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VENTILATOR GRAPHICS

VENTILATOR GRAPHICS. LOOPS AND CURVES. dr.r.selvakumar. Some definitions…. Inspiratory flow time: beginning of flow to end of flow during inspiration Inspiratory pause time:time in inspiration where flow is zero Inspiratory phase time: Insp.flow time+insp.pause time.

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VENTILATOR GRAPHICS

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  1. VENTILATOR GRAPHICS LOOPS AND CURVES dr.r.selvakumar

  2. Some definitions… • Inspiratory flow time: beginning of flow to • end of flow during inspiration • Inspiratory pause time:time in inspiration where • flow is zero • Inspiratory phase time: Insp.flow time+insp.pause • time

  3. Some definitions…contd Expiratory flow time,Exp.pause time Exp.phase time Inspiratory flow rate: rate at which gas flows into the pt expressed as volume per unit of time Peak pressure: max. pressure during the insp.phase time Plateau pressure: resting pressure during the insp.pause

  4. Some definitions…contd • Resistance: ratio of the change in driving • pressure to the change in flow rate.cmH2O/L/sec • Compliance: ratio of a change in volume to a change in pressure

  5. Insp phase time flow pause Flow 0 flow pause Exp.phase time

  6. hold volume 0

  7. plateau pressure peak 0

  8. AIRWAY PRESSURE WAVE FORM peak plateau 20 normal 40 High airway resistance

  9. Press.cont.ventilation Volume cont.ventilation

  10. LOOPS: Dynamic relationship between two variables on a graph

  11. NORMAL P-V LOOP End inspiration exhalation V O l U M e inspiration pressure

  12. NORMAL FLOW-VOLUME LOOP +30 exhalation Flow lpm FRC TV inspiration

  13. CONTROLLED VENTILATION - No ins.pause P-V LOOP • Double convex • Begins at zero volume and near zero pressure • Ins. Slope – compliance • End of insp- peak press and TV attained

  14. volume Normal P-V loop 900 TV 600 300 Peak pressure

  15. Normal flow-volume loop • Smoothly curved,rectangular insp.limb • Upper triangular exp.portion • Apex – peak exp.flow • Slope of exp.flow- reflects the resistance • And recoil pressure of the entire ventilatory system

  16. Cont.ventilation with PEEP • P-V loop shifts to the right • Begins at the PEEP value

  17. Insp.pause volume pressure

  18. Controlled ventilation with insp.pause • After peak press. Is reached,there is a pause • During pause,press. drops to a plateau level • Insp.volume will increase during insp.pause

  19. SPONTANEOUS RESPIRATION • starts at zero • inspiration- airway press is negative. • loop moves on to left • End of insp- press. Becomes zero • Exhalation-pree.becomes positive,volume drops

  20. volume -10 10 20 pressure

  21. Normal F-V loop-spon.respiration exhalaton 30 lpm 600 volume inspiration

  22. P-V loop –spon.breathing with PEEP exhalation inhalation F-V loop- lower flows during insp and expiration

  23. SPON.BREATH DURING CONT.VENTILATION 900ml Spon.breath 10 pressure

  24. Spon.breath during cont.ventilation If it occurs during expiration,the pressure drops and volume increases As the pt exhales,press. increases briefly and volume drops

  25. F-V Loop-spon.breath in cont.ventilation Breath occurs during inspiration Sudden increase in ins.flow and volume As the breath is exhaled,flow & volume move towards zero

  26. Fighting with ventilator 600ml 30 Inhalation at the beginning of ventilator insp. So loop moves to the left of the vertical axis marked decrease in compliance

  27. OPEN LOOP 900ml pressure

  28. Open F-V loop 30 lpm

  29. OPEN LOOP A loop should return to its starting point Gap between the end and starting points Exhaled volume is less than inhaled volume Causes: uncuffed ETT,LMA,leak Partial disconnection tension pnemothorax extreme absorption of N2O

  30. An open F-V loop 30 lpm 600 ml There is still exp.flow when the next insp. Is commenced COPD

  31. OVERSHOOT LOOP exhaled volume is more than the inspired volume

  32. P-V loop in decreased compliance Normal loop Loop shifted To right and down PEEP may restore the curve back towards left

  33. 60 lpm F-V loop- decreased compliance Flow will be increased during exhalation with a higher peak and steeper slope

  34. P-V loop – increased resistance 500 ml 10 30 pressure

  35. CHANGES IN RESISTANCE: • Higher insp.pressure required to • deliver the given flow • TV reduced • Curve shifted right and down • Large internal area • Loop may be open if air trapping

  36. P-V loop in emphysema No problem in inflating lungs Exhalation - press.drops with little change in volume until the end of exhalation Open loop

  37. F-V loop in emphysema 30 lpm Insp. Almost normal Severe reduction in exp.flow Loop may be open

  38. F-V LOOPS IN OBSTRUCTIVE PATHOLOGY Fixed tracheal obs Both are restricted Extra thoracic obs Ins.plateau Normal expiratory flow

  39. Intra thoracic obstruction airway collapse during exhalation Normal ins. flow

  40. RESTRICTIVE LUNG DISEASE • increase in elastic recoil • associated with high exp.flow and • deep descending flow • As disease progresses, lung volume decreases • And the loop becomes tall and narrow

  41. 60 lpm RESTRICTIVE DISEASE

  42. normal One lung intubation DLT deeply placed

  43. BALL VALVE OBSTRUCTION

  44. BALL VALVE OBSTRUCTION Tip of the tube impinging on the side wall of trachea Press. Rises rapidly with little increase in volume Until press is sufficient to overcome the obstruction. The vol. Increases and press.drops. If the press. drops low enough, there will be again an obstruction to flow,creating another notch on the upswing of the loop

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