PULMONARY MECHANICS GAS TRANSPORT I PULMONARY MECHANICS RESPIRATORY

PULMONARY MECHANICS GAS TRANSPORT

I. PULMONARY MECHANICS • RESPIRATORY MUSCLES • LUNGS ELASTICITY • COMPLIANCE • WORK OF BREATHING II. TRANSPORT OF GASES • O 2 • CO 2

FORCES PARTICIPATING IN RESPIRATION ACTIVE FORCES performed by respiratory muscles PASSIVE FORCES represented by: lungs elasticity chest elasticity QUIET RESPIRATION INSPIRATION - active forces of inspiratory muscles prevail EXPIRATION - passive (elastic) forces only 1

I. PULMONARY MECHANICS • RESPIRATORY MUSCLES • LUNGS ELASTICITY • COMPLIANCE • WORK OF BREATHING II. TRANSPORT OF GASES • O 2 • CO 2

RESPIRATORY MUSCLES accessory muscles external intercostals internal intercostals INSPIRATORY EXPIRATORY diaphragm abdominal muscles 2 a

INSPIRATORY muscles QUIET breathing diaphragm (≥ 80 % ) external intercostals (≤ 20 % ) FORCED breathing accessory inspiratory muscles (scalene muscles, …) EXPIRATORY muscles Only at FORCED breathing internal intercostals muscles of the anterior abdominal wall (abdominal recti, …) 2 b

I. PULMONARY MECHANICS • RESPIRATORY MUSCLES • LUNGS ELASTICITY • COMPLIANCE • WORK OF BREATHING II. TRANSPORT OF GASES • O 2 • CO 2

AIR SALINE G 200 NG LUNGS ELASTICITY EM VOLUME (ml) 150 PT YI FIL LIN DEFLATION 100 50 0 HYSTERESIS LOOP INFLATION opening pressure 1 k. Pa = 7. 5 mm Hg 0. 4 0. 8 1. 2 1. 6 2. 0 INTRAPULMONARY PRESSURE (k. Pa) INHERENT TISSUE ELASTICITY LUNGS ELASTICITY (elastin and collagen fibres) SURFACE TENSION FORCES (physical properties of air-liquid interface) 3

LAW OF LAPLACE spherical structures r P 2 T P= r T ? P 1 P 2 P 1 > P 2 P distending pressure (transmural P) r radius T surface tension PATHOLOGY COLLAPSE OF ALVEOLI EXPANSION OF ALVEOLI ATELECTASIS BULLOUS EMPHYSEMA 4

SURFACTANT SURFACE TENSION LOWERING AGENT EFFECT MAINLY IN THE EXPIRED POSITION PHOSPHOLIPID dipalmitoyl fosfatidyl cholin ALVEOLAR EPITHELIAL CELLS exocytosis of lamellar bodies surfactant cycle surfactant macrofage TYPE II specialized granular epithelial cells PRODUCTION OF SURFACTANT TYPE I thin epithelial cells DIFFUSION OF GASSES fatty acids, choline, glycerol, amino acids, etc. ) INFANT RESPIRATORY DISTRESS SYNDROME PATCHY ATELECTASIS AFTER CARDIAC SURGERY 5 a

AIR SALINE G 200 NG EM VOLUME (ml) 150 PT YI FIL LIN DEFLATION HYSTERESIS LOOP INFLATION 100 opening pressure 50 0 Factors involved in HYSTERESIS LOOP 0. 4 0. 8 1. 2 1. 6 2. 0 ALVEOLAR PRESSURE (k. Pa) LAPLACE LAW (opening pressure of alveoli) Dynamic changes in the DENSITY OF SURFACTANT MOLECULES during inspiration and expiration 5 b

I. PULMONARY MECHANICS • RESPIRATORY MUSCLES • LUNGS ELASTICITY • COMPLIANCE • WORK OF BREATHING II. TRANSPORT OF GASES • O 2 • CO 2

COMPLIANCE (VOLUME STRETCHABILITY) relaxation pressure curve +1 end of quiet expiration 0 -1 VC V P RV -2 -100 -50 0 50 V P V FRC relaxation volume Müller´s maneuver C = e +2 Valsalva´s maneuver exp maxim irat ory al curv +3 ins max pir im ato al ry cur ve change of the volume V ( l ) STATIC MEASUREMENT IN CLOSED SYSTEM 100 150 alveolar pressure PA (mm Hg) TOTAL RESPIRATORY SYSTEM (lungs and chest) 200 P compliance is decreased stiffness of the tissue compliance is increased stiffness of the tissue 18

I. PULMONARY MECHANICS • RESPIRATORY MUSCLES • LUNGS ELASTICITY • COMPLIANCE • WORK OF BREATHING II. TRANSPORT OF GASES • O 2 • CO 2

ELASTIC (STATIC) WORK WELAST (J) CLOSED SYSTEM lung volume V (l) 2 elastic forces of the chest and lungs act in the same direction relaxation pressure curve relaxation CHEST pressure curve LUNGS PPL 1 0 -15 LUNGS transpulmonary pressure PA PTP = PA - PPL relaxation pressure curve TOTAL SYSTEM ? TV 500 ml expiratory reserve volume PA PTP (PA-PPL) elastic force of the chest is zero TOTAL SYSTEM intrapulmonary pressure CHEST intrapleural pressure PPL elastic forces of the chest and lungs are in equilibrium 0 pressure ΔP (mm Hg) +15 7

TOTAL ELASTIC (STATIC) WORK OF INSPIRATORY MUSCLES AT QUIET INSPIRATION (V ~ 500 ml) WTOTAL ELASTIC insp = WLUNG + (-WCHEST) STRETCHING against elastic forces of the lungs ELASTIC RECOIL of the chest ELASTIC FORCES OF THE CHEST HELP inspiratory muscles to increase thoracic cavity 8 a

ACTIVE AND PASSIVE (ELASTIC) FORCES IN RESPIRATORY SYSTEM Felast-chest 0 Fmuscle Felast-lungs tidal volume at quiet inspiration (~500 ml) STATES OF BALANCE PATM PA INSPIRATION VT 0 PPL air ways VT CHEST LUNGS RESPIRATORY SYSTEM (LUNGS and CHEST) RESPIRATORY SYSTEM: elastic forces of lungs and chest are balanced CHEST: elastic force of the chest alone is zero at ΔV~ 1 l LUNGS: elastic force of the lungs is zero only when PPL = PATM ( pneumothorax ) 8 b

TOTAL WORK OF BREATHING (total work of respiratory muscles) ELASTIC (STATIC) WORK (65%) to overcome the elastic forces of the lungs and chest DYNAMIC WORK (35%) to overcome the resistance of air passages during the air movement – AERODYNAMIC RESISTANCE (~ 28%) to overcome the friction during the mutual movement of inelastic tissues – VISCOUS RESISTANCE (~ 7%) 9 a

RESISTANCE OF AIR PASSAGES HAGEN-POISEUILLE´S LAW (laminar flow Q) l … length r … radius η … viscosity Ohm´s law Re LAMINAR FLOW < 2000 < TURBULENT FLOW REYNOLDS NUMBER Re Critical velocity r v ρ η … radius … velocity … density … viscosity 9 b

TOTAL WORK OF RESPIRATORY MUSCLES [J] DURING RESPIRATORY CYCLE AT QUIET BREATHING change in volume (ml) 500 N ex pir ±WELAST DYNAMIC PRESSURE-VOLUME DIAGRAM WINSPIR = WELAST + WDYN insp W DY N W ins p DY WDYN WEXPIR W +WWDYN EXPIR == -WELAST + expir DYN expir 0 3. 0 1. 5 change in pressure ΔP (mm Hg) WDYN = WDYN insp + WDYN expir DYNAMIC WORK WDYN is done to overcome aerodynamic resistance frictional (viscose) resistance WDYN is finally transformed into heat energy (loss of energy) 10

INCREASED RESISTANCE OF AIR PASSAGES CLINICAL IMPLICATION OBSTRUCTIVE LUNG DISEASE (asthma bronchial) elastic work 1 E 0. 5 I 0 0. 2 0. 4 0. 6 change in pressure (k. Pa) NORMAL LUNGS 1 k. Pa = 7. 5 mm Hg change of volume (l) 1 E I additional work of expiratory muscles 0 0. 2 0. 4 0. 6 changes in pressure (k. Pa) Expiratory muscles are active to overcome the resistance of air passages 11

I. PULMONARY MECHANICS • RESPIRATORY MUSCLES • LUNGS ELASTICITY • COMPLIANCE • WORK OF BREATHING II. TRANSPORT OF GASES • O 2 • CO 2

tetramer HAEMOGLOBIN γ Hb 4 + 4 O 2 ↔ Hb 4 O 8 oxygenation DEOXY Fe 2+ HAEM Fe α 1 nm N N N Fe N fetal Hb N N N α OXY N N βγ β porfyrin N polypeptide chain N O 2 Fe 3+ (methaemoglobin) oxidation polypeptide chain 12

O 2 saturation of haemoglobin (%) CO O 2–HAEMOGLOBIN DISSOCIATION CURVE 100 a CO Hb plateau area v BOHR EFFECT (↓p. H, ↑CO 2) deoxy. Hb- + H+→ H-Hb p. H, CO 2 50 P 50 ↑BPG (2, 3 -bisphoglycerate) steep portion ↑temperature fetal Hb physiological range 0 50 PCO O 2 (mm Hg) myoglobin 100 methaemoglobin physically dissolved O 2 (1. 4%) 13

I. PULMONARY MECHANICS • RESPIRATORY MUSCLES • LUNGS ELASTICITY • COMPLIANCE • WORK OF BREATHING II. TRANSPORT OF GASES • O 2 • CO 2

TRANSPORT OF CO 2 HAMBURGER CHLORIDE SHIFT HCO 3 - CO 2 + H 2 O CA Cl- H 2 CO 3 H+ + HCO 3 - Cl- H-deoxy. Hb H+ + deoxy. Hb. H 2 O CA – carbonic anhydrase 14

CO 2 CO 2+ H 2 O CO 2 HCO 3 Na+ Cl- Na. HCO 3 - + H+ K+ KHCO 3 Hb. CO 2 physically dissolved (~5. 3%) CO 2 + Hb-NH 2 CO 2 + H 2 O Hb. O 2 H 2 O Hb. NH-COO- (carbamino-Hb) (~5. 3%) HCO 3 - + H+ (~89. 3%) ~60% in plasma, ~29% in red blood cell 15

total CO 2 content (mmol/l) CO 2 DISSOCIATION CURVE 30 25 deoxygenated blood 20 a HALDANE EFFECT ? v physiological values in arterial and venous blood oxygenated blood 15 10 1 Hb. NH. COO 2 5 physically dissolved CO 2 10 20 30 40 50 60 Hb- + H+ 70 CO 2 + H 2 O oxygenated blood in the lungs H 2 CO 3 TISSUES: DEOXY-Hb binds H+ more readily (weaker acid) ↑ amount of chemically bound CO 2 LUNGS: is released from OXY-Hb ↓ amount of chemically bound CO 2 HHb deoxygenated blood in peripheral tissues PCO 2 (mm Hg) H+ DEOXY-Hb H+ + HCO 3 - Hb- + H+ HHb 16

PROCESSES UNDERLYING TRANSPORT O 2 AND CO 2 IN RED BLOOD CELLS OCCUR SIMULTANEOUSLY FACILITATE EACH OTHER TISSUES uptake of CO 2 by blood binding of O 2 to Hb release of O 2 from Hb LUNGS release of CO 2 from blood BOHR´s AND HALDANE´s EFFECTS 17

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