1、Anatomy of the Lower Airway,Anatomy of the Lower Airway,Occlusion of the bronchioleSmooth muscleForeign body (not shown)Inflammation,Lung Volumes & Capacities,Total lung capacity (TLC) in a typical adult male is 6 litersMuch of inspired air does not enter alveoliTidal Volume (VT)volume of gas inhale
2、d/exhaled during a single ventilatory cycleUsually 5-7 cc/kg (typically 500 cc),Lung Volumes & Capacities,Dead Space Air (VD)Air remaining in air passageways, unavailable for gas exchange (usually 150 cc)Anatomic dead spacetracheabronchiPhysiologic dead spaceformed by factors like disease or obstruc
3、tionExamples: COPD & atelectasis,Lung Volumes & Capacities,Minute Volume Vmin(minute ventilation)amount of gas moved in and out of respiratory tract per minute(tidal volume - dead space volume) X RRFunctional Reserve Capacity (FRC)after optimal inspiration, the optimum amount of air that can be forc
4、ed from the lungs in a single exhalation,Lung Volumes & Capacities,Alveolar Air (alveolar volume) VAAir reaching alveoli for gas exchangeUsually 350 ccInspiratory Reserve (IRV)Amount of gas that can be inspired in addition to tidal volumeExpiratory Reserve (ERV)Amount of gas that can be expired afte
5、r a passive (relaxed) expiration,Lung Volumes & Capacities,Ventilation,Defined as movement of air into & out of lungsInspirationstimulus from respiratory center of brain (medulla)transmitted via phrenic nerve to diaphragmdiaphragm flattens during contractionintercostal muscles contractribs elevate a
6、nd expandresults in intrapulmonic pressure (pressure gradient)results in air being drawn into lungs & alveoli inflated,Ventilation,ExpirationStretch receptors in lungs signal respiratory center via vagus nerve to inhibit inspirationHering-Breuer ReflexNatural elasticity of lungs passively expires ai
7、r (in non-diseased lung)Control via PonsApneustic & Pneumotaxic centers,Ventilation,ChemoreceptorsCarotid bodies & Aortic archStimulated by PaO2, PaCO2 or pHPaCO2 considered normal neuroregulatory control of ventilationsHypoxic Drivedefault regulatory controlSenses changes in Pa02,Ventilation,Other stimulations or depressants to ventilatory drivebody temp: w/ fever & w/hypothermiadrugs/meds: increase or decreasepain: increases but occasionally decreasesemotion: increasesacidosis: increasessleep: decreases,
