Respiratory Physiology
Respiration: General
• Purpose- To stay alive
• Speech is an overlaid function
• Respiratory patterns different for:
– Breathing for life
– Breathing for speech
Relationship of Lung, Thorax & Abdomen
• Motion of rib cage & diaphragm cause volume
change (inc. & dec)
• Surface of lungs linked to surface of thoracic walls
& diaphragm
– Linkage- Fluid interface between pleura
• Visceral Pleurae- lines lung
• Parietal Pleurae- lines thoracic cavity
• Pleural cavity- space between visceral & parietal linings
• Thoracic & diaphragm movement cause LV inc. &
dec.
– Inhalation: Lung volume and pressure
Pleural Linkage
• Function of surface tension of the fluid
in pleural space
– e.g.. Wet sheets of glass (resist separation
but free to move)
• Only surface tension accounting for
pleural linkage? No, linkage a function
of:
– Fluid transport out of pleural space
– Elasticity of pleura itself
Linkage: Diaphragm & Rib Cage
• Diaphragm attaches to inferior rib cage
– rib cage expands = increase in diaphragm
circumference
– contraction of diaphragm elevates lower rib
cage (Superior fibers & costal attachment)
– Rib cage & diaphragm not independent
Linkage: Diaphragm & Abdomen
• Linked via interposed abdominal viscera
– abdominal cavity bound by 2 moveable
walls
• Diaphragm above
• Muscular abdominal walls anterior and lateral
• Lowering diaphragm increases
abdominal pressure
– Drives abdominal wall out
Intrapleural Pressure
Insp
Larynx
Trachea
Exp
Alveolar
Pressure
Pressure
(cm H2O)
Intrapleural
Pressure
Lungs
Visceral Pleura
Parietal Pleura
Volume
(Liters)
Lung
Volume
Time (Seconds)
Percent Vital Capacity
Respiratory Volumes
Inspiratory Volume
Reserve
Vital Capacity
Total Capacity
Tidal Volume
Expiratory Volume
Reserve
Residual Residual
Volume Volume
Tidal
Volume
Resting
Expiratory
Level
Functional
Residual
Capacity
Inspiratory Reserve Volume
Vital
Capacity
Total Lung Capacity
Inspiratory
Capacity
Tidal Volume
(Increasing Activity)
Expiratory Reserve Volume
Residual Volume
Spirometer for measuring
respiratory volume
Measurement of Respiration
• Respiratory flow, volumes & capacities are
measured using a spirometer
Amount of water displaced
gives you estimate of the air
required to displaces it
Recording
Drum
Air Chamber
Water
Measurement of Respiration
Manometer
-Measures Pressure;
more force used the
higher the water rises
cm H2O
Respiration for Life
• Quiet respiration & Forced respiration
– Economy of effort
– Minimum departure from the resting volume
– Relaxed balance exists between tendencies of thorax
expansion & lung collapse
– Balance is typically at 35-40% of vital capacity
(amount available for use)
– Quiet inspiration= the volume of air that can be
inhaled from a resting level with muscle contraction
– Quiet expiration= Passive process by elastic recoil of
lungs & abdomen
Quiet Respiration
Insp.
Exp.
Percent of Vital Capacity
40%
60%
40
Resting Volume
0
Resting Tidal
Volume
*Volume of air move called resting tidal volume
*40% of cycle spent on inspiration; 60% of cycle spent on
expiration
Forced Respiration
• Increased energy demands for air exchange in
lungs
– muscular support recruited for insp. & exp.
– Forced insp.= ?
– Forced expiration=?
• Go beyond resting inhalation or exhalation=
recruit muscle involvement
• Time spent about the same as in quiet respiration
Respiration for Life
• Ventilation
– Actual movement of air in the conducting
respiratory pathway
– Air distributed: 3 million alveoi; perfused
(picks up oxygen) through 6 million capillaries
– Diffussion takes place (actual gas exchange
across alveolar-capillary membrane)
Development
• Developmental Changes (infancy-adulthood):
– Increase in VC
– VC increases fairly regularly with age
– Young adult 3.5-5 times the lung volume of a 5 year
old child
– VC depends on volume of lung tissue
– Peak reached in late teens or 20’s
– Decrease after early 20’s & reduction of diaphragmatic
action
– Residual volume increase with age
Vital Capacity Based on Age & Gender
VC (ml)
Male
Female
Age (Years)
Typical Respiratory Volumes & Capacities in
Adults
Volume/
Capacity
VC
Resting TV
TLC
Females (cc) Males (cc) Average (in cc)
3200 cc
4800 cc
4000 cc
450cc
600 cc
525cc
4800 cc
6000 cc
5100 cc
Females: VC in ml= 21.78- (0.101 x age in years) x ht.in cm
Males: VC in ml= 27.63- (0.112 x age in years) x ht.in cm
Breathing for Speech
• Same respiratory equipment and measures of
air volume &lung capacity apply for speech
breathing
• Difference? How & Why they are used!
– Life- Objective to move O2 & CO2 in & out of
lungs
• resistance interferes
– Speech- Objective to have air under pressure;
force vocal folds to vibrate
• Achieve pressure by resisting airflow
Respiratory Pressures
• Alveolar Pressure
• Intrapleural Pressure
• Subglottal Pressure
• Intraoral Pressure
• Atmospheric Pressure
Respiratory Pressures
Atmospheric
Intraoral
Subglottal
Intrapleural
Respiratory Pressures
• Atmospheric (Patm): Exerts pressure on
earth’s surface; our reference with which to
compare resp. pressures (zero)
• Intraoral (Pm): Pressure within the mouth
• Subglottal (Ps): Pressure below the vocal
folds
• Intrapleural (Ppl): Pressure in the space
between the parietal and visceral pleura
Reading
• Readings:
– Seikel: Ch. 4, (Pgs.121-142)
– Maue-Dickson: Ch.3 (Pgs. 81-87)