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بسم الله الرحمن الرحیم

بسم الله الرحمن الرحیم. Basics of Mechanical Ventilation. Normal breath. Normal breath inspiration animation, awake. Lung @ FRC= balance. Diaghram contracts. -2cm H 2 0.  Chest volume.  Pleural pressure. -7cm H20. Alveolar pressure falls. Air moves down pressure gradient

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بسم الله الرحمن الرحیم

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  1. بسم الله الرحمن الرحیم

  2. Basics of Mechanical Ventilation

  3. Normal breath Normal breath inspiration animation, awake Lung @ FRC= balance Diaghram contracts -2cm H20 Chest volume Pleural pressure -7cm H20 Alveolar pressure falls Air moves down pressure gradient to fill lungs

  4. Normal breath Normal breath expiration animation, awake Diaghram relaxes Pleural / Chest volume  Pleural pressure rises Alveolar pressure rises Air moves down pressure gradient out of lungs

  5. منحنی تغییرات : 1) فشار – زمان 2) حجم – زمان 3) جریان – زمان را در یک سیکل تنفسی طبیعی رسم کنید:

  6. Normal breath Pressure Expiration +3 +2 +1 0 -1 -2 -5 Inspiration

  7. Normal breath Pressure Expiration +3 +2 +1 0 -1 -2 -5 Inspiration volume Time

  8. Normal breath Expiration FLOW Inspiration

  9. Expiration Normal breath +3 +2 +1 Pressure 0 -1 -2 -5 Inspiration volume Inspiration FLOW Expiration

  10. Ventilator breath inspiration animation Air blown in 0 cm H20  lung pressure Air moves down pressure gradient to fill lungs +5 to+10 cm H20  Pleural pressure

  11. Ventilator breath expiration animation Similar to spontaneous…ie passive Ventilator stops blowing air in Pressure gradient Alveolus-trachea Air moves out Down gradient  Lung volume

  12. منحنی تغییرات 1) فشار 2) حجم 3) جریان را در یک سیکل تنفس مصنوعی رسم کنید:

  13. +3 +2 +1 Mechanical breath Normal breath Pressure 0 -1 -2 -5 volume FLOW

  14. Origins of mechanical ventilation • Negative-pressure ventilators (“iron lungs”) • Non-invasive ventilation first used in Boston Children’s Hospital in 1928 • Used extensively during polio outbreaks in 1940s – 1950s • Positive-pressure ventilators • Invasive ventilation first used at Massachusetts General Hospital in 1955 • Now the modern standard of mechanical ventilation The iron lung created negative pressure in abdomen as well as the chest, decreasing cardiac output. Iron lung polio ward at Rancho Los Amigos Hospital in 1953.

  15. Several ways to ..connect the machine to Pt • Oro / Naso - tracheal Intubation • Tracheostomy • Non-Invasive Ventilation

  16. Ventilation = Inspiration + Expiration Inspiration = 1) Start or Triggering 2) inspiratory motive force or control or Mode 3) termination of inspiration or Cycling Expiratory Phase Maneuvers

  17. Classification(the Basic Questions) A. Trigger mechanism • What causes the breath to begin? B. Limit variable • What regulates gas flow during the breath? C. Cycle mechanism • What causes the breath to end? B C A

  18. 2 1 3 4 The four phases of each ventilatory cycle

  19. Inspiration Expiration volume Time

  20. Cycling volume inspiratory motive force or control or Mode Start Time

  21. Cycling Vs. Limiting Pressure Pressure Limited Cycled Time Time

  22. چهار مرحله تنفس مکانیکی را نام ببرید: 1) 2) 3) 4)

  23. Triggering the Ventilator • flow trigger • pressure trigger • volume Trigger • Time Trigger • Other techniques: Neurally Adjusted Ventilatory Assist (NAVA) • Chest impedance • Abdominal movement Flow triggering is considered to be more comfortable, Increasing the trigger sensitivity: decreases the work of breathing accidental triggering and unwanted breaths

  24. Trigger • Which Trigger is correct? • flow trigger • pressure trigger • volume Trigger • Time Trigger Mandatory

  25. all the breaths with mandatory inspiratory cycling Spontaneous Unsupported Mandatory

  26. Trigger • Which Trigger is correct? • flow trigger • pressure trigger • volume Trigger • Time Trigger

  27. Trigger • Which Trigger is correct? • flow trigger • pressure trigger • volume Trigger • Time Trigger supported Mandatory

  28. Trigger • Which Trigger is correct? • flow trigger • pressure trigger • volume Trigger • Time Trigger supported Mandatory Synchronized

  29. Mandatory (VCV) Triggered (PSV) spontaneous and mandatory spontaneous and mandatory inspiratory cycling

  30. No mandatory inspiratory cycling all the breaths are pressure-targeted and trigger inspiratory-cycled

  31. Which Trigger? • flow trigger • pressure trigger • volume Trigger • Time Trigger • Non of the above

  32. Expiration Inspiration Air IN Air OUT

  33. Time Constant = C X R A certain amount of time is necessary for pressure equilibration (and therefore completion of delivery of gas) to occur between proximal airway and alveoli. TC, a reflection of time required for pressure equilibratlon, is a product of compliance and resistance. In diseases of decreased lung compliance, less time is needed for pressure equilibration to occur, whereas in diseases of increased airway reslstance, more time is required. Expiratory TC is increased much more than inspiratory TC in obstructive airway diseases, because airway narrowing is exaggerated during expiration.

  34. 3-5 time constant

  35. C = 100 cc/ Cm H2O R = 1 Cm H2O / L / Sec Time Constant = ? = R.C =100 cc/ Cm H2O X 1 Cm H2O / L / Sec = 0.1 Sec Time Constant C = 50 cc/ Cm H2O R = 1 Cm H2O / L / Sec TC= ? = R.C =50 CC / Cm H2O X 1 Cm H2O / L / Sec = 0.05 Sec C = 100 cc/ Cm H2O R = 2 Cm H2O / L / Sec Time Constant = ? = R.C =100 CC/ Cm H2O X 1 Cm H2O / L / Sec = 0.2 Sec

  36. C = 40 cc/ Cm H2O R = 4 Cm H2O / L / Sec Inspiratory Time = ?? TC = C x R = 0.16 IT = 3 x 0.16 = 0.48

  37. Selection of Appropriate Inspiratory Time TI too long TI too short T I = 3-5 time constant Tc = C x R TI is usually initiated at: 0.5-0.7 sec for neonates, 0.8-1 sec in older children, 1-1.2 sec for adolescents and adults need to be adjusted through : individual patient observations and according to the type of lung disease. T I + T E = Time Cycle F ( RR ) = 60/TC I T E T F= 60/ TI +TE T I = 3-5 time constant Tc = C x R Many ventilators ask the user to set the I:E ratio and respiratory rate

  38. V T = 100 cc TI = 0.8 sec Inspiratory Flow = ? Inspiratory Flow = 100 / 0.8 = 125 cc/sec (7.5 L/ Min )

  39. RR = 60 I:E = ½ IT = ? ET = ? F= 60/ TI +TE 60 = 60 / TI + 2TI = 60/ 3TI IT = 0.33 ET = 0.66 • IT= 0.8 ET= 1.2Sec • RR=? F= 60/ TI +TE RR = 60 / 0.8+1.2 = 30

  40. Inspiratory Flow/Pressure/Volume Pattern Decelerating Square Accelerating Sinusoidal Inspiratory Rise Time time

  41. Pressure-controlled inflation Inspiratory Rise Time Pmax = Pinf + PEE

  42. Effect of a pressure-limit on a volume-controlled breath

  43. Cycling Termination of Inspiration (Cycle) 1)Time-cycled 2)Volume-cycled 3) flow-cycled

  44. Pressure Controlled Ventilation Cycling at 25% Flow VT

  45. Pressure Controlled Ventilation respiratory resistance and compliance are both lower both the resistance and compliance of the respiratory system are higher Cycling at 25% Flow IT> IT<

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