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Neonatal ventilation

By Dr Bikash Shrestha

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Neonatal ventilation

  1. 1. VENTILATION FUNDAMENTALS Dr Bikash Shrestha Fellow Neonatology (NNF, India) MD Paediatrics (AFMC, Pune, India)
  2. 2. OVERVIEW  REPSIRATORY PHYSIOLOGY  VENTILATOR BASICS
  3. 3. RESPIRATORY PHYSIOLOGY  Basic characteristics  Oxygenation  Ventilation  Lung volumes  Lung mechanics
  4. 4. BASIC CHARACTERISTICS-1  Higher respiratory rate
  5. 5. BASIC CHARACTERISTICS-2  Higher propensity to respiratory failure – More cylindrical thorax of newborns – Horizontal placing of ribs – Compliant chest wall-lower propensity to spring out – Closing volume almost equal to FRC
  6. 6. BASIC CHARACTERISTICS-3  Higher propensity to respiratory failure – Diaphragmatic attachment more horizontal – Low muscle mass and less type I muscle fibers – Liver is relatively larger organ – Dramatic increase in airway resistance (Narrow airway) – Lung growth takes place in centripetal direction with relatively larger anatomic dead space
  7. 7. OXYGENATION-1  Extraction of oxygen from the atmosphere and delivery into the mitochondria  Directly correlated with the partial pressure of oxygen in the alveoli (PAO2)  Partial pressure of oxygen in artery (PaO2)  Alveolar arterial oxygen gradient (PAO2 – PaO2) = 5 - 15 mm Hg
  8. 8. ALEVOLAR GAS EQUATION
  9. 9. HYPOXEMIA-1  Hypoxic gas mixture (Low FIO2)  High altitude (Low PB)  Hypoventilation (High PACO2)
  10. 10. HYPOXEMIA-2  Increased alveolar arterial oxygen gradient (PAO2 – PaO2)  Ventilation perfusion mismatch (shunts)
  11. 11. HYPOXEMIA-3 Ventilation perfusion mismatch (shunts)
  12. 12. VENTILATION-1  Elimination of CO2 from the blood through the alveolus  PaCO2 is proportional to minute ventilation (VE)  PaCO2 is accurately correlated to mean alveolar minute ventilation
  13. 13. VENTILATION-2 Problem in ventilation (PaCO2) –Reduced RR –Reduced tidal volume –Increased dead space
  14. 14. LUNG VOLUMES
  15. 15. LUNG MECHANICS  Elastic recoil  Compliance  Resistance  Time constant
  16. 16. ELASTIC RECOIL-1 The tendency of stretched objects to return to their original state
  17. 17. ELASTIC RECOIL-2  The forces tending and resisting to collapse are equal at a point close to FRC or resting state
  18. 18. ELASTIC RECOIL-3  Surface tension is correlated with elastic recoil  Surface tension follows Laplace law P = 2T R
  19. 19. ELASTIC RECOIL-4
  20. 20. ELASTIC RECOIL-5
  21. 21. COMPLIANCE-1 Change in volume resulting from a given change in pressure
  22. 22. COMPLIANCE-2
  23. 23. RESISTANCE  Resistance is resulted due to friction  Viscous resistance and airway resistance  VR-Generated by tissue elements moving past one another  AR-Generated within the respiratory tract against the gas flow R = P1-P2 V(Flow)
  24. 24. TIME CONSTANT-1  Time necessary for the alveoli to discharge 63% of TV
  25. 25. TIME CONSTANT-2  Pressure changes at alveoli lag behind at the proximal airway  Inspiratory and expiratory time constants
  26. 26. TIME CONSTANT-3
  27. 27. TIME CONSTANT-4  3 time constants lead to 95% equilibrium of alveolar and proximal airway  R (Resistance) X C (Compliance)=0.15 secs  3 time constants = 0.45 secs
  28. 28. VENTILATOR BREAKTHROUGHS
  29. 29. KENNEDY TRAGEDY  1963-Patrick Bouvier Kennedy (34 wks POG/2.1 kg)  RDS-succumbed at 39 hrs
  30. 30. VENTILATOR BASICS
  31. 31. VENTILATOR BASICS  Introduction  Basic terminologies  Oxygenation-MAP  Modes of ventilation  Pulmonary graphics
  32. 32. INTRODUCTION  Movement of gas into and out of lungs by an external source connected directly to the patient  Supportive, non therapeutic technology  Most neonatal ventilators based on Ayer’s T-piece
  33. 33. AYER’S T-PIECE
  34. 34. BASIC PARTS  Pressurized source  Blending chamber  Flow control  Exhalation valve
  35. 35. BASIC TERMINOLOGIES  PIP – Peak inspiratory pressure  PEEP – Positive end expiratory pressure  Rate - Frequency  Ti – Time allowed for inspiration  Te – Time allowed for expiration  IE ratio – 1:1 to 1:3
  36. 36. MEAN AIRWAY PRESSURE-1  Average airway pressure over a given interval of time (PAW)  Area under the curve of pressure time curve for one breath divided by total cycle time
  37. 37. MEAN AIRWAY PRESSURE-2
  38. 38. MODES OF VENTILATION-1  Three factors – How each breath is initiated – How gas flow is controlled during delivery – How the breath is terminated
  39. 39. MODES OF VENTILATION-2  Breath initiation – Controlled – Synchronized or patient triggered  Gas flow control – Pressure – Volume  Flow termination (Cycling) – Volume cycling -Time cycling – Pressure cycling -Flow cycling
  40. 40. MODES OF VENTILATION-3
  41. 41. PULMONARY GRAPHICS-1  Introduction – Relatively new (1980’s) – Microprocessor development (1990’s)  Basis – Sensor with tungsten wire at the proximal airway – Heated wire anemometer technology – Gas flow results in cooling of the wire – Electricity required to bring it back to original temperature is converted to signals
  42. 42. PULMONARY GRAPHICS-2  Colors – Inspiration (Red-machine) (Yellow-patient) – Expiration (Blue) – Auto calibrating (Green)  Common signals – Pressure (cm of H2O) – Volume (mL) – Flow (mL/sec)
  43. 43. PULMONARY GRAPHICS-3
  44. 44. PULMONARY GRAPHICS-4  Cyclic phases – A -Initiation of inspiration – B -Peak inspiration – C -End inspiration – D -End expiration
  45. 45. “Primum non nocere” (First do no harm) The first tenet of Hippocratic oath
  46. 46. REFERENCES  M Keszler. Update on mechanical ventilator strategies. Neoreviews. 2013;14:e237.  AK Ghuman, RG Khemani, CJL Newth. Pediatric applied respiratory physiology-the essentials. Pediatrics and Child Health. 2013;23:7.  PD Sly, RA Collins. Physiological basis of rspiratory signs and symptoms. Pediatric Respiratory Reviews. 2006;7:84-88.  PC Rimensberger. Pediatric and Neonatal Mechanical Ventilation- From Basics to Clinical Practice. Berlin. Springer-Verlag. 2015.  JP Goldmsith, EH Karotkin. Assisted Ventilation of the Neonate. 5th ed. USA. Saunders-Elsevier Imprint. 2015.  SM Donn, MC Mammel. Neonatal Pulmonary Graphics-A Pocket Atlas. New York. Sprigner. 2015.
  47. 47. DESIRABLE CME’S  Basics of neonatal ventilation  Pulmonary waveforms fundamentals  Non invasive neonatal ventilation  Newer modes of ventilation  CPAP-Essential tool in NICU’s
  48. 48. THANK YOU

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