Ventilation
process that moves gases between the external environment and the alveoli.
Downward contraction of diaphragm
Ventilation process
oxygen is carried from the atmosphere to the alveoli and CO2 is carried from the alveoli to the atmosphere
Atmospheric pressure
also barometric pressure is force exerted by air(gases) that surrounds the earth-and the body
760 mmHg
normal sea level barometric pressure
Pressure gradient
a gas or a liquid always moves from an area of high pressure to an area of low pressure. in order for gas to flow from one point to another there must be a pressure difference.
Inspiration
when atmospheric pressure is higher than intra-alveoli the air moves down the gas pressure gradient, gas moves from atmospheric to the alveoli
Expiration
when the intra-alveolar pressure is greater than atmospheric pressure the air again moves down a pressure gradient, air flows from the alveoli to atmosphere.
diaphragm relaxes
Boyle's Law
volume of gas varies inversely proportional to its pressure at a constant temp
P1 X V1=P2 X V2
Boyle's Law Ventilation
thoracic cavity increases in size(volume) the pressure in the thoracic cavity decreases. This causes air to move down the pressure gradient from the atmosphere to the alveoli. When the thoracic cavity decreases in size(volume), the pressure increases. Thi
Equilibrium point
gas flow continues until the pressure in the lungs equals the pressure in the atmosphere. Once point is reached gas flow stops.
Diaphragm Inspiration
contracts downward
Diaphragm Expiration
relaxes and moves upward
Normal pressure
during normal conditions the intrapleural pressure during inspiration and expiratoin are always below the barometric pressure
1.5 cm
Normal breathing at rest the excursion of diaphragm...
3 to 6cmH2O (2 to 4mmHg)
normal breathing at rest, pleural pressure change
6 to 10cm
during deep inspiration, the diaphragm can move..
-50cmH2O
during deep inspiration pleural pressure can drop...
70-100cmH2O
during forced expiration pleural pressure can reach...
Driving pressure
pressure difference between two points in a tube or a vessel. The force moving gas or fluid through a tube or vessel, if gas pressure at a beginning of a tube is 20mmHg and the pressure at the end of the same tube is 5mmHg, then the driving pressure is 15
Transrespiratory pressure
Is the difference between the barometric(atmospheric) pressure and the alveolar pressure. When the transrespiratory pressure is the pressure gradient difference between the mouth pressure (atmospheric pressure) and the alveolar pressure
Transairway pressure
transrespiratory pressure
Prs equation
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Prs
transrespiratory pressure-causes airflow in and out of the conducting airways, it represents the driving pressure that forces gas in or out of the lungs
Transmural pressure
pressure difference that occurs across the airway wall. pressure outside the airway-pressure inside the airway
Positive transmural pressure
when pressure is greater within the airway than the pressure outside the airway
Negative transmural pressure
when the pressure is greater outside the airway than the pressure inside the airway
Transpulmonary pressure
difference between the alveolar pressure and the pleural pressure. in a normal lung the alveolar pressure is always greater than the pleural pressure and it maintains lungs in an inflated state
Transthoracic pressure
difference between the alveolar pressure and the body surface pressure. It is responsible for expanding the lungs and chest wall in tandem.
Flail chest
each time a patient nhales, the transpulmonary and transthoracic pressure gradients cause his broken ribs to sink inward/ causes inspiration volume to decrease. during exhalation ribs buldge outward
Pendelluft
the movement of air back and forth between the lungs, resulting in increased dead space ventilation.
Chest wall
has the natural tendency to move outward or to expand as a result of the bones of the thorax and surrounding muscles
The Lungs
has the natural tendency to move inward or collapse because of the natural elastic properties of the lung tissue
Lung compliance
how readily the elastic force of the lungs accepts a volume of inspired air. Determines how much air, in liters, the lungs will accommodate for each centimeter of water pressure change
0.2L/cmH2O
normal compliance, the lungs and the chest wall are equal at...
Functional Residual Capacity (FRC)
under normal conditions, the lungs and chest wall recoil to a resting volume.
Hooke's Law
when elastic body is acted by 1 unit of force the elastic body will stretch 1 unit of length. when force exceeds limits the substance will break
Elastance
natural ability of matter to resond directly to force and to return to its original resting position or shape after external force no longer exists
tension pneumothorax
pressure during mechanical ventilation causes the lung unit to expand beyond its elastic capability the lung could rupture, allowing alveolar gas to move into the pleural space cause the lungs to collapse
Surface tension
Maintains shape of water droplet/ insects to stay afloat water
Dynes/cm
Surface tension measured
LaPlace's Law
The liquid film that lines the alveolus resembles bubble or sphere, high transpulmonary pressure must be generated to keep small alveoli open
Pulmonary surfactant
Keeps smaller alveoli from collapsing. It is stored in type two cells
Critical opening pressure
High pressure with little volume change required to overcome the liquid molecular force during the formation of a new bubble (similar to high pressure required to blow up new balloon)
Atelectasis
complete alveolar collapse
Dynamic
study of forces in action
Airway resistance
pressure difference between the mouth and the alveoli (transrespiratory pressure) divided by blow rate. Change in pressure of change in volume
N2
accurate way to measure blood volume
CO2
Is used mostly in neonatal/ used to treat PPHN
Heliox
mixture is 70/30 or 80/20, oxygen and helium. use for severe asthmatics
Kinetic molecular theory
air molecules moving around it creates an energy/ cut in half its called collision, then your pressure goes up
Inspiration v/p
volume goes up-pressure goes down. Diaphragm moves down
Expiration v/p
volume goes down-pressure goes up. Diaphragm moves up causing less volume and more pressure
Laminar Flow
refers to a gas flow that is streamlines. Gas molecules move through the tube in a pattern parallel to the swides of the tube, this flow patern occurs at a low flow rate and low-pressure gradient
Turbulent Flow
refers to gas molecules that move through a tube in a random manner. Gas flow encounters resistance from both the sides of the tube and from the collision with other gas molecules. Occurs at high flow rates and high pressure gradient. Chaotic
Time Constant
product of airway resistance and lung compliance. Necessary to inflate a particular lung region to about 60% of its potential filling capacity.
Dynamic complicance
how readily a lung region fills with gas during a specific time period
Frequency dependent
faster ventilator rate, the smaller volume of air moved.
Tidal volume
volume of air that normally moves into and out of the lungs in one quiet breath
Alveolar ventilation
inspired air that reaches the alveoli
Dead space ventilation
inspired air that does not reach the alveoli
Types of Dead Space
anatomic, alveolar, and physiologic
Anatomic Dead Space
volume of gas in the conducting airways: nose, mouth, pharynx, layrnx, lower airways down but not the respiratory bronchioles.
1ml/lb (2.2ml/kg)
volume of anatomic dead space--IDBW
example-150lbs is 150ml of inspired gas would be anatomic dead space gas
Apnea
complete absence of sponaneous ventilation. causes alveolar oxygen tension to rapidly decrease and the alveolar CO2 tension and arterial CO2 tension to increase. Death within minutes
Eupnea
normal, spontanous breathing
Biot's breathing
short episodes of rapid, uniformly deep inspirations followed by 10 to 30 seconds of apnea.
-first pattern was seen from patient suffering from meningitis
Hyperpnea
increased depth (volume) of breathing with or without an increased frequency
Hyperventilation
Increased alveolar ventilation (produced by any ventilatory pattern that causes an increase in either the ventilatory rate or the depth of breathing) that causes the PAco2 and Paco2 to decrease.
Hypoventilation
Decreased alveolar ventilation (produced by any ventilatory pattern that causes a decrease in either the ventilatory rate or the depth of breathing) that causes the PAco2 and Paco2 to increase.
Tachypena
A rapid rate of breathing
Cheyne-Stokes breathing
Ten to 30 seconds of apnea, followed by a gradula increase in the colume and frequency of breathing, followed by a gradual decrease in the volume of breathing until another period of apnea occurs. As the depth of breathing increases, the PAco2 and Paco2 f
Kussmaul's breathing
Both an increased depth (hyperpnea) and rate of breathing. This ventilatory pattern causes the PAco2 and Paco2 to decline and the PAo2 and Pao2 to increase. Is associated with diabetic acidosis (ketoacidosis)
Orthopnea
A condition in which an individual is able to breathe most comfortably only in the upright position
Dyspnea
Difficulty in breathing, of which the individual is aware