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VENTILATION

VENTILATION

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VENTILATION

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  1. VENTILATION CMV SPONTANEOUS LFPPV HFPPV Disadvantages - TC1. Pulmonary - Barotrauma2 Cardiac3. Renal4. Brain5. Other Organs

  2. VENTILATION Prof. Mehdi Hasan Mumtaz

  3. VARYING TC • Compliance Resistance • Modes of Ventilation • - IMV • - VMMV • - SIMV • SIMV • PEEP • PSV - VIQ Mismatch - BaroNelufltsma

  4. VENTILATION Partial Ventilatory Support Full Ventilatory Support

  5. Acceptable blood gases.(permissive hypercapnoea) Alteration of ventilatory pattern to reduce lung stress. (low peak, mean end expiratory pressure low minute volumes). Use of artificial membrans or Artificial lung assist (ALA). 1. ECMO. 2. ECCO2R. 3. IVOX. CONCEPT OF “LUNG REST”

  6. ASSISTED VENTILATION “Incorporation ofSpontaneous Breaths” • Paw • VT • Pulmonary Circulation • Organ Perfusion • Harmonious relationship between patient & Ventilator.

  7. ASSISTED VENTILATION Advantages of Spontaneous Ventilatory Effects • lnspiratorv assist • Mechanical ventilation • Peak airway pressure • Venous return • Less effect on return renal function • Less sedation. • Muscle Relaxation • Muscle weakness • Impaired gut motility • Suppression of cough reflex.

  8. PROPORTION ASSISTVENTILATION (PAV) • Younes 1992 First Described & Used • Pattern of Operation • Advantages • Greater Comfort • No fighting with machine • Less Sedation • Less ParalysIs • Preservation respiratory control • Less airway pressure

  9. VENTILATION Volume Controlled (VC) Vs Pressure Controlled (PC) 1. VOLUME CONTROLLED VT = Preset or constant F = Preset MV = constant Mechanics change - airway pressure change - monitor carefully

  10. VENTILATION Volume Controlled (VC) Vs Pressure Controlled (PC) 2. PRESSURE CONTROLLED - lnspiratory pressure = Preset or constant - Inspiratory flow = High initially - decelerate rapidly - VT&MV = Monitor on time constant = Monitor volumes carefully PC-IRV = Recommended in ARDS

  11. VARYING I:E RATIO Collapsable Alveoli Kept Open • External PEEP • Internal PEEP (Auto PEEP) • VT. •  ET. • TC. Compliance Resistannce

  12. VARYING I:E RATIO • Regional • Whole resp system • Ventilator system Narrow tube • Ventilator System Slow PEEP valve • Slow alveolar compartment = auto PEEP. • Fast alveolar Compartment = need ext. PEEP

  13. INVERSE RATIO VENTILATION (IRV) • 1871 Reynolds - First Proposed- Neonates • 1980 Baun et al • 1983 Ravizza etal • 1984 Cole et al • 1989 Abraham Yoshihama • 1992 Barbas etal Advocated for ARDS

  14. INVERSE RATIO VENTILATION (IRV) ADVANTAGES: • More homogenous ventilation • Opens CoIIapsible alveoli • Intrinsic PEEP -Regional -Individual • Slow compartment • Faster compartment • (Prepondrance in ARDS) • Improvement in gas exchange. Contra-indication = obstructive lung disease

  15. BIPAP “PC-ventilation with unrestricted spontaneous breathing at anymoment of ventilatory cycle” • Baum et al 1989 first described (Evita). • Rouby et al 1992 intermittent mandatory pressure release ventilation (IMPRV). • Sydow et al 1993 BIPAP + APRV.

  16. SUBDIVISION No spontaneous breathing Spontaneous breathing at low pressure Spontaneous breathing at high pressure level Spontaneous breathing at both CPAP level. • CMV – BIPAP • IMV – BIPAP • APRV – BIPAP • GENUINE - BIPAP

  17. VC-IRV VT=8-12ml/KG I:E=2:1-3:1 PEEP=5cmH2O F=10-15min RESULT: No significant change from VC conventional ventilation BIPAP-APRV CPAP = 15-30CM FOR 2-4 S PRESSURE TO RELEASE = 5 cmH2O for 0.5-0.78 Peak airway pressure -low Peak & mean pressure low in 24 hrs. Progressive alveolar recruitment.

  18. ADVANTAGES • Less MV • Partial Spontaneous Breathing. • Low peak airway pressure. • Less impairment of P. circulation. • Improved O2 delivery. • Effective alveolar recruitment.

  19. AIRWAY PRESSURE RELEASE VENTILATION (APRV) 1987 - Down & Group (Stock etal 1987) “Spontaneous breathing at preset (CPAP) interrupted by short (1-1.5S) releases of pressure plateau for further expiration”

  20. AIRWAY PRESSURE RELEASE VENTILATION (APRV) • Useful features: • Reduces lung volume. • High airway pressure. • Intrinsic PEEP in slow alveoli. • Preservation of Spontaneous breathing. • Less baro/voluntrauma. • Reduction in circulatory compromise. • Better ventilation/perfusion. • Application of APRV • BIPAP. • IMPRV.

  21. PERMISSIVE HYPERCAPNOEA “1990 - Hickling” • VT •  PIP. • PCO2. Extrinsic PEEP • Maintain PaW Intrinsic PEEP ADVANTAGES •  Barotrauma •  Volutrauma •  Physiological effect DISADVANTAGES = Hypercarbia Compensation - HCO3 & Kidney - HCO3 infusion

  22. Selection Criteria Mean airway P x FIO2% OI = -------------------------------- Post-ductal Pa02 Complications Intracranial Pulmonary • Bleeding Nasal UmbIicaI artery Chest tube site • NeurologicaI Handicap • Septic Procedure: Warning • Clinical assessment. • Radiological assessment. • Lung compliance.

  23. Criteria A. Fast Selection criteria - PaO2<6.6 - PaCO2=3.9-5.9 - F102= 1.0 - PEEP> 5cmH2O for 5min B. Slow Selection Criteria 48hrs assessment with conventional therapy - PaO2<6.6 - PaCO2=3.9-5.9 - F102= 0.6 - PEEP> 5cmH2O for 15min - QS/QT> 30% at FIO2 1.0&PEEP =5cmH20

  24. ECCO2R “VENTILATION SPARING MANOEUVRE” CO2 - Remove by circuit. O2 - Transfer by lung. • 1978 Gattinoni.  Oxygenation by entrainment C PAP. • FRC-kept normal. L FPPV+PEEP • CO2- Removed – Veno –Venous circuit. • Less ventilatory P- less barotrauma. • More lung rest.

  25. ECCO2R • Less circuit as compared to ECMO. • Less flow 1-1.5L/min=2.5L/m2/min. • Less heparinisation. • Modification – hemofilteration. • >85% HCO3  metabolic acidosis. • Direct base = THAM, NaoH. • Indirect = acetate & lactate. • Complications. • Bleeding. • Platelet consumption.

  26. IVOX “Gas exchange without Extracorporeal circuit” • Hollow fibre gas transfer membranes. • Gas exchange. • Surface area-fibre bundles.(0.21-0.52m2) Ext. diameter = 7-10mm. • Gas flow. • Venacava blood flow. • HB.

  27. IVOX • Gas transfer=100mIO2 and 75ml CO2/min. • Indications. • Reversible pathology. • Patient waiting for lung transplant. • Shunt fraction >25% <35%. • IVC>15 mm. • NO-systemic bacteraemia. • NO-coagulopathy.

  28. VENTILATION IN LIQUID PHASE “Hysteresis” phenomenon observed during Insuflation of lungs is due to surface “tension” effect, which can be eliminated by substituting saline to the air. CHARACTERISTICS OF LIQUID: • Stable • Absence of toxicity • High Solubility for O2 & CO2 • Low Surface tension • Should not locally suplant surfactant • Should not be absorbed capillans/Lymph • Expelled by lungs.

  29. VENTILATION IN LIQUID PHASE • Example: • - “Fluorocarbon” • - Density 1.76 mg/ml • - Surface tension -15 dynes/cm • ADVANTAGES: • Uniform expansion. • Uniform Gas exchange. • Improvement of compliance

  30. HIGH FREQUENCYVENTILATION Adverse effects of LFPPV 1. Time constant = C o< R Barotrauma 2. CO O2 delivery Tissue perfusion Use of modes Definition “Ventilation above 4 times the normal rate for the subject” • Adult =15x4=60 (1Hz/min). • Neonate=30x4=120 (2Hz/min)

  31. HIGH FREQUENCYVENTILATION GOALS “Reduction in transpulmonary pressure difference” Smaller Vt   Peak & Mean airway pressure   Barotrauma.  Reduction of Co.

  32. MODE OF HIGH FREQUENCYVENTILATION • HFPPV - Oberg & Sjostrand • HFJV - Klain & Smith • HFO - Lunken Heimer VTMode Frequency min-1 ml/kg. HFPPV 60-120 (1-2 Hz) 3-5 HFJV 60-240 (1-4 Hz) 2-5 HFO 180-1200 (3-20Hz) 1-3

  33. PHYSIOLOGICAL EFFECTS 1. GAS EXCHANGE VD/VT  efficiency (Large min v.) ARTERIAL OXYGENATION • F102 • VA (Alveolar Ventilation) • Lung Volume 2. AIRWAY PRESSURES • VT airway  airway P. Transpulmonary P. I:E Ratio • Normocapnoea + F  airway P depends

  34. PHYSIOLOGICAL EFFECTS 1. Pressure generator - mean P. Constant. FVT peak airway P. Intrinsic PEEP, V.Mode airway pressure PEEPimprove oxygenation 2. Flow generator  peak mean ENP P. & F above Initial FPPV

  35. 3. VENTILATION Lung volume (intrinsic PEEP). Thoracic compl. 3. Factors Intrinsic. T. Compliance. Even distribution (Time constant) 4. VENTILATORY DRIVE Reflex suppression 1. Vagal afferents. 2. non -vagal afferents. Cause = Lung Volume frequency Advantage = less sedation required

  36. 5. CIRCULATION • BP. • Pulmonary P. • CVP • Intra-Pulmonary shunt • Fluctuations in P. • Fluctuations in ICP. • Urine flow. Unchanged

  37. PHYSIOLOGICAL BASIS OF GAS TRANSPORT • Across alveolar capillary membrane independent of mode of ventilation. • From alveoli to mouth. • Low F. large V. -VT>VD no problem. • High F. low volume. 1. VT>VD=if normocpnic (F=15-75) VT(70%)VD (50%) VD/VT Ratio (0.6-0.8) Necessitate MV o< Freq needed.

  38. PHYSIOLOGICAL BASIS OF GAS TRANSPORT 2. VT=VD (120-300) Effective VD<VD anat. VT exceeds VD anat by 1.2  Conductive G. trans P. VT 0.8-1.2 VD anat. Eff. VD<VD anat.

  39. VT < VD (F300-2400) (VD:VT = 1.2-2.0) 4- additional Gas Transport Mechanisms 1. Direct alveolar ventilation. 2. Pendeluft. 3. Convective Streaming. 4. Augmented (Taylorian) dispersion.

  40. VT < VD BEST FREQUENCY 60-1201 min • Anaesthesia - airway surgery - lung surgery • Management of high compliance conditions - Broncho - P. Fistula - Bullous emphysenia • Weaning from ventilation

  41. CLINICAL APPLICATIONS 1. ANAESTHESIA a. Surgery on Conducting airways & Lungs b. Laryngoscopy, microsurgery, Laser surgery on larynx   c. Tracheal resection & tracheostomy d. Bronchoscopy. 2. RESUSCITATION Percutaneous Trannstracheal Jet Ventilation with 100% O2. - Direct delivery of 02 below cords. - Intrinsic PEEP. - Pulsatile Expired gas flow prevent aspiration.

  42. CLINICAL APPLICATIONS 3. ICU Broncho-pleural fistula. 4. OTHER ADVANTAGES - Weaning - Endobronchial Sunction

  43. DIFFERENTIAL LUNG V • WHOLE – L.V. • LOBAR – V. WHY DLV - NEEDED? • Variable Time Constant • TC = R o< C

  44. APPROACHES TO IMPROVE SURVIVAL IN SEVERE ARDS 1. Improvement of basic ventilatory regimen PCV+PEEP+Permisive hypercapnoea. 2. Adjunctive supportive measures. - Body position changes. - Reduction of pulmonary oedema. 3. Sophisticated ventilatory measures. - DLV. - HFJV. 4. Future therapeutic approaches. - Selective manipulation of pul blood flow e.g. inhalation of nitric oxide. - Artificial surfactant. - Intravascularr oxygenation (IVOX).

  45. INDICATIONS FOR VENTILATORY SUPPORT

  46. HEAD INJURY • Coma – GCS<8 • NOT • Obeying • Speaking. • Eye opening. • Loss of protective laryngeal reflexes. • Ventilatory in-sufficiency. • Hypoxaemia (PaO2 <9KPa on air. <13KPa on O2. • Hypercarbia PaCO2>6kPa. • Spontaneous hyperventilation • PaCO2<3.5Kpa. • Respiratory arrhythmias.

  47. HEAD INJURY - INIDCATIONS BEFORE TRANSFER • Deteriorating conscious level. • Bilateral fracture mandible. • Copious bleeding in mouth. • Seizures.

  48. IPPV Indications COPD-Failure “Failure of conservative treatment” Hypoxia Acidosis Worsening Respiratory m fatique. Non-arousable somnohance PaO2<50 with O2 therapy but PH not<7.26

  49. CMV INITIATION • Mode of ventilation. • Inflation volume. • Respiratory rate. • Inspired O2 level.