Review of Mechanical Ventilation In The Name of GOD Review of Mechanical Ventilation Mohsen Savaie MD, CCM Anesthesiologist, Intensivist Assistant Professor

Mechanical Ventilation Support Gas Exchange Manage Work of Breathing Ventilation goals are Avoid Lung Injury 2/28

Abbreviations VT : Volume of each respiration FiO2 : Fraction of inspiratory O2 (%) RR : Respiratory Rate Ti : Inspiratory Time MV : Volume that is inhaled or exhaled per min Te : Expiratory Time PEEP : Positive End-Expiratory Pressure I:E Ratio : Ti/Te CPAP : Continuous Positive Airway Pressure PIP : Peak Inspiratory Pressure IPPV : Intermittent Positive Pressure Ventilation Flow : Inspiratory Flow Rate (Lit/Min) Trigger : Factor that Start Inspiration (T, P, Flow) 3/28

Pressure Graph of Mechanical Ventilation Peak Pressure Plattue Pressure PEEP t t 4/28

Timing of Mechanical Ventilation Respiratory cycle time Inspiratory time Expiratory time Inspiratory pause time Volume The time from the end of one inspiration to the beginning of the next is called the expiratory time Inspiratory flow time Time 5/28

Timing of Mechanical Ventilation 3 secs 2 secs 1 sec  Respiratory rate without changing Inspiratory time or inspiratory flow 0.5 s Flow Volume If the respiratory rate is increased the respiratory cycle shortens. If the inspiratory time is kept constant this will result in a change in I:E ratio. As the inspiratory flow has not been changed the inspiratory flow and pause times have not changed. Set: RR, Insp Time, Flow rate Time 6/28

Timing of Mechanical Ventilation 3 secs 1 sec 2 sec 0.5 s Volume So we also need to decrease the set inspiratory time Time Set: RR, Insp Time, Flow rate 7/28

Modes of Mechanical Ventilation Volume Controlled (A)CMV : (Assisted) Controlled Mechanical Ventilation (S)IMV : (Synchronized) Intermittent Mandatory Ventilation MMV : Mandatory Minute Ventilation Pressure Controlled PCV : Pressure Controlled Ventilation (P) SIMV : Pressure SIMV Spontaneous PSV (ASB) : Pressure Support Ventilation (Assisted Spontaneous Breathing) Other Modes APRV, PRVC, BIPAP, NAVA, Smart, NIV, VAPS, ASV, PAV, HFPPV, HFJV, HFOV 8/28

Control Mandatory Ventilation (CMV) P Tidal Volume Respiratory Rate Flow : 40-60 lit/min Peak Pressure t 9/28

Assist Control Mechanical Ventilation (ACMV) Volume Control (Maquet) IPPV (Drager) S-CMV (Hamilton) P Tidal Volume Respiratory Rate Trigger : 1-5 Flow : 40-60 lit/min Peak Pressure t 10/28

SIMV Mandatory breath Mandatory breath Pressure support breath Pressure PEEP Time Flow Time Trig Trig Trig Trig Setting : TV, RR, Trigger : 1-5, Flow : 40-60 lit/min, Peak Pressure, Pressure Support, PEEP, T insp (I/E) 11/28

PRVC (Pressure Regulated Volume Control) (Auto flow Ventilation) PRVC (Pressure Regulated Volume Control) P Deliver a set TV at the minimum pressure level necessary, according to the airways/lung/thorax mechanics. Constant pressure during the entire inspiration. 60 t P aw cmH 2 SEC 1 2 3 4 5 6 -20 120 12/28

Pressure Control Ventilation (PCV) Fio2 Peak Insp Pressure Respiratory Rate PEEP PC above PEEP Pressure PEEP Time Flow Time A constant pressure is applied to the airway during inspiration. This results in a high initial flow which falls to zero or close to zero by the end of inspiration. As a result of this flow pattern oxygenation may be improved. Volume 13/28 Time

Note that the pressure is applied to the proximal end of the ETT and is not the pressure in the alveoli as some of the pressure will be dissipated across the ETT and the major airways. 14/28

Pressure Support Ventilation (PSV) =Assisted Spont Breathing (ASB) Fio2 Trigger : 1-5 Pressure Support 6-20 PEEP VSV ? Pressure PS above PEEP PEEP Set % of max inspiratory flow Constant preset airway pressure supplied during inspiration. The patient is able to able to control the respiratory rate and the inspiratory time. By varying respiratory effort he is also able, to some extent, to control the tidal volume. As a result the tidal volume, inspiratory flow and inspiratory time may all vary from breath to breath [Click on slide now to zoom in on flow waveform] Cycling from inspiration to expiration occurs when inspiratory flow decreases to a set percentage of the maximum inspiratory flow. This percentage is set using the inspiratory cycle-off control Flow Volume 15/28

BIPAP Bi-Level Positive Airway Pressure Allows Spontaneous Breathing during the Mandatory Breaths Spontaneous Breathing BIPAP The standard Mandatory Ventilation modes used in every ICU are IPPV and PCV (very seldom). Both Ventilation Modes guarantee the Patients Ventilation: IPPV, guarantees a Minute Volume, PCV guarantees that the pressure will never pass a previously set Pmax level. But both modes interact poorly with the patient, as you can see in the drawings. The Ventilator will start fighting the patient, because the vent is only able to do what it was instructed to do, give mandatory strokes one after the other regardless of the patients efforts. Other events like coughing will also interrupt ventilation, creating high airway pressures. The consequences are well known: alarms and sedation of the patient. So the patient won't suffer anymore from an inconsiderate ventilator that does not allow him to breath spontaneneously (by the way the patient will be very quiet and unable to do anything). The patient's spontaneous breathing is surpressed... (The blue part of our lung drawing is inactive, there is no creation of negative pressures by expansion of the diaphragm of the lung, only the red part the positive pressure generated by the mandatory strokes is still there) PCV 16/28

BIPAP Bi-Level Positive Airway Pressure Pinsp Rise Time The time it takes to achieve Pinsp PEEP The standard Mandatory Ventilation modes used in every ICU are IPPV and PCV (very seldom). Both Ventilation Modes guarantee the Patients Ventilation: IPPV, guarantees a Minute Volume, PCV guarantees that the pressure will never pass a previously set Pmax level. But both modes interact poorly with the patient, as you can see in the drawings. The Ventilator will start fighting the patient, because the vent is only able to do what it was instructed to do, give mandatory strokes one after the other regardless of the patients efforts. Other events like coughing will also interrupt ventilation, creating high airway pressures. The consequences are well known: alarms and sedation of the patient. So the patient won't suffer anymore from an inconsiderate ventilator that does not allow him to breath spontaneneously (by the way the patient will be very quiet and unable to do anything). The patient's spontaneous breathing is surpressed... (The blue part of our lung drawing is inactive, there is no creation of negative pressures by expansion of the diaphragm of the lung, only the red part the positive pressure generated by the mandatory strokes is still there) Ti Ti - Inspiratory phase lungs are maintained distended at set Pinsp Te Te – Expiratory phase Lungs are prevented from complete collapse by set PEEP 17/28

BIPAP and Synchronisation with Spontaneous Breathing BIPAP Bi-Level Positive Airway Pressure BIPAP and Synchronisation with Spontaneous Breathing P Exp. Trigger t Insp. Trigger The standard Mandatory Ventilation modes used in every ICU are IPPV and PCV (very seldom). Both Ventilation Modes guarantee the Patients Ventilation: IPPV, guarantees a Minute Volume, PCV guarantees that the pressure will never pass a previously set Pmax level. But both modes interact poorly with the patient, as you can see in the drawings. The Ventilator will start fighting the patient, because the vent is only able to do what it was instructed to do, give mandatory strokes one after the other regardless of the patients efforts. Other events like coughing will also interrupt ventilation, creating high airway pressures. The consequences are well known: alarms and sedation of the patient. So the patient won't suffer anymore from an inconsiderate ventilator that does not allow him to breath spontaneneously (by the way the patient will be very quiet and unable to do anything). The patient's spontaneous breathing is surpressed... (The blue part of our lung drawing is inactive, there is no creation of negative pressures by expansion of the diaphragm of the lung, only the red part the positive pressure generated by the mandatory strokes is still there) Exp.Trig. Window Insp.Trig. Window Dual PAP Ventilation (BIPAP+PS) 18/28

Oxygenation Failure Ventilatory Failure Increase PEEP and Pinsp Increase delta Pinsp – Peep ( Increase TV) Change Tinsp or RR Increase frequency (RR) The Evita will always be synchronised with the Patient's Breathing so that there are less mismatches. The Ventilator always waits to give the mandatory stroke the moment when the patient is making and inspiratory effort or no effort at all (Flow is zero). For the exhalation the vent also waits until the patient is exhaling or there is no further flow at all. If this is not case, i.e. the patient is exhaling when there should the inspiratory phase, Evita waits until the patient has finished her/his exhalation, and then gives the mandatory stroke. (For the exhalation phase it is the same as inspiration but the other way around). So Evita has smooth synchronization with the patient, and the flexible trigger window adapts the valve's behaviour to the patient's requirements, avoiding mismatches. 19/28

Airway Pressure Release Ventilation (APRV) Continuous positive airway pressure (Inspiration) with regular, brief, intermittent releases in airway pressure (Expiration). Positive pressure drives oxygenation. The timed releases of pressure aid in CO2 clearance. It is the primary mode of choice for patients with ARDS. 20/28

Airway Pressure Release Ventilation (APRV) In diseased lung they become important 21/28

APRV Setting 22/28 P High : = Plattue Pressure P Low (Release) : = 0 T High : = 4 -15 seconds (0.5-2 each times) T Low : = 0.5–0.8 seconds Frequency should always be less than 12 Patient must be encouraged to breathe spontaneously during APRV 22/28

Adaptive Support Ventilation (ASV) Very easy mode presented by Hamilton corporation. You set only the patients weight or height and percent of calculated minute volume that must be delivered by machine, then lventilator automatically set best RR and TV to provide minute ventilation. 23/28

Volume vs Pressure Modes ? Volume Modes TV is constant Inspiratory pressure varies Inspiratory flow is constant Pressure Modes TV varies Inspiratory pressure is constant Inspiratory flow varies 24/28

Which Mode is Better ? Apnoeic patient : Control of minute ventilation important → → Volume Assist Control Control of peak pressure important → → Pressure Assist Control Intermittent spontaneous breaths → → SIMV Regular spontaneous breaths and improving condition → → PS 25/28

Problem Solving Low O2 Saturation High PCo2 Other Problems ? 26/28 Increase FiO2 Check Patient and Circuit Increase PEEP Increase Inspiration Time High PCo2 Check Patient and Circuit Increase TV Increase RR Other Problems ? 26/28

Clinical Pearls Ventilator kills your patient unless you prevent it from doing so! The best mode is the most suitable and comfortable mode for patients (not for you). Patient fight with your mistakes not with the ventilator! Calm your patient with opioids & Hypnotics, not relaxants. ‌Nebulizers & Humidifiers are your guardian angels. Use lab. tests to conform diagnosis not to diagnose. Plan and order nutrition professionally. Plan for and manage the stress of ETT & IPPV. 27/28

Thanks for your attention