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