ventilator graphics in anesthesia machinepptx

This is a ppt on ventilator graphics and its meaning in anesthesia

1. VENTILATOR GRAPHICS Dr .Gunasekaran D r.Dhatchinamoorthy

2. Definitions Ventilation - Movement of air into and out of the lungs Respiration - Exchange of oxygen and carbon dioxide between an organism and its environment Internal and external respiration

3. Compliance T he relative ease with which the structure distends. It can be defined as the opposite, or inverse, of elastance E lastance is the tendency of a structure to return to its original form after being stretched or acted on by an outside force C = ΔV/ΔP C ompliance of the respiratory system is the sum of the compliances of both the lung parenchyma and the surrounding thoracic structures Normal= 100ml/cm H2O(50-170) Resistance is a measurement of the frictional forces that must be overcome during breathing. T he anatomical structure of the airways and the tissue viscous resistance offered by the lungs and adjacent tissues and organs Raw = (PIP − Pplateau )/flow (where PIP is peak inspiratory pressure); or Raw = PTA/flow Resistance

4. Types of Mechanical ventilators: Negative-pressure ventilators Positive-pressure ventilators.

5. Types of Positive-Pressure Ventilators 1- Volume Ventilators. 2- Pressure Ventilators 3- High-Frequency Ventilators

6. Flow VOLUME Pressure Time FiO2 R.R. Control variable

7. Inspiration Expiration Time (sec) Flow (L/min) Phase variables of a Breath Trigger Limit Cycle Trigger Time Pressure Flow Cycle Time/Volume Pressure Flow

8. Inspiratory Trigger Normally set automatically 2 modes: Airway pressure Flow triggering

9. Triggering Time (sec) Patient Machine Pressure (cmH 2 0)

10. ● Sensitivity( trigger Sensitivity ) The sensitivity function controls the amount of patient effort needed to initiate an inspiration Increasing the sensitivity (requiring less negative force) decreases the amount of work the patient must do to initiate a ventilator breath. Decreasing the sensitivity increases the amount of negative pressure that the patient needs to initiate inspiration and increases the work of breathing.

11. Types of Waveforms Scalars and Loops: Scalars: Plot pressure, volume, or flow against time. Time is the x-axis Loops: Plot pressure or flow against volume. (P/V or F/V). There is no time component.

12. Types of Ventilator Waveforms: Scalars and Loops Scalars are waveform representations of pressure, flow or volume on the y axis vs time on the x axis pressure vs time scalar flow vs time scalar volume vs time scalar Inspiratory arm expiratory arm

13. Types of Loops P-V Loop F-V Loop Expiratory arm Inspiratory arm Inspiratory arm Expiratory arm

14. Understanding the flow-time waveform There are two components to the flow-time waveform The inspiratory arm: Active in nature The character is determined by the ventilatory flow settings. The expiratory arm: Passive in nature The character is determined mainly by elastic recoil of the patients lungs and airway resistance. Also affected by patient respiratory effort (if any) There are two commonly used types of flow patterns available on most ventilators The ‘square wave’ or ‘constant flow’ pattern The ‘ramp’ (decelerating) type pattern

15. The ‘square wave’ flow pattern The inspiratory flow rate remains constant over the entire inspiration. time flow Inspiratory arm Expiratory arm The expiratory flow is passive and is determined by airways resistance and the elastic recoil of the lungs

16. The ‘decelerating ramp’ flow pattern The inspiratory flow rate decelerates as a function of time to reach zero flow at end inspiration For a given tidal volume, the inspiratory time is higher in this type of flow pattern as compared to the square wave pattern time flow Inspiratory arm Expiratory arm

17. Understanding the basic ventilator circuit diagram ventilator Diaphragm These two systems are connected by an endotracheal tube which we can consider as an extension of the patients airways. The ventilator makes up the first part of the circuit. Its pump like action is depicted simplistically as a piston that moves in a reciprocating fashion during the respiratory cycle. The patient’s own respiratory system Makes up the 2 nd part of the circuit. The diaphragm is also shown as a 2 nd piston; causing air to be drawn into the lungs during contraction. ET Tube airways Chest wall

18. Understanding airway pressures The respiratory system can be thought of as a mechanical system consisting of a resistive (airways) and elastic (lungs and chest wall) element in series Diaphragm ET Tube airways Chest wall P PL Pleural pressure P aw Airway pressure P alv Alveolar pressure Lungs + Chest wall (elastic element) Airways (resistive element) The contribution of airway resistance pressure depends on the rate of airflow and the underlying resistance (caliber) of the airways Flow resistance The contribution of the elastic element (lungs + chest wall) depends on the degree of lung inflation and the underlying compliance of the lungs and the chest wall Volume compliance P aw = Flow Resistance + Volume Compliance

19. Understanding basic respiratory mechanics The total ‘ airway’ resistance (R aw ) in the mechanically ventilated patient is equal to the sum of the resistances offered by the endotracheal tube (R ET tube ) and the patient’s airways ( R airways ) Thus the equation of motion for the respiratory system is P applied (t) = P res (t) + P el (t)

20. ventilator Diaphragm P peak P res R ET tube R airways P res P plat Understanding the pressure-time waveform using a ‘square wave’ flow pattern time pressure After this, the pressure rises in a linear fashion to finally reach P peak . Again at end inspiration, air flow is zero and the pressure drops by an amount equal to P res to reach the plateau pressure P plat . The pressure returns to baseline during passive expiration P res

21. Now let’s look at some different pressure-time waveforms using a ‘square wave’ flow pattern This is a normal pressure-time waveform With normal peak pressures ( P peak ) ; plateau pressures ( P plat )and airway resistance pressures (P res ) time pressure P peak P res P plat P res time flow ‘Square wave’ flow pattern Normal values: P peak < 40 cm H 2 O P plat < 30 cm H 2 O P res < 10 cm H 2 O

22. Waveform showing increased airways resistance time pressure P peak P res P plat P res The increase in the peak airway pressure is driven entirely by an increase in the airways resistance pressure. e.g. ET tube blockage P aw = Flow Resistance + Volume + PEEP Compliance time flow ‘Square wave’ flow pattern Normal

23. Waveform showing increased airways resistance P peak P plat P res ‘Square wave’ flow pattern

24. Waveform showing high airway resistance due to high flow rates time pressure P peak P res P plat P res The increase in the peak airway pressure is driven entirely by an increase in the airways resistance pressure caused by excessive flow rates. Note the shortened inspiratory time and high flow e.g. high flow rates P aw = Flow Resistance + Volume + PEEP Compliance time flow ‘Square wave’ flow pattern Normal Normal (low) flow rate

25. Waveform showing decreased lung compliance The increase in the peak airway pressure is driven entirely by the decrease in the lung compliance. Increased airways resistance is often also a part of this scenario. time pressure P peak P res P plat P res e.g. ARDS P aw = Flow Resistance + Volume + PEEP Compliance Normal time flow ‘Square wave’ flow pattern

26. Waveform showing decreased lung compliance P peak P plat P res ‘Square wave’ flow pattern

27. Now lets look at the same pressure-time tracings using a ‘decelerating ramp’ flow pattern High Raw: (e.g. asthma) Normal High flow: (Note short Inspiratory time) Low C L : e.g. ARDS Normal PIP Normal P plat High PIP High PIP High P plat Normal P plat Normal P plat High PIP pressure time

28. LOOPS P-V Loop F-V Loop Expiratory arm Inspiratory arm Inspiratory arm Expiratory arm

29. P/V loop

30. Components of P/V loop

31. Abnormalities in P/V loop Alveolar over distention Increased WOB

32. F/V Loop

33. Abnormalities in F/V loop Increased R aw Air leak

34. Each additional assisted breath at prefixed tidal volume or pressureTrigger: ventilator or patient Limit: Flow / volume or Pressure Cycling: volume or time Assist Control

35. Pressure Flow Volume (L/min) (cm H 2 O) (ml) Time (sec) SIMV Mode Spontaneous Breath

36. SIMV + PS Ventilation

37. CMV

38. PSV Time (sec) Pressure (cm H 2 O) Volume (mL) Flow (L/m) Set PS level Rise Rise Time Courtesy: Prof J V Divatia

39. Volume Control Pressure-Time waveform. X. Inspiration time Y. Pause time Z. Expiration time 1. Start of Inspiration 2. Peak inspiratory pressure 3. Early inspiratory pause pressure 4. End inspiratory pause pressure 5. Early expiratory pressure 6. End expiratory pressure Flow-Time waveform. X. Inspiration time Y. Pause time Z: Expiration time 7. Peak inspiratory flow 8. Zero flow phase 9. Peak expiratory flow 10. Slope decelerating expiratory limb 11. End expiratory flow Volume-Time waveform. X. Inspiration time Y. Pause time Z. Expiration time 12. Start of inspiration 13. The slope represents current delivery of inspiratory tidal volume 14. End inspiration 15. The slope represents current patient delivery of expiratory tidal volume

40. Pressure Control Pressure-Time waveform. X. Inspiration time Z. Expiration time 1. Start of Inspiration 2. Peak inspiratory pressure 3. End expiratory pressure Flow-Time waveform. X. Inspiration time Z. Expiration time 4. Peak inspiratory flow 5. End inspiratory flow 6. Peak expiratory flow 7. End expiratory flow Volume-Time waveform. X. Inspiration time Z.: Expiration time 8. Start of inspiration 9. End inspiration 10. End expiration

41. Thanks