Neonatal assisted ventilation

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Neonatal assisted ventilation

  1. 1. Neonatal Assisted Ventilation Haresh Modi, M.D.Aspirus Wausau Hospital, Wausau, WI.
  2. 2. History of Assisted VentilationNegative pressure :Spirophore developed in 1876 with manual device to create negative pressure chamber
  3. 3. History of Assisted VentilationNegative pressure : Dr. Philips Drinker used this idea to develop “Iron lung” in 1929, So many survived “Polio out break” Some to date.
  4. 4. Woman in iron lung celebrates 60th birthdayAfter contracting polio, Dianne Odell has spent most of her life in machine Updated: 3:37 p.m. CT Feb 21, 2007 Associated Press ReportJACKSON, Tenn. - A Jackson woman who contracted polio 57 years ago and continues to rely on an iron lung to breathe recently celebrated her 60th birthday, defying doctors expectations that she could live so long and so fully. Dianne Odell, who turned 60 last week, is among only 30 to 40 people in the U.S. who depend on the devices.
  5. 5. History of Assisted VentilationPositive Pressure : “Respirator Kit” used to revive apparently dead by blowing air into the lungs or rectum in 1770s in London
  6. 6. History of Assisted Ventilation Positive pressure :The Aerophore pulmonaire :-developed by French Obstetrician for short termventilation of newborns in 1879
  7. 7. History of Assisted VentilationPositive pressure :The Fell-O’Dwyreapparatus developed inNew York forintermittent positivepressure ventilation,1896
  8. 8. Neonatal Assisted Ventilation1. Applied Pulmonary Mechanics2. Gas Exchange During Assisted Ventilation3. Ventilator Management4. Practical Hints For Assisted ventilation
  9. 9. Applied Pulmonary MechanicsPressure Gradient is Required to Overcome1.Elastic Properties of Lungs and Chest Wall (Compliance)2. Resistance to Airflow by Airway and Lung Tissue (Resistance)
  10. 10. Applied Pulmonary Mechanics Δ Volume (L) Compliance = Δ Pressure (cm H2O) In neonate chest wall is very distensible so does not contribute substantial elastic load when compared to lungs. Total compliance ∞ Lung compliance In RDS most striking abnormality is DECREASED LUNG COMPLIANCE
  11. 11. Applied Pulmonary MechanicsPressure Gradient is Required to Overcome1.Elastic Properties of Lungs and Chest Wall (Compliance)2. Resistance to Airflow by Airway and Lung Tissue (Resistance)
  12. 12. Applied Pulmonary Mechanics Resistance is inherent property of lungs to resist airflow Δ Pressure(cm H2O) Resistance = Δ Flow (L/Sec)Airway resistance ∞ length of airway ∞ 1/radius of airwayViscous resistance ∞ lung tissueRDS does not contribute to resistance but ET tube does
  13. 13. Applied Pulmonary MechanicsRelationship of Compliance and Resistance :Time Constant (sec)= Resistance × Compliance Time Constant(sec) = Resistance(30cm H2O/L/sec) × Compliance(0.004L/cm H2O) = 0.12sec × 5 = 0.6 seconds
  14. 14. Gas Exchange During Assisted Ventilation1. Carbon Dioxide (CO2) Elimination2. Oxygen (O2) Uptake
  15. 15. Gas Exchange During Assisted VentilationCO2 Elimination :Alveolar Ventilation = (Tidal volume – Dead space)(Frequency) With a pressure ventilator TV determined by (PIP – PEEP)
  16. 16. Gas Exchange During Assisted VentilationO2 Uptake : Mean Airway Pressure(Paw) linear direct relations ↑Paw = ↑ PaO2 Regardless of change in FiO2 Paw optimizes lung volume and ventilation-perfusion matching
  17. 17. Gas Exchange During Assisted VentilationPaw is augmented by : 1. Inspiratory flow (K) 2. Peak Inspiratory Pressure (PIP) 3. I:E Ratio(TI, TE) 4. Positive End Expiratory Pressure (PEEP) 1 2 3 4 Paw=K(PIP-PEEP)[TI/(TI+TE)]+PEEP
  18. 18. Ventilator Management 1. Flow : Increase in flow will give square wave ventilation, will Increase Paw and therefore oxygenation.Higher flow is crucial, when TI is shorter
  19. 19. Ventilator Management2. Peak Inspiratory Pressure (PIP) : Δ PIP(Press.Vent.) = Δ TV (Volu.Vent.) Advantages : Disadvantages : 1. O2 Uptake 1. Barotrauma Air leaks 2. CO2 Elimination 2. BPD
  20. 20. Ventilator Management 3. I:E Ratio :Reversed I:E Ratio = ↑Paw = ↑OxygenationNo change in TV= No change in AV=No change in PaCO2
  21. 21. Ventilator ManagementFrequency (Rate) : Rate= AV= CO2 elimination= PaCO2Short TI= TV= MVShort TE=gas trapping= FRC= compliance with over distention= inadverant PEEP=Pneumothorax
  22. 22. Ventilator Management4. PEEP :↑ PEEP(at lower range)= Better recruitment of lungs = ↑ PaO2↑ PEEP(at higher range)=Over distention=↓Cardiac Output=↓PaO2, ↑PaCO2PEEP just above Critical closing Pressure prevents atelectesis
  23. 23. Gas Exchange During Assisted VentilationRelative effectiveness of Paw on Pao2 : 1.↑ PIP &PEEP more than ↑ I:E ratio 2.↑ PEEP at higher range is ineffective 3.↑Paw=↑Over distention=↑RL Shunt 4.↑ Paw = ↓Cardiac output
  24. 24. Ventilator ManagementInspired Oxygen Concentration (FIO2) :When increasing vent. support first increase FIO2 to.60 to .70 before increasing pressure which mayprevent BPDWhen weaning vent. support first decrease FIO2 to .40to.50 before decreasing pressure. Pressure should beweaned before weaning FIO2 further to prevent PTX.
  25. 25. Gas Exchange During Assisted VentilationSummary :-
  26. 26. Ventilator ManagementHFOV :Ventilation above critical closing pressure at ↑PEEP &↑Paw =↑PaO2↓∆P at alveolar level=↑ alveolar ventilation = ↓PaCO2
  27. 27. Practical Hints for Assisted VentilationIndications for Assisted Ventilation :1. Respiratory acidosis with pH < 7.20 to 7.252. Severe hypoxemia, PaO2 < 50 torr. With FIO2 > 0.703. Apnea complicating RDS4. Persistent Fetal Circulation
  28. 28. Practical Hints for Assisted Ventilation Initial Ventilator Settings : Normal RDS PIP 12-18 cm H2O 20-25 cmH2O PEEP 2-3 cmH2O 4-5 cmH2O Rate 10-20 per minute 20-40 per minute I:E Ratio 1:2 to 1:10 1:1 to 1:3
  29. 29. Practical Hints for Assisted Ventilation Acceptable Blood Gas Values : pH 7.25 – 7.45 PaO2 50 – 80 torr PaCO2 35 – 50 torr With more maturity even higher PaCO2 are tolerated as long as pH is maintained above 7.25
  30. 30. Practical Hints for Assisted Ventilation Weaning Strategy : 1. First decrease pressure <18 2. FIO2 <0.40 3.Rate <15 4. CPAP of 3 to 4 to overcome ET resistance
  31. 31. Practical Hints for Assisted VentilationSummary :
  32. 32. Practical Hints for Assisted Ventilation
  33. 33. Lung DevelopmentSignificant Milestones :1. At 3-4 wks. Lung bud from esophagus.2. At 15-16 wks. Segmentation of bronchi complete.3.At 23-25 wks. Type II pneumatocyte develops.4.At 24 wks. Onwards surfactant production.5.At 34 wks onwards PG production.Note : Lung maturity lags behind by 2-4 wks in maternal diabetes.
  34. 34. Composition of Surfactant
  35. 35. Role of L/S Ratio and PG

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