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MP - Lecture 25
Airways, Ventilation, and Properties of Gases
| Question | Answer |
|---|---|
| Medical Physiology – Lecture 25 | Airways, Ventilation, and Properties of Gases |
| In a steady state: | Nothing is building up or depleting (Consumption Rate = Input Rate) |
| At the beginning of exercise, O2 consumption is briefly: | Higher than O2 intake |
| At the end of exercise, O2 intake is briefly: | High than O2 consumption |
| O2 moves by: | Diffusion down partial pressure gradients |
| Increase in partial pressure gradient differences causes hypoxia because: | No molecular O2 pump to move against upward gradients |
| Path of O2 transport: | Inspired > Alveolar > Arterial > Venous > Tissue (reverse for CO2) |
| Airway conducting zones are: | Nose, larynx, trachea, bronchi, and bronchioles |
| Volume of conducting airways makes up the: | Anatomic dead space, ~150 mL |
| How much gas exchange occurs between air and blood in conducting zones? | No gas exchange |
| Functions of conducting airways | Move air by bulk flow, warm and humidify inspired air, and remove particles |
| Removal of particles in conducting airways is by: | Filtration Impaction, mucocilliary escalator |
| Cystic fibrosis patients have abnormal: | CFTR Cl- channels causing inadequate fluid secretion |
| Geometry of airway represents balance between: | Anatomic dead space (large airway) and airway resistance (small airway) |
| Total cross-sectional area in airway geometry is: | Increasing from trachea to terminal bronchiole |
| Laying down causes FRC to: | Decrease |
| Decrease in FRC when laying down is due to: | Gravity no longer able to help relax and depress abdominal contents |
| Total Lung Capacity = | TLC = IRV + TV + ERV + RV |
| Functional Residual Capacity = | FRC = ERV + RV |
| Vital Capacity = | VC = IRV + TV + ERV |
| Spirometry measures: | Changes in volume |
| Volumes measured by spirometer are: | IRV, TV, ERV, and VC |
| Spirometer cannot measure: | RV or related values TLC and FRC |
| Measuring FRC is done by: | Helium dilution method |
| Helium Dilution Method | Helium concentration in lungs equals concentration in spirometer after many breaths because of low helium solubility |
| At the end of expiration, anatomic dead space contains: | Unexpired alveolar air |
| At the end of inspiration, anatomic dead space contains: | Humidified atmospheric air |
| Initial portion of inspired air (~150 mL) into alveoli is: | Old unexpired air from anatomic dead space |
| Latter portion of inspired air (~350 mL) into the alveoli is: | New humidified atmospheric air |
| Alveolar air expired or new air in alveoli = | VT – VD |
| Minute Ventilation = | VT x (Breaths/Min) |
| Alveolar Ventilation = | (VT – VD) x (Breaths/Min) |
| Measure anatomic dead space by: | (Fowler) Inspire 100% O2 and measure % N2 in expired air |
| Expiration in Fowler method contains: | No N2 in first 150 mL, followed by ~70% N2 in alveolar air |
| Anatomic dead space in fowler curve is: | Point of inflection |
| Sigmoid shape of Fowler curve due to: | Mixing of gases |
| Partial Pressure = | P = nRT/V |
| PO2 in Dry Air = | (0.21) x (760 mmHg) = 160 mmHg |
| Pressure of water in humidified in alveolar air is: | 47 mmHg |
| PO2 in Humidified Air = | (0.21) x (760 – 47) mmHg = 150 mmHg |
| Rate of diffusion for dissolved gases at equilibrium is: | No net diffusion |
| Driving for diffusion of gas is: | Partial pressure gradient |
| At equilibrium there is more CO2 than O2 dissolved because: | CO2 has 20x the solubility of O2 |
| Concentration of dissolved gas is directly proportional to: | Partial pressure |
| Slope of line in solubility curve depends on: | Solubility coefficient, different for each gas |
Created by:
emyang
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