Lecture 16: Mechanics, lung volumes, ventilation Flashcards
Pulmonary Ventilation
alternating flow of air into and out of lungs
due to actions of various resp. muscles
Inspiratory muscles function
expand rib cage
drive airflow INTO lungs
expiratory muscles function
depress rip cage
force air OUT of lungs
passive process
diaphragm is relaxed (dome shape)
Thoracic cage includes
ribs
costal cartilages
thoracic vertebrae
sternum
Respiratory Mechanics
how resp. muscles move the rib cage
respiratory pump
resp muscles, rib cage, pleural membranes, lung elastic tissues
designed to change shape of rib cages
causes pleural membranes to move out, dec pleural fluid, lungs out as well
Inspiratory Muscles (list)
diaphragm (primary)
external (and internal) intercostals (secondary)
move ribs up and out, expand rib cage
Sternocleidomastoid: elevate sternum
sclaenes: elevate top two ribs
Expiratory Muscles (list)
internal intercostals: pull ribs down and in, dec dimater of rib cage
Abdominal muscles: depress lower ribs, elevate diaphragm up into thorax
reduce throacic diameter and force air out of lungs
inc pressure in lungs
Inspriation pressure
pressure in lungs LOWER than pressure in atmosphere
Expiration pressure
pressure in lungs HIGHER than pressure in atmosphere
Respiratory mechanics
ventialtion depends on periodic pressure changes in lungs
Pressure changes in lungs depend on…
pleural membranes!
Inspeiration respiroatory mechanics ex
parietal pleura pulled outward
visceral pleura moves with it
so do lungs
Transpulmonary Pressure (P tp) equation
Ptp= Palv- Pip
Pip
intra plural pressure
space that surrounds lungs
Palv
intraalveolar pressure
pressure in alveoli
aka intrapulmonary pressure
Transpulmonary Pressure (P tp)
diff between Pip and Palv
cjamge pressure of plureal flud to affect lung pressure
pleural fluid pressure
NEGATIVE
so lungs don’t collapse
why lungs want to collapse
made from elastic tissue
inspiration begins
contraction of diaphragm
contraction of diagphragm causes thoracic cage to
enlarge
INSPIRATION
when thoracic cage enlarges…
interpleural pressure decreases
INSPIRATION
when interpleural space decreases
alveolia open
air pressure in alveoli decreases
INSPIRATION
pressure gradeint of air in inspiration
atmosphere down to lungs
INSPIRATION
when diaphragm relaxes
elastic tissue in lungs go inward
lungs recoil… air
is compressed
alveolar pressure rises ABOVE ATMOSPHERIC PRESSURE
EXPIRATION
pressure gradeint of air in inspiration
lungs out to atmopshere
End expiratory lung volume is the
period between breaths
during the end expiratory lung volume… relationship of pressures
atmospheric pressure=alveolar pressure
pleural pressure is less than atmopheric pressure
WHY? Lung wants to collapse all the time
more pull=greater negative volume
recoil direction of chest wall
outward
recoil direction of lungs
inward
opposing forces of chest wall and lungs result
negative pleural pressure
pull lung tissue to keep it from deflating
Spirometers meassure
lung volume subdivisions: vital capacity residual volume expiratory reserve volume inspiratory reserve volume tidal volume total lung capacity Inspiratory capacity FRC?
Functional residual capacity (FRC)
volume that fresh air MUST mix with in order to inc lung O2 stores and dec lung CO2 stores
ERV+RV
Large FRC
labored breathing
obstructive lung diseases (athsma, COPD)
small FRC
large fluctuations in O2 and CO2
inspiratory restiction
expiratory restriction
too little CO2 makes you
light headed
Lung Compliance def
ease at which lungs are inflated
lung compliane equation
delta Vl/ delta Ptp
things that decrease compliance
asbetosis
things that thicken or stiffen lung tissue
things that increase compliance
emphysema
very compliant lung because of breakdown of alveolar tissues, result in connected alveoli
air gets trapped some places
raises FRC as well
Pulmonary ventilation
rate of lung ventilation
Pulmonary ventilation (l/min) equation
tidal vol (L/breath) X breathing freq (breath/min)
alveolar ventilation
air that ACTUALLY ventialtes alveoli
alveolar ventilation equation (L/min)
(tidal vol-dead space vol) X breathing frequency
(l/breath) X (breath/min)
dead space= everywhere but resp. bronchioles and alveoli