of abdominal walls) also pushed out

Answer 36

- Increase in FRC, higher general lung volume - Greater swings in pleural pressure for same change in volume → Need greater work As we get closer to TLC, chest wall starts having positive recoil so elastic work = Pcw + P lungs → much greater Inspire at much more negative pressures, but expire around the same pressures

Answer 37

Diaphragm length is inversly proportional to abdominal volume → increase in abd volume (with asthma for example) → less force from can be generated by diaphragm as it shortens (at 60% of optimal length, can't generate any force) Conclusion: maximal transdiaphragmatic pressure declines with shortening of diaphragm *Force-length curve for skeletal muscle

Answer 38

When you lie down, FRC falls, breathe closer to RV. In healthy subject, not a problem When exercise → breathe out below FRC but mean liung volume is still more elevated (NOT that) Fibrotic lung → but not physiological

Answer 39

It becomes larger as you need more transpulmonary pressure to overcome the resistance *Loop around the static pressure-volume curve of the lung

Answer 40

It is optimized/minimized to different tidal volumes and frequencies at fixed alveolar ventilation and dead space → rate and depth of breathe chosen to minimize the work rate Total work = Dynamic (resistive, viscous) work + elastic work Work rate = work/breath * frequency With high frequency → elastic work goes down and viscous work goes up Optimized ~ 15 breaths/min If more shallow breating → dead space takes greater proportion of ventilation → total ventilation must be higher) If deep breathes → more elastic recoil at higher volumes for each breath (higher muscular cost) → more elastic work *Optimization seen across different species

Answer 41

Work rate increases substantially - FEV1 falls with more narrow airways - Different persons experience different degrees of energy expenditure

Answer 42

When pleural pressure becomes very positive → equal pressure point after which aways collapse (pressure goes down gradually from alv → mouth during exp. because of resistance) This point determines maximal expiratory flow *Same gradient of pressure between alveolar compartement and choke point no matter the pleural pressure *Happens even if alveolar pressure increases also in response to higher alveolar pressure

Answer 43

1. Airway resistance upstream from choke point 2. Recoil of the lungs Dynamic collapse of the lungs → same no matter the pleural pressure Also the properties of the lungs following this equation: V max = Area of airways* srqt(A/gas density * transmural pressure difference/change in airway area (airway stiffness)) *Comes down to elastic recoil of the lungs Choke point = area of airways where smallest expiratory flow is allowed

Answer 44

Women generally have bigger airway:lung volume ratios → higher predicted FEV1/FVC