Modes of Ventilation

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MODES OF VENTILATION Dr Deepa C MD

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MODE A pattern in which breaths are delivered to a patient and it is characterized by a group of different ventilator variables set in varying combinations and fashions SET VARIABLES Respiratory rate Tidal volume or Pressure Inspiratory flow Inspiratory time/pause I:E ratio PEEP Inspiratory trigger

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A. TRIGGER VARIABLE What initiates the breath.. B . LIMIT VARIABLE What governs the gas delivery.. C . CYCLE VARIABLE What terminates the breath.. BASIC PHASE VARIABLES A B C

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TRIGGER – time, flow, pressure LIMIT – pressure, flow, volume CYCLE – flow, time, volume, pressure Each breath/mode can be categorised by these three variables

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Controlled Mandatory Ventilation (CMV) Intermittent Mandatory Ventilation (IMV) Pressure/Volume Control Ventilation (PCV) Assist Control (AC) – Pressure/Volume Bilevel Positive Airway Pressure (BiPAP) Airway Pressure Release Ventilation(APRV) Synchronized Intermittent Mandatory Ventilation (SIMV) Pressure Support Ventilation (PSV) Continuous Positive Airway Pressure (CPAP) Mandatory Minute Ventilation (MMV) Adaptive Support Ventilation (ASV) Proportional Assist Ventilation (PAV) Volume Assured Pressure Support (VAPS) Pressure Regulated Volume Control (PRVC) Volume Ventilation Plus (VV+) Inverse Ratio Ventilation (IRV) Neurally Adjusted Ventilatory Assist (NAVA)

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Pressure modes Volume modes

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Mandatory modes of ventilation CONTROLLED MANDATORY VENTILATION (CMV OR IPPV) INTERMITTENT MANDATORY VENTILATION (IMV) Triggered (Spontaneous) 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) BILEVEL POSITIVE AIRWAY PRESSURE VENTILATION (BIPAP)

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CONTROLLED MANDATORY VENTILATION (CMV)

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Delivers the preset tidal volume at a time triggered respiratory rate Ventilator controls both the tidal volume and respiratory rate of the patient Should only be used with a combination of sedatives and neuromuscular blockers CMV

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ASSIST/CONTROL MODE

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Mandatory mechanical breath either - Patient triggered - spontaneous inspiratory efforts(assist) - Time triggered - preset respiratory rate (control) Pt initiates all breaths, but ventilator cycles in at initiation to give a preset tidal volume Pt controls rate but always receives a full machine breath ASSIST/CONTROL MODE ASSIST MODE

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INTERMITTENT MANDATORY VENTILATION

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INTERMITTENT MANDATORY VENTILATION – IMV Periodic volume or pressure targeted breaths occur at set interval (time triggering) Between mandatory breaths, the patient breathes spontaneously at any desired baseline pressure without receiving a mandatory breath

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Different from Control : pt can initiate own breaths Different from Assist : spontaneous breaths are not supported by machine Ventilator always delivers breath, even if pt is exhaling Breath stacking is the complication INTERMITTENT MANDATORY VENTILATION

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SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION (SIMV)

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SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION (SIMV) Ventilator delivers control breath (mandatory) to the patient at or near the time of spontaneous breath- TIME - TRIGGERED Mandatory breaths are synchronised with the patients spontaneous breathing effort to avoid breath stacking  PATIENT - TRIGGERED

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SYNCHRONIZATION WINDOW or TRIGGER WINDOW Time interval just prior to the scheduled delivery of the time-triggered mandatory breath during which ventilator is responsive to the patient’s spontaneous inspiratory efforts. 0.5 sec 0.5 sec

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If the patient fails to initiate ventilation within a predetermined interval, the ventilator provides a mandatory breath at the end of the time period

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IMV & SIMV

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IMV & SIMV

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PRESSURE SUPPORT VENTILATION Patient triggered ; Pressure limited ; Flow cycled Inspiration initiated by – Negative pressure / flow change (patient) Expiration initiated by – Decreasing flow (patient)

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PRESSURE SUPPORT VENTILATION (PSV) Patient determines RR, VE, inspiratory time Purely spontaneous mode

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PSV

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Flow cycling occurs when the ventilator detects a decreasing flow, which represents the end of inspiration This point is a percentage of peak flow measured during inspiration Bear 1000 – 25% of peak flow Servo 300 – 5% of peak flow No single flow-cycle percent is right for all patients Flow Cycling During PSV

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PSV during SIMV

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CPAP CPAP + PSV

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Helpful for improving oxygenation in patients with refractory hypoxemia and a low FRC Adjusted to provide the best oxygenation with the lowest positive pressure and the lowest FiO₂

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Pressure control mode Volume control mode Pressure assist/control mode Volume assist/control mode IPPV or CMV mode SIMV – pressure controlled SIMV – volume controlled SIMV – PC + PSV SIMV – VC + PSV CPAP +/ PSV

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Synchronized Transitions Spontaneous Breaths Spontaneous Breaths P aw cmH 2 0 60 -20 1 2 3 4 5 6 7 BIPAP Two levels of pressure and hi/low are set At either pressure level the patient can breathe spontaneously

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At either pressure level the patient can breathe spontaneously Spontaneous breaths may be supported by PS

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Spontaneous breaths may be supported by PS If PS is set higher than PEEP H , PS supports spontaneous breath at upper pressure

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P aw cmH 2 0 60 -20 1 2 3 4 5 6 7 8 Spontaneous Breaths Releases AIRWAY PRESSURE RELEASE VENTILATION (APRV) a bi-level form of ventilation with sudden short releases in pressure to rapidly reduce FRC and allow for ventilation

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Provides two levels of CPAP and allows spontaneous breathing at both levels when spontaneous effort is present Both pressure levels are time triggered and time cycled Inverse I:E ratio inverse I:E ratio

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Allows spontaneously breathing patients to breathe at a high CPAP level, but drops briefly (approximately 1 second) and periodically to allow CPAP level for extra CO₂ elimination (airway pressure release) Mandatory breaths occur when the pressure limit rises from the lower CPAP to the higher CPAP level

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Allows inverse ratio ventilation (IRV) with or without spontaneous breathing (less need for sedation or paralysis) Improves patient-ventilator synchrony if spontaneous breathing is present Improves mean airway pressure Improves oxygenation by stabilizing collapsed alveoli Allows patients to breath spontaneously while continuing lung recruitment Lowers PIP ADVANTAGES

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Variable VT Could be harmful to patients with high expiratory resistance (i.e., COPD or asthma) Auto-PEEP is usually present Caution should be used with hemodynamically unstable patients Asynchrony can occur if spontaneous breaths are out of sync with release time DISADVANTAGES AND RISKS

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PATIENT COMFORT LEVEL 0 10 Controlled Mechanical Ventilation Assist Control Ventilation Synchronized Intermittent Mandatory Ventilation Bilevel Positive Airway Pressure Ventilation Pressure Support Ventilation Spontaneous Ventilation

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Type Manufacturer; ventilator Name Dual control within a breath VIASYS Healthcare; Bird 8400Sti and Tbird VIASYS Healthcare; Bear 1000 Volume-assured pressure support (VAPS) Pressure augmentation Dual control breath to breath: Pressure-limited flow-cycled ventilation Siemens; servo 300 Cardiopulmonary corporation; Venturi Volume support Variable pressure support Dual control breath to breath: Pressure-limited time-cycled ventilation Siemens; servo 300 Hamilton; Galileo Drager ; Evita 4 Cardiopulm corpn ; Venturi Datex-Ohmeda ; Engstrom Pressure-regulated volume control (PRVC) Adaptive pressure ventilation Autoflow Variable pressure control PCV – Volume Guaranteed Dual control breath to breath: SIMV Hamilton; Galileo Adaptive support ventilation (ASV) Dual-Controlled Modes New Modes of Ventilation

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Adaptive Support Ventilation (ASV) Proportional Assist Ventilation (PAV) Volume Assured Pressure Support (VAPS) Pressure Regulated Volume Control (PRVC) Inverse Ratio Ventilation (IRV) Neurally Adjusted Ventilatory Assist (NAVA)

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EXERCISES

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P aw cmH 2 0 60 -20 1 2 3 4 5 6 7

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P aw cmH 2 0 60 -20 1 2 3 4 5 6 7 8

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Thank you