呼吸科呼吸系统

Unit 5: Respiration,Definition of RespirationThe process that human body exchanges gases with the atmosphere.orThe process of taking up oxygen and removing carbon dioxide from cells in the body.,12/2/2017,1,Dyspnea & Apnea,Dyspnea means that there is air hunger. Apnea means no breathing.,When you cant breathe, nothing else mattersSlogan of the American Lung Association,12/2/2017,3,Main Topics,5.1. Pulmonary ventilationThe ventilatory pumpMechanics of ventilationElastic and non-elastic resistancesStatic lung volumeDynamic lung ventilation 5.2. Gas exchangeGas diffusionFactors that affect gas exchangeVentilation-perfusion ratio (VA/Q)5.3. Gas transport in the bloodOxygen, carbon dioxide, carbon monoxide poisoning5.4. The control of ventilationRespiratory center and the basic respiratory patternVoluntary control Chemosensory reflexesMechanical reflexes,12/2/2017,4,2017/12/2,Who am I?,Name: 詹 仁知E-mail: Location: 6-338,5,网上学习材料,复旦大学上海医学院生理学精品课程/第五章自测题库/document/tkch-5.pdf,12/2/2017,6,Conducting Zone and Respiratory Zone,Type 1 alveolar cellsThese cells are derived from type II alveolar cells and provide a thin layer of cytoplasm which covers about 80% of the gas exchange zone.Type II alveolar cellsThese cells allow the formation of surfactant and other enzymes.Type III alveolar cellsThese cells are the main lung defence system they are the alveolar macrophages.,Main Functional Events of Respiration,12/2/2017,9,Terminology,Pulmonary ventilation （肺通气）The inflow and outflow of air between the atmosphere and the lung alveoli.Gas exchange（肺换气)Diffusion of oxygen and carbon dioxide between the alveoli and the blood inside the pulmonary capillaries. Gas transport in the blood （气体在血液中的运输） Transports of oxygen and carbon dioxide in the blood and body fluid to and from the tissue cells. Tissue gas exchange（组织换气）The exchange of oxygen and carbon dioxide between blood and cells in different tissues.,12/2/2017,10,Terminology-Continued,External Respiration (外呼吸)Exchange of gases between the atmosphere and the blood in pulmonary capillaries. It consists of pulmonary ventilation and gas exchange.Internal Respiration (内呼吸)The exchange of oxygen and carbon dioxide between blood and cells in different tissues.It consists of tissue gas exchange and biological oxidation.,12/2/2017,11,Summary,1. Breathing is essential to life.2. The primary function of respiration is to provide oxygen for metabolic needs and to remove carbon dioxide from cells in the body.3. The main functional events of respiration are pulmonary ventilation, gas exchange, gas transport in the blood and tissue gas exchange.,12/2/2017,12,5.1. Pulmonary Ventilation,DefinitionPulmonary ventilation refers to the inflow and outflow of air between the atmosphere and the lung alveoli.,12/2/2017,13,Two Phases of the Breathing Cycle,Inspiration or inhalation（吸气）Inspiration is the movement of air into the lungsExpiration or exhalation（呼气）Expiration is the movement of air out of the lungs,12/2/2017,14,2017/12/2,15,Normal Quiet Breathing vs. Forced Breathing （平静呼吸vs.用力呼吸）,Abdominal Breathing vs. Thoracic Breathing（腹式呼吸vs.胸式呼吸）,12/2/2017,16,Lung Ventilation（肺通气）,Driving forceAgainstResistance,12/2/2017,17,5.1.1. The Ventilatory Pump,Chest wall（胸壁）Spine, ribs and sternumRespiratory musclesThe diaphragm（膈肌）The main inspiratory muscleThe intercostal muscles（肋间肌）The external intercostal muscles (inspiratory muscles)The internal intercostal muslces (expiratory muscles)Pleural cavity（胸膜腔）,12/2/2017,18,The Pleural Cavity （胸膜腔）,The pleural cavity is the potential space between the lungs and the chest wall, containing a small amount of pleural fluid,12/2/2017,19,Respiratory Muscles（呼吸肌）,1. InspiratoryDiaphragm（膈肌）External intercostal muscles（肋间外肌）,2. Accessory（辅助）Scalene（斜角肌）Sternocleidomastoid muscles（胸锁乳突肌）,3. ExpiratoryAbdominal musclesInternal intercostal muscles（肋间内肌）,12/2/2017,20,The Diaphragm（膈肌）,The most important muscle for inspiration,Contraction of the diaphragm pushes the abdominal contents（腹腔内容物） downward and lifts the ribs（肋骨） upward and outward, increasing the volume of the thoracic cavity in 3 directions.,12/2/2017,21,Pressures in Different Compartments,Barometric pressure （大气压）The atmosphere the air we breathe and live in, experts a pressure known as barometric pressure (PB).Pleural pressure or intrapleural pressure（胸膜腔内压）The pressure in the pleural space between the lung and the chest wall is pleural pressure (Ppl). A decrease in pleural pressure causes the lungs to expand. The pleural pressure starts to decrease in the beginning of until the end of inspiration. Alveolar pressure or intrapulmonary pressure（肺内压）Alveolar pressure is the pressure inside the alveoli; it determines inward or out flow of air.Transpulmonary pressure（跨肺压）Transpulmonary pressure is the pressure difference across the lung wall (PA Ppl).,12/2/2017,22,The Negative (subatmospheric) Pleural Pressure,In normal quiet breathing, the pleural pressure is negative (lower than the atmosppheric pressure).Elastic recoil（弹性回缩）of the lungs and chest wall results in negative pleural pressure.The pleural pressure changes according to breathing cycle with the maximal negative pleural pressure reaches just the end of inspiration due to the biggest elastic recoil of the lungs.Forced expiration can result in a positive pleural pressure.,12/2/2017,23,Wind blows,When pressure difference between two adjacent compartments exists,12/2/2017,24,From Pressure Differences to Airflow,The difference between alveolar pressure and barometric pressure is the direct driving force for ventilation.Inspiratory muscle contraction is the primary driving force for ventilation.Negative alveolar pressure (lower than the atmospheric pressure) results in inspiration whereas positive alveolar pressure causes expiration.For any given cycle of breathing, there is a time point where alveolar and the barometric pressures are equal (the end of ispiration or just before expiration),12/2/2017,25,1. The pleaural (or intrapleaural) pressure reaches its maximum negative level at the end of inspiration.2. At the end of ispiration or just before expiration, the alveolar and the barometric pressures are equal.3. Flow rate increases (or decreases ) in parallel with alveolar pressure.,Conclusions Drawn from the Left Figure,12/2/2017,26,Boyles Law,12/2/2017,27,Inspiratory Muscles Contract,Thoracic Cavity Expands,Pleural Pressure Becomes more Negative,Transpulmonary Pressure Increases,Alveolar Pressure Becomes Subatmospheric,Air Flows into the Lungs until Alveolar Pressure Equals Atmospheric Pressure,P1XV1 = P2XV2,Boyles Law,Sequential Events Occur during Inspiration,Lungs tend to Inflate,12/2/2017,28,Sequential Events Occur during Expiration,Relaxation of Diaphragm,Thoracic Cavity Shrinks,Negative Pleural Pressure Decreases,Transpulmonary Pressure Becomes Small,Alveolar Pressure Rises above the Atmospheric Pressure,Lung Volume Tends to Decrease,Air Flows out the Lungs until Alveolar PressureEquals Atmospheric Pressure,P1XV1 = P2XV2,Boyles Law,12/2/2017,29,The Significance of a Negative Pleural Pressure,Keeps the lungs to be inflated as it is demonstrated in pneumothorax (气胸).Promotes the returns of venous blood and lymphatic fluid (淋巴液).,12/2/2017,30,Pneumothorax (气胸),A condition in which air has entered and expanded the normally closed pleural space, driving pleural pressure up toward atmospheric pressure, and resulting in partial or complete collapse of the lung.,12/2/2017,31,Consequences of Pneumothorax,Hypoxia（缺氧） due to shunt (blood passes through those collapsed alveoli).Decrease in venous blood return due to compression of vena cava, resulting in lower cardiac output and consequently hypotension (circulatory collapse).,12/2/2017,32,Cases of Pneumothorax,Case 1: A patient who underwent stomach surgery under epidural anesthesia has symptoms of anxiety, intensified abdomen breathing and low blood pressure with decreased pulse pressure.Case 2: A patient with history of emphysema presented to ER with difficult breathing and cyanosis. Chest X-ray showed no signs of collapsed lung.,12/2/2017,33,Summary on Driving Forces for Ventilation,The negative pleural pressure results from the elastic recoil of the lungs and the chest wall, keeping the lungs to be inflated.Chest wall movement caused by the contraction of inspiratory muscles mainly the diaphragm is the primary driving force for ventilation, leading to changes in alveolar pressure.The pressure difference between the alveoli and the atmosphere is the direct driving force for ventilation, leading to inhalation or exhalation.,12/2/2017,34,Inspiratory Muscles Contract,Thoracic Cavity Expands,Pleural Pressure Becomes more Negative,Transpulmonary Pressure Increases,Alveolar Pressure Becomes Subatmospheric,Air Flows into the Lungs until Alveolar Pressure Equals Atmospheric Pressure,P1XV1 = P2XV2,Boyles Law,Sequential Events Occur during Inspiration,Lungs tend to Inflate,12/2/2017,35,Sequential Events Occur during Expiration,Relaxation of Diaphragm,Thoracic Cavity Shrinks,Negative Pleural Pressure Decreases,Transpulmonary Pressure Becomes Small,Alveolar Pressure Rises above the Atmospheric Pressure,Lung Volume Tends to Decrease,Air Flows out the Lungs until Alveolar PressureEquals Atmospheric Pressure,P1XV1 = P2XV2,Boyles Law,12/2/2017,36,Sequential Events Occur during Expiration,Relaxation of Diaphragm,Thoracic Cavity Shrinks,Negative Pleural Pressure Decreases,Transpulmonary Pressure Becomes Small,Alveolar Pressure Rises above the Atmospheric Pressure,Lung Volume Tends to Decrease,Air Flows out the Lungs until Alveolar PressureEquals Atmospheric Pressure,P1XV1 = P2XV2,Boyles Law,12/2/2017,37,5.1.2. Mechanical Properties of the Lungs and Chest Wall,How the lungs inflate and deflate not only depend on transpulmonary pressure but also elastic properties of lungs and chest wall.Three terms (elastic recoil, stiffness and distensibility) are used to describe the elastic properties of the lungs and chest wall.,12/2/2017,38,Stiffness, Distensibility and Elastic Recoil,Stiffness （硬度） is defined as resistance to be stretched or inflated. Distensibility（可扩张性）is the term applied to the ease with which the lungs can be stretched or inflated.Elastic recoil （弹性回缩） is defined as the ability of a stretched or inflated lung to return to its resting volume (FRC). Distensibilty and elastic recoil are inversely related to each other.,12/2/2017,39,Lung Compliance (CL),Lung compliance (CL) is a measure of distensibility.CL is defined by change in volume per change in pressure. It can be written as CL = volume/pressure.Where volume equals change in volume and pressure equals change in pressure. CL is the slope of the pressurevolume curve.,12/2/2017,40,Measurement of CL in Humans,12/2/2017,41,Factors that Affect CL,Elastic recoil Inversely relatedLung volumeProportionally related Surface tension (will be analyzed later)Inversely related,2017/12/2,42,Pathological Conditions That Are Associated with Reduced CL,Damage of elastin fibers e.g., COPDFibrosis Pulmonary hypertension/congestion Increases stiffness of the lungs Alveolar atelectasis e.g. after prolonged period of ventilation Reduced surfactant (increased surface tension) e.g. artificial ventilation, prematurity,12/2/2017,43,Obstructive and Restrictive Disorders Affect CL differently,2017/12/2,44,Obstructive disease,Restrictive disease,Restrictive lung diseases are associated with increased collagen fibers (胶原纤维).Obstructive lung diseases (emphysema and COPD) are associated with damage of elastin fibers (弹性纤维).Smoking damages elastin fibers, causing emphysema (肺气肿).,Elastic Recoil of Chest Wall,The chest wall has elastic property.The outward of elastic recoil of the chest wall aids long expansion whereas the inward of elastic recoil of lung pulls in the chest wall.At about 67% of total lung capacity, chest wall is in its natural position. If lung volume is less than 67% of TLC, the chest wall tends to recoil outward.If lung volume is more than 67% of TLC, it tends to recoil inward.,12/2/2017,45,Changes in Chest Wall Compliance Are Less Common,Pathologic situations preventing the normal movement of the rib cage, such as distortion of the spinal column, Pathologic (cancer) or physiologic (pregnancy) reasons increasing the intraabdominal pressure,Stiff chest, such as broken ribs.,12/2/2017,46,What is Surface Tension?,Surface tension is a property of the surface of a liquid. It is what causes the surface portion of liquid to be attracted to another surface, such as that of another portion of liquid. In alveoli, the surface of alveolar membrane is moist and is in contact with air, producing a large air-liquid interface. The surface tension prevents the expansion of alveoli and rises resistance for ventilation.,12/2/2017,47,How Does Surface Tension Affect Lung Compliance？,The experiment was done in an isolated lung. The lung was inflated and deflated in a stepwise fashion, first with air and then with saline.With air-filled lungs, the gas-liquid interface creates surface tension (the relation is different for inspiration and expiration). In the saline-filled lung, air-liquid interface is eliminated as its surface.,12/2/2017,48,Works are Needed to Expand the Lungs,Surface tension causes a decrease in lung compliance.Two thirds of the work required to inflate the lung is spent to overcome surface tension (gray area).To expand the lungFirst to overcome the surface tension (gray area)Then to overcome the elastic recoil (blue area).,12/2/2017,49,Surface Tension Affects Alveolar Stability,*P indicates internal pressure that is needed to keep an alveolus to be inflated.*T indicates surface tension* R is the radius of an alveolus,12/2/2017,50,拉普拉斯(1749-1827),Pulmonary Surfactant: Source & Chemistry,Pulmonary surfactant is a lipoprotein rich in phospholipid (磷脂).The principal agent responsible for its surface tension-reducing properties is dipalmitoylphosphatidylcholine (DPPC,二磷脂酰卵磷脂).Alveolar type II cells synthesize and store lung surfactant.Infants born before gestational week 26 produce little surfactant.,12/2/2017,51,Physiological Functions of Surfactant,Increases lung compliance and consequently reduces ventilatory resistanceStabilizes alveoliKeeps the alveoli “dry”,12/2/2017,52,2017/12/2,53,Infant Respiratory Distress Syndrome,/radio/topic710.htm.,Summary on Lung Compliance,Lung compliance (CL) is defined as change in volume per change in pressure. CL is a measure of lung distensibility; it is inversely related to stiffness.Abnormally low lung compliance indicates a stiff lung, which means more work is needed to inflate the lung to bring in a normal tidal volume. Abnormally high lung compliance results in increased static volumes (RV, VC, FRC etc).,12/2/2017,54,Summary on Surface Tension,The surface tension is a force that prevents alveoli to be opened and rises resistance for ventilation,12/2/2017,55,Summary on Surfactant,ProductionPulmonary surfactant is a lipoprotein rich in phospholipid (mainly dipalmitoylphosphatidylcholine, DPPC ) and is manufactured by the alveolar epithelial type II cells. FunctionSurfactant reduces surface tension within the alveoli which helps to increase the compliance of the lung and thus lower respiratory resistanceIt improves alveolar stabilityIt keeps alveoli dry by opposing water movement from the pulmonary interstitium,5.1.3. Ventilatory Resistance,Elastic resistance (70% of total)It is a static resistance that prevents the lungs to be inflated.It results from elastic recoil (30%) and surface tension (70%).Non-elastic resistance (30% of total)It is a dynamic resistance, resulting from the movement of air.It consists of inertial resistance (惯性阻力), viscous resistance (粘滞阻力) and airway resistance (80% of non-elastic resistance).,12/2/2017,57,Surface Tension and Elastic Recoil Make Up Elastic Resistance,To expand the lung 1. First to overcome the surface tension (gray area) 2. Then to overcome the elastic recoil (blue area)Two thirds of the work required to inflate the lung is spent to overcome surface tension. One third of the work required to inflate the lung is spent to overcome the elastic recoil.Elastic resistance consists of two components: surface tension and elastic recoil.,12/2/2017,58,Airway Resistance,It makes the largest proportion (80%) of non-elastic resistance. I can be estimated by Raw = P (PA-PB)/V (gas flow),12/2/2017,59,Factors that Affect Airway Resistance,The diameter of the airwaysThe number of airwaysThe lung volume,12/2/2017,60,Where Does the Airway Constitute the Site of Largest Airway Resistance?,The medium-sized airways (2 mm)?OrThe small airways (2 mm)?,12/2/2017,61,The medium-sized bronchi (2 mm) actually constitute the side of highest resistance along the bronchial tree. Although the small radii of bronchioles (2 mm) might predict that they would have the largest resistance, they do not because of their parallel arrangement.Early changes in resistance in the small airways may be “silent” and go undetected because of their small overall contribution to resistance.,12/2/2017,62,Neurohumoral Control of the Airways,Michoud et al,12/2/2017,63,The Smooth Muscle Tone of Airways is Controlled by Nerves,Sympathetic adrenergic fibersBronchial dilation & inhibition of gland secretion.Parasympathetic cholinergic postganglionic fibersBronchial constriction & increased mucus secretionNon-adrenergic non-cholinergic neuronal fibersBronchcoconstrictory effects (tachykinins, substance P or neurokinin etc.)Bronchodilatatory pathway (nitric oxide and vasoactive intestinal peptide),12/2/2017,64,2-adrenergic Receptors and cholinergic Mus