1. Patient-Ventilator Synchrony & Successful Weaning Shao-Hsuan Hsia, MD Pediatric Critical Care and Emergency Medicine Chang Gung Children’s Hospital

2. What is your interpretation? Does these two patients “synchronize” ventilator? Can we “wean” these patients smoothly?

5. WEANING AND EXTUBATION

9. Pressure Trigger 4 2 0 -2 Paw (cm H2O) Time (secs) 0.25 0.50 Pressure Trigger WOB

11. Pressure vs Flow Trigger 4 2 0 -2 Paw (cm H2O) Time (secs) 0.25 0.50 0.4 0.3 0.2 0.1 0 -0.1 -0.2 Flow (ml/sec)

19. Effects of ETT on Vent WOB Flow (L/min) Work (Joules/min) 6.5 ETT 6.0 ETT 5.5 ETT 4.5 ETT 4.0 ETT

22. Ventilator Response Time 4 2 0 -2 Paw (cm H 2 O) Time (secs) 0.25 0.50 Trigger Set at -0.1ml/sec or -1cm H 2 0 Delayed Response 0.4 0.3 0.2 0.1 0 -0.1 Flow (ml/sec)

24. Flow and Airway Pressure Decelerating Square Sine Ascending Flow Airway Pressure Time Area =Mean Airway Pressure

25. Flow and Airway Pressure Decelerating Square Flow (l/sec) Airway Pressure (cmH 2 0) MAP = Area Under Curve PIP PIP Gas Distribution

30. Determination of effective tidal volume Can you calculate the tidal volume “lost” due to the distensibility of the ventilator circuit and compensate for it? calculated effective Vt = Vt at exp valve ﹣[circuit compliance  (PIP-PEEP)]

33. Results: Infant Circuit The Vt as measured at the ETT was on average only 56% of that measured at the expiratory valve of the ventilator. Vt(ml) p Exp valve Vt 70.4 ± 31.1 Calcuated Vt 59.2 ± 28.8 <0.0001 Pneumotach Vt 39.4 ± 21.5 <0.0001

35. Circuit Compliance Calculations Calculating effective tidal volumes are not sufficient because of multiple uncontrolled variables: -in-line suction catheters -condensation -secretions -EtCO2 adapters -humidifiers / heaters -etc.

36. Results: Pediatric Circuit The Vt as measured at the ETT was on average 73% of that measured at the exp. valve of the ventilator. Vt(ml) p Exp valve Vt 185.4 ± 96.6 Calcuated Vt 167.8 ± 94.6 0.16 Pneumotach Vt 135.3 ± 75.8 0.03

42. Mechanical graphics 0 15 30 45 75 150 250 Airway Pressure(cmH2O) Volume(ml) Vt=145ml PEEP PIP=42 2Y ARDS Low compliance Dynamic compliance=Vt/(PIP-PEEP)=3.9 Ins Exp

45. Gas-trapping or intrinsic PEEP Time inspiration exspiration Flow (L/sec) 0 Pressure (cmH2O) 0 Incomplete exhalation (gas trapping) Intrinsic PEEP=5, set PEEP=5, total=10 I:E=1:0.8

46. Reduction of Gas-trapping Time inspiration exspiration Flow (L/sec) 0 Pressure (cmH2O) 0 Exhalation complete Intrinsic PEEP=0, set PEEP=5, total=5 I:E=1:1.5

49. Termination sensitivity

54. WOB During Pressure Support PS = 15 cmH2O PS = 5-10 cmH2O PS = 0 cmH2O Volume Pressure

56. SIMV with Pressure Support Flow Pressure Volume control Pressure support

61. Extubation Criteria in Peds Khan , CCM ,1996 Successful extubation predictors: Variable Low-risk value High risk value Vtspont 6.5cc/kg 3.5 cc/kg FiO2 0.30 >0.40 Paw <5 cm H2O >8.5 cm H2O OI 1.4 4.5 FrVe 20% 30% PIP 25 cm H2O 30 cm H2O Cdyn 0.9 cc/kg/cm H2O <0.4 cc/kg/cm H2O

63. End-tidal CO2

64. Area p=q

65. X=alveolar ventilation, Y=alveolar dead space, Z=airway dead space, Y+Z X+Y+Z Vd/Vt=

67. Results: Individual Outcomes P<0.001 NIV(6),PPV(2) 2/10(20%) 0.65-0.95 NIV(3) 6/9(67%) 0.51-0.64 NIV(1) 24/25(96%) 0.10-0.50 Failed Extubation Successful Extubation Vd/Vt