lecture 26 Flashcards

1
Q

what are the mix of gases we breath?

A

78% nitrogen
21% oxygen
0.033% CO2

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2
Q

dalton’s law

A

the total pressure exerted by a mixture of gases equals the sum of pressures exerted by all individual gases

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3
Q

partial pressure of O2 in atmosphere

A

160 mm Hg

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4
Q

partial pressure of CO2 in atmosphere

A

0.25 mm Hg

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5
Q

Hypoventilation

A
  • decreasing our ventilation rate below 12 breaths/min
  • PO2 will decrease because we slow down breathing
    PCO2 will increase because we’re blowing out less CO2 (CO2 will build up)
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6
Q

hyperventilation

A
  • increasing our ventilation rate below 12 breaths/min
  • PO2 will increase because your bringing in more
  • PCO2 will decrease because your blowing out more CO2
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7
Q

Alveolar partial pressures and explain the reasoning behind it

A

PO2: 100 mm Hg
PCO2: 40 mm Hg
- because stale air and anatomical dead space and diffusion happens right away

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8
Q

O2 and CO2 diffuse across_________________

A

alveolar epithelial cells (type 1) and capillary endothelial cells

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9
Q

rate of diffusion is governed by ficks law

A

Rate of diffusion is directly proportional to:
1. Surface Area (A)
2. Membrane permeability (D= diffusion constant)
3. Partial pressure gradient (P)

Rate of diffusion is inversely proportional to
1. Diffusion distance (T): membrane thickness and interstitial fluid
- T is squared

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10
Q

Gases diffusing down there partial pressure gradient

A

Pulmonary circulation:
- alveolar PO2 > venous PO2 (100>40)
- alveolar PCO2 < venous PCO2 (40<46)

Systemic circulation:
- arterial PO2 > tissue PO2 (100>40)
- arterial PCO2 < tissue PCO2 (40<46)

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11
Q

Hypoxia

A

Oxygen depleted state

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12
Q

Factors that decrease the amount of O2 reaching alveoli

A
  1. low O2 content in atmosphere
  2. Low alveolar ventilation
    - decreased lung compliance (loose elasticity or compliance can impair O2 uptake
    - increased airway resistance (bronchoconstriction, paracrine factors, autonomic control
    - CNS depression (drugs, alcohol overdose)
  3. Rate and depth of breathing
  4. Adequate perfusion of alveoli
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13
Q

What can impair rate of gas exchange

A
  1. Emphysema
  2. Asthma
  3. Fibrotic lung disease
  4. Pulmonary edema
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14
Q

Emphysema

A
  • is distruction of alveolar wall which decreases surface area for gas exchange
  • loss of elastance
  • happens when u smoke a lot
    Result: Decrease surface area available for gas exchange which decreases diffusion rate and potentially lead to hypoxia
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15
Q

Asthma

A
  • local or systemic release of broncoconstrictors which increase resistance in air ways
  • not enough air getting into lungs in the first place
  • partial pressure gradient decreases
    Result: partial pressure of O2 will be much less than 100 mm Hg because O2 isn’t getting into the alveoli in the first place
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16
Q

Fibrotic lung disease

A
  • build up of scar tissue which can be result from exposure of asbestos
  • the dense fibrous tissue is neither elastic or compliant. If lungs are becoming fibrotic they are not as compliant therefore it will become difficult to fill lungs with air which will reduce the partial pressure gradient and the scar tissue will increase thickness
17
Q

Pulmonary edema

A
  • when there is a build up of fluid between alveolar epithelial cells and capillary endothelial cells which is called interstitial fluid
  • often a result of heart failure
  • increase the thickness
    Result decrease in rate of diffusion which decreases oxygen uptake and can lead to hypoxia