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Ventilator waveform analysis: often ignored bedside assessment

Ventilator waveform analysis: often ignored bedside assessment. Dr. Tang Kam Shing ICU, Tuen Mun Hospital. Introduction. Basic parameters measured by ventilator Pressure Flow Volume (as an integration of flow) Time

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Ventilator waveform analysis: often ignored bedside assessment

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  1. Ventilator waveform analysis: often ignored bedside assessment Dr. Tang Kam Shing ICU, Tuen Mun Hospital

  2. Introduction • Basic parameters measured by ventilator • Pressure • Flow • Volume (as an integration of flow) • Time • From these parameters, basically 5 types of curves commonly available from ventilators • Pressure-time curve • Flow-time curve • Volume-time curve • Pressure-volume curve • Flow-volume curve

  3. Introduction • The curves are basically the result of the mechanical interaction between the ventilator and the respiratory system • Important to know the setting on the ventilator before you try to make sense of the waveforms • Volume control or pressure control? • What is the cycling variable? • Important to know whether the patient is relaxed and sedated or actively breathing • Major impact on the interpretation of waveforms

  4. Use of waveforms • Measurement of: • Peak insp. Pressure • plateau pressure • Auto-PEEP • Detection of over-inflation or gas trapping • Serial change in resistance and compliance • Patient-ventilator synchrony

  5. Flow-time curve • For VCV • Basically the TV, Ti and flow waveform you set determine the insp. pattern of flow-time curve in VCV in most cases • Expiratory pattern more useful • For PCV • Both insp. and exp. flow depend on the driving pressure and resp. mechanics

  6. VCV Normal flow-time curve

  7. PCV Normal Flow-time curve

  8. PCV in sedated patient What is the problem? Compliance or resistance? ↑ resistance ↓ compliance

  9. Flow-time curve PCV What is the abnormality? Any other possibilities? Patient with ↑ resp drive, insp when exhalation not complete yet

  10. Active expiration After NMB

  11. Blue tracing conventional ventilator tracing Red tracing at tip of OETT What is the cause of the spike of A? (artefact ∵ not shown at ET tip pressure) What is the cause of the spike of C?

  12. What is the problem? What is the reason of the spike?

  13. Asynchrony: Double triggering

  14. VCV Flow starvation Too low flow rate

  15. PCV ventilation What is the abnromalities? What can we do?

  16. What is this? What is this?

  17. Pressure-time curve of VCV

  18. Pressure-time curve in VCV Which is increased resistance? Which is decreased compliance?

  19. Measuring AutoPEEP Waterfall effect

  20. PV loop after treatment What is the problem? Compliance or resistance? Normal lung compliance: 50ml/cmH2O InitialPV loop

  21. PV loop after treatment What is the problem? Compliance or resistance? Initial PV loop

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