1. Department of Critical Care Medicine Kovai Medical Center and Hospital

2. MONITORING OF MECHANICALLY VENTILATED PATIENT DR.T.GOPINATHAN MD., IDCCM.,EDIC Consultant Intensivist Kovai Medical Center and Hospital

3. GOALS OF MECHANICAL VENTILATION  Decrease the WOB and improve patient comfort  Maintain adequate gas exchange to keep body in relative homeostasis

4. Monitoring : monere - meaning ‘to warn’ Goals of continuous monitoring :  Baseline measurement – initial plan, reference for future  follow real time specific physiological values that changes rapidly – alerts for adverse events  Assessment of therapeutic intervention OBJECTIVE

5.  Monitoring gas exchange Oxygenation Ventilation  Monitoring lung and chest wall mechanics Pressure Volume Flow Compliance Resistance RESPIRATORY

6.  Clinical signs and symptoms - Nonspecific, late  ABG  PULSE OXYMETRY  CAPNOGRAPHY  The clinical significance of hypoxia/hypercapnia depends on Chronicity of Compensatory mechanisms and tolerance of vital organs GAS EXCHANGE

7.  Pulsatile signal generated by arterial blood  Difference in the absorption spectra of oxyHb and Hb.  Determines O2 saturation by absorption spectrophotometry PULSE OXYMETRY

8.  Advantages: Inexpensive Accuracy - Spo2 below 80% Direct measurement Continuous Non-invasive Pleth variability index PULSE OXYMETRY

9.  Shape of oxygen dissociation curve  Dyshemoglobinemia  Dyes  Nail polish  Ambient light LIMITATIONS OF PULSE OXYMETRY  False alarms  Motion artifact  Skin pigmentation  Low perfusion state

10. Advantages: Direct measurement of PaO2 and PaCO2 Also gives values for acid-base status and electrolytes Disadvantages: Not specific or sensitive Calculates saturation Requires invasive procedure Intermittent sampling - miss events ABG

11. Factors influencing values: PaO2 varies Age Altitude Sampling techniques: air bubble, heparin PaCO2 remains relatively constant ABG

12. Efficacy of oxygen exchange Alveolar gas equation  PAO2 = PIO2 – (PaCO2/R) AaDO2 = PAO2 – PaO2 Oxygenation index : PaO2/(FiO2 X Paw) PaO2/FiO2 OXYGENATION

13. PaCO2 is directly measured in blood. PaCO2 is a measure of ventilation - CO2 elimination Increased PaCO2 PaCO2 = VCO2/ ( Vt –Vd ) RR VENTILATION.

14. Between ETT and expiratory limb of vent tubing Expired CO2 against time Healthy subjects, V/Q ≈ 1, EtCO2 ≈PaCO2 Information about RR and rhythm ETT placement (obstr, discon, kinking) Determine dead space, CO and PE Best PEEP, PaCO2 – P ET CO2 difference CAPNOGRAPHY

16. ABNORMAL EtCO2 WAVEFORMS ASTHMA/ COPD

17. Hypoventilation ABNORMAL EtCO2 WAVEFORMS Hyperventilation

18. Describe how to use graphics to more appropriately adjust the patient ventilator interface. Identify adverse complications of mechanical ventilation. OBJECTIVES OF VENTILATOR GRAPHICS

19. Pmus + PrS = (R x Flow) + V/C Muscle pressure + ventilator pressure =flow resistance pressure +Elastic recoil pressure EQUATION OF MOTION

20. LOOPS Pressure vs Volume Flow vs volume SCALARS Pressure vs. Time Flow vs. Time Volume vs. Time SCALARS & LOOPS

21. Mode of ventilation Independent variables Dependent variables Waveforms that will be useful Waveforms that normally remain unchanged Volume Control/ Assist- Control Tidal volume, RR, Flow rate, PEEP, I/E ratio P aw Pressure-time: Changes in P ip, P plat Flow-time (expiratory): Changes in compliance Pressure-volume loop: Overdistension, optimal PEEP Volume-time Flow time (inspiratory) Flow-volume loop Pressure Control P aw, Inspiratory time (RR), PEEP and I/E ratio V t, flow Volume-time and flow- time: Changes in V t and compliance Pressure-volume loop: Overdistension, optimal PEEP Pressure-time Pressure support/ CPAP PS and PEEP V t, and RR, flow, I/E Ratio Volume- time Flow- time (for V t and V E ) MODE OF VENTILATION -> USEFUL WAVEFORMS

22. PRESSURE TIME

23. 12 3 4 56 20 Sec P aw cmH 2 O Pressure Ventilation Volume Ventilation PRESSURE TIME

24. time pressure time flow time pressure HIGH AIRWAY RESISTANCE

25. time pressure P aw(peak) = Flow x Resistance + Volume x 1/compliance + PEEP HIGH FLOW RATE

26. 30 Time (s) -10 1 2 aw P cmH 2 O Adequate flow Flow set too low 3 INADEQUATE FLOW - VCV

27. time pressure DECREASED COMPLIANCE

28. 12 3 4 56 SEC 120 EXH INSP Expiration V. LPM Inspiration PIFR PEFR Ti Te Vt FLOW - TIME

29. 123456 SEC 120 -120 V. LPM CHANGING FLOW WAVEFORM IN VCV: EFFECT ON INSPIRATORY TIME

30. 123456 SEC 120 -120 V. LPM EXPIRATORY FLOW RATE AND CHANGES IN EXPIRATORY RESISTANCE

31. The transition from expiratory to inspiratory occurs without the expiratory flow returning to zero 123456 SEC 120 V. LPM DETECTING AUTOPEEP

32. Expiration SEC 800 ml 234561 VTVT Inspiration Vt Ti Te VOLUME Vs TIME CURVE

33. 12 3 4 56 SEC 1.2 -0.4 V T Liters A A = exhalation that does not return to zero Leak Volume LEAKS

34. Expiration SEC 800 ml 234561 VTVT Inspiration TiTe End Expiratory Hold PEEP i PEEP e MEASUREMENT OF AUTOPEEP

35. PV Loops FV Loops LOOPS

36. Inspiration Expiration v 02040602040-60 P aw cmH 2 O Assisted breath controlled breath spontaneous breath ASSISTED BREATH

37. PV LOOP-INCREASED RESISTANCE PCV

38. DECREASED COMPLIANCE

39. WORK OF BREATHING

40. COPD

41. LEAK

42. B A 0 20 40 60 -20 -40 -60 0.2 0.4 0.6 LITERS P aw cmH 2 O C A = inspiratory pressure B = upper inflection point C = lower inflection point VTVT OVERDISTENSION

43. NORMAL FLOW-VOLUME LOOPS

44. Flow Volume Peak Expiratory Flow Peak Inspiratory Flow Tidal Volume Inspiration Expiration FV LOOP – VOLUME CONTROL

45. ETT OR CICUIT LEAKS

46. AUTOPEEP

47. 2 1 1 2 3 3 V LPS. VTVT INSP EXH BEFOREAFTER 2 1 1 2 3 3 V LPS. BRONCHODILATOR RESPONSE

48. Identify mode Detect auto-PEEP Determine patient-ventilator synchrony Assess and adjust trigger levels Measure the work of breathing Adjust tidal volume and minimize overdistension Assess the effect of bronchodilator admn. USES

49. Detect equipment malfunctions Determine appropriate PEEP level Evaluate adequacy of inspiratory time in pressure control ventilation Detect the presence and rate of continuous leaks Determine appropriate Rise Time USES

50. No monitoring device, no matter how simple or complex, invasive or non- invasive, inaccurate or precise will improve outcome unless coupled to a treatment, which itself improves outcome

51. Thank you