Term
| Intrapleural & Intrapulmonary pressures |
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Definition
+ Intrapleural: 756mmHg (-4mmHg)
+ Intrapulmonary: 760mmHg |
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Term
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Definition
Pulmonary compliance is a measure of how easy it is to stretch the lungs during inflation.
c=v/p |
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Term
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Definition
| Evident when observing the compliance of the lung on inspiration vs expiration. The difference in compliance is due to the additional energy required in inspiration to recruit and inflate alveoli. |
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Term
| Elastic forces determining lung compliance |
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Definition
+ Tissue elasticity (due to elastin & collagen fibres) 1/3
+ Surface tension (air-liquid interface) 2/3 |
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Term
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Definition
| Resistance = constant x length x radius^4 |
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Term
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Definition
| Mixture of phospholipids, proteins and calcium ions that reduce surface tension from 70 to 5-30 dynes. As alveoli collapse, surfactant density increases stabilising alveolar size. Produced by type 2 endothelial cells. |
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Term
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Definition
| Volume of conducting airways, nasal cavity and pharynx. Equals about 150mL. |
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Term
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Definition
| Includes non-functioning alveoli and may be up to 2L. |
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Term
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Definition
| Minute volume = RR x Vt (e.g. 12bpm x 0.5L = 6L/min) |
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Term
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Definition
| Va= RR x (Vt- dead space) |
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Term
| 2 main categories of lung disease |
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Definition
+ Obstructive (increased airway resistance)
+ Restrictive (reduced lung or thoracic compliance restricts ability of lung to expand) |
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Term
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Definition
| Tendency for a structure to return to its original shape. Opposite of compliance. Thus E=P/V |
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Term
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Definition
+ Increase pulmonary compliance
+ Prevent atelectasis (lung collapse)
+ Facilitate recruitment of collapsed airways |
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Term
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Definition
| P1V1 = P2V2 given temperature is constant |
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Term
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Definition
| 21% of total gas, therefore 21% of 760mmHg = 160mmHg |
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Term
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Definition
| The pressure exerted by a dissolved gas depends on the concentration of free gas molecules. If they are chemically bound to water, they do not count. CO2 is 24 times more soluble than O2. |
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Term
| 5 factors affecting rate of gas diffusion through respiratory membrane |
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Definition
+ Thickness of membrane
+ Surface area of membrane
+ Diffusion coefficient of gas
+ Pressure difference across membranes
+ Pressure difference/ distance |
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Term
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Definition
| O2/Hb dissociation curve shifts to the right when pH decreases. This is seen in the alveoli where CO2 is lost and capillary pH increases, increasing the amount of Hb saturated with O2. |
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Term
| Factors shifting the O2/Hb dissociation curve to the right |
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Definition
+ Decreased pH
+ Increased CO2
+ Increased temperature
+ Increased DPG |
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Term
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Definition
+ 7% as CO2
+ 23% as Hgb-CO2
+ 70% as HCO3- |
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Term
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Definition
| Binding of O2 to Hb in the alveoli displaces CO2 from Hb. This is driven by increased acidity forcing HCO3- to combine with H+ to H2CO3 which dissociates into H20 and CO2 and as oxyHb binds CO2 less strongly. |
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Term
| Ventilation-perfusion ratio |
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Definition
| Alveolar ventilation (RRx (Vt-deadspace)) / CO (blood flow). Not always matched, greatly diminishing the performance of the lungs. |
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Term
| Effect of gravity on perfusion |
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Definition
| Hydrostatic pressure above heart is +15cmH2O as opposed to -15cmH20 below. Thus at rest, very little blood flows through the top of the lungs. |
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Term
| Three zones of blood flow of lungs |
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Definition
Zone 1 = No blood flow as alveolar air pressure exceeds capillary pressure at all stages of cardiac cycle.
Zone 2 = Intermittent flow as alveolar air pressure exceeds capillary pressure except during peaks.
Zone 3 = Continuous blood flow as capillary pressure always exceeds alveolar air pressure. |
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Term
| Hypoxic pulmonary vasoconstriction |
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Definition
| Pulmonary resistance vessels constrict when PaO2 is low to redistribute blood away from areas of low ventilation and reduces shunted blood flow. |
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