physiology of respiration. overview boyle’s law passive and active respiration torque, elasticity,...

Physiology of Respiration

Overview Boyle’s law Passive and active respiration Torque, elasticity, and gravity Volumes and capacities Pressures Posture and lung volume Muscle activity during speech

Respiration and Boyle’s Law

Respiration The exchange of gas between an organism

and its environment. Inspiration: Drawing air into the

respiratory system. Expiration: Process of evacuating air from

the lungs during respiration.

Boyle’s Law Boyle’s Law: Given a gas of constant

temperature, as volume is increased, pressure will decrease.

Air pressure: Force exerted on walls of a chamber by molecules of air.

Natural law states that air will flow to equalize pressure.

Boyle’s Law Positive pressure: Produced by:

Adding air particles to a fixed volume Or decreasing the volume of a container that

has been sealed from contact with the outside Negative pressure: Produced by:

Removing air particles from a fixed volume Or increasing the volume of a container

sealed from contact with the outside

Quiet vs. forced inspiration Quiet inspiration:

Inhalation of air during periods of rest. Primarily diaphragmatic action.

Forced inspiration: Inhalation of air during periods of physical

activity (including singing & preparing to speak). Utilizes diaphragm and external intercostals, as well as accessory muscles.

Passive vs. Active expiration Passive expiration:

Relaxing of muscles used for inspiration driven by torque, elasticity, and gravity

Active expiration: Thoracic contraction forces air out of the

lungs beyond that which is expired in passive expiration

Torque, elasticity, and gravity

Quiet vs. forced inspiration

Active vs. passive expiration

Torque, elasticity, and gravity Torque:

twisting of a shaft (or in this case a rib) while not permitting one end to move.

Elasticity: The force associated with maintaining an object’s

shape – a restoring force

Gravity: Pulls abdominal viscera downward and pulls rib cage

down to resting positioning.

Volumes vs. Capacities Air volume:

Quantity of air held in the lungs. Measured in liter (L), mililiters (ml), or cubic centimeters (cc).

Capacity: Functional units. Refer to combinations of volumes

that express physiological limits. Same units as volume

Respiratory cycle One complete inspiration and expiration

Volumes and Capacities Normative data:

Males vs. females Males greater volumes, and thus capacities.

Volumes peak between 20-30 years and then steadily decline

VC a function of body, age, weight, and height.

Pressures of the Respiratory System

Pressure Atmospheric pressure:

Pressure outside the body. Intrapleural pressure:

Pressure in the space between parietal and visceral pleurae of the thoracic cavity.

Alveolar pressure: Pressure within alveoli.

Intraoral pressure: Pressure within the mouth.

Subglottal pressure: Pressure below the vocal folds.

Pressure-Quiet respiration The interaction of these pressures and muscle

contraction are responsible for respiration. Contraction of diaphragm decreases intrapleural

pressure Lungs expand, dropping alveolar pressure. Relax diaphragm, intrapleural pressure increases. Alveolar pressure increases and air leaves lungs.

Pressures of the Respiratory Tissues During inspiration muscle activity

overcomes forces of torque, elasticity, and gravity. Inspiration is an active process.

During exhalation, passive forces of torque, elasticity, and gravity are utilized.

Pressures of the Respiratory Tissues The more an elastic matter is distorted, the

greater the forces of restoration that drive that matter back to its resting position

The greater the amount of thoracic expansion, the more forcefully it will be driven back to resting (relaxation) volume and the more difficult it will be to hold in its expanded state

Relaxation Pressure Curve

Tidal Volume

Relaxation Pressure Curve 38% of vital capacity represents

equilibrium or zero pressure. Recoil pressures of tissues allow for

expiration of ~ 55% VC. After 55% VC, muscle of expiration are

more active.

Pressures and Muscle Activity of Speech

Pressures of Speech Subglottal pressure

Minimal speech pressure 3-5 cm H2O

Conversational speech pressure: 7 cm H2O

Syllable stress

Maintaining pressure Inhalation

Speech vs. Quiet inhalation

Exhalation Speech vs. Quiet expiration

Speech pressure curve

Muscle Activity during Speech

Controlling speech pressure: Checking action: Activation of the muscles of

inspiration and abdominal positioning during expiration to control flow of air.

Inspiration Diaphragm and external internal intercostals and

preparatory abdominal activity

Expiration Internal intercostals, External obliques, rectus

abdominis, & latissimus dorsi

Review

Review Torque, elasticity, and gravity Volumes and capacities

volumes make up capacities Pressures

Atmospheric Alveolar Intrapleural

Muscle activity during speech Checking action

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Respiration and the Thorax

The Rib-Lung “Battle” The ribs are curved bones that are under substantial

force to “straighten out” Therefore, they are in a sense pulling the thorax apart, or

expanding it laterally The lungs are under significant pressure to shrink

In cadavers, the lungs often tear themselves away from the lining of the thorax, and shrink like a dried sponge

Therefore, they are, in a sense, pulling the thorax toward the midline

The lungs and ribs, then, establish a state of equilibrium, or a baseline size for the thoracic cavity from which an individual will make various manipulations

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Respiration and the Thorax Inspiration, or inhalation

Musculature Diaphragm receives innervation to contract from the

medulla, which is the lower brainstem Pulls downward, which enlarges the thoracic space Simultaneously, the intercostal muscles are stimulated

Two sets of intercostal muscles or “inter-rib” muscles External intercostals – connect the osseous portions of the

ribs across the outsider (lateral) surface Internal intercostals – connect osseous portion of ribs to

cartilaginous portion, near sternum - Two sets of internal intercostals

Interchondral portion – connects the cartilaginous portion of ribs Interosseus portion – connects the bony portion of the ribs

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Active/Passive Breathing

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Inspiration, or inhalation: Muscle action Diaphragm lowers when it contracts, analogous to

lowering the floor of the barrel Intercostal muscles contract The external intercostals raise the ribcage The interchondral portion of the internal

interchondrals twist the ribs up and out Additional muscles, the scalenes, and

sternocleidomastoid also elevate the ribcage The cumulative action, then is one in which the ribs

are elevated, and twisted outward, thereby enlarging the thoracic cavity

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Speech Breathing – Considerations regarding lung/thorax volume A far larger inspiration is required for active breathing The expiration phase consists of two portions

Initiallly, the passive contraction of the thorax is slowed by the muscles of inspiration

After the relaxation volume is reached, if the speaker wishes to continue, additional thoracic contraction must be carried out

The passive forces of expiration, then, provide a “background force” that diminishes as the thorax approaches, then reaches its relaxation volume

Active Expiration is continued through the contraction of muscles that raise the diaphragm, and further lower the ribcage

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Speech breathing – distinct from quiet respiration because the expiration phase takes on far greater importance, and requires far more time Inspiration phase is often exaggerated by increased

contraction of rib elevators The release of air is regulated and slowed relative to

the passive expiration of quiet breathing

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Respiration and the Thorax Speech Breathing: Regulating the expiration

Contraction of the muscles of inspiration slows the passive expiration

Slowing the passive expiration provides the talker the opportunity to shape the expiration into speech sounds

During quiet respiration, 40% of the respiratory cycle is inspiration, 60% expiration

During active, or speech breathing, the proportions change to 90-10 favoring expiration

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Respiration and the Thorax Speech Breathing – Considerations regarding

lung/thorax volume Tidal Volume – the amount of air exchanged in a typical,

quiet respiration cycle - About 0.5 liters Vital Capacity – the maximum amount of air that can be

exchanged in a person’s respiration cycle - About 5 liters Total lung capacity includes about another 2 liters (the

residual volume) that is typically not expelled Therefore tidal volume is about 10% of the vital capacity The amount of air in the lungs when the V. folds are open

and the pressure is equal with the atmosphere is the relaxation volume

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Speech Breathing – Considerations regarding lung/thorax volume A far larger inspiration is required for active breathing The expiration phase consists of two portions

Initiallly, the passive contraction of the thorax is slowed by the muscles of inspiration

After the relaxation volume is reached, if the speaker wishes to continue, additional thoracic contraction must be carried out

The passive forces of expiration, then, provide a “background force” that diminishes as the thorax approaches, then reaches its relaxation volume

Active Expiration is continued through the contraction of muscles that raise the diaphragm, and further lower the ribcage

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Speech Breathing – Expiration phase Contraction of abdominal muscles

Pushes abdominal viscera toward the backbone Squeezes the fluids/tissues upward (can’t go inferiorly

(pelvis), or posteriorly (vertebral column) Elevates the diaphragm (raises the floor of the thorax)

Contraction of the interosseous portion of the internal interchondrals Pulls the ribs closer together and down

Overall action of speech expiration is to produce a gradual release of sub-glottal air pressure The rate at which the pressure is expelled is held constant

through the muscle control outlined above

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Speech Breathing – Expiration phase Correlation between the power of speech and

the rate of expiration Intense speech requires a more powerful expelling

of air Therefore the air is used up more quickly, and loud

speech cannot be sustained as long as normal speech The pressure level is sustained, as in normal speech,

but at a higher level

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Respiration and the Thorax Differences between loud and normal speech

About 25% of the vital capacity is used for normal speech

Loud speech requires far more subglottal pressure, therefore more air to sustain the speech – estimates place the amount at about 40% of the vital capacity

Additional strain is then placed on the valving mechanism (the vocal folds) when loud speech is generated

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Respiration and the Thorax Voice disorders

May be due to problems with respiration in cases where insufficient subglottal air pressure is generated

May also result from difficulty coordinating the muscles of respiration Such difficulty would reduce the effectiveness of the power

source for speech For example, talker may not raise the ribcage in synchrony

with the lowering of the diaphragm

physiology of respiration. overview boyle’s law passive and active respiration torque, elasticity,...

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