1、Absolute Basics of Mechanical Ventilation,Dr David HowellConsultant in Intensive Care, Respiratory and Acute Medicine,Aims and Objectives,Define Positive Pressure Mechanical VentilationExplain Continuous Mandatory Ventilation (CMV)Explain Synchronised Mandatory Ventilation (SIMV)Explain Pressure Sup
2、port Ventilation (PSV)Explain Basic Ventilator SettingsNot a Talk on Physiology of Mechanical Ventilation,What you Encounter,Positive Pressure Mechanical Ventilator,Lots of Monitors and Knobs to Turn,Some are More Complicated than Others,Weaning Screen/standard protocol,Long Term Weaning/Individual
3、plan,Weaning,Non-Invasive Ventilation,Non-invasive support,Tracheostomy,Intubation,Extubation Decannulation,Standard Ventilation,Advanced Ventilation,Invasive support,Optimising the Pt for weaning,Prone Position,Nitric Oxide,Suctioning,Humidification,NIV is defined as ventilatory support provided vi
4、a a tight fitting mask or similar interface as opposed to invasive support, which is provided via a laryngeal mask, endotracheal tube or tracheostomy tube.Tight fitting masks deliver can CPAP, BIPAP or NIV via the mechanical ventilator.,NIV vs. Invasive Mechanical Ventilation,The work of breathing u
5、sually accounts for 5% of oxygen consumption (V02). In the critically ill patient this may rise to 30%.Invasive mechanical ventilation eliminates the metabolic cost of breathing.,Indications for Mechanical Ventilation,Inadequate oxygenation (not corrected by supplemental O2 by mask).Inadequate venti
6、lation (increased PaCO2).Retention of pulmonary secretions (bronchial toilet). Airway protection (obtunded patient, depressed gag reflex).,Indications for Mechanical Ventilation,Intubation,1 Airway: oral Guedel airway to lift tongue off posterior pharynx to facilitate mask ventilation during pre-int
7、ubation phase. 2 Liquids: stop feed and aspirate ng tube. 3 Suction: extremely important to avoid pulmonary aspiration. 4 Oxygen: preoxygenate patient and ensure a source of O2 with a delivery mechanism (ambu-bag and mask) is available.,Bare Essentials for Intubation ALSOBLEED,5 Bougie: to facilitat
8、e tube insertion in more difficult airway. 6 Laryngoscope: have a long and short blade available. 7 Endotracheal tube: for average adult, cuffed oral endotracheal tube 7.0 for women and 8.0 for men. 8 End tidal CO2: to confirm correct position of tube. 9 Drugs: an induction agent, muscle relaxant, s
9、edative are usually required.,Bare Essentials for Intubation ALSOBLEED,Principles of Mechanical Ventilation,ET tube Ventilator Tubing Major Airways,Alveoli,PEEP,Positive pressure ventilation involves delivering a mechanically generated breath to get O2 in and CO2 out.Gas is pumped in during inspirat
10、ion (Ti) and the patient passively expires during expiration (Te).The sum of Ti and Te is the respiratory cycle or breath.,Principles of Mechanical Ventilation,Flow,Pressure,Principles of Mechanical Ventilation,Ti,Te,Ti,Te,In the fully ventilated patient, positive pressure breaths are delivered eith
11、er as preset volume or pressure continuous mandatory breaths (CMV) breaths.The mechanical ventilator triggers the breath and switches from inspiration to expiration when the preset volume, pressure (or time) is achieved/delivered.During CMV the patient takes no spontaneous breaths.CMV is usually use
12、d in theatre and in very unwell ICU patients.,Principles of Mechanical Ventilation,Principles of Mechanical Ventilation,Volume control,Tidal volume is presetUsually 500 mlsAirway Pressure is Variable,Pressure control,Inspiratory Pressure is presetUsually 15-20 cm H20Tidal Volume is Variable,Mandator
13、y breaths are delivered during inspiration, to generate a tidal volume (Vt), at a set rate (f), the quotient of which is the minute volume (MV). Minute Volume = Tidal Volume x frequencyIn volume control ventilation, an inspiratory flow rate is also set.The ratio of the time spent in inspiration:expi
14、ration (I:E ratio) is usually 1:2.,Principles of Mechanical Ventilation,Flow,Pressure,Ti,Te,Ti,Te,Principles of Mechanical Ventilation,Volume Control Breath,Pressure Control Breath,Mechanically ventilated patients usually receive positive end-expiratory pressure (PEEP), to overcome the loss of physi
15、ological PEEP provided by the larynx and vocal cords.PEEP is delivered throughout the respiratory cycle and is synonymous to CPAP, but in the intubated patient.Standard PEEP setting is 5 cm H20.Sedation is often required to prevent ventilator-patient asynchrony.,Principles of Mechanical Ventilation,
16、Basic Settings on the Ventilator,Tidal VolumePressure controlled breath (15-20 cm H20)Volume controlled breath (500 mls)Rate (frequency) (10-12 breaths/minute)Positive end expiratory pressure (PEEP) (5 cm H20)FiO2 (0.21-1)Peak airway pressure (PAP),Principles of Mechanical Ventilation,Why is the pea
17、k airway pressure (PAP) important?Ventilator Induced Lung Injury (VILI).Mechanical ventilation is injurious to the lung.Aim PAP 35 cm H20.,Flow,Pressure,Ti,Te,Ti,Te,Principles of Mechanical Ventilation,Volume Breath,Pressure Breath,35 cm H20,Pneumothorax,Principles of Mechanical Ventilation,Dont for
18、get that the peak airway pressure will also include the PEEP that is added,Once stabilised on CMV, the level of ventilatory support may be reduced (weaning).This can be done by providing a mixture of synchronised intermittent mandatory breaths (SIMV) and spontaneously triggered pressure supported br
19、eaths (PSV).,Principles of Mechanical Ventilation,Ventilator assisted breaths are synchronized with the patients breathing to prevent the possibility of a mechanical breath on top of a spontaneous breath.However, the patients attempt at a breath would not be enough to generate an adequate tidal volu
20、me on its own, hence the term pressure support.,Principles of Mechanical Ventilation,Pressure support is only delivered during inspiration and the patients attempt at breathing triggers the breath rather than the ventilator.A standard level of pressure support delivered in inspiration is 20 cm H20,P
21、rinciples of Mechanical Ventilation,SIMV and Pressure Support Ventilation,Ventilator,Patient,As patients improve, mandatory breaths are withdrawn and receive pressure-supported breaths alone.Finally, as tidal volumes improve, the level of pressure support is reduced and then withdrawn so patients br
22、eathe spontaneously with PEEP alone.Extubation can now be contemplated. Spontaneous modes of breathing should always be encouraged as respiratory muscle function is maintained,Principles of Mechanical Ventilation,Pressure Support Ventilation,Patient,Patient,To succeed, the initiating cause of respir
23、atory failure, sepsis, fluid and electrolyte imbalance and nutritional status should all be treated or optimised. Failure to wean is associated with:Ongoing high V02. Muscle fatigue.Inadequate drive. Inadequate cardiac reserve.,Successful Weaning and Extubation,Weaning screens exist to help select p
24、atients for extubation. In the unsupported patient, if f/Vt is 100, extubation is likely to be unsuccessful.There is some evidence to support extubation to NIV, particularly in patients with COPD.,Successful Weaning and Extubation,Continuous Mandatory Ventilation (CMV)Pressure control Volume control
25、No spontaneous breathingVentilator triggers breathSynchronised intermittent mandatory ventilation (SIMV)/Pressure Support Ventilation (PSV)Pressure control (SIMV)Volume control (SIMV)Some spontaneous breathing is allowed (PSV)Mixture of ventilator and patient triggered breaths,Basic Ventilatory Mode
26、s: Summary,Pressure Support Ventilation (PSV) Spontaneous breathing with inspiratory support All patient triggered breathsPEEP/CPAP (5 cm H20) Entirely spontaneous breathing Consider extubation,Basic Ventilatory Modes: Summary,Basic Ventilatory Modes: Summary,Mode O2 Respiratory Rate Inspiratory Act
27、ion Inspiratory Time Expiratory Action,Standard Ventilator Settings MORITE,Mode CMV, Volume Control O2 0.5 (50% 02) Respiratory Rate 12/minute Inspiratory Action Set Vt at 500 mls Inspiratory Time Set I:E ratio 1:2 Expiratory Action Set PEEP at 5 cm H20 Be Aware PAP 35 cm H2O,Standard Ventilator Settings MORITE,Patient Requiring Basic Invasive Mechanical Ventilation,Spontaneously Ventilating Patient Failing Conventional Therapy,Escalation,BIPAP,Patient Position,Humidification,CMV (VCV or PCV),PSV,PEEP/CPAP,NIV on ICU,BIPAP on Ward,IMV (VCV or PCV),De-escalation,CPAP on Ward,
