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Fick's Law J = DA (∆C/ ∆X) Hemoglobin-O2 Binding Curve

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Fick's Law J = DA (∆C/ ∆X) Hemoglobin-O2 Binding Curve Trachea (Generation #1) Conducting Airways Generations 1-16 Primary Bronchi (Generation #2) 2o Bronchi (Generation #3) Respiratory Zone Generations ~17-23 Respiratory Bronchioles Alveoli Atmospheric Air PB=0 High O2 (150 mmHg) PB=0 CO2 ~ 0 Inspiration Expiration Alveolar Air O2 ~100 mmHg PA<0 PA>0 CO2 ~ 40 mmHg O O venous 2 arterial venous 2 arterial CO2 CO2 Hemoglobin-O2 Binding Curve 100 Arterial 20 HbO Chest Wall 2 80 Venous content O (ml Lung Lung 15 60 Stuck ↑CO2 10 Together 40 Air leak 2 % Hb Saturation % Hb 5 Pneumothorax 20 /dl) Fick’s law Lung collapses & Chest expands 0 0 J = DA (ΔC/ ΔX) 0 20 40 60 80 100 PaO2 (mm Hg) 1 Inspiratory Inspiratory Reserve Capacity PO2=100 mm Hg PO2=100 mm Hg O2 O2 y t 14 ml O2/dL 14 ml O2/dL i c a Vital p a Capacity C g n FEV u 1.0 L VT l a t o T Expiratory PO2=100 mm Hg PO2=100 mm Hg O O Reserve 1 s 2 0.3 ml O2/dL 2 0.3 ml O2/dL dissolved FRC 20 ml O /dL HB-O 2 2 Residual Volume Inspiratory Inspiratory Forced Vital Capacity Flow-Volume Curves Reserve Capacity TLC y t i c a Vital FEV1.0 p FVC a Capacity C g 4.5 L n u ~6 L L VT l RV a 500 ml 1 sec t o Expiratory Flow Rate Flow Expiratory T FEV1.0 = 4 L Expiratory FVC = 5 L TLC RV Reserve % = 80% FRC 2.6 L Lung Volume 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 ↑VT). Tachypnea – increased frequency of respiration. Hyperventilation – increased alveolar ventilation (PACO2 <37 mm Hg). Hypoventilation – decreased alveolar ventilation (PACO2 >43 mm Hg). Atelectasis – closed off alveoli, typically at end exhalation. Cheyne-Stokes Respiration – Cycles of gradually increasing and decreasing VT. Dyspnea- Feeling of difficulty in breathing. Orthopnea- Discomfort in breathing unless standing or sitting upright. PIP - Intrapleural pressure (pressure in space between visceral and parietal plurae) PTP - Transpulmonary pressure (distending pressure of airway) PACO2 - Alveolar PCO2 (partial pressure of CO2). PaCO2 - arterial PCO2. PvCO2 - venous PCO2 PAO2 - Alveolar PO2 PaO2 - arterial PO2 PvO2 - venous PO2 PECO2 - PCO2 of exhaled air FECO2 – fraction of exhaled air which is CO2 (i.e. A= Alveolar, a= arterial, v= venous, E = exhaled, I = inspired) VE – Expired volume (liters) • • VE – ventilation (liters/min) (V = dV/dt) • VA – Alveolar ventilation (liters/min) • Q – Blood Flow (liters/min) 2 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 H20 TLC 6.0 L VT 500 ml FVC 4.5 L PAO2 100 mm Hg PaO2 (21% O2) 90-95 mm Hg PaO2 (100% O2) >500 mm Hg FEV1.0 / FVC >75% Frequency 10-12/min PaCO2 40 ± 3 mm Hg • Arterial pH 7.37-7.43 VA (norm) 5 ± 0.5 L/min • PvO2 40 mm Hg VE (norm) 7 ± 0.7 L/min • PvCO2 46 mm Hg V (max) 120-150 L/min E [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 Wall Recoil Lung Lung volume Force Intrapleural Increasing space P = -2 pl Normal Stuck FRC P = -5 Together pl Ppl= -8 Lung P = 0 As we remove air Wall pl Recoil volume from pleural space Force Decreasing the lung expands & the chest wall gets pulled in. Normal Emphysema Fibrosis Pneumo- ↓ lung recoil ↑ lung recoil thorax Balance of Forces Determines FRC Hooke’s Law: F = -kx Chest Wall Recoil Intrapleural space volume Force Increasing P = -2 pl Normal FRC P = -5 P = -8 Lung pl pl Wall Ppl = 0 volume Recoil Decreasing Force Normal Emphysema Fibrosis Pneumo- ↓ lung recoil ↑ lung recoil thorax 3 ↑Surface Area ∝ ↑Surface Tension Lung Surfactant Plasma Surfactant s 40% Dipalmitoyl Lecithin si re 25% Unsaturated Lecithins te 8% Cholesterol ys H 27% Apoproteins, other phospholipids, glycerides, fatty acids Surface Area (relative) 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 Lung Static Lung Compliance Curve Surfactant Normal 1. Reduces Work of Breathing 2. Increases Alveolar Stability Expiration (different sizes coexist) 3. Keeps Alveoli Dry VT Lung Volume FRCN Inspiration Surface Area (relative) Detergent Water 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 30 60 80 PIP (cm H2O) Surface Tension (dynes/cm) Static Compliance Curves Emphysema (high compliance) Balance of Forces Determines FRC Hooke’s Law: F = -kx Chest Wall Normal Recoil Intrapleural VT space volume Force Increasing PIP = -2 FRCE Normal Fibrosis FRC (low compliance) P = -8 Lung VolumeLung P = -5 VT Lung IP IP FRCN Wall V PIP = 0 volume T Decreasing FRC Recoil F Force 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 Intrapleural Pressure, PIP (cm H2O) Normal Emphysema Fibrosis Pneumo- ↓ lung recoil ↑ lung recoil thorax 4 Regional- Apex to Base Differences Norm Lung Volume Apex Chest -8 Wall Inspiration Apex Lung Volume Lung Inspiration Apex Base -5 Lung has weight Base Alveolar Volume ++ Alve Ventilation ++ 2 0 -2 -4 -6 -8 -10 -12 -14 PIP (cm H2O) Base PIP = -2 Regional- Apex to Base Differences Apex to Base Differences Low Lung Volume (shifts to lower V) Normal Lung V Apex ΔV Apex ΔV Low Lung V Lung Volume Lung Lung Volume Lung 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 PIP (cm H2O) PIP (cm H2O) Respiratory Cycle Static Compliance Curves VT (L) PIP time 0.4 Respiratory Cycle Single V Breath T -5 Rest FRC 0.2 0 Air -7 Inspiration Flow - 0 Inspiration Expiration End -5 P PB=0 P = 0 -8 IP A Inspiration Normal PTP O 2 + -6 Expiration PTP cm H P End Expi- IP 0 -5 Expiration -8 The dashed trace is the PIP ration-FRC required to overcome recoil forces +0.6 (ot P taken from compliance curve). P TP Lung Volume VT A More P (solid curve) is required to (cm H2O) IP 0 overcome airway resistance to flow. N.B. ΔP = P -P ∝ Resist•Flow. FRCN A B Inspiration -0.6 +1 Air Flow (L/s) 0 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 -1 1 2 3 4 Pleural Pressure, P (cm H O) time (sec) pl 2 5 Respiratory Cycle Respiratory Cycle P time P time V (L) pl V (L) pl 0.4 T 0.4 T Respiratory Cycle Respiratory Cycle Single VT Breath Single VT Breath 0.2 0 -5 Rest FRC 0.2 0 -5 Rest FRC Air Air 0 Inspiration Expiration -8 Inspiration 0 Inspiration Expiration -8 Inspiration Flow - Flow - -5 Ppl (cm H2O) -5 Ppl (cm H2O) End End PB=0 -8 PB=0 -8 PA= 0 Inspiration PA= 0 Inspiration + -6 Expiration + -6 Expiration -8 -8 +0.5 End Expi- +0.5 End Expi- Air Flow 0 -5 Air Flow 0 -5 (L/s) ration-FRC (L/s) ration-FRC 0 0 Case of ZERO The linear Dashed trace is the Ppl Resistance required to overcome recoil forces. -0.5 -0.5 More Ppl (solid curve) is required to overcome airway resistance to flow. +1 +1 N.B. ΔP = PA-PB ∝ Resist•Flow. PA (cm H2O) PA (cm H2O) 0 0 -1 1 2 3 4 -1 1 2 3 4 time (sec) time (sec) Respiratory Cycle P time V (L) pl 0.4 T Respiratory Cycle Subsegmental v = Flow/A Single VT Breath Bronchi 0.2 0 -5 Rest FRC NR= ρDv/η ρ=density Air D= diameter 0 Inspiration Expiration -8 Inspiration Flow - v= velocity -5 Ppl (cm H2O) η= viscosity End PB=0 P = 0 -8 A Inspiration Resistance + -6 Expiration 8ηl -8 R= ——— πr4 +0.5 End Expi- Air Flow 0 -5 Conducting Resp (L/s) ration-FRC Resistance k•number Zone Zone 0 Case of HIGH R= ————— Resistance A2 -0.5 +1 Total Cross Sectional Area Sectional Cross Total PA (cm H2O) 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 2 2 2 (AT =n An ) Dynamic Compression of Airways Mild Expiratory Effort (P+13) -5 Normal at FRC 0 0 ↓ Recoil PTP=+5 PPl -PA= -5 Normal Emphysema Airway Resistance Airway Fibrosis Lung Volume 6 Dynamic Compression of Airways Dynamic Compression of Airways Mild Expiratory Effort (P+13) Strong Expiratory Effort (P+30) Mild Expiratory Effort (P+13) Strong Expiratory Effort (P+30) +13 +13 -5 +8 Normal at FRC +25 Normal -5 +8 Normal at FRC +25 Normal +13 +13 +8 +25 +25 0 +13 840 30 25 20 15 10 5 0 0 +13 840 30 25 20 15 10 5 0 PTP=+5 PTP=+5 P -P = -5 EPP EPP P -P = -5 EPP EPP Pl A Equal Pressure Point Pl A Equal Pressure Point (in supported airways) (in supported airways) -2 +11 Emphysema +28 Emphysema -2 +11 Emphysema +28 Emphysema Pursed-lips +11 Hi Resist 0 13 10 8 6 4 2 0 30 25 20 15 10 5 0 0 13 10 8 6 4 2 0 30 29 28 27 25 20 0 PPl-PA=-2 Low VL& PPl-PA=-2 Low VL& EPP EPP Basal Alv EPP EPP Basal Alv Moves toward the mouth also like this in unsupported airways also like this & supported airways Normal Forced Vital Capacity Inspiration Obstructive Restrictive Volume Normal ↑airway resist ↑lung recoil ↑ Recoil TLC TLC TLC FEV1.0 FEV1.0 Restrictive FEV FVC FVC 1.0 FVC RV 1 sec RV 1 sec ↑Resistance RV 1 sec Obstructive FRC time (sec) FEV1.0 = 4 L FEV1.0 = 1.2 L FEV1.0 = 2.7 L FVC = 5 L FVC = 3.0 L FVC = 3.0 L % = 80% % = 40% % = 90% Flow-Volume Curves Forced expiration Inverted Effort Independent limb Inspiration in forced expiration.
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