PHYSIOLOGY OF RESPIRATION
Breathing during the life span
• we first breath at birth
• pressure at the birth canal squeeze the thorax expelling liquid amniotic and setting
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the stage for the first inspiration which come as a result of elastic recoil of the
compressed thorax
in c-section delivery suction is used to clear the air way also setting up the stage for
the first inspiration
chemical changes in the blood influence the respiratory center in the brain and a
regular respiratory pattern starts
as we go from infancy to adulthood respiratory anatomy and physiology changes
the capacity of the lungs increases with age
with advanced age the lungs and bronchi sink to a lower position in the thoracic
cavity
lung capacity depends largely on the volume of lung tissue and also on the
movements of the chest walls
Movements of Chest Wall
• vertical expansion of chest wall (diaphragm)
• lateral and anterior-posterior expansion of chest wall (all other muscles of inspiration)
Lung Volume
• lung volume is the amount of air in the lungs
• we can measure lung volume using an spirometer
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Spirometer
is an instrument that provides measures of respiratory volumes and capacities
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Volumes
refer to a specific amount of air that the lungs can hold
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Capacities
refer to combination of volumes that express physiological limits
Lung Volumes & Capacitites
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tidal volume
inspiratory reserve volume
expiratory reserve volume
residual volume
vital capacity
total lung capacity
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Tidal Volume (TV)
is the volume of air exchanged in one cycle of respiration
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Inspiratory Reserve Volume (IRV)
is the volume of air that can be inhaled after a tidal inspiration
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Expiratory Reserve Volume (ERV)
is the volume of air that can be expired following passive, tidal expiration
the volume of air present in the resting lungs after a passive exhalation – resting
lung volume (RLV)
Residual Volume (RV)
• is the volume of air remaining in the lungs after maximum exhalation
• that is, after maximum exhalation almost one fourth of total lung capacity will remain
as residual volume
• this is air in the pulmonary tubing that cannot be forced out without opening the chest
and deflating the lungs completely
Vital Capacity (VC)
• is the volume of air inspired after a maximal expiration (VC=IRV+TV+ERV)
• this is the maximum usable volume of air that can be inhaled and exhaled
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Total Lung Capacity (TLC)
is the sum of inspiratory reserve volume, expiratory reserve volume, tidal volume, and
residual volume
Lung capacity during the life
the capacity of the lungs increases with age (until the early twenties)
capacity of the lungs can be measured as vital capacity
peak vital capacity is reached in the late teens or early twenties, decreasing along
with diaphragmatic action thereafter
residual volume increases with age - a smaller volume of air is available for
exchange of oxygen and carbon dioxide
Breathing rate during life span
• rate of respiration is determined by lung capacity and efficiency of respiratory
exchange, both of which are greater in the older child or adult than in the infant
– the respiratory structures increase in size with age
– larynx, trachea and lungs increase in size
– a newborn has a trachea that is one third as long as the adult’s and one fourth of
the diameter
– the cartilaginous rings of the newborn trachea are soft
• the breathing rate decreases with age
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• premature and newborn infants have high breathing rates, ranging between 30-90
breaths/minute
• irregularity of breathing rate is not uncommon in the infant
• in the late childhood and early adulthood a lower and fairly stable rate of about 10 to
22 breaths/minute is established
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Breathing for life
respiration is movement of air in and out of lungs
a respiratory cycle involves one inspiration/inhalation and one expiration/exhalation
inhalation (inspiration) is the portion of the respiratory cycle in which air is sucked
into the lungs
exhalation (expiration) is the portion of the respiratory cycle in which air is forced
out the lungs
respiration can be Quiet or Forced
Respiration
• quiet respiration
– quiet inspiration
– quiet expiration
• forced respiration
– forced inspiration
– forced expiration
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Quiet Respiration
quiet respiration or quiet breathing is breathing when at rest
it reflects the volume of air that can be inhaled from a resting level with contraction of
the diaphragm and external intercostal muscles
it is a passive process resulting from elastic recoil of lungs and abdomen
when the passive expiratory forces reach the resting level, the respiratory cycle is
read to be repeated
during quiet respiration the resting tidal volume of air is manipulated by quiet
inspiration (40% of the cycle) and quiet expiration (60% of the cycle)
that is, the duration of inspiration and expiration during quiet breathing are not very
different
– inspiration takes about 40% of the respiratory cycle
– while expiration takes about 60%
quiet inspiration reflects the volume of air that can be inhaled from a resting level
with contraction of the diaphragm and the external intercostal muscles
quiet expiration is a passive process resulting from elastic recoil of lungs and
abdomen
resting tidal volume is the volume of air moved during quiet inspiration and
expiration
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Forced Respiration
forced respiration or forced breathing involves muscular effort on exhalation as well
as on inhalation
respiration that goes beyond the resting level (the level at which passive forces are
depleted)
the deeper a person breathes the more muscles will be recruited for forced inspiration
and forced expiration
forced inspiration is accomplished when the accessory muscles of inhalation assist
the diaphragm and the external intercostal muscles
forced expiration is accomplished with active forces of abdominal and thoracic
exhalatory muscles that supplement the passive forces of expiration
Purpose of Respiration
• in breathing for life the objective is to move oxygen-laden air into and carbon dioxide
out of the lungs - flow of air free and facilitated
• in breathing for speech production the objective is to generate air pressure, which
can force the vocal folds to vibrate or can expel a burst of air into plosion (stops),
frication (fricatives) or a combination of both (affricates) - to achieve pressure
requires the air flow be resisted
Air Pressure
• pressure is the result of compression of air in the lungs, which provides the source for
speech
• there are two ways to achieve the pressure needed for speech production
– by adjusting the expiratory force of the respiratory pump
– by adjusting airway resistance
– that is, by adjusting airway resistance and/or adjusting the expiratory force of the
respiratory pump we can affect the pressure within the lungs
• alveolar pressure is the pressure measured within the lungs
• subglottal pressure is the pressure measured within the trachea below the vocal
folds
• intraoral pressure is the pressure measured within the mouth
Pressure Requirements for Speech Production
Control of air pressure during speech production is needed during
– variations in stress from syllable to syllable
– variations in loudness level in phrases
– variations in intensity from sound to sound within the syllable
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Volume Requirements for speech production
• speech breathing requires greater volume of air than quiet breathing
• considering the amount of air inhaled above resting volume we can see the following
differences
– quiet breathing uses 10 to 15 % of vital capacity, that requires inhaling up to 55%
of vital capacity
– conversational speech uses around 25% of vital capacity, that requires inhaling up
to 60-65% of vital capacity
– loud speech uses around 40% of vital capacity, that requires inhaling up to 80% of
vital capacity
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Breathing rate/depth for speech production
during speech production the length of breath depends on how much we choose to
say in a phrase
most people inhale and exhale 10 to 20 times per minute during quiet breathing
making a short statement will take no longer than a quiet breath
sustaining a long, loud phrase will require a deep inspiration of air, which will continue
to use past the resting volume level down to forced expiratory levels (usually
exhalation goes no lower than 35% of vital capacity
the duration of most of what we have to say falls between 80% and 35% of vital
capacity
Duration
whether resting or after heavy exercise, the duration of inhalation is about the same
of exhalation
when we prepare to produce sound, whether whisper, argue, sing, or converse we
take a quick breath (inhale) and spend a much longer time producing sound on
exhalation
10% of the respiratory cycle will be spent inhaling
90% of the respiratory cycle will be spent exhaling (and producing sound)
duration of expiration, however, is affected by how breathy the tone is or how loud
during breathier voice we use shorter phrases than during full voice
Respiratory Mechanics of Speech
• meeting the pressure requirement for speech production involves controlling two
components of speech expiration
– effects of changes in lung volume during phrase
– active expiratory forces needed to maintain required alveolar pressure for the
phrase
Relaxation Pressure and Lung Volume
• the deeper the inspiration the greater the resistance of elastic lung tissue and air sacs
against greater stretching and inflation
• the elastic recoil from inspiration, supplemented by gravity and untorquing of rib
cartilages results in relaxation pressure, the passive expiratory force
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increase in loudness
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increase in length of phrase
need for greater volume of air
increase in depth of inspiration
passive resistance of elastic recoil force mounts
greater relaxation pressure
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Maintaining Alveolar Pressure for Speech
for any given alveolar pressure needed for speech, a different balance of active and
passive muscular forces will be required to maintain that pressure at each lungvolume level
at the beginning of speech both inspiratory and expiratory muscles are often used
conversely, expiratory muscles are also used to some extent during inhalation
the volume of air inhaled will be affected by length of the phrase, loudness and
breathiness of the tone, and the need for oxygen
the frequency of inspiration, a flexible requirement, is determinant of the volume that
must be inhaled: the more frequent the breaths, the smaller the volume needed per
breath, but shorter the phrases will be
the other flexible requirement is duration of the phrase. It is the other side of the coin
from frequency of inhalation. The longer the phrase must be, the farther apart the
breaths must be
the remaining requirements of stress and articulation involve what can be thought of
as refined adjustments superimposed on the respiratory mechanics of loudness
control
changes in stress tend to occur from syllable to syllable at a rate of about 6 per
second - such appears to be accomplished with a little pulse of alveolar pressure
applied by a brief contraction of expiratory muscles and shut off, presumably, by
opposition from the inspiratory muscles
articulatory changes occur at a rate of 14 per second - articulatory requirements are
met by how much intraoral pressure is permitted to squirt air from the reservoir
(lungs), where it is held under alveolar pressure - the intraoral pressure fluctuations
during articulation have virtually no effect on alveolar pressure in the lungs
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