Gas Exchange

An Introduction to Gas Exchange

Lecturer: Sally Osborne, Ph level. D. Department of Cell & Physiological Sciences Email: [email protected] ubc. ca Beneficial link: www.sallyosborne.com Required Reading: Respiratory Physiology: A Medical Approach, Shwarrtzstein & Parker, Chapter a few (pp 95-100; 111112).


1 . Separate the following terms: minute, alveolar and dead space ventilation; and anatomic, alveolar and physiologic deceased space. 2 . Specify the partial demands of CARBON DIOXIDE and O2 in the alveoli, mixed venous and arterial blood in normal individuals. 3. Making use of the alveolar ventilation equation, discuss the factors that decide the incomplete pressure of carbon dioxide inside the alveoli and define the terms hyperventilation and hypoventilation. 4. Be able to calculate the PAO2 using the simplified alveolar-air equation. 5. Using Fick's law of diffusion, designate the key elements that affect the exchange of oxygen over the alveolar capillary membrane. 1 ) Ventilation: Day, Alveolar and Dead Space Ventilation is known as a general term for the movement of air into and from the lung. The symbol intended for ventilation is usually V. Sixth is v stands for amount and the department of transportation for " per device time”. Day ventilation can be described as more specific term referring to the total amount of surroundings moved in or out of your lungs each minute. By convention, minute ventilation is typically scored as the number of air expired per minute and symbolized VE. It is helpful to remember that EMPIEZA is the item of the tidal volume expired, written as VT or perhaps VE as well as the respiratory level, RR. VDS 150ml


For each tidal volume (VT) of 500 ml surroundings inspired, one hundred and fifty ml remains in the conducting airways. This volume is called the anatomic dead space (VDS) as it does not participate in gas exchange. That merely goes in and therefore leaves the conducting air passage. The remaining three hundred and fifty ml with the tidal inhale enters the alveoli (VA) and participates in gas exchange. Remember that this 350 ml inspired air mixes with efficient residual ability (FRC), regarding 2400ml l of surroundings already in the lungs. Standard values for dead space and alveolar ventilation are derived within the right.

VA 350 cubic centimeters

VE = VT X RR = 500X12 = 6. zero L/min SE TILL ATT DU AR = VIRTUAL ASSISTANT X RR = 350X12 = 5. 2 L/min VDS =VDS X RR = 150X12 = 1 ) 8 L/min

FRC sama dengan 2400 milliliters In this number, the entire performing zone is definitely represented as being a single tube and the respiratory system zone like a single water tank.

Alveolar air flow (VA) is a volume of atmosphere breathed each minute that: 1) reaches the alveoli and 2) participates in gas 1

exchange. Dead space ventilation (VDS) refers to the portion of day ventilation it does not participate in gas exchange. Dead space fresh air includes air flow of 1) the anatomic dead space: the area of each breath of air that makes its way into the executing airways and 2) the alveolar lifeless space: atmosphere that actually reaches the alveoli but will not participate in exchange (e. g. air that reaches a great alveolus that is not perfused). In healthy people, alveolar deceased space is about 25 ml and deemed relatively unimportant. The total of the anatomic and twangy dead space is referred to as the " physiologic dead space”.

2 . The value of Partial Pressure ideals of Back Carbon Dioxide and Oxygen In the lungs, when blood actually reaches the end of any pulmonary capillary, gas exchange is complete and the incomplete pressure of oxygen and carbon dioxide inside the blood is in equilibrium together with the partial pressure of these smells in the back. Therefore , it is vital to be aware of the factors that determine the partial pressure of oxygen and co2 in the alveoli, as they in return, affect the incomplete pressure of those gases inside the arterial bloodstream supplying the tissues.

dry air PO2 (mmHg) PCO2 (mmHg)

one hundred sixty 0

encouraged air

one hundred and fifty 0

back gas

90 40

mixed venous blood

40 46

arterial blood

95 40

You need to remember the normal PCO2 and PO2 values underneath standard barometric pressure conditions listed in the table above.

2 ....



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