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68 Cards in this Set
- Front
- Back
Tidal volume (VT):
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Tidal volume (VT): Amount of air that enters or leaves the lung in a single respiratory cycle
(500 mL). |
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Functional residual capacity (FRC):
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Functional residual capacity (FRC): Volume of gas in the lungs at the end of a passive expiration;
the neutral or equilibrium point for the respiratory system (2,700 ml.). |
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Inspiratory capacity (IC):
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Inspiratory capacity (IC): Maximal volume of gas that can be inspired from FRC (4,000
mL). |
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Inspiratory reserve volume (IRV):
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Inspiratory reserve volume (IRV): Additional amount of air that can be inhaled after a normal
inspiration (3,500 mL). |
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Expiratory reserve volume (ERV):
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Expiratory reserve volume (ERV):Additional volume that can be expired after a normal expiration
(1,500 roll. |
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Residual volume (RV):
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Residual volume (RV):Amount of air in the lung after a maximal expiration (1,200 mL).
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Vital capacity (Ve):
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Vital capacity (Ve): Maximal volume that can be expired after a maximal inspiration (5,500mL).
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Total lung capacity (TLC):
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Total lung capacity (TLC): Amount of air in the lung after a maximal inspiration (6,700 mL).
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Что измеряют при помрщи спирометрии?
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A spirometer can measure only changes in lung volume
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Two common indirect methods измерить TLC and FRC are:
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Two common indirect methods are:
1. Helium dilution 2_ Plethysmography |
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Total ventilation=minute volume = minute ventilation это?
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Total ventilation =minute volume = minute ventilation. It is the total volume of air moved in or out (usually the volume expired) of the lungs per minute.
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.как вычислить Total ventilation?
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VE.= VT X f
VE. = total ventilation VT = tidal volume f :: respiratory rate |
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Normal resting values would be; VT =
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500 mL
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Dead Space
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Regions of the respiratopr system that contain air but are not exchanging 02 and CO2 will
blood |
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Какие виды Dead Space?
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Anatomic dead space
Alveolar dead space Physiologic dead space |
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Anatomic dead space
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Anatomic dead space includes the conducting.zone, which ends at the level s
the terminal bronchioles. Significant gas exchange (02 and CO2) with the blood occurs onl in the alveoli. |
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Какой объем Anatomic dead space?
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The size of the anatomic dead space in mL is approximately equal to a person's weight i
pounds. Thus a 150-lb individual has an anatomic dead space of 150 rnl., |
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Composition of theanatomic dead space and the respiratory zone
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.The respiratory ZOne is a veryconstant environment. Under resting conditions, rhythmic ventil;
tion introduces a Small volume into a much larger respiratory zone. Thus, the partial pressure I gases in the alveolar compartment changes very little during normal rhythmic ventilation. |
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Composition at the End of Expiration (Before Inspiration)
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At the end of an expiration, the anatomic dead space is filled with air that originated in the alvec
or respiratory zone. Thus, the composition of the air in the entire respiratory system is the sao at this static point in the respiratory cycle.. This also means that a sample of expired gas tab near the end of expiration (end tidal air) is representative of the respiratory zone. |
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Composition at the End of Inspiration (Before Expiration)
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The first 150 mL of any inspiration fills the dead space with room air, and the first 150 mL to
reach the alveoli consists of dead space air (same composition as alveolar gas). The last 150 ml, of inspired air remains in the dead space. This can be considered dead-space ventilation. Beyond 150 ml., room air is added to the respiratory zone. This also means that after the first ISO mL through the remainder of inspiration, the dead space contains humidified room air. |
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Alveolar dead space
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Alveolar dead space
Alveoli containing air but without blood flow in the surrounding capillaries. |
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Physiologic dead space
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Physiologic dead space
This is the total dead space in the lung system (anatomic dead space plus alveolar dead space). |
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Alveolar Ventilation
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Alveolar ventilation represents the room air delivered to the respiratory zone per minute. The
first 150 mL of each inspiration comes from the anatomic dead space and does not contribute to alveolar ventilation. |
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Alveolar Ventilation
VA= |
VA= (VT-Vd)X f
VA = alveolar ventilation VT ;;: tidal volume V0 = dead space f = respiratory rate |
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The alveolar ventilation per inspiration is
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The alveolar ventilation per inspiration is 350 ml.,
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Increases in the Depth of Breathing
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There will be equal increases in total and alveolar ventilation per breath, since dead space volume
is constant. If the depth of breathing increases from a depth of 500 mL to a depth of 700 mL, the increase in total and alveolar ventilation would be 200 mL |
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Increases in the Rate of Breathing
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Increases in the Rate of Breathing
There will be a greater increase in total ventilation than in alveolar ventilation, because the increased rate causes increased ventilation of dead space and alveoli. For every additional inspiration with a tidal volume of 500 mL, total ventilation would increase 500 rnl., but alveolar ventilation would increase by only 350 mL (assuming dead space is 150 mL). |
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Muscles of Respiration
Inspiration |
The major muscle of inspiration is the diaphragm. Contraction of the diaphragm enlarges the
vertical dimensions of the chest. Also utilized are the muscles of the chest walL Contraction of these muscles causes the ribs to rise and thus increases the anterior-posterior dimensions of the chest |
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Muscles of Respiration
Expiration |
Expiration
Under resting conditions, expiration is normally a passive process; i.e., it is due to the relaxation of the muscles of inspiration. When it is active, the muscles of the abdominal wall can be considered the main muscles of expiration. The contraction forces the diaphragm up into the chest. Included would be external oblique, rectus abdominal, internal oblique, and transverse abdominal muscles. |
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In respiratory physiology, they are usually given as ern H20.
1 cm H20 = |
Units ofpressure
In respiratory physiology, they are usually given as ern H20. 1 cm H20 = 0.74 mrn Hg (I mrn Hg = 1.36cm H20) |
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the two main forces acting on
the lung: |
lung recoil and intrapleural pressure.
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Lung Recoil
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• Represents forces that develop in the wall of the lung as the lung expands.
• As the lung enlarges, recoil increases; as the lung gets smaller, recoil decreases. • Recoil, as a force, always acts to collapse the lung. |
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Intrapleural Pressure
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• Represents the pressure in the thin film of fluid between the lung and the chest wall.
Subatmospheric pressures (-) act as a force to expand the lung, and positive pressures (+) act as a force to collapse the lung. During normal restful breathing, intrapleural pressure is always subatmospheric (or negative) and thus acts as a force to expand the lung. When intrapleural pressure is a greater force than lung recoil. the lungs expand. When the recoil force is greater than that created by intrapleural pressure, lung volume will be decreasing. ~en the force of recoil and intrapleural pressure are equal and opposite, a static state exists, and lung size will be constant. |
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MECHANICS UNDER RESTING CONDNONS
Before Inspiration |
The glottis is open, and all respiratory muscles are relaxed (FRC). This is the neutral or equilibrium
point of the respiratory system (Figure VII-I-4). Intrapleural pressure is negative at FRC because the inward elastic recoil of the lungs is opposed by the outward-directed recoil of the chest wall. The intrapleural force and recoil force are equal and opposite, and because no air is flowing through the open glottis, alveolar pressure must be zero.Byconvention, the atmospheric pressure is set to equal zero. |
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MECHANICS UNDER RESTING CONDmONS
During Inspiration |
1. Inspiration is induced by the contraction of the diaphragm and some accessory muscles
that expand the chest wall. The net result is to make intrapleural pressure more negative. The greater the contraction, the greater the change in intrapleural pressure and the larger the force trying to expand the lung. 2. The expansion of the lung causes the gases in the alveoli to expand, creating a slightly negative alveolar pressure, This causes air to flow into the lung. |
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MECHANICS UNDER RESTING CONDmONS
End of Inspiration |
End of Inspiration
1. The lung expands until the recoil force increases to equal intrapleural pressure. Once the forces are again equal and opposite, the lung is at its new larger volume. 2. The inflowing air returns alveolar pressure toward zero, and when it reaches zero, airflow stops. Under resting conditions, about 500 mL of air flows into the lung system in order to return alveolar pressure back to zero. |
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MECHANICS UNDER RESTING CONDmONS
Expiration |
Expiration
L Expiration under resting conditions is produced simply by the relaxation of the muscles of inspiration. 2. Relaxation ofthe muscles of inspiration causes intrapleural pressure to return to -5 cm H2O. 3. Lung deflation begins and continues until the recoil force decreases to again equal intrapleural pressure. Once this occurs, the lung system is back to FRe. 4. Deflation of the lung compresses the gases in the alveoli, creating a slightly positive alveolar pressure. This causes air to flow out of the lungs. 5. The outflowing air returns alveolar pressure toward zero, and when it reaches zero, airflow stops. |
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Intrapleural pressure during a normal respiratory cycle
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Under resting conditions, it is always a subatrnosphere pressure.
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Intraalveolar pressure during anormal respiratory cycle
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Intraalveolar pressure is slightly negative during inspiration and slightly positive during expiration.
By convention, total atmospheric pressure = O. |
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EFFECTS OF INTRAPLEURAL PRESSURE ON PULMONARY BLOOD
FLOW AND VOLUME Inspiration |
• Intrapleural pressure becomes more negative (decreases).
• Systemic venous return and right ventricular output are increased. • An increase in the output of the right ventricle will delay the closing of the pulmonic valves and may result in a splitting of the second heart sound. Pulmonary vessels expand, and the volume of blood in the pulmonary circuit increases. • Venous returns to the left heart, and the output of the left ventricle is decreased, causing decreased systemic arterial pressure. • Expansion of the right atrium and the ensuing drop in blood pressure cause 11 reflex increase in heart rate (sinus arrhythmia), |
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EFFECTS OF INTRAPLEURAL PRESSURE ON PULMONARY BLOOD
FLOW AND VOLUME Expiration |
Intrapleural pressure becomes more positive (increases).
• Systemic venous return and output of the right ventricle are decreased. Pulmonary vessels are compressed, and the volume of blood in the pulmonary circuit is decreased. • The return of blood and output of the left ventricle are increased, causing increased systemic arterial pressure. The right atrium is compressed, and the blood pressure is increased, causing a reflex decrease in heart rate, AValsalva maneuver will also increase intrapleural pressure and central venous pressure and decrease venous return. |
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POSITIVE~PRESSURERESPIRATION
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Assisted Control Mode Ventilation (ACMV
Positive End-Expiratory Pressure (PEEP} |
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Assisted Control Mode Ventilation (ACMV)
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Assisted Control Mode Ventilation (ACMV)
Inspiratory cycle initiated by patient or automatically if no signal is detected within a specified time window. |
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Positive End-Expiratory Pressure (PEEP}
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Positive End-Expiratory Pressure (PEEP}
Volume cycled rather than pressure or timed cycled is the most common. In some cases, the opening of the lung to the pleural space may function as a valve allowing the air to enter the pleural space but not to leave. Strong inspiratory efforts promote the entry of air into the pleural space, but during expiration, the valve doses and positive pressures are created in the chest cavity. Ventilation decreases but the positive pressures also decrease venous return and cardiac output. Controlled mode-machine-triggered Assist mode-inspiratory cycle initiated by the patient CPAP-continuous airway pressure in spontaneous breathing patients PEEP {positive end-expiratory pressurej-s-positive pressure is applied at the end of the expiratory cycle to decrease alveolar collapse. Small alveoli have a strong tendency to collapse, creating regions of atelectasis. The largeralveoli are also better ventilated, and supplementary oxygen is more effective at maintaining a normal arterial P02, One downside to positive pressure ventilation and accentuated by PEEP is a decrease in venous return and cardiac output. Positive pressure ventilation and the addition of PEEP are illusrrated below. |
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PNEUMOTHORAX
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• Intrapleural pressure increases from a mean at -5 em H20 to equal atmospheric pressure.
Lung recoil decreases to zero as the lung collapses. • Chest wall expands. At FRC, the chest wall is under a slight tension directed outward. It is this tendency for the chest wall to spring out and the opposed force of recoil that creates the intrapleural pressure of -5 cm H20. |
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Tension pneumothorax
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Tension pneumothorax most commonly develops in patients on a positive-pressure ventilator,
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Lung compliance is
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Lung compliance is the change in lung volume (tidal volume) divided by the change in surrounding
pressure. This is stated in the following formula: dV Compliance = dP |
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Increased Lung compliance means Reduced Lung compliance means
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Increased compliance means more air will flow for a given change in pressure.
Reduced compliance means less air will flow for a given change in pressure. |
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Increased lung compliance also occurs with
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Increased lung compliance occurs with aging and with a saline-filled lung.
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Components of lung Recoil
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Lung recoil has two components:
1. The tissue itself, more specifically, the collagen and elastin fibers of the lung. The larger the lung, the greater the stretch of the tissue and the greater the recoil force. 2. The surface tension forces in the fluid lining the alveoli. Surface tension forces are created whenever there is a liquid-air interface (Figure VII-I-II). Surface tension forces tend to reduce the area of the surface and generate a pressure. In the alveoli, they act to collapse the alveoli; therefore, these forces contribute to lung recoil. Surface tension forces are the greatest component of lung recoil. The relationship between the surface tension and the pressure inside a bubble is given by the law of LaPlace. p= Tr p= pressure T= tension r == radius |
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If wall tension is the same in two bubbles, the smaller bubble will have
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If wall tension is the same in two bubbles, the smaller bubble will have the greater pressure.
it follows that small alveoli tend to be unstable. They have a great tendency to empty into larger alveoli and collapse (creating regions of atelectasis) Collapsed alveoli are difficult to reinflate. |
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Surfactant has three main functions:
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1. It lowers surface tension forces in the alveoli. In other words, surfactant lowers lung recoil
and increases compliance. 2. It lowers surface tension forces more in small alveoli than in large alveoli. This promotes stability among alveoli of different sizes by decreasing the tendency of small alveoli to collapse (decreases the tendency to develop atelectasis). 3. It reduces capillary filtration forces and thus reduces the tendency to develop pulmonary edema. A negative intrathoracic pressure is a force promoting capillary filtration. Low recoil means an intrapleural pressure closer to atmospheric, and under these conditions it is not a significant force promoting filtration. |
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Respiratory Distress Syndrome (RDS)
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Infant respiratory distress syndrome (hyaline membrane disease): deficiency of surfactant
Adult respiratory distress syndrome (ARDS): acute lung injury |
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Adult respiratory distress syndrome ( : acute lung injury via the following:
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• Bloodstream-Sepsis-develops from injury to the pulmonary capillary endothelium,
leading to interstitial edema and increased lymph flow. This leads to injury and increased permeability of the alveolar epithelium and alveolar edema. The protein seepage into the alv~oli reduces the effectivenessof surfactant. Neutrophils have been implicated in the progressive lung injury from sepsis. • Airway-Gastric aspirations-v-direct acut~ injury to the lung epithelium increases permeability of the epithelium followed by edema. |
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The symproms ARDS) include:
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The symproms include:
I. Increased lung recoil and decreased lung compliance. At a given lung volume, intrapleural pressure willbe more negative. A greater change in intrapleural pressure is required to inflate the lungs. 2. Atelectasis There is a greater tendency for small alveoli to collapse. Once collapse occurs. it is difficult to reinflate these alveoli. This is illustrated in curve B in Figure VII-I-l3. Here a very negative intrapleural pressure (inspiratory effort) is required to reinflate the alveoli. 3. Pulmonary edema Because a deficiency of surfactant increases recoil, a more negative intrathoracic pressure is required to maintain a given lung volume. Very negative intrapleural pressures represent a large force promoting capillary filtration. |
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AIRWAY RESISTANCE
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Radius of an Airway
1 Resistance ~ radius4 In the branching airway system of the lungs, it is the first and second bronchi that represent most of the airway resistance. |
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Parasympathetic nerve stimulation produces
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Parasympathetic nerve stimulation produces bronchoconstriction. -
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Circulating catecholamines produce
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Circulating catecholamines produce bronchodilation,
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что происходит с AIRWAY RESISTANCE во время вдоха?
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During inspiration, intrapleural pressure is decreasing, which produces greater transverse
stretch that opens the airways. Consequently, airway resistance decreases during inspiration. The more negative the intrapleural pressure, the lower the resistance of the airways. |
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PULMONARY FUNCTION TESTING
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Vital Capacity (VC)
(FEY1) (FVC) |
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(FEY1). the forced expiratory volume in 1sec is?
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During the FVCmaneuver, the volume of air exhaled in the first second
is called the forced expiratory volume in 1sec (FEY\). |
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dynamic compression of the
airways is? |
Normal people can exhale only 80% of their VC in 1 second because during a forced expiration,
intrapleural pressure becomes positive and the airways are compressed. Compression of the airways limits expiratory flow rates. This compression is called "dynamic compression of the airways |
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Obstructive pulmonary disease
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Obstructive disease is characterized by an increase in airway resistance that is measured as a
decrease in expiratory flow rates. Examples are chronic bronchitis, asthma, and emphysema |
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Obstructive pattern
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Total lung capacity (TLC) is normal or larger than normal, but during amaximal forced expiration
from TLC, a smaller than normal volume is slowly expired. |
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Obstructive FEV1 =
FVC |
FEV1 < 80%
FVC |
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Restrictive FEV1 =
FVC |
FEV1 > 80%
FVC |
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Restrictive pulmonary disease
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is characterized by an increase in elastic recoil-e-a decrease in
lung compliance-which is measured as a decrease in all lung volumes. Reduced vital capacity with low lung volumes are the indicators of restrictivepulmonary diseases |
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Restrictive pattern
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TLC is smaller than normal, but during a maximal forced expiration from TLC, the smaller volume
is expired quickly and more completely than in a normal pattern; therefore, even though FEVr is also reduced, the FEY/FVC is often increased. However, the critical distinction is low FVCwith low FRCand RV. |