Pulmonary Flashcards
Most important muscles that raise the rib cage to facilitate inspiration
Diaphragm 75%
1 external intercostals
2 SCM
3 anterior serratus
4 scalenes
Muscles that pull ribs downward during expiration
1 abdominal recti
2 internal intercostals
Elastic recoil of lung, chest wall and abdominal structures
Pressure of fluid in thin space bet lung pleura and chest wall pleura
Pleural pressure
Pleural pressure is
slightly negative -5 cmH20 beginning inspiration
Normal inspiration creates a more
negative pleural pressure from -5 to -7.5
Pressure of air inside the lung alveoli
Alveolar pressure 0cm when glottis is open and no airflow
During inspiration, to cause inward flow alveolar pressure must
fall to slightly below atm pressure at -1cmH20
During expiration, alveolar pressure rises to +1cmH2O
Difference between pleural and alveolar pressure; measure of elastic force in lungs that tend to collapse lungs at each instant of respiration
Transpulmonary pressure
Recoil pressure
Extent to which lungs will expand for each unit increase in transpulmonary pressure
Compliance
Everytime the transpulmo pressure increases by 1cm H2O the lung volume after 10-20 sec will expand by 200mL
Compliance is determined by
1 elastic forces of lung tissue
2 elastic forces by surface tension of fluid lining inside walls of alveoli and other lung air space
Elastin forces of lung are determined by
elastin and collagen
Surface active agent in water greatly reducing surface tension of alveoli and subsequently, decrease the work of breathing
Complex phospholipid secreted by Type II epithelial cell
Surfactant
Produced in terminal saccular stage
Tendency of water molecules on surface to contract via their strong attraction for one another such as in raindrop
In alveoli, it attempts to force air out of alveoli through bronchi leading to alveolar collapse
Created by attractive forces between water molecules producing collapsed alveoli
Surface tension
Surfactants are secreted by
type II alveolar epithelial cells
Most important components of surfactant
1 dipalmitoylphosphatidylcholine
2 Ca ion
Blocking the passages leading to alveoli lead to
Inc surface tension and collapse creating positive pressure attempting to push the air out
Pressure from blocked alveoli attempting to push air out =
Pressure = (2xsurface tension)/radius of alveolus
Reducing alveolar surface tension
Reduces effort required by muscles to expand lungs
Pressure is inversely proportional to
radius of alveoli
hence in small babies, tendency to collapse is much greater due to greater pressure, smaller radius and lack of surfactant
Law of Laplace
Collapsing pressure = 2 x surface tension/aveolar radius
Inspiration 3 fractions
Work of breathing
1 compliance work / elastic work - req to expand the lungs against lung and chest elastic forces
2 tissue resistance work - req to overcome viscosity of lung and chest wall
3 airway resistance work - req to overcome airway resistance to movement of air into lungs
Volume of air inspired or expired with each normal breath amounting to about 500mL in adult male
Tidal volume
Extra volume of air that can be inspired over and above normal tidal volume when the person inspires with full force
Equal to about 3000 mL
Inspiratory reserve volume
Maximum extra volume of air that can be expired by forceful expiration after end of a normal tidal expiration
Amounts to 1100 mL
Expiratory reserve volume
Volume of air remaining in lungs after most forceful expiration
Averages about 1200 mL
Residual volume
Total Lung Capacity =
TLC = IRV + TV + ERV + RV
Pulmonary volumes
1 TV
2 IRV
3 ERV
4 RV
Pulmonary capacities
1 Inspiratory capacity
2 functional residual capacity
3 vital capacity
4 total lung capacity
Amount of air a person can breathe un beginning at normal expiratory level and distending lungs to maximum amount
IRV + TV
Inspiratory capacity
Amount of air that remains in lungs at the end of normal expiration 2300 mL
ERV + RV
Functional residual capacity
Maximum amount of air a person can expel from lungs after first filling the lungs to maximum extent and then expiring to maximum extent 4600mL
IRV + TV + ERV
Vital capacity
Maximum volume to which lungs can be expanded with the greatest possible effort 5800mL
VC (TV+IRV+ERV) + RV
Total lung capacity
RV =
RV = FRC - ERV
TLC =
TLC = FRC + IC
Lung volumes and capacities directly measured by spirometry
FRC
ERV
IC
TLC
Total amount of new air moved into respiratory passages each minute
TV x RRperminute
Minute respiratory volume
Minute ventilation
Ave 6L/min
Air that fills passages where gas exchange does not occur
Portions of the lungs that are ventilated but in which no gas exchange occurs
Dead air space
All space of respiratory system other than alveoli and closely related gas exchange areas
Volume of conducting airways not involved in gas exchange
150mL
Anatomic dead space
When not only the anatomic dead space is taken into account but also the nonfunctional alveoli
Sum of the anatomic and alveolar dead spaces
Physiologic dead space
Total volume of new air entering alveoli and adjacent gas exchange areas each minute
Ventilated alveoli that are not perfused
Negligible amount
Alveolar ventilation per minute
Alveolar ventilation =
VA = freq x (VT - VD)
Freq respiration per minute
VT tidal volume
VD physiologic deadspace
The greatest amount of resistance to airflow occurs through
passages of larger bronchioles and bronchi near trachea
bec these are relatively few in comparison with the approximately 66k parallel terminal bronchioles with only minute amount of air must pass
Substances that cause bronchiolar constriction by mast cell
Histamine
Slow reactive substance of anaphylaxis
Cilia beats continually and the direction of their power stroke is always toward
the pharynx
beat upward
Cilia in the lungs
beat upward
Cilia in the nose
Beat downward
Nasal cavity function
Warming
Humidifying
Filtering
Removal of particles by air hitting many obstructing vabes (conchae, septum, turbulence)
turbulent precipitation
Two circulations of the lungs
1 high pressure-low flow - systemic blood to trachea, bronchial, terminal bronchiole
2 low pressure-high flow - venous blood from body to alveolar capillary
Pulmonary artery has
Large compliance 7ml/min bec of large diameter and thin distensible vessel
Bronchial artery empties directly into
Pulmonary veins and left atrium rather than back to the right atrium making flow of L side of heart 1-2% greater
Systolic pulmo arterial pressure
Diastolic pulmo arterial pressure
Mean pulmonary arterial pressure
25mmHg
8mmHg
15mmHg
Left atrial pressure is estimated using
Pulmonary wedge pressure
Cath in pulmonary artery with direct connection to pulmonary capillary
5mmHg but bec of direct connection only 2-3mmHg greater than left atrial pressure
In response to a dec in oxygen in air alveolar (below 70%) the adjacent blood vessels
constrict
vascular resistance inc 5x at extremely low O2 level
believed to be due to a vasocon secreted by alveolar epithelial cell
In systemic vessels, a low oxygen concentration will promote
vasodilation
Vasoconstriction in pulmo vessels is important bec
poor ventilation will drive blood flow to be shunted to areas that are better aerated for maximal gas exchange
Zone 1 of lungs
No blood flow during all portions of cardiac cycle (collapsed)
Alveolar air pressure greater than arterial pressure
Zone 2
Intermittent flow during peaks of pulmonary arterial pressure
Systolic arterial pressure rises higher than alveolar air pressure (blood flow) 10cm above midlevel of heart
Diastolic arterial pressure falls below alveolar air pressure
Zone 3
Continuous flow
Arterial pressure and pulmonary capillary pressure greater than alveolar air pressure all the time
During supine, blood flow is entirely on
zone 3
Zone 1 no blood flow occurs in abnormal conditions such as
Upright person breathing against positive air pressure
Low pulmo systolic arterial pressure in severe blood loss
During exercise, pulmonary vasculature pressure rises enough
converts lung apices from zone 2 to 3 pattern
During heavy exercise, blood flow through lungs increase but accomodated by
1 inc no. of open capillaries
2 distending capillaries and inc rate of flow through each capillary
3 inc pulmonary arterial pressure
First two, dec vascular resistance