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1 Inspiratory Inspiratory Reserve Capacity P O2 =100 mm Hg P O2 - PDF document

Aug 29, 2022 •202 likes •383 views

Trachea (Generation #1) Conducting Airways Generations 1-16 Primary Bronchi (Generation #2) 2 o Bronchi (Generation #3) Respiratory Zone Generations ~17-23 Respiratory Bronchioles Alveoli Atmospheric Air High O 2 (150 mmHg) P B =0 P B =0

  1. Trachea (Generation #1) Conducting Airways Generations 1-16 Primary Bronchi (Generation #2) 2 o Bronchi (Generation #3) Respiratory Zone Generations ~17-23 Respiratory Bronchioles Alveoli Atmospheric Air High O 2 (150 mmHg) P B =0 P B =0 CO 2 ~ 0 Inspiration Expiration Alveolar Air O 2 ~100 mmHg P A <0 P A >0 CO 2 ~ 40 mmHg O 2 O 2 venous arterial venous arterial CO 2 CO 2 Hemoglobin-O 2 Binding Curve Arterial 100 20 HbO 2 content (ml O 2 /dl) Chest Wall % Hb Saturation Venous Lung 80 Lung 15 60 ↑ CO 2 Stuck 10 Together 40 Air leak 5 20 Pneumothorax Lung collapses Fick’s law & Chest expands 0 0 J = DA ( Δ C/ Δ X) 0 20 40 60 80 100 P aO2 (mm Hg) 1

  2. Inspiratory Inspiratory Reserve Capacity P O2 =100 mm Hg P O2 =100 mm Hg O 2 O 2 14 ml O 2 /dL 14 ml O 2 /dL y t i c a Vital p a Capacity C g n FEV 1.0 u V T L l a t o T Expiratory P O2 =100 mm Hg P O2 =100 mm Hg Reserve O 2 O 2 1 s 0.3 ml O 2 /dL 0.3 ml O 2 /dL dissolved FRC 20 ml O 2 /dL HB-O 2 Residual Volume Forced Vital Capacity Flow-Volume Curves Inspiratory Inspiratory Reserve Capacity TLC y Expiratory Flow Rate t i c a Vital FEV 1.0 p FVC a Capacity C ~6 L 4.5 L g n u V T L RV l 1 sec a 500 ml t o FEV 1.0 = 4 L T Expiratory FVC = 5 L TLC RV Reserve % = 80% 2.6 L Lung Volume FRC Residual Volume 1.5 L V. A Few Terms (for Your Convenience) Eupnia - Normal breathing. Apnea - cessation of respiration (at FRC). Apneusis - cessation of respiration (in the inspiratory phase). Apneustic breathing – Apneusis interrupted by by periodic exhalation. Hyperpnea – increased breathing (usual ↑ V T ). Tachypnea – increased frequency of respiration. Hyperventilation – increased alveolar ventilation (P ACO2 <37 mm Hg). Hypoventilation – decreased alveolar ventilation (P ACO2 >43 mm Hg). Atelectasis – closed off alveoli, typically at end exhalation. Cheyne-Stokes Respiration – Cycles of gradually increasing and decreasing V T . Dyspnea- Feeling of difficulty in breathing. Orthopnea- Discomfort in breathing unless standing or sitting upright. P IP - Intrapleural pressure (pressure in space between visceral and parietal plurae) P TP - Transpulmonary pressure (distending pressure of airway) P ACO2 - Alveolar P CO2 (partial pressure of CO 2 ). P aCO2 - arterial P CO2. P vCO2 - venous P CO2 P AO2 - Alveolar P O2 P aO2 - arterial P O2 P vO2 - venous P O2 P ECO2 - P CO2 of exhaled air F ECO2 – fraction of exhaled air which is CO 2 (i.e. A= Alveolar, a= arterial, v= venous, E = exhaled, I = inspired) V E – Expired volume (liters) • • = dV/dt) V E – ventilation (liters/min) (V • V A – Alveolar ventilation (liters/min) • – Blood Flow (liters/min) Q 2

  3. Some Typical Normal Values for Some Key Pulmonary Parameters FRC 2.6 L Max. exp flow 6-9 L/sec RV 1.5 L Compliance 60-100 mL/cm H 2 0 TLC 6.0 L V T 500 ml P AO 2 100 mm Hg FVC 4.5 L P aO2 ( 21% O 2 ) 90-95 mm Hg P aO 2 ( 100% O 2 ) >500 mm Hg FEV 1.0 / FVC >75% 40 ± 3 mm Hg P aCO2 Frequency 10-12/min • Arterial pH 7.37-7.43 5 ± 0.5 L/min V A (norm) • P vO2 40 mm Hg 7 ± 0.7 L/min V E (norm) P vCO2 46 mm Hg • V E (max) 120-150 L/min [Hb] 14-15 g/dL Max. insp flow 7-10 L/sec Balance of Forces Determines FRC Hooke’s Law: F = -kx Chest Chest Wall Increasing volume Wall Lung Recoil Lung Force Intrapleural space P pl = -2 Normal Stuck FRC Together P pl = -5 P pl = -8 Decreasing Lung volume As we remove air P pl = 0 Wall from pleural space Recoil the lung expands Force & the chest wall gets pulled in. Emphysema Fibrosis Pneumo- Normal ↓ lung recoil ↑ lung recoil thorax Balance of Forces Determines FRC Hooke’s Law: F = -kx Chest Wall Increasing volume Recoil Intrapleural Force space P pl = -2 Normal FRC P pl = -5 P pl = -8 Decreasing Lung volume Wall P pl = 0 Recoil Force Emphysema Pneumo- Fibrosis Normal ↓ lung recoil ↑ lung recoil thorax 3

  4. ↑ Surface Area ∝ ↑ Surface Tension Surface Area (relative) Lung Surfactant Plasma Surfactant Hysteresis 40% Dipalmitoyl Lecithin 25% Unsaturated Lecithins 8% Cholesterol 27% Apoproteins, other phospholipids, glycerides, fatty acids Detergent Water 30 60 80 Surface Tension (dynes/cm) Hysteresis Occurs During Dynamic Air Flow ↑ Surface Area ∝ ↑ Surface Tension Due to Surfactant reorientation & Airway Resistance Surface Area (relative) Static Lung Compliance Curve Lung Surfactant Lung Volume Normal 1. Reduces Work of Breathing 2. Increases Alveolar Stability Expiration (different sizes coexist) V T 3. Keeps Alveoli Dry FRC N Inspiration Detergent Water 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 P IP (cm H 2 O) 30 60 80 Surface Tension (dynes/cm) Static Compliance Curves Emphysema Balance of Forces Determines FRC (high compliance) Hooke’s Law: F = -kx Chest Wall Increasing Lung Volume Normal volume Recoil V T Intrapleural Force space P IP = -2 Normal FRC E Fibrosis FRC (low compliance) V T P IP = -5 P IP = -8 Decreasing Lung volume Wall FRC N P IP = 0 V T Recoil FRC F Force 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 Emphysema Pneumo- Intrapleural Pressure, P IP (cm H 2 O) Fibrosis Normal ↓ lung recoil ↑ lung recoil thorax 4

  5. Regional- Apex to Base Differences Norm Lung Volume Chest Apex -8 Wall Inspiration Apex Lung Volume Inspiration Apex Base -5 Lung has weight Base Alveolar Volume ++ Alve Ventilation ++ 2 0 -2 -4 -6 -8 -10 -12 -14 P IP (cm H 2 O) P IP = -2 Base Regional- Apex to Base Differences Apex to Base Differences Low Lung Volume (shifts to lower V) Normal Lung V Lung Volume Lung Volume Apex Δ V Apex Δ V Low Lung V Apex Base Alveolar Volume ++ Alve Ventilation ++ Base Base 2 0 -2 -4 -6 -8 -10 -12 -14 2 0 -2 -4 -6 -8 -10 -12 -14 P IP (cm H 2 O) P IP (cm H 2 O) Respiratory Cycle Static Compliance Curves P IP time V T (L) 0.4 Respiratory Cycle Single V T Breath -5 Rest FRC 0 0.2 Air -7 Inspiration - Flow 0 Inspiration Expiration End P B =0 -8 -5 P IP P A = 0 Normal Inspiration Lung Volume P TP cm H 2 O + -6 Expiration P TP End Expi- P IP Expiration 0 -5 The dashed trace is the P IP ration-FRC -8 required to overcome recoil forces +0.6 V T (ot P TP taken from compliance curve). P A More P IP (solid curve) is required to (cm H 2 O) overcome airway resistance to flow. 0 FRC N N.B. Δ P = P A -P B ∝ Resist•Flow. Inspiration -0.6 +1 Air Flow (L/s) 0 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 -1 Pleural Pressure, P pl (cm H 2 O) 1 2 3 4 time (sec) 5

  6. Respiratory Cycle Respiratory Cycle P pl time P pl time V T (L) V T (L) 0.4 0.4 Respiratory Cycle Respiratory Cycle Single V T Breath Single V T Breath -5 Rest FRC -5 Rest FRC 0.2 0 0.2 0 Air Air -8 Inspiration -8 Inspiration 0 Inspiration Expiration - 0 Inspiration Expiration - Flow Flow P pl ( cm H 2 O ) P pl ( cm H 2 O ) -5 -5 End End P B =0 -8 P B =0 -8 P A = 0 P A = 0 Inspiration Inspiration + Expiration + Expiration -6 -6 -8 -8 +0.5 +0.5 End Expi- End Expi- Air Flow 0 Air Flow 0 -5 -5 (L/s) ration-FRC (L/s) ration-FRC Case of ZERO 0 0 The linear Dashed trace is the P pl Resistance required to overcome recoil forces. More P pl (solid curve) is required to -0.5 -0.5 overcome airway resistance to flow. +1 +1 N.B. Δ P = P A -P B ∝ Resist•Flow. P A (cm H 2 O) P A (cm H 2 O) 0 0 -1 -1 1 2 3 4 1 2 3 4 time (sec) time (sec) Respiratory Cycle P pl time V T (L) 0.4 v = Flow/A Respiratory Cycle Subsegmental Single V T Breath Bronchi N R = ρ Dv/ η -5 Rest FRC 0.2 0 ρ =density Total Cross Sectional Area D= diameter Air -8 Inspiration 0 Inspiration Expiration - v= velocity Flow η = viscosity P pl ( cm H 2 O ) -5 End P B =0 -8 Resistance P A = 0 Inspiration Resistance 8 η l Expiration + -6 R= ——— -8 π r 4 +0.5 End Expi- Conducting Air Flow 0 -5 Resp (L/s) ration-FRC Zone k• number Zone 0 Case of HIGH R= ————— A 2 Resistance -0.5 +1 P A (cm H 2 O) 0 5 1 0 15 5 1 0 15 Airway Generation Airway Generation -1 1 2 3 4 time (sec) N.B. this is total x-sectional area (A T 2 =n 2 A n 2 ) Dynamic Compression of Airways Mild Expiratory Effort (P+13) -5 Normal at FRC Airway Resistance 0 0 ↓ Recoil P TP =+5 P Pl - P A = -5 Emphysema Normal Fibrosis Lung Volume 6

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