Department of Critical Care Medicine Kovai Medical Center and Hospital

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. OBJECTIVE • 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

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

6. GAS EXCHANGE • 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

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

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

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

10. ABG • 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

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

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

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

14. CAPNOGRAPHY • 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 – PET CO2 difference

15. CAPNOGRAPHY

16. 49 9 • ABNORMAL EtCO2 WAVEFORMS ASTHMA/ COPD mmHg RR

17. 48 8 24 35 • ABNORMAL EtCO2 WAVEFORMS Hypoventilation mmHg RR Hyperventilation mmHg RR

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

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

20. SCALARS & LOOPS SCALARS • Pressure vs. Time • Flow vs. Time • Volume vs. Time LOOPS • Pressure vsVolume • Flow vsvolume

21. MODE OF VENTILATION -> USEFUL WAVEFORMS

22. PRESSURE TIME

23. PRESSURE TIME 20 Pressure Ventilation Volume Ventilation Paw cmH2O Sec 1 2 3 4 5 6

24. flow time • HIGH AIRWAY RESISTANCE pressure pressure time time

25. HIGH FLOW RATE Paw(peak) = Flowx Resistance + Volume x 1/compliance + PEEP pressure time

26. Flow set too low • INADEQUATE FLOW - VCV 30 Adequate flow P aw Time (s) cmH2O 1 2 3 -10

27. DECREASED COMPLIANCE pressure time

28. FLOW - TIME 120 INSP Inspiration . PIFR Vt Te V SEC Ti LPM 1 2 3 4 5 6 Expiration PEFR EXH 120

29. CHANGING FLOW WAVEFORM IN VCV: EFFECT ON INSPIRATORY TIME 120 . V SEC LPM 1 2 3 4 5 6 -120

30. EXPIRATORY FLOW RATE AND CHANGES IN EXPIRATORY RESISTANCE 120 . SEC V LPM 1 2 3 4 5 6 -120

31. DETECTING AUTOPEEP 120 . V SEC LPM 1 2 3 4 5 6 The transition from expiratory to inspiratory occurs without the expiratory flow returning to zero 120

32. VOLUME Vs TIME CURVE 800 ml Vt • Inspiration • Expiration VT SEC Ti Te 1 2 3 4 5 6

33. LEAKS 1.2 A VT Liters SEC Leak Volume 1 2 3 4 5 6 -0.4 A = exhalation that does not return to zero

34. MEASUREMENT OF AUTOPEEP 800 ml • Inspiration • Expiration VT End Expiratory Hold PEEP i SEC PEEP e Ti Te 1 2 3 4 5 6

35. LOOPS PV Loops FV Loops

36. ASSISTED BREATH Assisted breath spontaneous breath controlled breath Expiration • Inspiration Paw v cmH2O -60 40 20 0 20 40 60

37. PV LOOP-INCREASED RESISTANCE PCV

38. DECREASED COMPLIANCE

39. WORK OF BREATHING

40. COPD

41. LEAK

42. OVERDISTENSION VT A = inspiratory pressure B = upper inflection point C = lower inflection point LITERS 0.6 A 0.4 B 0.2 C Paw 60 40 -60 -20 20 0 -40 cmH2O

43. NORMAL FLOW-VOLUME LOOPS

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

45. ETT OR CICUIT LEAKS

46. AUTOPEEP

47. 3 2 1 . V LPS 1 2 3 • BRONCHODILATOR RESPONSE BEFORE AFTER 3 INSP 2 1 . V LPS VT 1 2 3 EXH

48. USES • 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.

49. USES • 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

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