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2.6 BRS Cardiovascular & Respiratory > Ventilation and Gas Exchange > Flashcards

Ventilation and Gas Exchange Flashcards

1
Q

What is minute ventilation?

A

Volume of air expired per min
- measure gas entering/leaving lungs —> not
all reaches alveoli
= tidal volume x breathing frequency

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2
Q

What is RF?

A

Respiratory Rate —> breaths per min

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3
Q

What is Valv?

A

Alveolar ventilation —> volume of air reaching respiratory zone/min
- measure gas entering/leaving alveoli
= (tidal - dead space) x breathing frequency

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4
Q

What anatomical, alveolar and physiological dead space?

A

Dead Space = no gas exchange

Anatomical —> can’t perform gas exchange
- conducting zones (no alveoli)
- usually 150ml

Alveolar —> can perform gas exchange but don’t
- respiratory zones (have alveoli) with non-
perfused parenchyma (no blood supply)
- 0ml in healthy

Physiological —> alveolar + anatomical dead space

  • dec —> bypass conducting zones
    - eg. tracheostomy, cricothyrocotomy
  • inc —> extend conducting zones
    - eg. anaesthetic circuit, snorkle
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5
Q

What is hypoventilation vs hyperventilation?

A

Hypoventilation —> deficient ventilation
- can’t meet metabolic need
- inc PO2 —> acidosis
Hyperventilation —> excessive ventilation
- meet more than metabolic need
- dec PCO2 —> alkalosis

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6
Q

What is hypopnea, hyperpnoea, apnea, dyspnoea, bradypnoea, tachypnea and orthopnea?

A

Hypopnoea —> dec breath depth
Hyperpnoea —> inc breath depth
Apnea —> no breathing
Dyspnoea —> difficulty breathing
Bradypnoea —> breathing too slow
Tachypnoea —> breathing too fast
Orthopnoea —> positional difficulty breathing
(eg. lying down)

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7
Q

What is tidal, inspiratory reserve, expiratory reserve and residual volume?

A

Tidal —> air volume normally inhaled/exhaled
IRV —> extra air volume inspired with max force
ERV —> extra air volume expired with max force
Residual —> air volume remaining in the lungs after
max force expiration
- volumes —> don’t overlap on volume-time graph

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8
Q

What is inspiratory, functional residual, vital, and total lung capacity?

A

Inspiratory —> max air volume inspired after normal
expiration (above neutral point)
= IRV + TV
Functional residual —> air volume left in the lungs
after normal expiration
(below neutral point)
= ERV + RV
Vital —> max air volume inspired after max expiration
= IRV + ERV + TV
Total —> max air volume that the lungs can fill with
= IRV + ERV + TV + RV
- average 6L
- capacity —> sum of different volumes

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9
Q

Which 5 factors affect lung volume/capacity?

A
  1. Body size
  2. Sex
  3. Disease
  4. Age
  5. Fitness
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10
Q

What is the conducting vs respiratory zone?

A

Conducting —> no alveoli for gas exchange
- carry air to respiratory zones eg. bronchi
Respiratory —> alveoli for gas exchange

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11
Q

What is non-perfused parenchyma?

A

Alveoli with no blood supply —> respiratory zones with no gas exchange

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12
Q

What happens at the neutral position of the chest?

A

Ribcage —> naturally recoils out —> push chest out
Lung tissue —> naturally recoils in —> pulls chest in
Chest recoil = lung recoil —> equilibrium
- pleural cavity —> like vacuum
- chest recoil > lung recoil —> inspiration
chest recoil < lung recoil —> expiration
∴ skeletal muscle action required for ins/expiration

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13
Q

What is the neutral point?

A

Point where tidal volume exhaled (naturally holding breath)

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14
Q

What is negative vs positive pressure breathing?

A

Negative - Palv dec —> Palv < Patm —> air pulled in
- normal breathing:
—> diaphragm moves down
—> ribs move up and out
- full inspiratory muscle recruitment
Positive - Patm inc —> Palv < Patm —> air pushed in
- eg. mechanical ventilation, rescue breaths

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15
Q

What is Dalton’s Law?

A

Pressure of gas —> sum of the partial pressures
- Pgas = Σ Pgas1 + Pgas2 + Pgas3 + …

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16
Q

What is Fick’s Law?

A

Diffusion —> proportional to
- concentration gradient (P1-P2)
- surface area (A)
- diffusion capacity (D)
—> inversely proportional to
- surface thickness
- Vgas = (A/T) x D x [P1-P2]

17
Q

What is Henry’s Law?

A

Gas dissolved —> proportional to partial pressure at
equilibrium with the liquid
(constant temp)
- C(Dgas) = a(gas) x P(gas)

18
Q

What is Boyle’s Law?

A

Gas volume —> inversely proportional to pressure
(constant temp)
- Vgas = k / Pgas

19
Q

What is Charle’s Law?

A

Gas volume —> proportional to temp
(constant pressure)
- Vgas = k x Tgas

20
Q

What are the components of air?

A
  1. N2 (78%) —> pp 79.1 kPa
  2. O2 (21%) —> pp 21.3
  3. Ar (0.9%) —> pp 0.9
  4. CO2 (0.04%) —> pp 0.04
  5. Other - Ne, He, H2, Kr
21
Q

How is inspired air modified in the airways? (4)

A
  1. Warmed —> 37°C
  2. Humidified
  3. Slowed
  4. Mixed - with other air in airways

∴ Air in - PO2 = 21.3 kPa
- PCO2 = 0
- PH2O = 0
Conducting airways - PO2 = 20 kPa —> dec
- PCO2 = 0
- PH2O = 6.3 —> aq airways
Respiratory airways - PO2 = 13.5 —> dec
- PCO2 = 5.3 —> exchange out
- PH2O = 6.3 —> aq airways

22
Q

What is must O2 be delivered to tissues via Hb?

A

O2 solubility in blood alone —> too low —> not enough to cells (16 v 250) —> binds to Hb

23
Q

What is Hb?

A

Haemoglobin
Structure:
4 subunits of…
- Fe2+ —> in central tetrapyyrole porphyrin ring
- globin —> bonded at proximal histamine residue

Types:
- HbA —> 2α + 2β subunits
- main type
- HbA2 —> 2α + 2δ subunits
- HbF —> 2α + 2γ subunits

O2 Binding:
- Reversible —> bind at respiratory tissue
—> dissociate at metabolic tissue
- Co-operative - Hb allosteric ∵ central 2,3-DPG
—> O2 binding to a site —> inc binding
affinity of other empty sites

24
Q

What is the oxygen dissociation curve?

A

Graph of PO2 against HbO2 saturation (%) and Total O2 in blood (mL/dL)
- sigmoid shape
- start —> systemic tissue
- low HbO2 saturation —> O2 out of blood
- end —> pulmonary tissue
- high HbO2 saturation —> O2 into blood

25
Q

What makes an oxygen dissociation curve shift right or left?

A

Right:
- Temp inc
- Acidosis —> Bohr shift
- Hypercapnia —> inc CO2 —> acidosis
- 2,3-DPG inc

Left:
- Temp dec
- Alkalosis
- Hypocapnia —> dec CO2 —> alkalosis
- 2,3-DPG dec

26
Q

What makes an oxygen dissociation curve shift up or down?

A

Up:
- Polycythaemia
- O2-carrying capacity inc

Down:
- Anaemia
- O2-carrying capacity dec

27
Q

How does CO affect an oxygen dissociation curve?

A

Down and left
- inc HbCO —> irreversible binding —> dec HbO —>
dec capacity (down) and inc affinity (left)

28
Q

How are the oxygen dissociation curves different for HbF and myoglobin?

A

Myoglobin —> v. left
- v. high affinity for O2 —> stores O2
Foetal Hb —> left
- higher affinity for O2 —> take mother’s O2

29
Q

How is oxygen loaded into blood and unloaded at tissues?

A

Loading —> 2% in plasma
—> 98% bound to Hb

30
Q

How is CO2 loaded into the blood? (3)

A
  1. In plasma - as bicarbonate
    - CO2 + H2O —> H+ + HCO3-
    - non-enzymatic
  2. Bind to Hb - carbamino Hb (binds to amine end)
  3. In RBC - as bicarbonate
    - CO2 + H2O —> H+ + HCO3-
    - enzymatic —> carbonic anhydrase

2.6 BRS Cardiovascular & Respiratory (15 decks)

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