PULMONARY PHYSIOLOGYGary L. Weinstein M.D.Director of Pulmonary and Critical Care MedicinePresbyterian Hospital of Dallas

Physiology for DummiesGood Air In, Bad Air Out

Physiology for PsychologistsTake Slow, Deep, Cleansing Breaths

Physiology for InternistsRemember (review ?) your little orange book from 1st year med school on Respiratory Physiology by Dr. WestYou MUST understand normal physiology to understand abnormal physiologyYou may BORROW my tape on normal lung sounds (especially if you have insomnia)

PhysiologyThe respiratory system is composed of the conducting airways (nose, mouth, larynx, trachea, bronchial tree)the lungs (terminal bronchioles, alveoli)the parts of the CNS concerned with control of the system (pons, medulla, cortex, Vagus)the chest wall (muscles of respiration, rib cage)

Physiology Functions of the respiratory system includeO2 extraction from the external environmentCO2 elimination from the bodymaintenance of acid-base balance (along with other TRIVIAL organs)phonationdefense from the outside worldmetabolism (e.g. ACE I ACE II)

Physiology

Physiology

PhysiologyDefense: each day about 10,000 liters of air is inspired along with dust, pollen, ash, microorgansims, toxic gases, particulatesJobs includeair conditioning - by the time air reaches the alveoli, it is at body temp and 100 % humidifiedolfaction - a shallow sniff bring air to the nose but not to the lung allowing retreat

PhysiologyJobs (contd)filtrationnasal hairs trap 10 - 15 um particlesin addition, particles > 10 um impact onto the septum and turbinates as well as the nasopharynxtonsils and adenoids provide immunologic defense against biologically active materialsparticles 2 - 5 um sediment via gravity in the smaller airways and become trapped in the mucous that lines the airways, then are transported up and outparticles 0.1- 0.5 um mainly stay suspended as aerosols and about 80 % of them are exhaled

Physiology

Physiology

Physiology

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PhysiologyControl of VentilationCentral ControllerPons, medulla, ... Input output

Sensors EffectorsChemoreceptors, Respiratory muscleslung and other receptors

Physiology

PhysiologyLung and other receptors1) pulmonary stretch receptorslie within the airway smooth muscleimpulses travel in the vagus nerveresult in a slowing of respiratory rate 2) irritant receptorslie between airway epithelial cellsstimulated by noxious gases, cigarette smoke, inhaled dusts and cold airimpulses travel up the vagus and the reflex effects include bronchoconstriction and hyperpnea

Physiology3) J receptors (juxta-capillary)impulses pass up the Vagus and result in rapid, shallow breathingmay play a role in the dyspnea a/w left heart failure and ILD4) Nose and upper airway receptors respond to mechanical and chemical stimulation with sneezing, coughing and bronchoconstriction

Physiology5) Joint and muscle receptorsImpulses from moving limbs are believed to be part of the stimulus to ventilation during exercise

PhysiologyFun FactsAlveolar surface area is 50-100 square metersThere are approx. 300 million alveoli, each 1/3 mm in diameterThe blood-gas interface is approx. 0.5 micronsO2 and CO2 move by simple diffusionAnatomic dead space is approx. 1 ml/lb. body wtEach RBC spends about 1 sec in the capillary network and transverses 2 - 3 alveoliSurfactant, made by type II pneumocytes, dramatically lowers alveolar surface tension