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

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

Vital Capacity Based on Age & Gender

Male

Female

VC

(m

l)

Age (Years)

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

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)