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Pressure Volume Curve of the Respiratory System 吳健樑 馬偕醫院 胸腔內科.

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Presentation on theme: "Pressure Volume Curve of the Respiratory System 吳健樑 馬偕醫院 胸腔內科."— Presentation transcript:

1 Pressure Volume Curve of the Respiratory System 吳健樑 馬偕醫院 胸腔內科

2 Transmural Pressure of the Respiratory System

3 P A Alveolar pressure P I p Intraleural pressure P T p Transpulmonary pressure Pressure around the Balloon (Lung) 1.P TP = P A – P IP 2.P A = 0, if no air is flowing into the balloon 3.P IP is subatmospheric due to the recoil of the lung away from the jar 4.P TP = 0 – (-10) cmH2O = 10 cmH2O

4 Pressure Volume Curve of the Lung

5 Pressure Volume Vital Capacity % TLC % Pressure (cmH 2 O) Lung recoil is due to - surface tension - elastic and collagen fibers of the lung Resting lung FRC Pressure Volume Curve of the Lung

6 Pressure around lung (cmH2O) Volume (L) Pressure Volume Curve of the Lung 1.P-V curve defines the elastic property of the lung 2.Compliance = change in volume per unit change of pressure 3.Compliance quantifies the elastic property

7 Calculation of Compliance Pressure (cmH 2 O) Volume (ml)

8 Pressure around lung (cmH2O) Volume (L) ․ ․ ․ ․ Compliance of the Lung 1.The slope is the compliance 2. The line 1 represents high compliance 3. The line 2 is low compliance 1 2

9 Mechanics of Chest Wall Chest wall = all structures surrounding the lung that move during breathing –i.e. rib cages, diaphragm, abdomen wall & contents and mediastinal contents. Sometimes like a spring Sometimes like a balloon

10 Pressure Volume Curve of Chest Wall (I)

11 Pressure Volume Curve of Chest Wall (II)

12 Pressure Volume Vital Capacity % TLC % Pressure (cmH 2 O) Resting lung FRC Chest wall recoils in two directions CW recoils outward below 75% of VC CW recoils inward at volume > 75% of VC Residual volume Pressure Volume Curve of Chest Wall

13 Pressure Volume Vital Capacity % TLC % Pressure (cmH 2 O) Resting lung FRC Residual volume Pressure Volume Curve of the Respiratory System

14

15 Hysteresis of Air filled Alveolus

16 What Factors Contribute to Compliance Connective tissue of lung Surface tension Surfactant

17 What Factors Contribute to Compliance Connective tissue of lung Surface tension Surfactant

18 Surface Tension The weight in the bubble is the collapsing pressure of the bubble Law of Laplace (inward pressure of bubble): P =2 T/r (T:surface tension; r: radius)

19 MV Surfactant Surfactant is produced by type II alveolar cell. The type II cells have characteristic microvilli (MV).

20 Functions of Surfactant Surfactant is a DPPC (DiPalmitoyl Phosphatidyl Choline) protein with a hydrophobic at one end and hydrophilic at the other. Reduce surface tension by intermolecular repulsive force

21 Repulsive Force of Surfactant Molecule

22 Surfactant Depleted lung Influence of Surfactant on PV Curve of Lung

23 What Does Compliance Mean Compliance –easier to in/deflate –steep curve: less pressure needed for unit volume change Compliance –difficult to in/deflate –flat curve

24 Commonly Used Methods for Measuring PV Curve Supersyringe method Flow interrupter Low-flow method

25 The supersyringe technique  Disconnection   Time consuming  Volume loss P-V curve Methodology

26 The supersyringe technique P-V curve Methodology

27 The multiple occlusion technique  Complexity  Volume history  Recorded in / min… Servillo, 2000 P-V curve Methodology

28 Quin Lu, 1999 The low flow technique  Popular (many validation studies)  The P res should be known  And substracted…  Not usable in case of leak  Pmax should be adjusted  No way for the deflation P-V curve Methodology

29 Comparison of PV curves by Different Methods (Qin et al ARRCCM 1999)

30 Compliance (mL/cmH 2 0):  Volume/  pressure Why it is important? 1.Physiology: how much work to produce a volume. 2.Prognosis: Low/high C RS = poor prognosis 3.Treatments: PEEP/V T /recruitment maneuvers Why is it complex? 1.One point is not enough… 2.Affected by chest wall, abdomen, tube resistances… 3.Dynamic versus quasi-static… 4.Inflation or deflation curve…

31 Clinical Uses of P-V Curve

32 Normal Restrictive (ARDS) Obstructive (COPD) P-V curve The “Classical” Approach

33 P-V Curves in Different Stages of ARDS Airway Pressure, cmH 2 O Volume (%) Recovery stage Early stage Intermediate stage Fibrotic stage

34 Clinical Uses of P-V Curve

35 Nonrecruitable Atelectatic Recruitable Normal Pathophysiology Acute Respiratory Distress Syndrome

36 Non- recruitable Atelectatic Recruitable Normal Acute Respiratory Distress Syndrome Effects of PEEP PEEP

37 M. Tobin, NEJM 2001 P-V curve

38 Compliance (mL/cmH 2 0):  Volume/  pressure The 3 segmental analysis of the Venegas (JAP, 1998) model Best compliance Over distention of lung units Collapse of peripheral airways and lung units

39 Ventral Dorsal Gas-Tissue Ratio Distribution in Lung Region Gattinoni et al. JAMA 1993;269:2122

40 Gattinoni L, AJRCCM 2001 P-V curve The “Modern” Approach The sponge model and the superimposed pressure (SP)… gastissue

41 ‧ ‧‧ ‧ ‧ ‧ ‧ ‧ ‧ ‧ ‧ ●● ● ●●●● ● ● ● ● ● ● ● ● ● ●● ● ● ● ● Gas/Tissue Ration PEEP, cmH 2 O Gas/Tissue Ratio as A Function of PEEP Gattinoni et al. JAMA P flex

42 Clinical Uses of P-V Curve

43 P-V curve The “Modern” Approach SP0 SP5 SP10 SP15

44 P-V curve The “Modern” Approach UIP = end of recruitment LIP = start of recruitment Recruitment zone

45 CT findings of Lung recruitment during Inspiration

46 Pressure – Volume Curves in ARDS caused by Pulmonary and Extrapulmonary disease

47 P-V curve The “Modern” Approach Peter C. Rimensberger CRITICAL CARE MEDICINE 1999;27:

48 Maggiore, AJRCCM 2001 P-V curve The “Modern” Approach De-recruitment even at high PEEP. No correlation between V DER and the LIP. The steeper the curve in ZEEP (potential for recruitment) and the highest the volume recruited by PEEP

49 Clinical Uses of P-V Curve

50  V  Pst,rs  V  Pst,cw  Pst, L Surgical ARDS Medical ARDS UIP(V T =0.5) UIP(V T =0.7) LIP =18LIP =16 Impaired Lung and Chest wall mechanics in PV curves in ARDS Ranieri et al AJRCCM 1997

51 The P-V curve Conclusions Understanding the PV curve:  The LIP: start of recruitment  The UIP: end of recruitment  Middle part: recruitment zone Methodology:  Inflation and deflation  Pressure ramp method (?) Clinical implications:  Recruitment maneuver  Optimum PEEP Maximum volume at equivalent pressure Minimal hysteresis Minimum slope

52 Adjust PEEP Level Based on Pflex

53

54 UIP LIP

55 P-V loops on monitoring screen of MV

56 Plot of P-V loop from scalars of pressure and volume

57 P-V Loop: different resistance

58 C1C1 C2C2 C3C3 P-V loops: change in compliances

59 P-V loops: change in resistance

60 Work of Breathing

61 Esophageal Balloon The balloon should be cm long and 3.2 – 4.8 cm perimeter The volume is 0.5 ml Latex Balloon

62 Position of Esophageal Balloon

63 Methods of Confirmation of Optimal Balloon Placement 1.Dynamic occlusion test –Compare the change in Pm and Pes during serial inspiratory efforts against occluded airway 2.Stomach placement –Insert catheter into stomach first, then pull back into esophagus until negative pressure waveform

64 Pm (cmH2O) Pes (cmH2O) Tracing of Volume, Pes and Pm during a dynamic occlusion test

65 Clinical Uses of Esophageal Pressure Measurement To determine the presence of dynamic intrinsic PEEP To assess the lung mechanics and respiratory mechanics (work of breathing) To interpret pulmonary properly vascular pressures during hemodynamic monitoring

66 Determination of Dynamic PEEPi using Esophageal Pressure

67 Pressure Waveform Indicating The Presence of auto-PEEP

68 Different Static and Dynamic auto-PEEP

69 -40 Esophageal pressure (cmH 2 O) C cw Esophageal pressure (cmH 2 O) Volume (ml) Plots of Esophageal pressure vs volume during Unassisted and Passive breathing C L,dyn

70 Esophageal pressure (cmH 2 O) Volume (ml) Esophageal pressure vs volume during unassisted ventilation Elastic work Resistive work C L,dyn C cw

71 Influence of Pleural Pressure on Hemodynamic Monitoring LA High Pleural Pressure Normal Low Myocardial Compliance P pl = PEEP x {C L / C L + C CW }


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