Respiratory Physiology
Dec 16, 2015
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
Larynx
Trachea
Lungs
Visceral Pleura
Parietal Pleura
AlveolarPressure
IntrapleuralPressure
Pressure(cm H2O)
Volume(Liters)Lung
Volume
Time (Seconds)
Insp Exp
Respiratory Volumes
Total Capacity
Vital Capacity
ResidualVolume
Inspiratory Volume Reserve
Tidal Volume
Expiratory Volume Reserve
ResidualVolume
Per
cen
t V
ital
Cap
acit
y
Tot
al L
un
g C
apac
ity
TidalVolume
InspiratoryCapacity
Vit
al
Cap
acit
y
Expiratory Reserve Volume
Inspiratory Reserve Volume
Tidal Volume(Increasing Activity)
Residual VolumeResting
ExpiratoryLevel
FunctionalResidualCapacity
Spirometer for measuringrespiratory volume
Measurement of Respiration
• Respiratory flow, volumes & capacities are measured using a spirometer
Amount of water displacedgives you estimate of the air
required to displaces it
Air Chamber
Water
RecordingDrum
Measurement of Respiration
cm H2OManometer
-Measures Pressure; more force used the higher the water rises
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
40%
Insp.60%
Exp.
Resting TidalVolume
Resting Volume
0
40
Per
cen
t of
Vit
al C
apac
ity
*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
Typical Respiratory Volumes & Capacities in Adults
Volume/Capacity Males (cc)Females (cc) Average (in cc)
VC 4800 cc3200 cc 4000 cc
TLC 6000 cc4800 cc 5100 cc
Resting TV 600 cc450cc 525cc
Males: VC in ml= 27.63- (0.112 x age in years) x ht.in cm
Females: VC in ml= 21.78- (0.101 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 (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