Get ready for information about respiratory physiology Respiration

Get ready for information about respiratory physiology

Respiration: Physiology • Three forces involved in breathing 1. Torque: during inspiration, the ribs have been elevated and twisted (at chondral portion). Release of muscular pull (end of inspiration) causes ribs to unwind. The force (torque) generated causes a restoration force (return to neural rib position). Elasticity: lungs are highly elastic and have been stretched during inhalation due to expansion of the thorax. When inspiratory muscles stop contracting, then lungs want to return to their resting shape and size. 2.

3. Gravity: gravity acts on ribs to pull them downward (during passive exhalation) and works on abdominal viscera with a downward force that helps increase the area for the lungs (during inhalation). Mcdb. colorado. edu/courses/2115/units/ Other/ribcage%20 movie. mov Animation of rib and diaphragm movements.

• BREATHING for LIFE • Inspiration: Active contraction of diaphragm, external intercostals and possibly scalene muscles expands thoracic cavity. Lungs through linkage to thorax, expand too*. Negative press. is created in lungs, thus air rushes in until intra-alveolar pressure = to atmospheric pressure. • Exhalation: Muscles of inhalation cease to contract. The dilated thorax-lung complex generates slightly positive pressure and air is exhaled. Restoring forces provided by abdominal contents under pressure, lung elasticity, and ribs which have been elevated and twisted will "unwind" to provide torque. The expiratory forces are passive or nonmuscular during passive expiration. **

• Lung volumes: 1. Tidal volume: (TV) Vol. of air inhaled and exhaled during a single expiratory cycle. Varies according to: * – Adult male: 600 cc at rest • 1670 cc light work • 2030 cc heavy work – Adult female: 450 cc at rest. 2. Inspiratory Reserve Vol: (IRV) Quantity of air which can be inhaled beyond that inhaled in a tidal vol. @1500 cc- 2500 cc 3. Expiratory Reserve Vol: (ERV): amt. of air that can be forcibly exhaled following quiet/passive exhalation @1500 cc 4. Residual Vol. : (RV): quantity of air that remains in lungs and airways after max. exhalation--ranges from 1000 to 1500 cc in yg. adult males+

• Dead air spaces: No matter how deeply we inhale, @150 cc of residual vol. is nonfunctional for respiratory purposes-called dead air--remains in dead air spaces (nasal cavity, trachea, bronchioles)--it is last to be inhaled and first to be exhaled. • Yawn = What causes a yawn? • Hiccup = spasm of diaphragm – Persistent = last more than 48 hours – Intractable = last longer than a month • Causes – CNS problems (stroke, injury) – Metabolic problems – Irritation of nerves

• 1. 2. Lung capacities**: Inspiratory capacity (IC): maximum vol. of air that can be inhaled from resting expiratory level (REL) (REL = state of equilibrium between lungs and thorax). Vital capacity (VC): quantity of air that can be exhaled after maximum inhalation – Young adult males= 3500 to 5000 cc (aver = 4600 cc or 4. 6 L) – Young adult females= 3100 cc aver. – Measurement influenced by size, sex, & age – Maximum reached in 20’s; declines there after (see next slide) **Lung volumes refer to physical differences in lung volume, while lung capacities represent different combinations of lung volumes

3. Functional residual capacity (FRC): quantity of air in lungs and airways at resting expiratory level = 38% of VC 4. Total lung capacity (TLC): vol. of air within lungs and airways at end of max. inspiration

Vital Capacity Based on Age & Gender VC (ml) Male Female Age (Years)

Respiratory Volumes Percent Vital Capacity Inspiratory Volume Reserve Vital Capacity Total Capacity Tidal Volume Expiratory Volume Reserve Residual Volume 2. What does pink bracket represent?

• Influences on Volumes and Capacities 1. Body position: Interpretation

2. • Role of residual volume It provides air in alveoli for aerating the blood, EVEN though air exchange may not be taking place. If this residual air were not there, then O and CO 2 would rise and fall with each breath. 3. Factors affecting VC (besides body position when measure taken): age, strength of respiratory muscles, pulmonary compliance (distensibility of lung-thorax unit) – Restrictive pulmonary disorders: anything that damages or destroys lung tissue, causes it to be fibrotic or edematous, obstructs alveoli, or restricts lung expansion and contraction. – http: //www. wilkes. med. ucla. edu/lungintro. htm • Lung sounds – A. Pulmonary fibrosis: Lungs have lost elasticity due to fibrous (scarring or thickening) tissue building up in lungs. • Causes include: sand, asbestos, coal dust, fiberglass • Some cases are idiopathic or cryptogenic (or perhaps autoimmune) • EX: cryptogenic fibrosing alveolitis: The thickening and scarring reduces the amount of oxygen that can pass into the blood vessels from affected alveoli. Therefore, as the disease progresses, less oxygen than normal is passed into the body when you breathe • EX: idiopathic pulmonary fibrosis

asthma

– B. Asthma is a respiratory disease of the bronchi and bronchioles. The symptoms include wheezing, shortness of breath, and sometimes a cough that will expel mucus. The airways are very sensitive to irritants which can include pollen, dust, animal dander, and tobacco. Even being out in cold air can be an irritant. When exposed to an irritant, the smooth muscle in the bronchioles undergoes spasms. – Most asthma patients have at least some degree of bronchial inflammation that reduces the diameter of the airways and contributes to the seriousness of the attack. – Asthma is not curable, but IS treatable.

– C. Emphysema: slowly progressive disease. – Bronchioles become filled with mucus and are cut off from alveoli. – Alveoli lose elasticity and may rupture. • Would this affect inhalation or exhalation? • Exhaling becomes hard…etc. – Capillaries that surround alveoli break apart. – Lungs less able to exchange oxygen for carbon dioxide. – Normal lung tissue replaced with thickened/scarred (fibrosis) tissue.

• Relaxation Pressure Curve (BLACK LINE): • Pressure you can create without any muscular involvement--also could be called recoil pressure curve. • In order to generate the right hand side of the curve, ask person to take in 100% of vital capacity, relax completely and let elasticity, etc. take over (measure air flow at mouth). • Diagram is linear until reach outer limits at extremes of vol. which suggests that limits of distensibility and compressibility are being approached.

Chest cavity/thorax; Lungs; Relax pressure curve • p

During breathing (quiet, speech, etc. ) • At lung vol. above 38%VC, inspiratory process is active • At lung vol. below 38%VC, expiratory process is active. • Lung volume at 38% termed resting expiratory level (REL) • *Any time a system moves away from equilibrium, the action is ACTIVE.

• A. Recoil pressure from lungs is equal to thorax (chest cage) • B. At B, chest cage is at equilibrium point (resting volume), thus rib cage doesn’t generate recoil pressure at 55% of VC. Only recoil force from lungs is available from this point (C). .

• D. As more air is inspired, both the chest cage and the lungs produce increasing recoil forces, as both want to decrease in size (they are being stretched further and further). • When air is passively exhaled, the system goes back to A, or resting level.

• E. As air is exhaled below resting level, negative recoil pressure is generated, as thorax wants to expand due to increased compression. At same time, lung is producing less recoil pressure, as it approaches equilibrium.

• • Inspiration: Types Quiet inspiration: – Air flows from regions of higher pressure to regions of lower press. – When airways open and respiratory pump is in neutral position at resting expiratory level (rem. lungs & thorax operate as unit), resp. apparatus assumes a natural resting position (lungs somewhat expanded, thorax somewhat compressed) – Outside air = press. of inside air. – Expansion of the lung/thorax decreases alveolar air press. Air rushes in until at end of inspiration cycle, alveolar press= atmospheric press. Thus, alveolar press. = to outside air press. at two times—end of exhalation and end of inspiration. – Accomplished mainly by diaphragm, with help from the external intercostals The forces of inspiration must overcome (a) resistance to air flow thru respiratory airways, (b) resistance to deformation of respiratory tissue, (c) elastic recoil of lungs/thorax unit Forced inspiration: more vigorous in nature than quiet inspiration. Accessory m. are used to help diaphragm & external intercostals increase thoracic volume (e. g. , scalenus, sternocleidomastoid).

• Expiration • Quiet or passive expiration: use of recoil forces (passive forces; nonmuscular). Energy created in stretched elastic tissue is released and lung/thorax unit recoils back to neutral position. – The farther away you go from the neutral position during inhalation, the greater are the restoring forces for the lungs as compared to the thorax. Only lungs generating restoring force at this lung volume

• Active expiration • Muscular force is used – Abdominal – Thoracic muscles Must use muscular forces when exhaling below REL

• What happens when speech occurs? • Changes occur in the breathing cycle when we breath for speech. – Quiet breathing = 40% inhalation; 60% exhalation – Breathing for speech = 10% inhalation; 90% exhalation

What Volume of air is inhaled per cycle? • For life breathing, it is about one-tenth of our vital capacity or approximately 500 ml. • For speech breathing, it depends on the projected length of the utterance and may vary from 25 to 65 percent of our vital capacity.

• • What about muscular activity when breathing for speech? During breathing for speech, muscles of inspiration and expiration are at least minimally active. – Example: External intercostals are active during inhalation to raise ribs, and are active during initial portion of exhalation to brake the descent of lung-thorax unit. At the same time, internal intercostals are active. • The internal intercostals are important for the production of stressed syllables.

• How does the relaxation pressure curve relate to inhalation and exhalation for speech? – Air pressure is needed for vibration of the vocal folds--@ 6 -7 cm H 2 O for normal loudness. – This pressure must be maintained despite a lung volume that decreases as we exhale during speech. – By looking at the passive pressures available, we can determine muscular activity.

Respiratory Mechanisms for Speech • • • To speak, we need a certain amount of subglottic pressure (Ps) (pressure below the vocal folds necessary to maintain vibration). Ps varies between 6 -10 cm H 20. Further, we constantly change pitch, loudness, and duration of syllables when speaking, requiring adjustments between muscular forces and relaxation forces for constant Ps. Ps for comfortable speech @ 6 cm Ps for loud speech @10 cm Ps for singing @20 -25 Ps for soft speech = @3 As a person speaks, lung volume decreases, but air flow (required for voicing) and pressure remain constant. • 55% VC Ps pressure needed for speech Active Expiratory pressure Passive expiratory pressure, but it’s excessive for speech. Use inspiratory muscles to check. Relaxation pressure enough to generate Ps, but continued phonation requires abdominal muscles

Glass must be at least 12 cm in height. The pressure of the water is directly proportional to the depth of the straw. Thus, 6 cm H 2 O of water pressure = straw 6 cm deep in water. 5 cm pressure for 5 sec = sufficient air pressure for speech

• How do we maintain constant positive subglottal pressure needed for speech? • For any given speech act (and Ps pressure needs), a different balance of active and passive muscular forces are required to maintain adequate pressure at the differing lung volumes. • Speech also requires us to designate stress in words, sentences. • How do we signify stress? – Pitch – Loudness – Duration • Stress is accomplished at the respiratory level by little pulses of increased Ps pressure through the brief contraction of expiratory muscles (ESP internal intercostals). 1 – 3 cm H 2 O change

• To achieve subglottic pressure necessary for speech, we can: – Adjust expiratory force OR – Adjust airway resistance • Muscles involved in sustaining expiratory force: – Abdominal muscles active during onset of phonation for speech (and singing), and during lung volumes below @55 % vital capacity. • When inhaling for speech, the greater the volume of air we inhale, the greater the need is to check the excessive relaxation pressure that is generated

• “Respiratory Center“ is located in the pons and medulla oblongata of the brain stem. It is part of the autonomic system and as such is not controlled voluntarily (we can control some aspects of breathing [e. g. , during speech, or singing]; voluntary control over this automatic activity (breathing) is managed by or is the domain of the cerebral cortex. • While resting, the respiratory center sends out action potentials that travel along the phrenic nerves into the diaphragm and the external intercostal muscles of the rib cage, causing inhalation. Relaxed exhalation occurs between impulses when the muscles relax.

Respiratory Centers • Pontine respiratory center reduces duration of inspiration (thus can cause respiration to increase or decrease); receives input from higher centers (e. g. , cortex) and thus adjusts inspiration for speech, exercising, etc. • VGR = sends motor (contraction) signals for 2 seconds to diaphragm and external intercostals for tidal inhalation. They also fire expiratory neurons for 3 seconds to allow passive OR active expiration. These set rhythmicity of tidal or resting respiratory cycle. • DGR = are involved in altering the pattern for ventilation in response to the physiological needs of the body for O 2 and CO 2 exchange and for blood acid-base balance related to metabolic demands.

SUMMARY Cortical level : voluntary control over respiration for activities such as speech, singing, coughing, etc. Medullary rhythmicity center: sets basic respiratory rate, and adjusts for levels of activity and metabolic demands. Pontine center: limits inhalation duration. Proprioceptive stretch receptors in the lungs, pleura, and thoracic wall convey information about the degree of the filling of the lungs

• Greater muscular pressure must be used to counteract the relaxation pressure at high lung volumes for SOFT speech, as compared to normal or loud speech. WHY?