Transcript c1a2b0da07c08a1x

To what extend human body is similar to
a machine ?
• Human body must have an energy source in both phases, electrical and
mechanical
• Human body consists of billions of engines (Cells)
• Cardiovascular system acts as a transport ways between these engines
to supply them with fuel and exclude wastes
Fuel cycle within the machine :
1- Food is digested in the digestive system
2 - Digested food is combined with oxygen (O2)
3- Oxygenated digested food is immersed to the cells and
combustion takes place to produce fuel
Why 80 % of air is nitrogen not oxygen ?
Air is inhaled through the nose or mouth and then
through the pharynx, larynx, and the trachea.
The trachea divides into the right and left bronchus,
each of which continues to bifurcate into smaller
and smaller bronchi and terminal bronchioles until
they form alveoli
Alveoli are the actual operating
units of the lungs
1- Perfusion: getting the blood to the pulmonary capillary bed.
2- Ventilation: getting the air to the alveolar surface
Human Body
Blood
Perfusion
Atmosphere
Air
Ventilation
where p is the partial pressure of the solute in the gas above the solution, c is the concentration of the
solute and kH is a constant with the dimensions of pressure divided by concentration.
Gas transfer velocity
α
Bubbles from liquids of low surface tension last longer than those of higher surface
tension, Why ?
Because liquids with higher surface tension form bubbles with high pressure
inside so rupture of these bubbles are easier.
Alveoli are lined with a liquid called surfactant, therefore they have tendency to get smaller due
to surface tension of the surfactant.
Surfactant is a unique liquid because it is unlike all liquids, it has not a constant surface tension.
Surface tension of the surfactant is mainly depends on the alveoli surface area.
Receiving various signals from the nervous system, the diaphragmatic muscles
contract and the diaphragm moves downward. As the diaphragm depresses, it creates
vacuum in the lungs and air rushes into the lungs to fill it. As the diaphragm relaxes,
it pushes the molecules closer together, increasing the internal pressure in the lungs.
The air flows from the lungs into the lower pressure outside the body.
160
Oxygen
Partial
Pressure
(PO2)
mmHg
120
Resting
100
60
Exercising
40
Time
CO has a very secure attachment with the same sites that oxygen binds
with in the blood molecules. This combination is 250 times higher than
the oxygen so it blocks them.
CO victims are placed in oxygen chamber
to enhance their PO2 with 3 atm that
enhance the PO2 by a factor 15.
This treatment is not long tern
treatment because
higher O2 is toxic.
The volume of the lungs during different stages of normal and deep breathing is a good diagnostic
of lung functionality. A relatively simple instrument, called the spirometer is used to measure
airflow into and out of the lungs and record it on a graph of lung volume (L) versus time (sec).
During normal breathing at rest, this is referred to as the tidal volume (TV) at rest . In other words
TV is “The amount of gas inspired or expired with each breath”.
During heavy exercise, the tidal volume (TV) is considerably larger. At the end of a normal
inspiration it is possible with some effort to further fill the lungs with air. The maximum amount of
additional air taken in is called inspiratory reserve volume (IRV). Similarly, at the end of a normal
expiration we can force more air out of the lungs and the maximum volume of additional expired
air is called expiratory reserve volume (ERV).
A modern
spirometer
An incentive
spirometer
A traditional and modern spirometer used to measure a lot of parameters
which deal with the lungs performance. The airflow in and out of the lungs is
recorded on a rotating chart. Water is used as an air-tight seal to keep air
within the counterbalance drum.
Note: The information collected by the spirometer
spirogram.
printed out on a chart called a
Tidal Volume
TV
Volume of air inspired and then expired during breathing in rest
Inspiratory Reserve Volume
IRV
Volume of air a person can inspire above tidal volume
Expiratory Reserve Volume
ERV
Volume of air a person can exhale below resting expiratory volume
Inspiratory Capacity
IC
Volume of a person can inspire above the resting expiratory volume
Residual Volume
RV
Volume of air left in lung after maximum expiratory effort
Functional Residual Capacity
FRC
Air remains in lung after normal expiration
Vital Capacity
VC
Maximum volume of air that can be inspired and then expired
Forced Vital Capacity
FVC
The same VC but under maximum expiratory force
Respiratory Volumes
-
Tidal Volume(TV)
Inspiratory Reserve Volume (IRV)
Expiratory Reserve Volume (ERV)
Residual Volume (RV)
-
Respiratory Capacities
Vital Capacity (VC)
Inspiratory Capacity(IC)
Functional Residual Capacity (FRC)
Total Lung Capacity (TLC)
This is the area of the respiratory system
(trachea and bronchi) in which air is not exposed to blood. (150 cm3)
This is the area of alveoli by act of some
diseases cannot perfuse the blood to O2.
Anatomical dead space can be measured using the Bohr equation. It is more
commonly used to calculate the latter.
Bohr equation states that the dead space (Vd) is calculated as follows:
Vd/Vt = PaCO2 – PeCO2
PaCO2
Where, Vd is dead space volume, Vt is tidal volume, PaCO2 is the partial pressure of
carbon dioxide in the arterial blood, and PeCO2 is the partial pressure of carbon
dioxide in the expired air.
Compliance
Is a measure of the tendency of a hollow organ to resist recoil toward its original
dimension upon removal of a distending or compressing force. It is a very
important physical characteristic of the lungs
Compliance
In adults
Liter/cm
=
compliance
Fibrosis in lung results in Stiff lungs
Flabby lung
=
0.18 - 0.27 liter/cm
small volume change in large pressure Change
large volume change in small pressure Change
Why infants with respiratory distress syndrome (RDS) have lungs with low compliance ?
RDS is a respiratory disorder that affects premature infants born about 6 weeks or more
before their due dates. In this situation, infant’s lungs cannot produce sufficient surfactant
which the liquid coats the inside of lung to keep lungs open to breathe air once they are
born. Oxygen insufficiency may be results in some physiological organs damage.
for electric circuit: V= IR then R = V/I (Volt/A)
Airways resistance is given by the following equation:
R= ∆P/V
where V = ∆V/∆t
(rate of air flow )
The time constant (t) of the lung is related to the airway resistance (R) and the compliance
(C= ΔV/ΔP)
t = RC
(sec)
Time constant of the lung is complicated since many parts of the lung are interconnected. If
one part of the lung has a larger time constant than other parts, it will not get its share of the
air and that part of the lung will be poorly ventilated. The amount of work done in normal
breathing account for a small fraction of the total energy consumed by the body (about 2%
at rest) but the work of breathing during heavy exercise may amount to 25% of the body's
total energy.
1The destruction of lung tissue reduces the springiness of the lungs. The lungs
become more compliant-a small change in pressure produces a larger than
normal change in the volume [C=∆V/∆P]. Much of the work of breathing is
done in overcoming the resistance of the airways R = ∆P/V
In emphysema walls of the alveoli are damaged by inflammation, hence alveoli
can lose their natural elasticity and become overstretched and ruptured.
Their will be a reduced number and strength of the springs which result in
expansion of the chest wall and narrowing of the major airways causing an
increase in airway resistance.
1- The lungs become flabby and expands as the reduced tension allows the
chest wall to expand.
2- The tissues do not pull very hard on the airways, permitting the narrowed
airways to collapse easily during expiration.
The person who has emphysema could be tested by being unable to blow out
a candle.
Asthma is another common obstructive disease, that causes the airways of the lungs to
swell and narrow (its volume decreases). The basic problem is also expiratory difficulty
due to the increased airway resistance [R= ∆P/V].
Some of this resistance is apparently due in part to swelling (edema) and mucus in the
smaller airways, but much of it is due to contraction of the smooth muscles around the
large airway. Lung compliance [C = ∆V/∆P ] is normal.
Functional residual capacity (FRC) [Lung volume after normal expiration] may be
higher than normal, since the patient often starts to inspire before completing a normal
expiration.
* Pet hair or dander
* Dust
* weather changes
* Chemical Pollution
* Pollen
* Infections
* Smoking
Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) provoke asthma in
some patients.
Many people with asthma have a personal or family history of allergies or eczema. Others
have no history of allergies.