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Ventilation of Patients with COPD and Asthma. Chronic lung diseases with airflow obstruction Asthma Chronic Bronchitis Emphysema.

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Presentation on theme: "Ventilation of Patients with COPD and Asthma. Chronic lung diseases with airflow obstruction Asthma Chronic Bronchitis Emphysema."— Presentation transcript:

1 Ventilation of Patients with COPD and Asthma

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3 Chronic lung diseases with airflow obstruction Asthma Chronic Bronchitis Emphysema

4 Chronic lung diseases with airflow obstruction Asthma Chronic bronchitis Emphysema

5 Asthma Emphysema Bronchitis

6 COPD CXR

7 Near fatal asthma Phenotypes Gradual Onset Sudden Onset

8 Near fatal asthma

9 Mechanical Venitlation of COPD & Asthma Exacerbations Objectives  Pathophysiology -PaCO 2 dederminants-Gas trapping -Work of breathing-Auto-PEEP  NIPPV -IPAP -EPAP  Mechanical ventilation -FIO 2 -PEEP -V T

10 Pathohysiology of Asthma/COPD Exacerbations Airway Inflammation Airway narrowing & obstruction Shortened muscles,  curvature  Frictional WOB  muscle strength VTVT  PaCO 2  pH  PaO 2 Gas trapping Auto- PEEP  VCO 2  V E  Elastic WOB VAVA PEEP IPAP MV? Steroids Abx? MV? IPAP MV BDs

11 Determinants of PaCO2 PaCO 2  VCO 2 V A  VCO 2  Work -Agitation -Seizures -  WOB  Metabolism -Fever -CHO -  T4  V A  V E -  RR -  V T -  V D (without  V E )

12 Oxygen Cost of Breathing Roussos, JCI 1959

13 PV Curve in COPD and Asthma (Stable) Macklem and Becklake, Ptp (cm H 2 O) V L (L) VTVT VTVT Normal/ Asthma Emphysema

14 PV Curve in COPD & Asthma (Acute Exacerbtion) Ptp (cm H 2 O) V L (L) VTVT VTVT Asthma Emphysema

15 Implication V T falls because FRC encroaches on TLC  Limited ability to  V T with MV/IPAP Best way to  PaCO 2 is to  VCO 2   WOB (frictional and/or elastic)   PaCO 2 even if V T, V E and V A are constant

16 Work of Breathing RVFRCTLC Total Work Elastic Work Frictional Work

17 Effect of V A /Q on PaCO 2 (Normal) VCO 2 = 100 ml/min PcCO 2 = 40 PaCO 2 = 40 PcCO 2 = 40 PvCO 2 = 46 PvCO 2 = 46 DCO 2 = 100 ml/min DCO 2 = 100 ml/min P A O 2 = 100 P A CO 2 = 40 P A O 2 = 100 P A CO 2 = 40 VCO 2 = 100 ml/min

18 Effect of V A /Q on PaCO 2 (Low V A /Q, Normal) PcCO 2 = 40 PaCO 2 = 40 PcCO 2 = 40 PvCO 2 = 46 DCO 2 = 50 ml/min DCO 2 = 150 ml/min HPV 50%  V E VCO 2 = 50 ml/min 50%  V E VCO 2 = 150 ml/min PvCO 2 = 46 P A O 2 = 50 P A CO 2 = 40 P A O 2 = 100 P A CO 2 = 40

19 Effect of V A /Q on PaCO 2 (Low V A /Q,, AECOPD) PcCO 2 = 44 PaCO 2 = 42 PcCO 2 = 40 PvCO 2 = 46 PvCO 2 = 46 DCO 2 = 50 ml/min HPV V E at max50%  V E VCO 2 = 50 ml/min VCO 2 = 100 ml/min DCO 2 = 150 ml/min P A O 2 = 50 P A CO 2 = 40 P A O 2 = 100 P A CO 2 = 40

20 Effect of V A /Q on PaCO 2 (Low V A /Q,, AECOPD,  F I O 2 ) PcCO 2 = 44 PaCO 2 = 44 PcCO 2 = 44 PvCO 2 = 46 PvCO 2 = 46 DCO 2 = 100 ml/min HPV V E constant50%  V E VCO 2 = 50 ml/min VCO 2 = 50 ml/min DCO 2 = 100 ml/min  FIO 2 P A O 2 = 100 P A CO 2 = 44 P A O 2 = 100 P A CO 2 = 44

21 Ventilation in COPD/Asthma Non Invasive VentilationAssessment of mechanics (resistance, auto-PEEP)Pressure or volume modes?Role of PEEPAdministering Bronchodilators

22 Ventilation in COPD/Asthma Non Invasive VentilationAssessment of mechanics (resistance, auto-PEEP)Pressure or volume modes?Role of PEEPAdministering Bronchodilators

23 Which Patients with COPD benefit from NIV ?

24 NIPPV Pathophysiology of AECOPD & Asthma is amenable to Rx with NIPPV  EPAP for auto-PEEP  IPAP for inspiratory Raw Will  work of breathing   VCO 2  At constant V A,  PaCO 2 and  pH May  V A May  mortality and intubation rate

25 Which Patients with COPD benefit from NIV ? Hospital Mortality 12% 2% NNT 8

26 NIV in Severe Asthma  17 Episodes of ARF due to asthma  2 patients required intubation for worsening PaC02  Duration of NPPV was 16±21 h.  All patients survived. Length of hospital stay was 5±4 days

27 Ventilation in COPD/Asthma Non Invasive VentilationAssessment of mechanics (resistance, auto-PEEP)Pressure or volume modes?Role of PEEPAdministering Bronchodilators

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29  Resistance Pressure Time Pressure Time Compliance Resistance  Peak Airway Pressure & Normal Plateau

30 Tidal ventilation Lung volume VT FRC V T V EE Time VEI I :E 1:1 I : E 1: 6 Air-trapping in Asthma/COPD Patients on Mechanical Ventilation

31 Assessment of Mechanics Auto-PEEP Raw= Peak - Plateau

32 Obstructive Airway Disease Beware of auto-PEEP!

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34 After the third breath, the airway was occluded at end-expiration using the end-expiratory hold function on the ventilator. During the period of zero flow, pressure in the alveoli and ventilator circuit equilibrate, and the plateau pressure reflects auto or intrinsic positive end-expiratory pressure (PEEPi), indicated by the arrow.

35 Giving CPAP to a patient who has auto-PEEP The increased work of breathing associated with auto-PEEP can be offloaded by applying CPAP to the trachea/mouth, and splinting open the connecting airways.

36 The use of external PEEP in the setting of auto-PEEP may be conceptualized by the "waterfall over a dam" analogy. In this analogy, the presence of dynamic hyperinflation and 10 cmH20 of auto-PEEP is represented in the top panel by the reservoir of water trickling over the dam represented by the solid block. In the middle panel, as long as the external PEEP is less than or equal to the amount of auto-PEEP, the amount of water in the upstream reservoir, representing dynamic hyperinflation, does not increase. However, once the amount of water in the reservoir does increase (bottom panel), dynamic hyperinflation worsens.

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39 Excessive Inspiratory Time Inspiration ExpirationNormalPatient Time (sec) Flow (L/min) Air Trapping Auto-PEEP } Increase WOB and “Fighting” of the ventilator

40 Ventilation in COPD/Asthma Non Invasive VentilationAssessment of mechanics (resistance, auto-PEEP)Pressure or volume modes?Role of PEEPAdministering Bronchodilators

41 Pressure or Volume Mode? Volume Predictable TV Peak-Plat gradient Monitor Plat Better acidosis control Pressure Minimise over- distension Monitor Tidal volume Excess volumes as airway resistance improves

42 Mechanical Ventilation of COPD & Asthma Exacerbations Mode:  AC vs IMV  PS  ? rest respiratory muscles: CMV  Better sleep with AC vs. IMV-PS  Ventilator-induced diaphragm changes (?) Triggering: key issue with either mode  PEEP to counter auto-PEEP  Major cause of patient-ventilator dissynchrony

43 Initial Ventilator Settings Inspiratory time 0.8 – 1.2 secs RR TV 6-8 ml/Kg Pplat < 30 cm H2O PEEP ??

44 Assessment of Hyperinflation CVS effects  disconnect Pplat PEEPi measurement

45 Reducing Hyperinflation Reduce rate Reduce tidal volume Increase expiratory time –Increase inspiratory flow rate –Increased Peak Airway Pressure Monitor (Pplat) Tolerate increased CO2 (minimise dead space) I : E 1: 6 I : E 1: 2

46 COPD flow and frequency As flow increased from 30 to 60 and 90 L/min (from right to left), frequency increased from (18 to 23 and 26 breaths/min, respectively), Auto-PEEP decreased (from 15.6 to 14.4 and 13.3 cm H2O, respectively) and end-expiratory chest volume also fell. Increases in flow from 30 L/min to 60 and 90 L/min also led to decreases in the swings in Pes from 21.5 to 19.5 and 16.8 cm H2O.

47 Hypercapnia: How permissive? Defence of intracellular pH Apnoeic oxygenation in dogs to pH 6.5 and PaCO2 of 55kPa Anaesthetic mishap with PaCO2 of > 300 mmHg (40 kPa) and pH of 6.6 survived without sequelae Am J Respir Crit Care Med 1994; 150:

48 Ventilation in COPD/Asthma Non Invasive VentilationAssessment of mechanics (resistance, auto-PEEP)Pressure or volume modes?Role of PEEPAdministering Bronchodilators

49 Ppl EPP Pel Palv Pao Waterfall Concept External & Internal PEEP 10

50 Effect of Auto-PEEP Patm = 0 P A = 0 Ppl = - 5 Normal airway resistance (end-exhalation) Pel = 5  Ppl needed to initiate inhalation: - 1 P A drops to - 1 relative to Patm - 5 Ptp = 5

51 Effect of Auto-PEEP P A = 10 Airway narrowing causing auto-PEEP P atm = 0Ppl = 2 Pel = 8  Ppl needed to initiate inhalation: Ptp = 8

52 Treatment of Auto-PEEP with PEEP or CPAP Airway narrowing with auto-PEEP: Treatment with PEEP P A = 10 PEEP = 10 Ppl 2 Pel = 8  Ppl needed to initiate inhalation: - 1 The only thing PEEP does is  work of breathing 2 2 Ptp = 8

53 Implication PEEP, EPAP, CPAP  No effect on V E, V T or V A   WOB (elastic) -  VCO 2 (on next breath) -  PaCO 2 (on next breath)

54 Treatment of Auto-PEEP with  V insp Longer time for exhalation, P A falls P A = 6 Ppl = 1 Pel = 6  Ppl needed to initiate inhalation: Ptp = 5 P atm = 0

55 External PEEP Reduce inspiratory muscle load Improve ventilator triggering 80% of PEEPi can be matched without increase PEEP tot Reduce hyperinflation by improving expiration

56 Titrating PEEP to PEEPi

57 Heliox and Obstructive Airway Disease Low density high thermal conductivity Reduce pressure gradient in turbulent flow Administered in –NIV –IPPV –Nebulisers Role in Asthma and COPD?

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59 Ventilation in COPD/Asthma Non Invasive VentilationAssessment of mechanics (resistance, auto-PEEP)Pressure or volume modes?Role of PEEPAdministering Bronchodilators

60 Theophylline Used for OVER 50 years Lack of benefit has been shown when aggressive inhalation B2-agonist + systemic corticosteroids

61 Administration of Bronchodilators

62 Nebuliser or MDI? Lung deposition of radiolabelled drug* –MDI 5.6% v Nebuliser 1.2% Urinary excretion** –MDI with spacer 38% –MDI in line 9% –Nebuliser 16% 4-10 puffs MDI effective in reducing R AW * Chest 1999; 115: **Am Rev Respir Dis 1990; 141:440–444

63 MDI adapters for use with MV circuits

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65 Myopathy in Asthma Steroid myopathy Muscle relaxants Polyneuropathy of the critically ill

66 Myopathy in Asthma Proximal muscle Subacute (3 weeks) Normal CPK Steroid myopathy Distal & proximal High myoglobin High CPK Muscle relaxants Sensorimotor Normal CPK Polyneuropathy of the critically ill

67 Principles of managing the ventilated patient with obstructive lung disease Provide adequate support for muscle rest with adequate pH and PO2 Do not over ventilate Minimize minute volume requirements Minimize the risk of barotrauma Maintain adequate bronchial hygiene Maintain appropriate nutrition


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