RESPIRATORY FUNCTIONS MECHANICS OF RESPIRATORY SYSTEM GAS TRANSPORT RESPIRATORY SYSTEM STEPS IN THE DELIVERY OF O2 TO THE CELLS airways alveoli alveolar-capillary m. capillary UTILIZATION OF O2 BY MITOCHONDRIA TRANSPORT OF O2 IN THE BLOOD DIFFUSION OF O2 ACROSS ALVEOLAR-CAPILLARY MEMBRANE DIFFUSION OF O2 FROM CAPILLARY TO THE CELLS 1 VENTILATION OF THE LUNGS INTERNAL RESPIRATION CO2 OUTPUT ~250 ml / min O2 UPTAKE ~300 ml / min AT REST AIR PASSAGES ANATOMICAL DEAD SPACE –CONDUCTING ZONE NASAL PASSAGES PHARYNX LARYNX TRACHEA BRONCHI BRONCHIOLES TERMINAL BRONCHIOLES 2 RESPIRATORY ZONE (GAS EXCHANGE) Total alveolar area ~100 m2 Other physiological functions: air is warmed, cleaned and takes up water vapour respiratory reflex responses to the irritants speech and singing (function of larynx –vocal corce) Folie8 předb cut aa ciliated cylindrical epithelium lamina propria visceral pleura smooth muscle cells cartilage blood vessels gland goblet cell mucus 4 AUTONOMIC INNERVATION of smooth muscle cells Muscarinic receptors: Acetylcholine activates bronchoconstriction PARASYMPATHETIC NS b-adrenergic receptors: Noradrenaline activates bronchodilatation SYMPATHETIC NS BRONCHUS Æ < 1 mm TERMINAL BRONCHIOLE f = 12/min VT = VA + VD VD part of tidal volume remaining in the dead space ~ 150 ml 5 4.2 l/min 6 l/min ALVEOLAR VENTILATION VA · = VA x f 1.8 l/min DEAD SPACE VENTILATION VD · = VD x f PULMONARY MINUTE VENTILATION V ∙ = VT x f VT tidal volume ~ 500 ml VA part of tidal volume entering alveoli ~ 350 ml 6 IN HEALTHY INDIVIDUALS both spaces are practically identical DEAD SPACE TOTAL GAS VOLUME NOT EQUILIBRATED WITH BLOOD (without exchange of gasses) ANATOMICAL dead space - volume of air passages FUNCTIONAL (total) dead space ANATOMICAL dead space + total VOLUME of ALVEOLI without functional capillary bed Folie10 před cut SPIROMETRY water seal subject inspiration expiration inverted bell 7 (measurements of lung volumes, capacities, functional investigations, …) pulley string Folie11 před cut bb LUNG VOLUMES TIDAL VOLUME VT EXPIRATORY RESERVE VOLUME ERV ~1.7 8 maximal inspiratory level RESIDUAL VOLUME RV ~1.3 maximal expiratory level end of quiet expiration DILUTION METHOD He INSPIRATORY RESERVE VOLUME IRV ~2.5 [l ] end of quiet inspiration He reservoir (Vr) RV ci 3 Calculation of residual volume RV from the initial and final He concentrations in reservoir (ci , cf). He reservoir (V) RV cf Þ Equilibration of the air in the residual volume and reservoir Principle of method: 1 Maximal expiration, 2 Repeated inspiration from and expiration into a reservoir (known volume Vr) with inert gas He (known concentration ci) Folie11 před cut bb maximal expiratory level maximal inspiratory level VC - the largest amount of air that can be expired after maximal inspiration VC VITAL CAPACITY = VT + IRV + ERV ~ 4.7 l VC 9 TLC TOTAL LUNG CAPACITY = VC + RV ~ 6.0 l TLC ~1.2 l RV FUNCTIONAL RESIDUAL CAPACITY <3.0 l end of quiet expiration INSPIRATORY CAPACITY >3.0 l FUNCTIONAL INVESTIGATION OF THE LUNGS TIMED VITAL CAPACITY (FEV1 - forced expiratory volume per 1 s) PULMONARY MINUTE VENTILATION RMV (respiratory minute volume) at rest (0.5 l x 12 breathes/min = 6 l/min) PEAK EXPIRATORY FLOW RATE (PEFR) (~10 l/s) MAXIMAL VOLUNTARY VENTILATION (MVV) (125-170 l/min) 10 V [l] Čas [s] 1 s FEV1 0 1 2 3 4 5 1 s V [l] Čas [s] 0 1 2 3 4 5 1 s V [l] Čas [s] Healthy people Obstruction disease FVC physiology values FVC physiology values FEV1=80% FEV1 lower than 70% Restriction disease FVC lower than physiology values FEV1 – as physiology value Flow – volume curve •PEF – peak expiratory flow •MEF – maximální maximal expiratory flow on the differential levels of FVC - 75 %, 50 % a 25 % FVC PEF MEF75% MEF50% MEF25% TLC IRV Vt ERV RV IRC VC FRC RV Graf změny intrapleur tlaku Graf změny objemu Graf změny plícního tlaku Obrzměny intrapleur tlaku Silbernagl pulmonalis parietalis PLEURA FORCES PARTICIPATING IN RESPIRATION 12 QUIET RESPIRATION EXPIRATION - only passive (elastic) forces are in action INSPIRATION - active forces of inspiratory muscles prevail PASSIVE FORCES represented by: ACTIVE FORCES performed by respiratory muscles lungs elasticity chest elasticity obr 2a cut RESPIRATORY MUSCLES accessory muscles external intercostals diaphragm internal intercostals abdominal muscles EXPIRATORY INSPIRATORY 13 INSPIRATORY muscles QUIET breathing diaphragm (> 80 % ) external intercostals (< 20 % ) EXPIRATORY muscles 14 internal intercostals muscles of the anterior abdominal wall (abdominal recti, …) Only at FORCED breathing accessory inspiratory muscles (mm. scalene) FORCED breathing in addition dýchábí žebra Silbernagl dychani Hrudní košSilbernagl Bucket-handle and water-pump handle effects Respiratory mechanics O2 20.98 % FO2 @ 0.21 N2 78.06 % FN2 @ 0.78 CO2 0.04 % FCO2 = 0.0004 Other constituents BAROMETRIC (ATMOSPHERIC) PRESSURE AT SEA LEVEL 1 atmosphere = 760 mm Hg PARTIAL PRESSURES OF GASSES IN DRY AIR AT SEA LEVEL PO2 = 760 x 0.21 = ~160 mm Hg PN2 = 760 x 0.78 = ~593 mm Hg PCO2 = 760 x 0.0004 = ~0.3 mm Hg 20 1 kPa = 7.5 mm Hg (torr) COMPOSITION OF DRY ATMOSPHERIC AIR obr 12 přech cut COMPOSITION OF ALVEOLAR AIR 760 mm Hg INSPIRED AIR EXPIRED AIR dead space O2 100.0 CO2 39.0 H2O 47.0 right heart left heart veins arteries periphery capillaries 21 760 mm Hg partial pressures in mm Hg 760 mm Hg N2 O2 158.8 CO2 0.3 N2 601.0 … O2 115.0 CO2 33.0 H2O 47.0 N2 564.0 … O2 95.0 CO2 41.0 H2O 47.0 N2 … … O2 40.0 CO2 45.0 H2O 47.0 N2 … … O2 40.0 CO2 45.0 H2O 47.0 N2 … … physiological shunts O2 100.0 CO2 39.0 ? ? obr 17 přech b cut obr 17 přech a cut HAEMOGLOBIN α α β β 1 nm Fe Fe N N N N N N N N DEOXY OXY N N N polypeptide chain polypeptide chain O2 Fe3+ (methaemoglobin) oxidation 25 fetal Hb γ γ Fe2+ tetramer porfyrin Hb4 + 4 O2 ↔ Hb4O8 oxygenation O2–HAEMOGLOBIN DISSOCIATION CURVE 100 50 PO2 (mm Hg) CO Hb 26 myoglobin fetal Hb 50 0 50 100 0 plateau area steep portion ↓ pH, ↑ CO2 ↑ BPG (2,3-bisphosphoglycerate) ↑ temperature methaemoglobin BOHR´S EFFECT (¯ pH, CO2) physiological range v a P50 physically dissolved O2 (1.4%) PCO (mm Hg) 16 P pressure r radius T surface tension LAW OF LAPLACE EXPANSION OF ALVEOLI P1 > P2 P1 P2 COLLAPSE OF ALVEOLI - ATELECTASIS P r T r T P 2 = ? PATHOLOGY 17a SURFACTANT SURFACE TENSION LOWERING AGENT obr 5 přech ALVEOLAR EPITHELIAL CELLS macrofage fatty acids, choline, glycerol, amino acids, etc.) surfactant surfactant cycle exocytosis of lamellar bodies PHOSPHOLIPID dipalmitoyl fosfatidyl cholin TYPE II specialized granular epithelial cells PRODUCTION OF SURFACTANT TYPE I thin epithelial cells DIFFUSION OF GASSES EFFECT MAINLY IN THE EXPIRED POSITION Surface tension •Water molecules are attracted to each other more strongly than gas molecules - there is a force acting inwards, towards the gaseous phase - in the case of a round alveolus to its center - tends to expel air from the alveoli - leading to its collapse END