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Basic ventilatory modes
This document discusses various modes of mechanical ventilation. It begins by covering advanced basics related to flow, time, pressure and volume control. It then describes the main categories of ventilation modes: mandatory modes like controlled mandatory ventilation which are time-triggered and time-cycled; triggered modes like CPAP and PSV which are patient-triggered; and hybrid modes like assist-control and SIMV which combine mandatory and spontaneous breaths. For each mode, it provides details on controls, targets, feedback and cycling. The document provides examples of pressure and volume graphs to illustrate different mode functions and interactions. It concludes with tables summarizing the key characteristics of different mandatory, triggered and hybrid ventilation modes.
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Basic ventilatory modes
- 1. BASIC MODES OF MECHANICAL VENTILATION MazenKherallah, MD, FCCP
- 2. POINTS OF DISCUSSIONS Advanced Basics: Flow and Time Limit and cycling Rise Time Volume vs Pressure Control Mandatory Modes of Ventilation Controlled Mandatory Ventilation (CMV or IPPV) Triggered Modes of Ventilation Continuous Positive Airway Pressure (CPAP) Pressure Support Ventilation (PSV) Hybrid Modes of Ventilation Assist Control Mode (A/C) Synchronized Intermittent Mandatory Ventilation (SIMV)
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- 5. ExpInsp RELATIONSHIP BETWEEN TIDAL VOLUME,INSPIRATORY TIME AND FLOW VT 1 Ti a VT 2 VT 3 Time Volume Flow= 30 L/min Flow= 15 L/min Flow= 37.5 L/min
- 6. ExpExpInspInspInsp RELATIONSHIP BETWEEN TIDAL VOLUME,INSPIRATORY TIME AND FLOW VT 1 Ti a Time Volume Ti b Ti c Flow= 30 L/min Flow= 20 L/min Flow= 60 L/min
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- 10. MANDATORY, SPONTANEOUS AND TRIGGEREDINSPIRATORY CYCLING M S Tsynch M M M MM M M S M Tsupp Tsupp Tsupp Tsupp Tsupp Tsupp S
- 11. VOLUME CONTROLLED INFLATION Time Flow Pressure Volume TT Tidal Volume
- 12. If compliance decreasesthe pressure increases to maintain the same Vt 11 22 33 44 55 66 SECSEC 11 22 33 44 55 66 PPawaw cmHcmH2200 5050 -20-20 120120 120120 SECSEC INSPINSP EXHEXH FlowFlow L/minL/min VOLUME CONTROL BREATHS Decreased Compliance
- 13. VOLUME CONTROL WITHEND- INSPIRATORY PAUSE Time Flow Pressure Volume T T Tidal Volume End Inspiratory Pause
- 14. PRESSURE CONTROLLED INFLATION Time Flow Pressure Volume TT Tidal Volume Rise Time Peak Inspiratory Flow
- 15. Inspiration Expiration 0 1 20 0 01 2 3 -3 0 20 0 21 20 0 0 1 2 3 -3 0 20 0 2 Inspiration Expiration Volume/Flow Control Pressure ControlVolume/Flow Control Pressure Control Time (s) Time (s) Paw Paw Pressure Volume Flow
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- 17. SPONTANEOUS BREATHING Time (sec)Time(sec) Flow (L/m) Pressure (cm H2O) Volume (mL)
- 18. CONTINUOUS POSITIVE AIRWAY PRESSURE (CPAP) Time(sec)Time (sec) Flow (L/m) Pressure (cm H2O) Volume (mL) CPAP Level
- 19. PRESSURE SUPPORT VENTILATION (PSV) Time(sec) Flow (L/m) Pressure (cm H2O) Volume (mL) Set PS Level Flow Cycling Better Efforts Longer Inspiration Patient Triggered, Flow Cycled, Pressure limited Mode
- 20. CPAP+PSV Time (sec)Time (sec) Flow (L/m) Pressure (cmH2O) Volume (mL) Set PS Level Flow Cycling Patient Triggered, Flow Cycled, Pressure limited Mode CPAP Level
- 21. TRIGGERED MODES OFVENTILATION PRESSURE SUPPORT VENTILATION Control Trigger Limit Target Cycle Pressure Patient Pressure Flow Patient Triggered Flow Cycled Ventilation
- 22. PRESSURE OR VOLUME-TARGETED VENTILATION Full to partial ventilatory support Augments the patients spontaneous VT Decreases the patient’s spontaneous respiratory rate Decreases patient WOB by overcoming the resistance of the artificial airway, vent circuit and demand valves Allows patient control of TI, Vm I, f and VT Set peak pressure Prevents respiratory muscle atrophy Facilitates weaning Improves patient comfort and reduces need for sedation May be applied in any mode that allows spontaneous breathing, e.g., VC-SIMV, PC-SIMV Requires consistent spontaneous ventilation Patients in stand-alone mode should have back-up ventilation VT variable and dependant on lung characteristics and synchrony Low exhaled VE Fatigue and tachypnea if PS level is set too low Advantages Disadvantages
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- 24. MANDATORY MODES OFVENTILATION CMV Control Trigger Limit Target Cycle Pressure Or Volume Time Time Time Triggered Time Cycled Ventilation
- 25. CONTROL MODE (PRESSURE-TARGETED VENTILATION) Flow (L/m) Pressure (cmH2O) Volume (mL) Time Triggered, Pressure Limited, Time Cycled Ventilation Time (sec) Time CyclingSet PC Level
- 26. CONTROL MODE (VOLUME-TARGETED VENTILATION) Flow (L/m) Pressure (cmH2O) Volume (mL) Time Triggered, Flow Limited, Volume Cycled Ventilation Time (sec) Preset VT Volume Cycling Time Cycling Dependent on CL & Raw
- 27. PRESSURE OR VOLUME-TARGETED VENTILATION Decreases the work of breathing (WOB) Helps maintain a normal PaCO2 Not able to assist the ventilator Advantages Disadvantages
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- 30. HYBRID MODES OFVENTILATION A/C Control Trigger Limit Target Cycle Pressure Or Volume Time Or Patient Time Time or PatientTriggered Time Cycled Ventilation
- 31. ASSISTED MODE (VOLUME-TARGETED VENTILATION) Flow (L/m) Pressure (cmH2O) Volume (mL) Patient Triggered, Flow limited, Volume Cycled Ventilation Time (sec) Preset peak Flow Time Cycling
- 32. ASSISTED MODE (PRESSURE-TARGETED VENTILATION) Flow (L/m) Pressure (cmH2O) Volume (mL) Patient Triggered, Pressure Limited, Time Cycled Ventilation Time (sec) Time CyclingSet PC Level
- 33. PRESSURE OR VOLUME-TARGETED VENTILATION Decreases the work of breathing (WOB) Allows patients to regulate respiratory rate Helps maintain a normal PaCO2 Alveolar hyperventilation Advantages Disadvantages
- 34. HYBRID MODES OFVENTILATION SIMV/PS Breath Type Control Trigger Limit Cycle Mandatory Pressure Or Volume Time Or Patient Time Spontaneous Pressure Patient Pressure Flow
- 35. SIMV (VOLUME TARGETED VENTILATION) Flow (L/m) Pressure (cmH2O) Volume (mL) Spontaneous Breaths M M M Time (sec)
- 36. SIMV+PS (VOLUME TARGETED VENTILATION) Flow (L/m) Pressure (cmH2O) Volume (mL) M TsuppTsynch Set PS Level Flow-cycled Time (sec)
- 37. SIMV + PS (PRESSURE-TARGETEDVENTILATION) Flow (L/m) Pressure (cm H2O) Volume (mL) Tsupp Tsynch Time Cycled Flow-cycled Tsynch Set PC Level Set PS Level Time (sec)
- 38. HYBRID MODE VENTILATION: SUPPRESSION Time(sec)Time (sec) M Tsupp MM Tsupp M M Tsupp Tsupp
- 39. HYBRID MODE VENTILATION: SYNCHRONIZATION (SIMV+PSV) Time(sec)Time (sec) Flow (L/m) Pressure (cm H2O) Cycles Triggered window for supported breaths Triggered window for synchronized breaths Mandatory Cycle Time M Tsupp Tsynch M Tsynch Tsupp
- 40. SIMV Maintains respiratory musclestrength by avoiding muscle atrophy Decreases mean airway pressure Facilitates ventilator discontinuation – “weaning”! When used for weaning, may be done too quickly and cause muscle fatigue Mechanical rate and spontaneous rate may asynchronous causing “stacking” May cause barotrauma or volutrauma Advantages Disadvantages
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- 42. Mandatory Modes ofVentilations Mandatory breaths Inspiratory cycling Time Time Time Time Control Volume Volume Volume (Pressure) Target/Limit - Pressure-limited Volume-targeted Feeadback - - Intra-breath Inter-breath Expiratory cycling Time Time Time Time Triggered Breaths Types None None None None Supported Breaths Control - - - - Target - - - - Feedback - - - - Expiratory Cycling - - - - Spontaneous Breaths During mandatory inspiration Not accommodated Not accommodated Not accommodated Accommodated Otherwise Not accommodated Accommodated Not accommodated Accommodated Synonyms IPPV (Draeger) Controlled Mandatory Ventilation Intermittent Mandatory Ventilation IPPV (Draeger): trigger off, autoflow off IPPV (Draeger): trigger off, autoflow on
- 43. Triggered Modes ofVentilations Mandatory breaths Inspiratory cycling - - - Control - - - Target/Limit - - - Feeadback - - - Expiratory cycling - - - Triggered Breaths Types Supported breaths Supported breaths Supported breaths Supported Breaths Control Pressure (Pressure) (Pressure) Target -- Volume-targeted Flow and Volume Feedback -- Inter-breath Intra-breath Expiratory Cycling Flow Flow Flow Spontaneous Breaths During mandatory inspiration - - - Otherwise - - - Synonyms Assisted Spontaneus Breathing (Draeger) Spontaneous Mode (Hamilton, Puritan Bennet) Pressure Support (Maquet Pressure Support Ventilation (Viasys) CPAP (Respironics) Volume Support (Maquet, Puritan- Bennett) Propotional Assist Ventilation, Proportional Pressure Suport (Draeger) Propotional Assist Ventilation Plus (Puritan-Bennet)
- 44. Hybrid Mode: AssistControl Mandatory breaths Inspiratory cycling Time or trigger Time or trigger Time or trigger Control Volume Pressure (Pressure) Target/Limit - - Volume-targeted Feeadback - - Inter-breath Expiratory cycling Time Time Time Triggered Breaths Types Mandatory pattern Mandatory pattern Mandatory pattern Supported Breaths Control - - - Target - - - Feedback - - - Expiratory Cycling - - - Spontaneous Breaths During mandatory inspiration Not accommodated Accommodated Accommodated Otherwise - - - Synonyms IPPVASSIST (Draeger) Synchronized cCntrolled Mandatory Ventilation (Hamilton) Volume Control (Maquet) VCV-A/C (Puritan-Bennett, Respironics) Volume A/C (Viasys) BIPAPASSIST (Draeger) P-CMV (Hamilton) Pressure Control (Maquet) PCV-A/C (Puritan- Bennett, Respironics) Pressure A/C (Viasys) Adaptive Pressure Ventilation CMV PRVC (Maquet) VC+A/C (Puritan- Bennet) PRVC A/C (Viasys) IPPV Assist Autoflow (Draeger)
- 45. Hybrid Mode: SynchronizedIntermittent Mandatory Ventilation Mandatory breaths Inspiratory cycling Time or trigger Time or trigger Time or trigger Control Volume Pressure (Pressure) Target/Limit - - Volume-targeted Feeadback - - Inter-breath Expiratory cycling Time Time Time Triggered Breaths Types Mandatory and supported pattern Mandatory and supported pattern Mandatory and supported pattern Supported Breaths Control Pressure Pressure Pressure Target - - - Feedback - - - Expiratory Cycling Flow Flow Flow Spontaneous Breaths During mandatory inspiration Not accommodated Accommodated Accommodated Otherwise Only if support is off Only if support is off Only if support is off Synonyms SIMV (Draeger, Hamilton) SIMV (VC)+PS (Maquet) VCV-SIMV (Puritan- Bennett, Respironics) Volume SIMV (Viasys) P-SIMV (Hamilton) SIMV(PC)+PS (Maquet) PCV-SIMV (Puritan- Bennett, Respironics) Pressure SIMV (Viasys) SIMV+Autoflow Adaptive Pressure Ventilation SIMV (Hamilton) SIMV (PRVC)+PS (Puritan-Bennett) PRVC SIMV (Viasys)
- 46. Hybrid Mode: Bi-LevelVentilatio Mandatory breaths Inspiratory cycling Time or trigger Time or trigger Time or trigger Time or trigger Control Pressure Pressure Pressure Pressure Target/Limit - - - - Feeadback - - - - Expiratory cycling Time or trigger Time or trigger Time or trigger Time or trigger Triggered Breaths Interaction Mandatory and supported Mandatory pattern and supported Mandatory and supported Mandatory and supported Supported Breaths Control Pressure Pressure Pressure Pressure Target - - - - Feedback - - - - Expiratory Cycling Flow Flow Flow Flow Spontaneous Breaths During mandatory inspiration Accommodated Trigers suuport to PEEP+Psupport If this>Phigh (Hamilton DuoPAP) Plow+Psupport If this>Phigh (Hamilton APRV) PEEPL+PsuppIf this>PEEPH (Puritan- Bennett) Triggers support to PRES HIGH + PSV if Thigh PSV is activated Tigger support to PSV above PHigh Otherwise Triggers support Triggers support to PEEP+Psupport (Hamilton) DuoPAP) Plow+Psupport (Hamilton APRV) PEEPL+Psupp (Puritan-Bennett) Triggers support to PREDSLOW=PSV Triggers support to PSV above PEEP Synonyms BIPAP (Draeger) DuoPAP/APRV (Hamilton) BiLevel (Puritan-Bennet) APRV/Bi-phasic (Viasys) Bi-vent (Maquet)
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Editor's Notes
- #13 How do you know the problem is with the patient? Look at your flow curve.
- #16 If follows from the equation of motion that the ventilator can control either the left side of the equation (ie, airway pressure) or the right side (ie, volume and flow). These curves illustrate the two basic approaches to ventilator control. If the ventilator controls flow, it controls volume indirectly (by definition) and vice versa. Usually, inspiratory flow is held constant during inspiration, causing volume and pressure to rise linearly. Inspiration ends (cycles off) when a preset tidal volume is met. In contrast, with pressure control ventilation, airway pressure may be held constant during inspiration. This causes inspiratory flow to decay exponentially from its peak value towards zero as volume rises exponentially. Inspiration usually ends after a preset inspiratory time or (in the case of pressure support) after a preset inspiratory flow threshold has been crossed. If inspiratory time is long enough (usually about 5 time constants) lung pressure will equilibrate with airway pressure and inspiratory flow will cease. You will note that for passive exhalation is exponential. That mean expiratory time must be at least 5 time constants long to exhale more that 99% of the tidal volume. As expiratory time becomes shorter than 5 time constants, gas trapping (ie, autoPEEP) occurs.