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mechanical ventilation basics.pptx
- 3. Indications Acute ventilatoryfailure Impending ventilatory failure Severe hypoxemia Prophylactic ventilatory suppport
- 4. Goals of ventilation Improving gas exchange Relieve respiratory distress Improving pulmonary mechanics Permit airway healing Avoid complications
- 5. Initial mode Ventilator mode Fullsupport Full WOB done by ventilator Partial support Mode that performs less than total WOB
- 6. Minute ventilation Formen MV = 4 × BSA (IBW/Height in m2) For women MV = 3.5 × BSA Increase by 9% for every 10 C above 370 C 20% for metabolic acidosis Decrease MV by 9% for every 10 C below 370 C
- 7. IBW For Female,IBW = 45.5 + 2.3 (Height in Inches-50) For Male, IBW = 50 + 2.3 (Height in Inches-50)
- 8. Tidal volume 6to 8 ml/kg of IBW. Required tidal volume increases linearly with body weight upto the IBW. Pplateau should be maintained less than 30 cm-H2O.
- 9. Respiratory rate RR= MV/TV 10 to 12/min. Target RR × Target PaCO2= current RR × current PaCO2 Target RR = current RR × current PaCO2/Target PaCO2
- 10. Tidal volume &RR • TV of 6 to 8ml/kg • RR of 12 to 18/min Normal • TV of 8 to 10 ml/kg • RR of 8 to 10/min COPD • TV of 4 to 6 ml/kg • Higher RR Restrictive
- 11. FiO2 Least possibleFiO2 to maintain SpO2 of > 94% FiO2 > 50% ---Free radicals production exceeds the scavenging effects (superoxide dismutase by type II epithelial cells). Increasing FiO2 will not have much improving oxygenation in patients with shunt or diffusion defect.
- 12. Time constant Timeconstant = C × R One time constant = 63% Two time constant = 86% Three time constant = 95% Four time constant = 98%
- 13. Compliance & AirwayResistance Cdyn = VT /Ppeak- PEEP Normal 100 ml/cmH2O On PPV: 50 ml/cmH2O Cstat = VT/Pplateau- PEEP Raw= Pressure/flow Normal: 0.5-2 cmH2O/liter/Second
- 14. TI & TE I:E = 1:2 to 1:3 TCT = TI + TE Example: RR 12/min & TI of 2 sec. TCT = 5 sec; TE of 3 sec. I:E = 2:3 = 1:1.5
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- 16. Flow Flow mustbe set to meet the patient’s demand. Flow should be higher at the beginning of inspiration. In COPD, keep higher flow thereby shorten the TI .
- 17. Flow Flow =VT/TI . If TV is 500 ml (0.5 l) & TI is 1 sec, then flow is 0.5 l/sec or 30 l/min In Galileo ventilator flow can not be set. We can set only the TV & TI. Flow pattern can be set in VCV & in PCV it is descending ramp pattern as default.
- 18. PEEP PEEP preventscollapse of the alveoli at the end of expiration. Optimal PEEP should be set according to the patient’s requirement. PEEP can not open up the alveoli rather it will maintain the patency of the already opened alveoli. Recruitment should be done to open up the collapsed alveoli.
- 19. PEEP PEEP increasesFRC. PEEP decreases the required FiO2. High PEEP in a patient with normal lung compliance can lead to deterioration in hemodynamics.
- 20. Pressure support PSis used to augment the patient’s breathing effort by reducing the airflow resistance. Airflow resistance can be caused by artificial airway, circuit, secretions. Initial PS = Ppeak - Pplateau Titrate PS to TV of 6 – 8 ml/kg.
- 21. Alarm settings Highinspiratory pressure alarm Apnea alarm Low minute volume alarm Low tidal volume alarm High RR alarm Low & high FiO2 alarm
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- 40. Ventilation mode Ventilation modeis defined as specific combination of breathing pattern, control type and operational algorithms. Chatburn, 2007
- 41. Chatburn’s Classification ofmodes Breathing pattern Control variable Volume Pressure Breath sequence CMV IMV CSV
- 42. Chatburn’s Classification ofmodes …..continued Targeting scheme Set point Dual Servo Adaptive Optimal Intelligent
- 43. Phases of respiration Changefrom expiration to inspiration Inspiration Change from inspiration to expiration Expiration
- 44. Phase variables Triggeringvariable Control Variable Cycling Baseline variable
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- 46. Trigger variable Timetrigger: time is the trigger for mandatory breaths Pressure trigger: ventilator senses the generation of negative pressure by the patient and support his breath with set PS Flow trigger: Continuous & constant base flow during later part of exhalation
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- 49. Control variable Itis a variable with which ventilator achieves the inspiration. Pressure, volume, time & flow. Common are pressure & volume. Pressure control: Pressure waveform & set pressure is constant. Volume & flow change Volume control: volume waveform & set volume is constant. Pressure changes.
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- 52. Baseline variable TEstarts from beginning of expiration to start of inspiration. Variable that is controlled during expiration. PEEP
- 53. Modes of ventilation ModePressure control Volume control Time trigger Flow/ Pressure trigger Time cycled Flow cycled CMV × × × CMV (A/C) × × × × P-CMV × × × P-CMV (A/C) × × × ×
- 54. Modes of ventilation ModePressure control Volume control Time trigger Flow/ Pressure trigger Time cycled Flow cycled SIMV (PS) × × × × × P-SIMV × × × × × SPONT (PS) × × APV cmv × × × × × APV simv × × × × × ×
- 55. Control settings Pcontrol • Pressureto be applied above PEEP during inspiration (mandatory) Psupport • Pressure to be applied above PEEP during inspiration (spontaneous) Flow pattern • Flow pattern for gas delivery
- 56. Control settings Flow trigger •Continuous & constant base flow during later part of exhalation Pressure trigger • Pressure drop below PEEP to begin a patient-initiated breath Pramp • Time required for the inspiratory pressure to reach the target
- 57. Control settings ETS • The% of peak inspiratory flow at which ventilator cycles for Spontaneous breaths Pause • % of total breath cycle time
- 58. SIMV Partial ventilatorysupport mode. Each SIMV interval includes mandatory time (Tmand) and spontaneous time (Tspont) portions. During Tmand ventilator waits for the patient to trigger a breath and if so it delivers a mandatory breath.
- 59. SIMV If patientdoes not trigger a breath, then ventilator delivers a mandatory breath. During Tspont, patient can take any number of spontaneous breaths.
- 60. Pressure support mode(SPONT) PS is used to augment the patient’s breathing effort by reducing the airflow resistance. Airflow resistance can be caused by artificial airway, circuit, secretions. Apnea backup should be enabled when using this mode. It is a patient triggered, pressure targeted, flow cycled breath.
- 61. Adaptive pressure modes Vtarget will be achieved with lowest possible pressure depending upon the lung characteristics. During short term post-operative ventilation, the delivered volume remains constant despite rapid changes in breathing activity. Ventilator assesses the V/P response. It uses V/P to calculate the lowest inspiratory pressure to achieve the Vtarget.
- 62. Adaptive pressure modes The minimal pressure delivered is 5 cm-H2O above the PEEP. Adaptive controller compares the measured VT & Vtarget. If measured VT = Vtarget then ventilator maintains the inspiratory pressure. If not so, inspiratory pressure gradually adjusted by upto 2 cmH2O per breath to attain the target level.
- 63. Adaptive pressure modes High pressure alarm limit setting should be atleast 10 cmH2O above the Ppeak. Blue band 10 cmH2O below the high-pressure limit. Inspiratory pressure range = (PEEP + 5 cmH2O) to (High pressure alarm limit – 10 cmH2O) APV-CMV & APV-SIMV modes.
- 64. Adaptive support ventilation ASV maintains an operator preset, minimum minute ventilation independent of patient’s activity. Target breathing is calculated based on Otis’ equation. With least work of breathing & with least possible ventilator applied pressure.
- 65. Adaptive support ventilation Advantages: Guide the patient using favorable breathing pattern Avoid rapid shallow breathing Avoids excessive dead space ventilation Avoids breath stacking Maintains a preset minimum minute ventilation Fully ventilate the patient in apnea or low respiratory drive Without exceeding Pplateau of 10 cmH2O below the upper pressure limit
- 66. Adaptive support ventilation User should set three important parameters: High pressure limit IBW % of minute ventilation
- 67. ASV Dead space= 2.2ml/kg of IBW Add 10% of body weight if using HME Longer than conventional catheter mount requires compensation Shorter ETT, TT have minor effects.
- 68. ASV – lungprotective rules strategy High VT limit: High pressure limit IBW ( 22ml/kg) Low VT limit: Atleast twice the dead space 4.4 ml/Kg High rate limit: fmax = target MV/minimum VT Minimum TI = 1 × RCexp Minimum TE = 2 × RCexp
- 69. ASV – optimalbreathing pattern Optimal breathing pattern is identical to the one a totally unsupported patient would choose naturally. ASV calculates the optimal RR based on %MV, IBW, RCexp. Once optimal RR is determined then optimal VT will be determined.
- 70. ASV Initial breaths: ASV employs SIMV mode initially. Three initial breaths are delivered. ASV compares actual & target VT and actual & target RR Mandatory breaths are pressure preset, time cycled; spontaneous breaths are pressure supported & flow cycled.
- 71. Dynamic adjustment ofbreath pattern Optimal breath pattern is revised with each breath according to the measurement of RCexp. Otis’ equation is applied & new target breathing pattern is calculated when respiratory system mechanics change.
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