生理學(xué)英文版教學(xué)課件：09-pulmonary ventilation-1

1、Respiratory Physiology Respiration is the process by which the body takes in & utilizes oxygen (O2), gets rid of carbon dioxide (CO2) A breath in, a breath out, 1215 times every minute may seem like a simple process, which supply oxygen for the whole body at the rest O2 reservation is 1550mL, O2 con

2、sumption is 250mL/min, only can be maintained for 6minOverview of Key Steps in RespirationPulmonary Ventilation Pulmonary Gas ExchangeTissue Gas ExchangeTransportExternal RespirationInternal RespirationThis section is divided into 3 parts: Pulmonary Ventilation Pulmonary Gas Exchange & O2 Transporta

3、tion CO2 Transportation & Respiratory Regulation Pulmonary Ventilation Definition: Inflow & outflow of air between the atmosphere & the lung 肺通氣：指肺與外界環(huán)境之間進(jìn)行氣體交換的過程Mechanism of Pulmonary Ventilation Movement of air into & out of lungs from higher pressure to lower pressure between atmosphere & lung P

4、ressure is inversely related to Volume (Law of Boyle: Volume x Pressure=constant)Ambient air pressure is constant =760mmHgIntra pulmonary pressure758mmHgInspiration & ExpirationIntra pulmonary pressure 763mmHgMuscles of Respiration DiaphragmContractDiaphragmVolume External Intercostal Muscles RibSpi

5、neRibsVolumeBoth actions occur simultaneously otherwise no effect Pulmonary Ventilation Respiratory Muscles is initial power Intrapulmonary Pressure is direct power Which is determined by the activity of the airways, the alveolus, the chest cavity & the respiratory Muscles Abdominal breathing: Activ

6、ity of diaphragm, seen at infant Thoracic breathing: Activity of external intercostal musclesNormally at adult, these two pattern respiration is combined Eupnea: Inspiration is an active process Expiration is an passive process Forced breathing / Deep breathing: Inspiration is an active process Expi

7、ration is an active processPattern of RespirationAirway Divisions Upper airway Nose, Pharynx Larynx Lower airway Trachea Bronchi LungsThe channel of the air inflow & outflow Warms & humidifies inspired airFilters & cleansGas exchangeFunction of the AirwaysUpper airwayLower airwayTracheobronchial Tre

8、e Cricoid Cartilage is more and more less Smooth muscle is more and more rich 1723Age-related changes in alveolar number & surface area in human lungAge Number of alveoli Alveolar surface area Skin surface area(106)(m2)(m2)Birth 242.80.28 years300320.9Adult 300751.8Pleural CavityIntrapleural pressur

9、e: Slightly Negative Pressure during quiet breathing Due to: 1. Lung always the constriction & inward recoil force exerted on thorax 2. Thorax always the outward expanding force on the lung Intrapleural pressure is negative during quiet breathing & becomes more negative with deep inspiration. At the

10、 end of a normal expiration, the lung & the chest wall are stretched in equal but in opposite directions, the stretched lungs have the potential to recoil inwardly, and the stretched chest wall has the potential to recoil outwardly. These equal but opposite forces cause intrapleural pressure to decr

11、ease below atmospheric pressureImportance of Intrapleural Pressure This is to allow lungs to expand Transpulmonary Pressure= (Intrapulmonary Pressure) -(Intrapleural Pressure) Facilitate venous & lymph return Respiratory pressure during breath are often expressed as relative pressure Barometric pres

12、sure(PB) is set at zero as relative pressureFormation of Intrapleural PressureJust at the moment of birth Pneumothorax Pleural Effusion Pathological Phenomena in Pleural CavityRespiratory ResistanceElastic ResistanceInelastic Resistance70%30%Elastic Resistance Definition: Tendency to return to initi

13、al size & structure after distension High content of elastin proteins Very elastic & resist distension Strong recoil abilityElastic Resistance70%LungThorax Lung may be considered as an elastic sac, lung always maintain a distensible state, so lung is always the resistance for inspiration Thorax also

14、 can be considered as an elastic element, But thorax is the resistance or impetus for inspiration or respiration depending on the volume state of thoraxLung Elastic ResistanceFrom :-1/3 lung tissue itself-2/3 caused by surface tension of the fluid that lies the inside wall of the alveoli & the air i

15、n alveoli Lung Elastic Resistance -1/3 lung tissueCL= V/ P P: Difference between alveolar pressure & intrapleural pressureCompliance of the lungs: the extend to which the lungs will expand for each unit increase in transpulmonary pressure Surface Tension in Alveoli - 2/3 Lung Elastic Resistance Law

16、of Laplace: Pressure (P) in alveoli is directly proportional to surface tension (T); and inversely proportional to radius of alveoli (r) Pressure in smaller alveolus would be greater than in larger alveolus, if T is constantInsert fig. 16.11CollapseExpandEffect of Alveoli Size on Alveoli PressureAir

17、 FlowAccording to :P=2T/rPPSurfactant Prevents Alveolar CollapsePulmonary Surfactant DPPC (60%): Produced by alveolar type II cells Lowers alveolar surface tension Balance the alveoli pressure with different radius by change the density of surfactant in alveoli As alveoli radius decreases, surfactan

18、ts density is high, the ability to lower surface tension increasesPulmonary SurfactantInfluence of Surface Tension : Inhibit alveoli to expand & increase the resistance to inspirationCause different alveoli pressure in different size alveoliIncrease the fluid suck from outside of alveoli Function of

19、 pulmonary surfactant:Lower the alveoli surface tension & Increase lung complianceBalance the alveoli pressure in different size alveoliDecrease the formation of interstitial fluid & the happening of pulmonaryedema Conclusion Neonatal Respiratory Distress Syndrome(NRDS)Lack of pulmonary surfactantIn

20、elastic Resistance30%Inertial ResistanceViscous Resistance Airway Resistance(8090%)Airway Resistance Definition: The resistance to the flow of air in the airways Due to: Internal friction between gas molecules Friction between gas molecules & the walls of the airwaysAirway ResistanceHave relationshi

21、p with：r of airway (氣道半徑）Type of air flowLung volumePoiseuille & Resistance(1)(3)(2) Airway Radius or diameter is Key factor Radius by , Resistance by 16 Fold - Think about bronchodilator here! Resistances in parallel are added as reciprocals: Resistance in series are added directly:Types of Air Flo

22、wLaminar Flow Concentric layers of gas flow parallel to the wall of the tube The velocity obeys Poiseuilles Law Because of: the velocity of gas flow is too great Passing by an obstruction Making a sharp turn Passing over a rough surfaceTurbulent FlowTurbulent Flow Does Gas flow by laminar or turbule

23、nt? Depend on: Re= (x V x D) / As Re is over than 2000, turbulent happens Clinical Importance: He instead of N2 to patientFor reducing the happening of turbulent Lung volume is another factor determining airway resistance (Emphysema)Why lung volume inverse ratio with airway resistance? Inspiration ,

24、lung volume increase, airwayoutwardstretch from lung increases Inspiration, intrapleural pressure decrease, transpulmonary pressure increase Inspiration, sympathetic nerve activity increasesAChNNE2AChNAChM3Sympathetic nerveParasympathetic nerveRelaxConstrict Control of Airway Smooth MuscleAirway Res

25、istance Increase Any factor that decreases airway diameter or increases turbulence will increase airway resistance Change with respiratory movement, e.g. expiration increase the airway resistance. Inspiration decrease the airway resistance, Asthma Parasympathetic Stimulation Emphysema: Expiration is

26、 more difficult than inspiration Rapid BreathingEvaluation of Pulmonary Ventilation Pulmonary Volume & Pulmonary CapacityPulmonary Volume Tidal Volume (TV)Volume of air inspired or expired during a normal inspiration or expiration (400600 ml) Inspiratory Reserve Volume (IRV)Volume of air inspired fo

27、rcefully after inspiration of normal tidal volume (15002000 ml) Expiratory Reserve Volume (ERV) Volume of air forcefully expired after expiration of normal tidal volume (9001200 ml) Residual Volume (RV) Volume of air remaining in the lung after the most forceful expiration (10001500 ml)Pulmonary Vol

28、umePulmonary Capacities Inspiratory Capacity (IC)Maximum volume that can be inspired after expiration during normal quiet breathingTidal Volume + Inspiratory Reserve Volume Functional Residual Capacity (FRC)Volume remaining in the lungs after normally quiet expirationExpiratory Reserve Volume + Resi

29、dual Volume (2500ml) Vital Capacity (VC) Maximum volume of air that can be exhale after maximum inspiration Tidal Volume + Inspiratory Reserve Volume+ Expiratory Reserve Volume (3500ml in male, 2500ml in female)Pulmonary CapacitiesVital Capacity (VC): Tidal Volume + Inspiratory Reserve Volume +Expir

30、atory Reserve Volume (3500ml in male, 2500ml in female)FVC - Forced Vital CapacityFEV-Forced Expiratory Volume(Timed Vital Capacity, TVC) FEV1,2,3 (Forced Expiratory Volume,1st,2nd,3rd second) Defines maximum air flow rate out of lung in initial 1,2.3 second intervalFEV1/FVC ratio is 83%FEV2/FVC rat

31、io is 96%FEV3/FVC ratio is 99%Reduced FEV1/FVC suggests obstructive damage to lung airways. e.g. Asthma / Bronchitis/ Emphysema FEV1/FVC is normal or above 83%, Restrictive damage of lung disease, e.g. Fibrosis / Pulmonary Edema Total Lung Capacity (TLC) Volume of gas in the lung after maximal inspi

32、ration Inspiratory Reserve Volumes + Expiratory Reserve Volumes + Tidal Volume + Residual Volume (5000ml in male, 3500ml in female)Pulmonary CapacitiesSpirometryRV, FRC, TLC can not be measured directly by itPulmonary Ventilation(Minute Ventilation)Definition: Total amount of air moved into or out o

33、f respiratory system per minute = TVRespiratory Frequency = 500(1218) = 69LAnatomic Dead SpaceAlveolar Dead Space Pulmonary Ventilation(Minute Ventilation)= TVRespiratory Frequency = 500(1218) = 69LAlveolar: gas exchangeDead spacePhysiological Dead Space= Anatomical Dead Space + Alveolar Dead Space

34、Physiological Dead Space Diseased lungs: Healthy Lungs: Physiological Dead Space = Anatomical Dead Space = Airways (constant)=150mlVAVDBlockedVesselVDVADefinition: How much air per minute enters the parts of the respiratory system in which gas exchange takes place = (TV-dead space gas volume) x Resp

35、iratory Frequency = (500-150) x 12 = 350ml x 12 = 4200ml Percentage of air exchange in alveolus = 350ml 2500ml (FRC) = 14%Alveolar Ventilation Definition:Maximum volume that can be inspired or expired forcefully per minute(3000ml,Vital Capacity x 4050,Respiratory Frequency,150L/min, = 25 times pulmonary ventilation)Most person can not sustain for longer than 1 minuteMaximal Voluntary Ventilation Percentage of Ventilation Reservation