What is Tidal volume? (TV)
the amount that goes in and out= usually small percentage of the breath potential -difference between the inspiration and expiration -can vary enormously depending on how hard we breath in, can be small in rest and big in exercise
What is Inspiratory capacity? (IC)
big breath in
What is inspiratory reserve volume? (IRV)
-the volume we could be using if we took a huge breath in -The maximum amount of air that can be breathed in during a deep inspiration.
What is expiratory reserve volume? (ERV)
volumes we can get get if expire a lot -the maximum amount of air that can be breathed out during active expiration.
What is Vital capacity? (VC)
-the potential breath when breathing maximally -The maximum capacity of the lungs minus the residual volume
What is residual volume? (RV)
-some air always stays in the lung this is it even if we breath out a lot -The leftover volume of "dead" air that is left over in the lungs after a forceful expiration
What is the functional residual capacity? (FRC)
-the air that stays in during normal breathing -The leftover volume of air after passive expiration
What is total lung capacity? (TLC)
-total of the air possible in lungs
How do you calculate Pulmonary ventilation (ml/min)?
Pulmonary ventilation (ml/min) = tidal volume (ml/breath) X respiratory rate (breaths/min)
How do you calculate tidal volume (TV)?
End-inspiratory vol - end-expiratory vol = tidal volume
What is anatomical dead space?
-dead space= the air that is in the upper airways and bronchi, then that isn't used for diffusion in the alveoli it comes in with the breath and leaves with breathing out Dead-space/tidal volume ratio : -33% in human & dog -50-75% in cattle & horse (resting state) -dead space stays about the same even in exercise but proportionally we will lose less, so bigger breaths= the percentage is smaller but the amount tsays the same
Why is dead space important?
-Dead-space ventilation important during exercise, thermoregulation -dead space is important to retain some CO2 which is important for pH maintanance = like in panting! and exercise have to have the dead space so CO2 is maintained
What enters the alveoli during inspiration?
combination of fresh air and the air from the previous breath
How do you calculate alveolar ventilation?
ssuming quiet breathing at rest: average values Alveolar ventilation = (500 ml/breath) - (150 ml dead space volume) x 12 breaths/min = 4,200 ml/min
What happens to Alveolar ventilation with: 1. Deep, slow breathing? 2. Shallow, rapid breathing
1.smaller proportion of dead space so the propotion will increase 2.more dead space so proprtion of the alveolar ventilation to the pulmonary ventilation will be smaller
What is perfusion?
perfusion= the flow of air going through
What is ventilation?
ventilation= getting the air in
How is ventilation and perfusion matched?
when change in ventilation= should affect the circulation around the alveoli so you can take up more O2 and dump more CO2 -Local control of individual airways supplying specific alveoli - Optimizes efficiency of O2 & CO2 exchange -Direction of effect is opposite to that in systemic arterioles (=-the circulation affaected by O2 and CO2 levels, normally low 02 leads to vasodilation= more flow in blood vessels but here! the opposite- vasoconstriction= the reason is that it is matching the uptake of oxygen not the coming in of it) -first point= the smooth muscle around bronchioles can change the diamater and even determine the participation of the alveoli
How is airflow and bloodflow regulated in an area in which blood flow (perfusion) is greater than airflow (ventilation)?
How is airflow and bloodflow regulated in an area in which airflow (ventilation) is greater than blood flow (perfusion)?
What partial pressure do the gasses in air and water (blood) sum up to?
Mixed gases in air & water (blood) exhibit individual partial pressures that sum to atmospheric pressure 760 mm Hg
- Depends on volume of gas (& solubility in liquid)
-Gases move down partial pressure gradients
Explain the exchange of gas due to pressure gradients, in and out of body?
given that at rest and good health the blood coming from the alveoli= about a 100 as well
gets to tissues loses the O2 some of it, drops to 40
then CO2 goes out as the pressure is higher in than out and the reverse with O2
What causes the air to leave lungs?
As the external intercostals & diaphragm contract, the lungs expand. The expansion of the lungs causes the pressure in the lungs (and alveoli) to become slightly negative relative to atmospheric pressure. As a result, air moves from an area of higher pressure (the air) to an area of lower pressure (our lungs & alveoli). During expiration, the respiration muscles relax & lung volume descreases. This causes pressure in the lungs (and alveoli) to become slight positive relative to atmospheric pressure. As a result, air leaves the lungs.
What is partial pressure?
t's the individual pressure exerted independently by a particular gas within a mixture of gasses. The air we breath is a mixture of gasses: primarily nitrogen, oxygen, & carbon dioxide. So, the air you blow into a balloon creates pressure that causes the balloon to expand (& this pressure is generated as all the molecules of nitrogen, oxygen, & carbon dioxide move about & collide with the walls of the balloon). However, the total pressure generated by the air is due in part to nitrogen, in part to oxygen, & in part to carbon dioxide. That part of the total pressure generated by oxygen is the 'partial pressure' of oxygen, while that generated by carbon dioxide is the 'partial pressure' of carbon dioxide. A gas's partial pressure, therefore, is a measure of how much of that gas is present (e.g., in the blood or alveoli).
the partial pressure exerted by each gas in a mixture equals the total pressure times the fractional composition of the gas in the mixture. So, given that total atmospheric pressure (at sea level) is about 760 mm Hg and, further, that air is about 21% oxygen, then the partial pressure of oxygen in the air is 0.21 times 760 mm Hg or 160 mm Hg.
How does the exachange of O2 and CO2 occur between the air and the blood?
The exchange of gases (O2 & CO2) between the alveoli & the blood occurs by simple diffusion: O2 diffusing from the alveoli into the blood & CO2 from the blood into the alveoli. Diffusion requires a concentration gradient. So, the concentration (or pressure) of O2 in the alveoli must be kept at a higher level than in the blood & the concentration (or pressure) of CO2 in the alveoli must be kept at a lower lever than in the blood. We do this, of course, by breathing - continuously bringing fresh air (with lots of O2 & little CO2) into the lungs & the alveoli.
How do the external intercostals plus the diaphragm contract to bring about inspiration?
Contraction of external intercostal muscles > elevation of ribs & sternum > increased front- to-back dimension of thoracic cavity > lowers air pressure in lungs > air moves into lungs
Contraction of diaphragm > diaphragm moves downward > increases vertical dimension of thoracic cavity > lowers air pressure in lungs > air moves into lungs:
Why is it a problem that the alveoli are coated by water?
The walls of alveoli are coated with a thin film of water & this creates a potential problem. Water molecules, including those on the alveolar walls, are more attracted to each other than to air, and this attraction creates a force called surface tension. This surface tension increases as water molecules come closer together, which is what happens when we exhale & our alveoli become smaller (like air leaving a balloon). Potentially, surface tension could cause alveoli to collapse and, in addition, would make it more difficult to 're-expand' the alveoli (when you inhaled). Both of these would represent serious problems: if alveoli collapsed they'd contain no air & no oxygen to diffuse into the blood &, if 're-expansion' was more difficult, inhalation would be very, very difficult if not impossible. Fortunately, our alveoli do not collapse & inhalation is relatively easy because the lungs produce a substance called surfactant that reduces surface tension.
What are the partial pressures of O2 and CO2 in resting condition in the alveoli, alveoli capillaries, and blood?
PO2 = 100 mm Hg
PCO2 = 40 mm Hg
Entering the alveolar capillaries
PO2 = 40 mm Hg (relatively low because this blood has just returned from the systemic circulation & has lost much of its oxygen)
PCO2 = 45 mm Hg (relatively high because the blood returning from the systemic circulation has picked up carbon dioxide)
-While in the alveolar capillaries, the diffusion of gasses occurs: oxygen diffuses from the alveoli into the blood & carbon dioxide from the blood into the alveoli.
Leaving the alveolar capillaries:
PO2 = 100 mm Hg
PCO2 = 40 mm Hg
Blood leaving the alveolar capillaries returns to the left atrium & is pumped by the left ventricle into the systemic circulation. This blood travels through arteries & arterioles and into the systemic, or body, capillaries. As blood travels through arteries & arterioles, no gas exchange occurs.
Entering the systemic capillaries:
PO2 = 100 mm Hg
PCO2 = 40 mm Hg
Body cells (resting conditions):
PO2 = 40 mm Hg
PCO2 = 45 mm Hg
Because of the differences in partial pressures of oxygen & carbon dioxide in the systemic capillaries & the body cells, oxygen diffuses from the blood & into the cells, while carbon dioxide diffuses from the cells into the blood.
Leaving the systemic capillaries:
PO2 = 40 mm Hg
PCO2 = 45 mm Hg
Blood leaving the systemic capillaries returns to the heart (right atrium) via venules & veins (and no gas exchange occurs while blood is in venules & veins). This blood is then pumped to the lungs (and the alveolar capillaries) by the right ventricle.
Why is alveolar PO2 100 mm Hg when atmospheric PO2 is 160 mm Hg?
At body Temp. PH2O vapour = 47 mm Hg ␣ PO2 150 mm Hg ie. dead-space (functional residual capacity)
␣ O2 is continually moving down its partial pressure gradient ␣ ie across alveoli into blood
-the air coming in is warmed and humidified so has larger vapor content= protection for the alevoli and also the partial pressure of this water is diluting the O2 and the dead space too the reulsting partial pressure= about 100
What are the factors influencing gas exchange at the alveolar membrane?
-Partial pressure gradient: Major determinant (PAO2 ␣ PcapO2)=Pcap 02= partial pressure in capillary
- Surface area of alveolar membrane (A) :
Constant at rest, rises during forced inspiration eg during exercise, decreases during some pathophysiological states(the larger the area the better it will be able to flow across also depends on how many alveoli participate= in big breaths =more)
-Thickness of air blood barrier (x):Constant at rest
rises during some pathophysiological states (the thicker it is the slower the movement of oxygen across
when horses go hard. increas ein the intestitial space fluid= so thicker air blood barrier= point where the limit is reached )
-Diffusion coefficient of gas (D )
␣ CO2 : 20x > O2
Rate of O2 movement = D . A . (PAO2 - PcapO2)/x