Physiology of Respiration Chapter 3

Respiratory Function Changes as we AgeExercise Suffer setbacks in health Passive Expiration Let the forces and tissues restore to a resting position Active Expiration Use muscular effort to push just a little farther

Expiration Eliminating waste products of respiration As you breathe in 10 times quietly Contract your diaphragm actively Simply relax the muscles and you expire/exhale ElasticityGravity

Expiration Lungs are highly elastic, porous tissue Sponge like In adult bodies- lungs do not completely fill up the thoracic cavity When stretched- they are stretched beyond their resting position Result of stretching is increased capacity and reserve

Expiration Adult lungs are never completely compressed, there is always a reserve of air within them Lungs expand- muscles are expanding the rib cage and then they relax, lungs return to their original shape and size Abdominal muscles stretch when you inhale and then they relax and return to their original length- they push the abdominal viscera back in and force the diaphragm up

Expiration Gravity Acts on the ribs to pull them back after they have been expanded – accessory muscles Works in favor of maximizing your overall capacity Pulls abdominal viscera down, leaving more room for the lungs Body position plays a significant role in efficiency of respiration

Measuring Respiration Respiratory Flow- rate of flow of air on/out Volume- measured in liters, mililiters, cubic cm Capacity

Lung Volume Individual breathes into the wet spirometer Causes a volume of water to be displaced Amount of water displaced gives an accurate estimate of the air that was required to displace it Results are charged on a “recording drum”

Respiration for Life Four stages for gas exchange Ventilation- air comes into the respiratory pathway Distribution- air is distributed to the 300 million alveoli Perfusion- oxygen poor blood migrates through to the 6 billion capillaries Diffusion- actual gas exchange across the alveolar-capillary membrane

Turbulence Lungs expand Air courses through the bronchi Some slight turbulence at the bifurcation of the bronchi but the air generally flows unimpeded. A small irregularity such as mucus or muscle spasm can greatly increase resistance to airflow

Respiratory Cycle Quiet respiration cycles of respiration per minute One cycle is ½ liter of air We process approximately 6-8 liters of air every minute (think of a 2 liter bottle)

Developmental Process of Respiration Alveoli will increase from about 25 million at birth to more than 300 million by 8 years of age. Conducting airways will grow steadily in diameter and length Adults breath cycles per minute Newborns average cycles per minute 5 year old- 25 cycles per minute Chart on p. 138

Volume and Capacities Volume Estimate the amount of air each compartment can hold Tidal Volume Inspiratory Reserve Volume Expiratory Reserve Volume Residual Volume Dead Air

Volume and Capacities Capacities Vital Capacity Functional Residual Capacity Inspiratory Capacity Total Lung Capacity

Tidal Volume Volume of air we breath in during a respiratory cycle Varies as a function of physical exertion, body size, and age Quiet Tidal Volume has an average for Adult males 600 cc Adult females 450 cc ¼ of a 2-liter soda bottle every 5 seconds Fill up three 2-liter bottles in one minute

Inspiratory Reserve Volume Volume that can be inhaled after a tidal inspiration Volume of air that is in reserve for use beyond the volume you would breath in tidally Sit quietly Breathe in and out until you become aware of your breath Tag each breath mentally with “in”/ “out” Stop breathing at the end of one of your inspirations Instead of breathing out- breathe in as deeply as you can Amount you inspired after you stopped is the IRV- average volume is liters

Expiratory Reserve Volume Amount of air that can be expired following passive, tidal expiration. Breathe in and out normally until you are aware of your breath Stop breathing right after you exhaled Then expire as completely as you can ERV- average is 1.0 liter Also referred to as resting lung volume- volume present in the resting lungs after a passive exhalation

Residual Volume Volume remaining in the lungs after a maximum exhalation No matter how forcefully you exhale, there is a volume of air that cannot be eliminated- approximately 1.1 liters Does not exist in the newborn

Dead Space Air Air in conducting passageways Air that cannot undergo gas exchange Adult has approximately 1/10 of a Liter Associated with Residual Volume (RV) because it is air that cannot be expelled

Vital Capacity Capacity available for speech Combination of the Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV) and Tidal Volume (TV) Represents the total volume of air that can be inspired after a maximal expiration Approximately 4 liters in an average adult

Functional Residual Capacity Volume of air remaining in the body after a passive exhalation Expiratory Reserve Volume (ERV) + Residual Volume (RV) Approximately 2.1 Liter

Total Lung Capacity Sum of all of the volumes Totals Approximately 5.1 Liters Different from the Vital Capacity because it includes Residual Volume (RV) which serves as a buffer in respiration in providing constant oxygenation when needed

Inspiratory Capacity Maximum inspiratory volume possible after tidal expiration Capacity of the lungs for inspiration (Tidal volume + Inspiratory reserve volume) Approximately 3 liters for adults

Effects of Age P. 142 and 143 Figure 3-6 As age increases, Vital Capacity decreases by about.1 liter per year in adulthood Vital Capacity steadily increases with body growth up to about age 20, holds steady through about 25 and then begins a steady decline Females have a smaller vital capacity throughout the life span

Effects of Age Residual Capacity increases with age Why? Individuals retain their functional Total Lung Capacity (that doesn’t decrease)- however, they have a reduction in function As we age, compliance of the lungs decrease which results in reduced ability to inflate the lungs Lung volume is constant but there is growth in the volume that is unavailable for direct gas exchange – residual volume- dead space air!

Respiration and Pressure Diaphragm contracts- air flows in Increased volume Negative pressure Diaphragm stops contracting- air flows out of the lungs Decreased volume Positive pressure

Pressures of the Respiratory System Alveolar pressure Intrapleural pressure Subglottal pressure Intraoral pressure Atmospheric pressure All are measured relative to atmospheric pressure is treated as a constant “0” against which to compare respiratory pressures

Alveolar Pressure Pressure that is present within the individual alveolus Inhalation: Air flows into the Alveoli and the volume increases. When volume increases, pressure decreases- negative alveolar pressure Exhalation: Air flows out of the Alveoli and the volume decreases. When volume decreases, pressure increases- positive alveolar pressure.

Alveolar Pressure Surfactant- Surface active solution- is released in the alveoli when the lungs are expanding Reduces surface tension which reduces the pressure of the alveoli Keeps the walls of the alveoli from collapsing Keeps fluid from the capillaries from being drawn into the lungs Promotes airflow Facilitates effort-free respiration

Intrapleural pressure Measure the pressure in the space between the parietal and visceral pleurae ALWAYS negative throughout respiration Lungs, inner thorax, and diaphragm are wrapped in this continuous sheet of pleural lining Its important to maintain this negative pressure within the intrapleural space to keep from the lungs collapsing

Alveolar and Intrapleural Pressure Diaphragm contracts- air flows in- alveolar pressure drops- intrapleural pressure becomes more negative as the diaphragm attempts to pull the diaphragmatic pleurae away from the visceral pleurae. (the volume- space between the two pleural linings increase) Diaphragm relaxes- air flows out, alveolar pressure increases, intrapleural pressure becomes less negative

Why does Intrapleural pressure remain negative? Lungs are in a state of continual expansion because the thorax is larger than the lungs Lungs are never completely deflated because of the residual volume

Subglottal Pressure The pressure measured beneath the level of the vocal folds Directly related to what is happening in the lungs as long as the vocal folds are open Air flows into the lungs- subglottal pressure will be negative Air flows out of the lungs- subglottal pressure will be positive

Subglottal pressure What happens when the vocal folds are closed? Blocks air flow Immediate increase in the subglottal air pressure as the lungs continue expiration When the pressure exceeds 3-5 cm H2O, the vocal folds will be blown open and voicing will begin. This is a critical pressure as it is a minimal requirement of respiration for speech

Intraoral Pressure Respiratory pressure measured above the vocal folds within the oral cavity When vocal folds are open- intraoral, subglottal and alveolar pressure are the same Closing the vocal folds causes the intraoral pressure to drop as the subglottal pressure increases

Muscles vs. Gravity Inspiration Use of muscular action to exert force and overcome gravity Stretch tissue and distend the abdomen Exhalation Uses elasticity and gravity to save energy Muscles relax and return to original state due to elasticity and gravity

Respiration for Speech Must maintain a steady flow of air at a relatively steady pressure Vocal folds require a minimum subglottal pressure of 3-5 cm H2O Conversational speech % of our vital capacity Loud speech uses lung volumes up towards 80% of vital capacity

Respiration for Speech How do we maintain the continuous flow of air upon expiration to use it for speech? The muscles of inspiration must intervene They “check the outflow of air” They impede the outflow of air to maintain a constant subglottal pressure This gives us control of phonation

Respiration for Speech Abdominal muscles remain in a state of graded tonic contraction during exhalation Respiratory cycle for speech is markedly different Long drawn out expiration to produce long utterances Short inspiration to maintain the smooth flow 10% of the respiratory cycle on inspiration 90% of the cycle on exhalation Does not change the amount of air we breathe in/out just alter how long we spend in each stage

Respiration for Speech We use a “checking action” when we exhale during speech Restrains the flow of air out of your inflated lungs by using the inspiratory muscles that got it there in the first place Creates respiratory control for speech Maintain constant flow of air through the vocal tract Helps to maintain the constant subglottal pressure to maintain phonation

Effects of Posture on Speech Supine position Gravity is pulling the abdominal viscera toward the spine Does not support inhalation or exhalation Muscles of inhalation must elevate both abdomen and rib cage against gravity Sitting posture Gravity is pulling the abdominal viscera down Pulling the rib cage down Supports efficient inhalation and exhalation

Pressures of Speech Two levels of pressure simultaneously Constant supply of subglottal pressure required to drive the vocal folds 3-5 cm H2O vocal folds move 7-10 cm H2O conversational speech Micro-control of that constant pressure Adding stress, intensity and pitch changes Increase subglottal pressure by 2 cm H2O to add stress

Pressure of Speech Speaking on expiratory reserve When we get down to the Resting Lung Volume and we have more to say Instead of using the muscles of inspiration to keep the air from flowing out We have to enlist the muscles of expiration to push beyond the RLV We continue talking beyond the point where we would normally take another breath The deeper our inhalation or the farther we go below RLV, the greater the force we have to overcome