Physiology 3120 Lecture Notes - Lecture 50: Obstructive Lung Disease, Carbon Monoxide Poisoning, Intrapleural Pressure
2 May 2018
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Human Physiology Lecture 50
Lung Diseases and Stresses
- Stress – lung is challenge but it is able to manage that situation
- Disease – lung function is impaired
Stress: ventilation perfusion matching
- For the diffusion of gases, you need oxygen to be in the air space and in
close proximity to the capillary bed BUT the bronchiole or capillary can
become obstructed (lung and blood vessels compensate)
o Oxygen can diffuse into the blood and carbon dioxide can diffuse
out of the blood into the air space, and you can exhale it
- The Blood gas barrier is very thin and has a very large surface area
- This allows for efficient gas exchange
- If there is a broncho-obstruction and the alveolar gas does not get to that
region OR reduction in blood flow to a certain region
- Obstruction of bronchiole:
o Hypoxia develops in the alveoli beyond the point of obstruction
o CO2 accumulates in the hypoxia area leading to decrease in pH
o Vasoconstriction to divert blood flow away from the hypoxic area – no need to perfuse
underventilated alveoli
- Inhale particles and they block air way to the alveoli
- Lung responds: vasoconstriction – in the alveoli the Pco2 will initially increase (still have gas
exchange happening)
o The PCO2 only increases so much – the partial pressure between the alveolar and the blood
is no longer there signals to cause vasoconstriction
o Regional pH (as it is related to PCO2) caused vasoconstriction to blood flow to direct it to
another area in the blood where there is blood coming through
o Lung tries to match the air with where the blood flow is
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Stress: ventilation perfusion matching
- Obstruction of blood flow:
o Blood flow to a bronchiole is reduced, meaning no increase in PCO2 in those alveoli
00 If you have an area of the lung where blood flow is limited or not there, the lung will
compensate by bronchoconstriction and direct the air to other regions of the blood
- For a lot of situations, the lung is able to do this
o Once this becomes too large of a problem (whole left lung does not receive air) – this is NOT
something you can compensate for
o For the smaller problems, the lung manages to match the ventilation with the blood diffusion
Note: compensatory mechanisms to match ventilation and perfusion manage to maintain normal gas
exchange when relative minor changes in either blood flow or airflow occur
- In diseases, mismatch of ventilation and perfusion leads to inadequate gas exchange
PNEUOMOTHORAX
Physical environment of the lung: negative intrapleural pressure
- Poke a hole in the diaphragm causing the intrapleural space = to the atmospheric pressure
o In the normal situation, we have atmospheric pressure inside the lung and outside the lung
▪ The lung wants to collapse; the rib cage wants to move out – the intrapleural
pressure is negative
o When you have a hole in the diaphragm, the intraplueral pressure is almost atmospheric and
the lung will collapse + rib cage will move out
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find more resources at oneclass.com
Pneumothorax
- Air in intrapleural space
- Spontaneous or injury
o Easier to get if you are short and skinny
o Ex. get stabbed which causes a hole in the rib cage
- Small pneumothorax or large one- air is going to leak into the
intrapleural space
- Small spontaneous pneumothorax may resolve without
treatment
- Treatment may include insertion of a chest tube
o Apply some vacuum or remove the air
- Smaller ones will resolve without treatment. Larger ones
require more care and treatment
INHALED PARTICLES AND POLLUTED AIR
- Surface area of lung = thin and large (size of tennis court)
o With the continuing movement of air in and out of the lung, there is continuous exposure to
particles present in the air
o Smaller the size of the particle = further it will travel in the lung
- Minute ventilation: 6-8 liters per minute at rest
o PER DAY: 11, 000 liters of air going into and out of your lungs
o PER YEAR: 4 million liters
- When all this air goes in and out of the lung – any particle or bacteria that is in the air goes into your
lung and if it is small enough, it gets exposed to this very large surface area that is also very thin
- Lung has a complicated and important system of trying to deal with the particles that are inhaled on
a daily basis
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Stress lung is challenge but it is able to manage that situation. The blood gas barrier is very thin and has a very large surface area. If there is a broncho-obstruction and the alveolar gas does not get to that region or reduction in blood flow to a certain region. For a lot of situations, the lung is able to do this: blood flow to a bronchiole is reduced, meaning no increase in pco2 in those alveoli. Note: compensatory mechanisms to match ventilation and perfusion manage to maintain normal gas exchange when relative minor changes in either blood flow or airflow occur. In diseases, mismatch of ventilation and perfusion leads to inadequate gas exchange. Physical environment of the lung: negative intrapleural pressure. Poke a hole in the diaphragm causing the intrapleural space = to the atmospheric pressure. Spontaneous or injury: easier to get if you are short and skinny, ex. get stabbed which causes a hole in the rib cage.
