呼吸系统的应激状态英文课件

THE RESPIRATORY SYSTEM UNDER STRESS,ZHJ,2,OBJECTIVES,Use the knowledge to predict the response of the respiratory system to three physiologic stresses Exercise Ascent to altitude Diving,3,Identifies the physiologic stresses involved in exercise Predicts the responses of the respiratory system to acute exercise Describes the effects of long-term exercise programs (training) on the respiratory system,4,Identifies the physiologic stresses involved in the ascent to altitude Predicts the initial responses of the respiratory system to the ascent to altitude Describes the acclimatization of the cardiovascular and respiratory systems to residence at high altitude,5,Identifies the physiologic stresses involved in diving Predicts the responses of the respiratory system to various type of diving,6,EXERCISE AND THE RESPIRATORY SYSTEM,Exercise,increase,Metabolism,(the working muscles),the demand for oxygen,the production of carbon dioxide,lactic acid production,the respiratory system,the cardiovascular system,7,EXERCISE AND THE RESPIRATORY SYSTEM,Acute Effects the effects of exercise in an untrained person are mainly a function of an increase in the cardiac output coupled with an increase in alveolar ventilation,8,EXERCISE AND THE RESPIRATORY SYSTEM,Mechanics of breathing Alveolar ventilation Pulmonary blood flow Ventilation-perfusion relationships Diffusion through the alveolar-capillary barrier Oxygen and carbon dioxide transport by the blood Acid-base balance,9,EXERCISE AND THE RESPIRATORY SYSTEM,Mechanics of breathing Elastic work of breathing Resistance work of breathing,Moderate exercise,Severe exercise,10,EXERCISE AND THE RESPIRATORY SYSTEM,Alveolar ventilation Tidal volume Frequency Anatomic dead space Alveolar dead space (if present) VD/VT,Moderate exercise,Severe exercise,11,EXERCISE AND THE RESPIRATORY SYSTEM,Pulmonary blood flow Perfusion of upper lung Pulmonary vascular resistance Linear velocity of blood flow,Moderate exercise,Severe exercise,12,EXERCISE AND THE RESPIRATORY SYSTEM,Ventilation-perfusion relationships Ventilation-perfusion matching Ventilation-perfusion ratio,Moderate exercise,Severe exercise,13,EXERCISE AND THE RESPIRATORY SYSTEM,Ventilation-perfusion relationships,Distance up the lung,top,bottom,rest,exercise,1,2,3,VA/Q,14,EXERCISE AND THE RESPIRATORY SYSTEM,Diffusion through the alveolar-capillary barrier Surface area Perfusion limitation Partial pressure gradients,Moderate exercise,Severe exercise,15,EXERCISE AND THE RESPIRATORY SYSTEM,At the tissues Oxygen unloading Carbon dioxide loading,Moderate exercise,Severe exercise,16,EXERCISE AND THE RESPIRATORY SYSTEM,PAo2 Pao2 Paco2 pHa Arteriovenous O2 difference,Moderate exercise,Severe exercise,or,、,17,Training Effects,The ability to perform physical exercise increases with training Alterations in the cardiovascular system and in muscle metabolism rather than changes in the respiratory system The increase of maximal oxygen uptake is mainly a result of an increased maximal cardiac output,18,Training Effects,Physical training lowers the resting heart rate and increases the resting stroke volume -inducing mitochondrial proliferation -increasing the concentration of oxidative enzymes - increasing the synthesis of glycogen and triglyceride,19,ALTITUDE AND ACCLIMATIZATION,PAo2 =PIo2-PAco2 /R+F PIo2 =0.21(PB-47torr) altitude (ft ) PB (torr) PIo2 PA co2 PAo2 15000 429 80.2 32 45 18000 380 20000 349 50000 87 63000 47 (the fluid in blood “boils”),20,ALTITUDE AND ACCLIMATIZATION,Acute Effects The symptoms are mainly due to hypoxia and may include: sleepiness decreased visual acuity laziness clumsiness a false sense of well-being tremors impaired judgment loss of consciousness blunted pain perception death increasing errors on simple tasks,21,ALTITUDE AND ACCLIMATIZATION,Acute Effects Acute mountain sickness a group of symptoms include headache dizziness breathlessness at rest weakness malaise nausea anorexia sweating palpitations dimness of vision partial deafness sleeplessness fluid retention dyspnea on exertion,These symptoms are a result of hypoxia and hypocapnia, and alkalosis or cerebral edema, or both.,22,ALTITUDE AND ACCLIMATIZATION,Control of breathing The decreased PAo2 and Pao2 result in stimulation of the arterial chemoreceptors rather than the central chemoreceptors Pao2 =45torr, minute ventilation is doubled Paco2 fall , causing respiratory alkalosis The pH of the cerebrospinal fluid increasing the central chemoreceptors is depressed by hypocapnia alkalosis,23,ALTITUDE AND ACCLIMATIZATION,Mechanics of breathing Rate and depth of breathing Interstitial fluid volume of the lung (vc in the first 24h) More turbulent airflow, resistance work of breathing Maximal airflow rates , due to decreased gas density,24,ALTITUDE AND ACCLIMATIZATION,Alveolar ventilation The anatomic dead space , the reflex bronchoconstriction , the opposing effect of increased VT VD/VT (in any event) Previously collapsed or poorly ventilated alveoli will be better ventilated Regional distribution of alveolar ventilation more uniform,25,ALTITUDE AND ACCLIMATIZATION,Pulmonary blood flow,Lung inflation,Arterial chemoreceptor,Sympathetic stimulation of the cardiovascular system,Cardiac output,Heart rate,Systemic blood pressure,Hypoxic pulmonary vasoconstriction,Cardiac output,Sympathetic stimulation of larger pulmonary vessels,Pulmonary artery pressure,Right ventricular work load,26,ALTITUDE AND ACCLIMATIZATION,Ventilation-perfusion relationships regional VA/Q more uniform,27,ALTITUDE AND ACCLIMATIZATION,Diffusion through the alveolar-capillary barrier PAo2 PVo2,Partial pressure gradients ,The thickness of the barrier,Pulmonary vascular distention,Higher lung volumes,28,ALTITUDE AND ACCLIMATIZATION,Oxygen and carbon dioxide transport by the blood PAo2 to be below the flat part of the oxyhemoglobin dissociation curve , causing a low arterial oxygen content Hypocapnia aid in oxygen loading in the lung and interfere with oxygen unloading at the tissues the hemoglobin concentration (the first 2d),29,ALTITUDE AND ACCLIMATIZATION,Cerebral circulation Hypocapnia is a strong cerebral vasoconstrictor Hypoxia cause cerebral vasodilation and can cause hyperperfusion The hyperperfusion and cerebral edema elevate intracranial pressure Lead to increase in sympathetic activity in the body increasing the possibility of pulmonary edema and promoting renal salt and water retention,30,ALTITUDE AND ACCLIMATIZATION,Acid-base balance hypocapnia respiratory alkalosis,31,ALTITUDE AND ACCLIMATIZATION,Acclimatization see the following four lists,32,table1,33,table2,34,table3,35,table4,36,DIVING AND THE RESPIRATORY SYSTEM,The major physiologic stresses involved in diving include Elevated ambient pressure Decreased effects of gravity Altered respiration Hypothermia Sensory impairment,37,DIVING AND THE RESPIRATORY SYSTEM,The severity of the stress involved depends on The depth attained The length of the dive Whether the breath is held or a breathing apparatus is used,38,DIVING AND THE RESPIRATORY SYSTEM,Physical principles At a depth of 33 ft of seawater (or 34 ft of fresh water) , total ambient pressure is equal to 1520 torr Follow Boyles law, at 33 ft of depth (2atm) lung volume is cut in half According to Daltons law, the partial pressures of the constituent gases also increase According to Henrys law, the amounts dissolved in tissues of the body increase,39,DIVING AND THE RESPIRATORY SYSTEM,Effects of immersion up to the neck (Mechanics of breathing) Averaging about 20 cm H2O Decrease FRC by about 50 percent ERV decreased by as much as 70 percent IRV is increased RV is slightly decreased VC and TLC are only slightly decreased The work of breathing increases by about 60 percent,40,DIVING AND THE RESPIRATORY SYSTEM,Effects of immersion up to the neck (Pulmonary blood flow) Augmenting venous return, by approximately 500ml Right atrial pressure increases from about -2 to +16 mmHg The cardiac output and stroke volume increase by about 30 percent Pulmonary blood flow and PAP increase Immersion diuresis (a few minutes,45folds),41,DIVING AND THE RESPIRATORY SYSTEM,Breath-hold diving (Mechanics of breathing) The total pressure of gases within the lungs is equal to ambient pressure The volume within the thorax must decrease proportionately Partial pressures of gases increase,42,DIVING AND THE RESPIRATORY SYSTEM,Breath-hold diving The diving reflex Demonstrate a profound bradycardia and increased systemic vascular resistance with face immersion (especially into cold water),43,DIVING AND THE RESPIRATORY SYSTEM,Breath-hold diving Gas exchange in the lungs Before a dive, PAo2 =120torr PAco2 =30torr During a breath-hold dive to a depth of 33 ft The transfer of oxygen from alveolus to blood is undisturbed vice versa, retention of carbon dioxide in the blood,44,DIVING AND THE RESPIRATORY SYSTE