Mechanics of Respiration PDF

(008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 OUTLINE v...

(008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 OUTLINE various conditions while minimizing energy I. RESPIRATORY SYSTEM costs; and II. MUSCLES OF VENTILATION 3. recruitment of respiratory muscles that can A. Movement of the Diaphragm contract appropriately for gas exchange B. Movement of the Rib Cage III. AIR MOVEMENT AND PRESSURE CHANGES IN THE LUNGS II. MUSCLES OF VENTILATION IV. PULMONARY VOLUMES AND CAPACITIES V. FUNCTION OF THE RESPIRATORY PASSAGES I. RESPIRATORY SYSTEM Primary goal: provide oxygen and remove carbon dioxide : gas exchange 4 major functions: 1. Pulmonary ventilation or bringing in air to alveoli 2. Diffusion of O2 and CO2 between alveoli and blood 3. Transport of O2 (from the lung to the body) and removal of CO2 from the body to the lungs 4. Regulation of respiration Lung Anatomical Structure/Function Relationships o lungs are contained in a space with a volume of Figure 1. Muscles of respiration. approximately 4 L, but they have a surface area for gas exchange that is the size of a tennis court (≈85 major muscles of respiration include the diaphragm, the m2 ). external intercostal muscles, and the scalene Circulatory Systems in the Lung muscles o The lung has two separate blood supplies, one for the Lungs can be expanded and contracted in 2 ways: uptake of O2 and removal of CO2 from the body 1. Downward and upward movement of the diaphragm to lengthen or shorten the chest (pulmonary circulation) and the other to supply O2 to lung tissue (bronchial circulation. cavity (this is usually done during quiet normal respiration) Pulmonary Circulation 2. Elevation and depression of the ribs to increase o begins in the right atrium of the heart and decrease the anteroposterior diameter of o The functions of the pulmonary circulatory system the chest cavity are: Refer to figure 1. Due to the downward pull of the 1. to reoxygenate the blood and release CO2, 2. to aid in fluid balance in the lung, and diaphragm, you increase the length of your lungs, this is 3. to distribute metabolic products to and from the done during normal respiration. But with heavy breathing, lung. your ribs are slanted forward and downward and pulling up the ribs would increase (about 20%) the Bronchial Circulation anteroposterior diameter bringing your ribs to almost o provides systemic arterial blood to the trachea, vertical line upper airways, surface secretory cells, glands, nerves, visceral pleural surfaces, lymph nodes, pulmonary arteries, and pulmonary veins A. MOVEMENT OF THE DIAPHRAGM o circulation is similar in structure to the systemic circulatory system and perfuses the upper Diaphragm: primary muscle for respiration respiratory tract accounts for 75% of the change in intrathoracic volume during quiet inspiration. Central Control of Respiration Normal breathing o Regulation of respiration requires: o Inspiration: contraction of the diaphragm pulls the 1. generation and maintenance of a respiratory lower surfaces of the lungs downward rhythm; o Expiration: the diaphragm simply relaxes, and the 2. modulation of this rhythm by sensory feedback elastic recoil of the lungs, chest wall and abdominal loops and reflexes that allow adaptation to structures compresses the lungs and expels the air. Page 1 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 Heavy breathing - alveolar pressure falls to -1 cm of water – that o Elastic forces not sufficient for rapid expiration pressure would be enough to pull 0.5 L of air into o Abdominal muscles contract to exhale more rapidly. lungs in 2 sec (quiet respiration) o The distance the diaphragm moves ranges from 1.5 o During expiration cm to as much as 7 cm with deep inspiration. - Alveolar pressure rises +1cm of water – expel 0.5 L of inspired air in 2 – 3 sec of respiration B. MOVEMENT OF THE RIB CAGE Transpulmonary Pressure o Difference between that in the alveolar pressure and Increase 20% of AP diameter during maximum inhalation pleural pressure o Muscles of Inspiration o Measure of the elastic forces in the lungs that tend - External intercostals to collapse the lungs at each instant of respiration, = when the external intercostals contract they called the recoil pressure. elevate the lower ribs, pushes the sternum o In the diagram (figure 2), you can see the different outward and increases the anteroposterior curves and relationships between pleural and diameter of the chest. alveolar pressure and the changes of volume of the - Sternocleidomastoid muscles lung. = Lift upward on the sternum o At rest, the pleural pressure is -0.5 cm of water and - Anterior serrati during inspiration, this pressure would fall in -7.5 cm = Lift many of the ribs of water. Concurrent with the change of the pleural - Scaleni pressure, is the increase of volume of air that would = Lift the first two ribs flow into your lungs (0 amount of air all the way to o Muscles of Expiration half a liter of air) - Abdominal recti o Alveolar pressure at rest, there’s a slight increase of - Internal intercostals negative pressure that is already pulling the.5L. Lungs float in the thoracic cavity Owing to the increase amount of air in the alveoli that Well – lubricated by the pleural fluid into lymphatic pressure would rise once again to 0 cm of water channels – slight suction between the visceral surface of meaning it is equal to atmospheric pressure but the the lung pleura and the parietal pleural surface of the volume change is already large. thoracic cavity (pleural pressure). III. AIR MOVEMENT AND PRESSURE CHANGES IN THE LUNGS Pleural Pressure o The pressure of the fluid in the thin space between the lung pleura and the chest wall pleura - At the beginning of respiration = -5 cm of water – pressure needed to hold lungs open during rest - During inspiration increases from -5 to -7.5 cm of water – due to the outward pull of the chest wall Alveolar Pressure o The pressure of the air inside the lung alveoli o If glottis opens and no airflow - equal pressure throughout the respiratory tree = atmospheric pressure - zero reference pressure (0 cm of water) - Zero reference: in equilibrium with the atmosphere o During inspiration Page 2 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 Figure 2. Changes in lung volume, alveolar pressure, pleural pressure and transpulmonary pressure during normal breathing. Transmural pressure across the chest wall o (Pw) is the difference between pleural (inside) pressure (Ppl) and the pressure surrounding the chest wall (Pb), which is the atmospheric pressure or body surface pressure Lung Compliance o Extent to which the lungs will expand for each unit increase in transpulmonary pressure o Total compliance of both lungs together averages about 200 mL of air per 1 cm of water transpulmonary pressure Compliance diagram of the Lung maintained at atmospheric pressure (0 cm H2O) and pleural pressure is changed in order to change the transpulmonary pressure. The presence of saline fluid in your alveoli would eliminate the elastic forces of your pulmonary surfactant. Surfactant and Surface Tension o Principle of surface tension - When water forms a surface with air, the water molecules on the surface of the water have an especially strong attraction for one another = water surface is always attempting to contract - In the alveoli: water surface is also attempting to contract → collapse of alveoli Figure 3. Compliance diagram in a healthy person. This = expel air through the bronchi (try to collapse diagram shows changes in lung volume during changes the alveoli) in transpulmonary pressure (alveolar pressure minus = elastic contractile force in the lung (surface pleural pressure) tension elastic force) o Characteristic is determined by elastic forces of the o Surfactant lungs - Surface active agent in the water 1. Elastic forces of lung tissue - Produced by type II alveolar epithelial cells = elastin and collagen fibers present in the - Most important components: parenchyma of lungs ✓ Dipalmitoyl phosphatidylcholine = In deflated lungs, these fibers are in an ✓ Surfactant apoproteins elastically contracted and kinked state; ✓ Calcium ions then, when the lungs expand, the fibers - DPPC (dipalmitoyl phosphatidylcholine): partly become stretched and unkinked dissolves in the water and the rest spreads over 2. Elastic forces caused by surface tension of the the surface alveolar fluid and fluid lining other lung spaces - helps prevent pulmonary edema o The tissue elastic forces tending to cause collapse of - Pure water = 72 dynes/cm the air – filled lung represent only about 1/3 of the - Fluids in alveoli but without surfactant = 50 total lung elasticity, whereas the fluid air surface dynes/cm tension forces in the alveoli represent about 2/3. - Fluid in alveoli with normal amount of surfactant = 5-30 dynes/cm So there’s a greater decrease in surface tension. Figure 4. Comparison of the compliance diagrams of saline – Lesser tension = lesser work needed to inhale or filled and air – filled lungs when the alveolar pressure is counteract the collapsing force of alveoli Page 3 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 o Occluded alveoli 1. To expand the lungs against the lung and - Positive pressure is produced in attempt to expel chest elastic forces, called compliance air work or elastic work. - Normal (with surfactant) = 4 cm of water 2. To overcome the viscosity of the lung and - Without surfactant = 18 cm of water chest wall structures called tissue resistance work. 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 = (2 × 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑡𝑒𝑛𝑠𝑖𝑜𝑛) ÷ 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝑎𝑙𝑣𝑒𝑜𝑙𝑢𝑠 3. To overcome airway resistance to movement of air into the lungs, called airway resistance work. o Therefore, surfactant is important in reducing the o Energy required for expiration effort of respiratory muscles to expand the lungs Quiet respiration: 3 -5% of total energy expended by o The lesser the diameter of the alveoli, the greater the body the surface tension, the greater the respiratory effort Heavy Exercise: increase in 50x of the original – significant in premature babies because this unit fraction of total energy expended is not yet developed in the normal mature surfactant o One of the limitations of the intensity of exercise is the leading to a condition acute respiratory distress ability of the person to provide energy for respiration. syndrome. If you don’t have much energy you cannot spend o Respiratory distress syndrome of the newborn much energy during respiration and that would limit - Have alveoli with radii less than one quarter that the amount of work/ exercise that you would be able of an adult person to achieve. - Surfactant does not normally begin to be o Work is performed by: secreted into the alveoli until between 6th and o respiratory muscles in stretching the elastic 7th months of gestations tissues of the chest wall and lungs (elastic work; - Many premature babies have little or no approximately 65% of the total work) surfactant in the alveoli when they are born, and o moving inelastic tissues (viscous resistance; 7% their lungs have an extreme tendency to of total) collapse. o moving air through the respiratory passages How a Pressure Gradient Is Created (airway resistance; 28% of total). o Air flows into and out of the lungs from areas of higher pressure to areas of lower pressure. In the absence of a pressure gradient, there is no airflow. IV. PULMONARY VOLUMES AND CAPACITIES o Thus, at end inspiration and at the end of exhalation, which are periods of time when there is no airflow, alveolar pressure (PA) is the same as atmospheric pressure (Pb), and there is no pressure gradient (Pb − PA = 0). Effect of the Thoracic Cage on Lung Expansibility o Compliance of the lung – thorax system is almost exactly ½ of the lungs alone - Combined system = 110 mL/cm - Lungs alone = 220 mL/cm o The compliance of the entire pulmonary system (lungs and thoracic cage) is measured while expanding the lungs of a totally relaxed or paralyzed Figure 5. A spirometer subject. Spirometry Work of Breathing o Method for studying the changes of volume inside the o Quiet breathing: muscles of respiration contract lungs / pulmonary ventilation during inspiration and passive relaxation during O2 and CO2 electrodes expiration (elastic recoil) ○ small probes sensitive to O2 or CO2 records o Work is defined as amount of energy against a continuously Po2 and Pco2. certain resistance Pulse oximeter ✔ 3 factors of respiratory work: Page 4 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 ○ used for chronic assessment of oxygenation - Equals the inspiratory reserve volume plus the and is carried out noninvasively which can be tidal volume easily placed on a fingertip. - 4600 mL Pulmonary Volumes - The maximum amount of air a person can expel o Tidal Volume from the lungs after first filling the lungs to their - The volume of air inspired or expired with each maximum extent and then expiring to the normal breath (500mL in the adult male) maximum extent o Inspiratory Reserve Volume o Total Lung Capacity - Volume of air that can be inspired over and - Equal to the vital capacity plus the residual above the normal tidal volume when the person volume inspires with full force (3000 mL) - About 5800 mL o Expiratory Reserve Volume - Maximum volume to which the lungs can be - The maximum extra volume of air that can be expanded with the greatest possible effort expired by forceful expiration after the end of a All pulmonary volumes and capacities are about 20-25% normal tidal expiration (1100 mL) less in women than in men, and they are greater in large o Residual Volume and athletic people than in small and asthenic people - volume of air remaining in the lungs after the most forceful expiration (1200 mL) this is the amount you cannot physically remove by breathing. Pulmonary Volumes and Capacities Normal values (ml) Volumes Tidal volume 500 Inspiratory reserve volume 3000 Expiratory volume 1100 Residual volume 1200 Capacities Inspiratory capacity 3500 Functional residual capacity 2300 Vital capacity 4600 Total lung capacity 5800 Table 1. Average Pulmonary Volumes and Capacities. Figure 6. A diagram showing respiratory excursions Pulmonary Capacities during normal breathing and during maximal inspiration o Inspiratory Capacity and maximal expiration - Equals the tidal volume plus the inspiratory reserve volume Determinants of Lung Volume - 3500 mL o The answer lies in the properties of the lung - Amount of air, beginning at the normal parenchyma and in the interaction between the lungs expiratory level and distending the lungs to the and the chest wall maximum amount o The lung contains elastic fibers that: - You can’t inhale more than this without 1. stretch when stress is applied, which results damaging lungs/ airway in an increase in lung volume, and o Functional Residual capacity 2. recoil passively when this stress is released, - Equals the expiratory reserve volume plus the which results in a decrease in lung volume. residual volume The elastic recoil of the lung parenchyma is - 2300 mL very high. - Amount of air that remains in the lungs at the Symbol Pulmonary Function end of normal expiration o Vital Capacity VT Tidal volume Page 5 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 FRC Functional residual capacity PaCO2 Partial pressure of carbon dioxide in arterial blood ERV Expiratory reserve volume PAO2 Partial pressure of oxygen in alveolar gas RV Residual volume PACO2 Partial pressure of carbon dioxide in alveolar gas IC Inspiratory capacity PAH2O Partial pressure of water in alveolar gas IRV Inspiratory reserve volume Ṛ Respiratory exchange ratio TLC Total lung capacity Q Cardiac output VC Vital capacity CaO2 Concentration of oxygen in arterial blood Raw Resistance of the airways to flow of air into the C𝑣 O2 Concentration of oxygen in mixed venous blood lungs Table 2. Abbreviations and Symbols used in Pulmonary C Compliance Function Studies VD Volume of dead space gas VC= IRV + VT + ERV VC = IC + ERV VA Volume of alveolar gas TLC = IC + FRC FRC = ERV + RV 𝑉̇ I Inspired volume of ventilation per minute Minute Respiratory Volume 𝑉̇ E Expired volume of expiration per minute o Total amount of new air moved into the respiratory 𝑉̇ S Shunt flow passages each minute o Equal to the tidal volume times the respiratory 𝑉̇ A Alveolar ventilation per minute rate per minute o Normal: 500 mL x 12 breaths/min = 6L/min 𝑉̇ O2 Rate of oxygen uptake per minute Alveolar Ventilation o Ultimate purpose of pulmonary respiration is to 𝑉̇ CO2 Amount of carbon dioxide eliminated per minute deliver O2-rich air into the respiratory segments of the respiratory system (alveoli, alveolar sacs, 𝑉̇ CO Rate of carbon monoxide uptake per minute alveolar ducts, and respiratory bronchioles) o Rate by which new air reaches respiratory DLO2 Diffusing capacity of the lungs for oxygen segments o Dead space air DLCO Diffusing capacity of the lungs for carbon monoxide - Part of the inspired air that does not reach the gas exchange area and fills up the conductive PB Atmospheric pressure part of the respiratory system - Normal dead space air = 150 mL in a young Palv Alveolar pressure male adult - It undergoes no changes in content of oxygen, Ppl Pleural pressure carbon dioxide or water. Because despite of inhaling so much that is still air that would PO2 Partial pressure of oxygen remain in your conductive portion (trachea, PCO2 Partial pressure of carbon dioxide larynx, bronchi, tertiary bronchioles). - Dead space air increases slightly with age PN2 Partial pressure of nitrogen - NOTE! Because of the dead space, rapid shallow breathing produces much less alveolar PaO2 Partial pressure of oxygen in arterial blood ventilation than slow deep breathing Anatomic vs Physiologic Dead Space Page 6 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 o Anatomic Dead Space o Greatest resistance occurs in the larger - Air in the conductive part of the respiratory bronchioles. The reason for this high resistance is system that there are relatively few of these larger bronchi o Physiologic Dead Space in comparison with the 65,000 parallel terminal - Air in alveoli with poor or absent circulation bronchioles, through which only a minute amount of o Normal: Anatomic dead space = Physiologic dead air must pass. o In diseased lungs, smaller bronchioles determine space airway resistance due to: o In normal lungs - there should be no poor or absent ✔ Muscle contraction circulation. So, the physiologic dead space should ✔ Edema in the walls almost be non-existent. ✔ Mucus plugs o In diseased lung – physiologic dead space maybe Nervous and local control of the bronchial 10x greater than anatomic dead space, or 1-2 liters musculature o In healthy individuals, the two dead spaces are o Weak sympathetic innervation due to few fiber identical and can be estimated by body weight. penetrating to central portions of the lungs - no o In disease states, no exchange may take place innervations, just your sympathetic innervation. between the gas in some of the alveoli and the o Very much susceptible to norepinephrine and blood, and some of the alveoli may be over epinephrine released in the gland – stimulate β- ventilated. adrenergic receptors to cause bronchial dilatation Rate of Alveolar Ventilation or contraction o One of the major factors determining the amount of Parasympathetic Constriction of the Bronchioles O2 in and CO2 is the alveoli o Derived from the vagus nerve o Equal to volume of new air entering the gas o Secretes acetylcholine – cause mild to moderate exchange areas times respiratory rate. constriction o When a diseases process such as asthma has already caused some bronchiolar constriction, superimposed parasympathetic nervous system stimulation often worsens the condition. o 12 x (500 – 150) = 4200 mL/min; 350 is the amount o Relax the passages by administration of drugs that that would go through gas exchange block the effects of acetylcholine, such as atropine o Alveolar ventilation per minute is the total volume of o Can also be activated from reflexes that originates from the lungs new air entering the alveoli and adjacent gas - Can be initiated by irritation of the epithelium by exchange areas per minute noxious gases, smoke, or dust Alveolar Gas Composition - Can also be due to micro emboli of small o O2 is transported across the alveolar membrane into pulmonary arteries the capillary bed, and CO2 moves from the capillary Local Secretory Factors often cause Bronchiolar bed into the alveolus Constriction o the partial pressures of the gases in the alveolus o Histamine and slow reactive substance of must equal the total pressure, which in this case is anaphylaxis atmospheric - released by mast cells during allergic reactions o Smoke, dust, noxious gases can also cause non- V. FUNCTION OF THE RESPIRATORY PASSAGES parasympathetic bronchoconstriction by acting on the lung tissue itself Trachea, bronchi and bronchioles Mucus lining the Respiratory Passageways, and o Airways kept open by cartilage rings and plates o From the larger bronchioles to the smallest tertiary Action of Cilia to Clear the Passageways bronchioles (1.5mm) kept open by transpulmonary o Mucus layer: keeps epithelium moist and traps pressure, same pressure that expand the alveoli - microparticles; always present throughout your alveoli enlarge, bronchioles also enlarge because respiratory tree not only in the alveoli (in the alveoli there is no cartilage present just smooth muscles. you have fluid there and surfactant), the mucus layer traps microparticles approximately all the way Resistance to airflow in the bronchial tree down to 10 µm by air compaction against mucus o Ideally in healthy normal individuals, almost no layer. resistance o 200 cilia on each epithelial cell beats 10-20x per second to clear this mucus layer into the pharynx - Page 7 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 from lower bronchioles, to the larynx and then to the o Air is almost completely humidified – to within 2-3% pharynx of complete saturation Cough Reflex o Air is partially filtered inside the nasal cavity. o Triggered by irritation in the carina, larynx, - Larger particles can be filtered out by the bronchioles and even the alveoli vibrissae but the most important filter is the o Airways collapse by the pressure, cartilage support mucus layer found inside the nasal cavity. invaginates particularly the trachea and makes Filtration function airways significantly narrower increasing the o Vibrissae – for larger particles pressure to bring out foreign noxious material o Turbulent precipitation – for smaller particles o Afferent nerves pass through the vagus nerve to the up to 6 µm medulla to trigger the following events: o The nasal turbulence mechanism is so effective 1. 2.5 L of air is rapidly inspired that almost no particles larger than 6 µm in 2. Epiglottis and vocal folds forcefully shut diameter enter the lungs through the nose. The 3. Abdominal muscles, and other muscles size is smaller than the size of red blood cells. expiration (internal intercostals) contracts o Gravitational precipitation – for particles 1 to against the closed glottis to raise the pressure 5 µm to 100mmHg o Lesser than 1 µm diffuse in the alveolar fluid and 4. Epiglottis and the vocal folds rapidly open and removed by alveolar macrophages or air is explosively expired (70-100 miles/hr) lymphatics - this is called your dust cells inside Sneeze Reflex the lungs o Similar to cough reflex – irritated nasal passages o Lesser than 0.5 µm remain suspended in the air o Afferent nerves pass through the CN V cranial nerve and are expelled during respiration to the medulla of the brain VOCALIZATION o Similar events occurs but in the final stage, the By-product of respiration uvula is depressed and air is passed through the Involves not only the respiratory system but also: nose instead of the mouth to clear out the foreign o Speech control centers in the brain material inside the nasal cavity o Respiratory control centers in the brain o Resonance and articulation structures in the oral and nasal cavities 2 Mechanical Functions o Phonation - production of the general sound of the voice - achieved by the larynx - larynx acts as vibrator - the vibrating elements are the vocal folds/ vocal cord o Articulation - modification of sound to an understandable sound - achieved by the structures of the mouth During normal breathing, the cords are wide open to allow easy passage of air During phonation, the cords move together so that the passage of air between them will cause vibration. Figure 7. Respiratory passages NORMAL RESPIRATORY FUNCTIONS OF THE NOSE The olfactory function of the nose is just a bonus or a secondary function. The primary function of the nose is respiration. Air conditioning functions o Air is warmed by the nose - 160 cm2 surface area of the turbinates and septum – rises to 1° F of the body temperature Page 8 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 The pitch of vibration is determined mainly by the degree Whispering: most damaging of stretch of the cords, but also by how tightly the cords are approximated to one another and by the mass of their edges Figure 9. Laryngeal function in phonation Ventilation/Perfusion Abnormalities and Shunts Anatomical Shunts o An anatomical shunt occurs when mixed venous blood bypasses the gas-exchange unit and goes Figure 8. Anatomy of Larynx directly into the arterial circulation o The blood that bypasses the gas-exchange unit is PHONATION thus shunted, and because the blood is - 2 vocal cords fully oppose against one another deoxygenated, this type of bypass is called a right- and air would pass right through that to cause to-left shunt. vibration the vocal cords and produce general o The effect of this right-to-left shunt is to mix vocalization deoxygenated blood with oxygenated blood, and it INTERMEDIATE POSITION (loud whisper) results in varying degrees of arterial hypoxemia. STAGE WHISPER (EERIE VOICE) Physiological Shunt - These 2 are the most damaging means of o A physiological shunt (also known as venous speaking admixture) can develop when ventilation to lung - It damages your vocal cords units is absent in the presence of continuing - Speaking - whisper perfusion. - Singing - falsetto o atelectasis (which is obstruction to ventilation of a gas-exchanging unit with subsequent loss of ARTICULATION AND RESONANCE volume) Organs of articulation Alveolar Hypoventilation o Lips - “O” shape of the lips o Ventilation insufficient to maintain normal levels of o Tongue- “R” movement of the tongue against CO2 is called hypoventilation. Hypoventilation the palate always decreases PaO2 and increases PaCO2. o Soft palate “NGA/NA” movement of soft palate - Different movement of the structures would Diffusion Abnormalities create different sounds o Abnormalities in diffusion of O2 across the alveolar- Resonators capillary barrier could potentially result in arterial o Mouth hypoxia o Nose and paranasal sinuses o An increased AaDO2 attributable to incomplete o Pharynx diffusion (diffusion disequilibrium) has been observed in normal persons only during exercise at high altitude (≥10,000 feet). o Alveolar capillary block, or thickening of the air- blood barrier, is an uncommon cause of hypoxemia. Mechanisms of Hypercapnia o Two major mechanisms account for the development of hypercapnia (elevated PCO2): hypoventilation and wasted, or increased, dead space ventilation. Page 9 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 TEST YOUR KNOWLEDGE 10. It is the maximum volume to which the lungs can be expanded with the greatest possible effort 1. During maximum inhalation, the AP diameter increases a. Vital Capacity a. 10% b. Total Lung Capacity b. 15% c. Inspiratory Capacity c. 20% d. Tidal Volume d. 30% 11. Equals the tidal volume plus the inspiratory reserve 2. The contraction of the diaphragm pulls lower surfaces of volume the lungs downward. a. Vital Capacity a. Forced Inhalation b. Total Lung Capacity b. Forced Exhalation c. Inspiratory Capacity c. Normal inhalation d. Tidal Volume d. Normal Expiration 12. True or False. Rate of alveolar ventilation is equal to the 3. The following are muscles of Inspiration except: volume of new air entering the gas exchange areas a. Sternocleidomastoid times respiratory rate. b. External Intercostal 13. The pressure that keeps the bronchioles open, and c. Internal Intercostal expands the alveoli. d. Anterior serrati a. Alveolar pressure 4. The extent to which the lungs will expand for each unit b. Transpulmonary pressure increase in transpulmonary pressure. c. Pleural pressure a. Lung compliance d. Recoil pressure b. Transpulmonary pressure 14. Measure of the elastic forces in the lungs that tend to c. Alveolar pressure collapse the lungs at each instant of respiration. d. Pleural pressure a. Alveolar pressure 5. This partly dissolves in the water and the rest spreads b. Transpulmonary pressure over the surface c. Pleural pressure a. O2 d. Recoil pressure b. DPPC 15. True or False. All pulmonary volumes and capacities c. Pure water are about 25-30% less in women than in men. d. CO2 16. The volume of air inspired or expired with each normal 6. Used for chronic assessment of oxygenation and is breath carried out noninvasively. 17. One of the major factors determining the amount of O2 a. O2 and CO2 electrodes in and CO2 b. Spirometry 18. Smoke, dust, noxious gases can also cause ________ c. Pulse oximeter acting on the lung tissue itself d. ABG analysis 19. True or False. Greatest resistance occurs in the larger 7. What is the normal volume of TV in an adult male? bronchioles. a. 2000ml 20. – 21. What are the 2 mechanical functions of b. 1500ml vocalization? c. 1000ml 22. Occurs when mixed venous blood bypasses the gas- exchange unit and goes directly into the arterial d. 500ml circulation. 8. Part of the inspired air that does not reach the gas 23. The blood that bypasses the gas-exchange unit is thus exchange area and fills up the conductive part of the shunted, and because the blood is deoxygenated, this respiratory system type of bypass is called a. Dead space air 24-25. Give the 3 organs of articulation b. Inspiratory reserve volume and soft palate 22. Anatomical Shunt 23.right-to-left shunt 24 – 25. Lips, tongue c. Expiratory reserve volume bronchoconstriction 19. True 20 – 21. Phonation and Articulation d. Residual volume 16. Tidal Volume 17. Alveoli 18. non-parasympathetic 9. True or False. Because of the dead space, rapid 1.C2.C3.C4.A5.B6.C7.D8.A9.False10.B11.C12.True13.B14.D15False shallow breathing produces more alveolar ventilation Answers: than slow deep breathing. Page 10 of 11 CMED 1C  (008) MECHANICS OF RESPIRATION DR. N. LACUESTA | 02/08/2021 REFERENCES 1. Guyton, A.C., Hall, J.E. Guyton and Hall Textbook of Medical Physiology. 13th ed., W. B. Saunders, 2015. 2. Doc N. Lacuesta PPT and Lecture 3. Berne and Levy 7th ed., Koepen, Stanton, (2018) Page 11 of 11 CMED 1C