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Ventilator
- 1. THEBASICSOF VENTILATOR SETTINGS SERIES2 DR. C.KANNAN POST GRADUATE PEDIATRICS MGMCRI
- 2. REVISION OF PART1 TIDAL VOLUME (VT) • Volume of gas that flows in and out of the chest during quiet breathing . • Normal tidal volume in children – 6-12ml/kg MINUTE VENTILATION (MV) • Product of tidal volume and ventilator rate. PEAK INSPIRATORY PRESSURE (PIP) • Highest that can be met during the inspiratory period
- 3. POSITIVE END EXPIRATORYPRESSURE (PEEP) • PEEP is the baseline positive pressure in the airway during expiration. • It is designed to keep alveoli from collapsing at the end of expiration. • PEEP prevents derecruitment of alveoli and it has protective effect in prevention of ventilator associated lung injury. • Normal PEEP 3-5cmH2O INSPIRATORY TIME AND I:E RATIOS • Normal I:E ratio is usually 1:1.5 to 1:2 • Altered by adjusting the inspiratory time.
- 4. DICUSSION • Anatomy ofthe ventilator • Modes in ventilator • How to start a ventilator ? • Disease based strategy
- 5. ANATOMY • Purified compressedair & oxygen • Either inbuilt cylinders or from wall outlet • Sophisticated software • Ensures the pattern of breath delivery • As set by the caregiver • Humidifier / Heat & Moist exchanger (HME)
- 6. Contd., • Ventilator hardware •Monitors • Pressure gauges / Flow & Volume sensors / Alarms / Graphics • Circuits – Reusable / Disposable • Two limbs – Inspiratory / expiratory • Heated wire present in both limbs - Prevents condensation • Water traps in dependent position in both limbs
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- 9. DETERMINANTS OF MODES •BREATH TYPE • Mandatory • Spontaneous • Assisted • CONTROL VARIABLE • Pressure control • Volume control • Dual control • TIME OF BREATH DELIVERY • CMV • Spontaneous • Assisted
- 10. MODES/ACTION BY TRIGGERINGLIMITING CYCLING MANDATORY Ventilator ventilator ventilator ASSISTED Patient / venti Patient / venti Patient / venti SPONTANEOUS Patient Venti / patient Patient 1. BREATH TYPE
- 11. 2. CONTROL VARIABLE A.PRESSURE CONTROLLED BREATHS • Pressure is set by clinician (Independent variable) • PIP / PEEP / Rate / Inspiratory time (Ti) • Volume (VT) can change (Dependent variable) • Determined by • Delta P (PIP – PEEP) • Compliance / Airway resistance / Circuit / Patient effort • Flow waveform is decelerating ( Pressure gradient )
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- 13. • Advantages • Riskof barotrauma is less • Improves gas distribution in heterogeneous lung mechanics • Satisfy patient demands in spontaneous breaths • Where airway is not fully sealed • Uncuffed tracheal tubes • Bronchopleural fistulas • Airleak syndromes
- 14. • Disadvantages • PCdoes not guarantee minute volume • Tidal volume changes depends upon compliance • If lung is stiff - TV reduces • If lung compliance improves - TV increases - Volutrauma • Hence close clinical monitoring is essential • To prevent hypo / hyperventilation
- 15. B. VOLUME CONTROLLEDBREATHS • Used in older children • Part of mandatory controlled mode (CMV / SIMV) • Tidal volume is set by clinician (Independent variable) • Pressure can change (Dependant variable) • Cycling mechanism is controlled by • Pre-set time (Ti) / Pre-set Volume • Flow wave form is constant
- 16. VC – FLOWCHART
- 17. • Advantages • Minuteventilation is guaranteed • Important in airway diseases ( B. Asthma / Bronchiolitis) • Disadvantages • High risk of barotrauma (Pressure fluctuates) • Flow is constant • Hence cant satisfy patient demand in spontaneous breaths • Smaller tidal volume will not be accurately delivered • In case of altered lung mechanics • Divided B/W circuit / Airways / Lungs
- 18. • Disadvantages • Ifthe patient worsens by • Eg., Takes more tidal volume by increased WOB • Ventilator senses high exhaled TV and reduces pressure • Reduced pressure support, further worsens WOB
- 19. 3. TIMING OFBREATH DELIVERY A. CONTROLLED MANDATORY / MECHANICAL VENTILATION (CMV) • CMV may utilise pressure / Volume / Dual control • Breaths initiated, limited and cycled by ventilator • Patient has no active role • Used in • Insufficient / Absent respiratory drive • Completely sedated patients
- 20. B. ASSISTED MODES •Used, when patient is making some effort • Breath may be triggered by patient / pre-set time • Whichever comes first • Rest of the breath completed by ventilator • Two types of assisted modes • Intermittent mandatory ventilation • Synchronised Intermittent Mandatory Ventilation
- 21. • Intermittent mandatoryventilation(IMV) • Gives partial ventilator support • Gradually increases patient’s WOB • Thereby strengthens respiratory muscles • Concurrently IMV breaths delivered to prevent fatigue • IMV breaths are delivered at set intervals • IMV breaths gradually reduced to CPAP, if patient improves
- 22. • Disadvantages • Breathstacking • Ventilator & Patient breaths at same time • Leads to high airway pressure • Breathing against the ETT – Burden for injured lungs
- 23. • Synchronised IntermittentMandatory Ventilation (SIMV) • Allows mechanical breaths to be given on patient demand • Breath stacking solved by inbuilt sensor, which • Synchronises patient’s spontaneous breaths to set rate • SIMV along with pressure or volume support is widely used • SIMV+PS / SIMV+VS
- 24. C. SPONTANEOUS MODES(CPAP / PSV / VS) Pressure Support Ventilation (PSV) • Used for patients with reliable and stable respiratory drive • To set PIP / PEEP / FiO2 • Setting VT / Ti / Rate is not required • Patient initiates breaths, F/B ventilator completes • Patient triggered / pressure limited / flow cycled • VT can be changed depending on compliance / resistance • If patient effort improves, pre-set PS may be reduced • Hence monitor RR / VTe / Patient effort
- 25. PSV – FLOWCHART
- 26. • CPAP • Elevationof baseline pressure during spontaneous breathing • PEEP is elevation of baseline pressure during mech. Ventilation • Open ups the collapsed alveoli
- 27. CPAP – FLOWCHART
- 28. HOW TO STARTA VENTILATOR ?
- 29. BEFORE CONNECTING TOVENTILATOR • System self check with circuit and test lung • Calculates the compressible volume • Thereby determines the VT • Pressure controlled ventilators are preferred in weight < 8kg • Ensure functioning humidifier / HME • Set an average PIP ( 10 – 12 cmH2O)
- 30. • Optimal PIPwill be determined by • Adequate chest rise • Good oxygenation • Hemodynamic stability • Blood gas PROVISION OF ALVEOLAR VENTILATION • Ventilator rate - According to age / Disease • VC • VT – 6-8 ml/kg • Further adjusted acc. to chest rise / air entry / bld. gases
- 31. • PC • PIP– 10 to 20 cmH2O / Above PEEP • Should produce adequate chest rise • VT will be generated from PIP – PEEP • I:E ratio - 1:2 • In obstructive disease • Keep prolonged expiratory time • Reduced rate
- 32. MAINTANANCE OF ADEQUATEOXYGENATION • FiO2 • In hypoxemic patients - Set initial FiO2 to 0.6 – 1.0 • Once improves reduce to non-toxic levels (< 0.5) • PEEP • 5 cmH2O or higher as needed • Optimal PEEP • Recruits collapsed alveoli / Maintains hemodynamics • Heterogeneous lung disease = 7-10 cmH2O • Diffuse lung disease = 10-15 cmH2O • Target SaO2 90% with FiO2 0.5 – 0.6
- 33. SETTING APPROPRIATE ALARMSETTINGS • Set alarm after final settings are made • Too narrow range - Frequent alarms / Ignored by care givers • Too wide range - Life threatening events will be missed • High pressure alarm • Set 8-10 cmH2O above the PIP • Once alarm rings • Inspiratory flow stopped / Gases vented out
- 34. • New onsethigh pressure alarm indicates • Worsening of lung mechanics • Increase in resistance / decrease in compliance • ETT issues – secretions / patient biting the tube • Low pressure alarms • Set 5-10 cmH2O below PIP • Common causes • Tube leaks / ventilator disconnections
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- 36. SETTINGS IN NORMALLUNG CNS PATHOLOGY (POOR RESPIRATORY DRIVE) • Ideal mode – SIMV – PC (Depends upon the patient’s effort) • PIP: 10-12 cmH2O • PEEP: 4-6 cmH2O • FiO2: 0.2-0.3 • PS: 10-12 cmH20 • I:E Ratio – 1:2
- 37. PARENCHYMAL LUNG DISEASES •ARDS / Pneumonia / Aspiration • Heterogeneous pathology • Atelectatic segment interspersed normal segments • CV > FRC / VQ Mismatch / Intrapulmonary shunting • Goals • Lung protective strategy • Reduce pressure / VT / Toxic oxygen levels
- 38. • Settings • LowVT - 6 ml/kg to maintain plateau pressure <30 cmH20 • Optimal PEEP, which gives • Saturation 86-90 % with FiO2 <0.6 • Optimal compliance with least over-inflation • Least hemodynamic instability
- 39. • How todetermine optimal PEEP ? • Gradually increase the PEEP with fixed Delta P • Monitor – Compliance (VTe) / O2 Saturation / Hemodynamics • After maximum recruitment (opening alveoli) • Oxygenation becomes static / Hemodynamics start worsens • Optimal PEEP achieved – Maintain PEEP slightly above this point • Same time risk of over inflation should be monitored • Ideal PEEP 7-10 in heterogeneous lung disease • 10-15 cmH2O in non pulmonary ARDS
- 40. AIRWAY DISEASES UPPER AIRWAYOBSTRUCTION • Epiglottitis / Croup / Post Extubation stridor / Burns • Use ETT size less than for age • Remove ETT when there is adequate peritubal leak LOWER AIRWAY OBSTRUCTION • Bronchiolitis • CPAP is better option with PEEP 6-10 cmH2O • If deteriorates after CPAP support • Go for mechanical ventilation
- 41. • Bronchial asthma •Goals • Relieve respiratory muscle fatigue • Reverse hypoxemia • Avoid worsening hyperinflation • Improve hemodynamic function • Settings • Use low tidal volumes (5-7 ml/kg) • To reduce plateau pressure <30-35cmH2O • PIP can be high • Accept high PCO2 / if Ph >7.2
- 42. • PRVC modeis appropriate • Set upper limit pressures / Reduced rate • Long exhalation time to prevent air trapping • Avoid reduction in inspiratory time < 0.5-0.6 sec • Set PEEP of two third of auto PEEP ( not >7-8 cmH2O) • Measured by expiration hold • Deep sedation / avoid suctions / pharmacotherapy • Early weaning and extubation is wise • While recovering tube may activate wheeze
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