Mechanical Ventilation is a Drug!!! Mechanical Ventilation is a drug I am an employee of Philips Healthcare Hospital Respiratory Care Group and they help me pay for my kids education Jim Laging, RRT, RCP Philips Healthcare Hospital Respiratory Care Group MV as a Drug: Outline MV: Indications for use Define indications for use Determine route of administration Invasive vs Non Invasive Determine appropriate dose A/C, PCV, SIMV, PS, CPAP /PEEP, and NIPPV Alarms Weaning and discontinuation Inadequate lung expansion Apnea Excessive work of breathing (WOB) Postoperative prophylaxis Closed head injury Need to reduce PaCO MV: Indications for use Indications for Advanced Airways Acute ventilatory failure Impending ventilatory failure Paradoxical breathing Accessory muscle use Hyperventilation Refractory hypoxemia Inability to protect airway Provision of adequate pulmonary toilet Facilitation of invasive mechanical ventilation
MV: Treatment Effects MV: Mechanism of Action Ventilation Oxygenation Pulmonary Mechanics Work of Breathing/Patient comfort Ventilation: Manipulation of Minute Ventilation Manipulation of CO 2 production Manipulation of Deadspace MV: Mechanism of Action Oxygenation: Manipulation of Mean airway pressure Manipulation of FiO 2 Manipulation of O 2 consumption MV: Mechanism of Action Pulmonary Mechanics Work of Breathing/Patient comfort MV as a Drug: Dosing Spontaneous Vs. Positive- Pressure Breathing First determine dose of total support: Full Ventilatory Support Partial Ventilatory Support Second determine mode that supports above decision Lastly determine the Dose of each parameter Pressure Volume I E I E I E I E Spontaneous Positive-Pressure
Ventilator Basics Defined Ventilator Basics Defined FIO 2 - fraction of inspired oxygen Rate - number of breaths per minute Tidal Volume - volume of each breath Sensitivity - how responsive the ventilator is to the patient s s efforts Peak Flow - the maximum flow rate used to deliver each breath to the patient Inspiratory Time - the time spent in the inspiratory phase of the ventilatory cycle I:E Ratio - the inspiratory time compared to the expiratory time; I + E = total cycle time Inspiratory Hold Time the breath will be held at end inspiration Flow Pattern - the shape of the curve representing the breath delivery; it can be square wave of decelerating Ventilator Basics Defined Mode - the manner or method of support provided by the ventilator Cycling: volume, time, pressure, flow - what cycles, or changes, the ventilator from one phase of the respiratory cycle to the other Limiting: volume, pressure, time - what limits the delivery of gas to the patient during the inspiratory phase Basic Ventilator Parameters FiO 2 titrate with pulse oximetry goal: < 50% Rate 10 to 20 bpm Tidal volume (V T ) 7 to 12 ml/kg Sensitivity Pressure, or flow triggered, Auto-Trak Peak flow controls how fast tidal volume is delivered Inspiratory time (I:E ratio) time spent in the inspiratory phase Flow pattern square vs. decelerating Mode of ventilation A/C, SIMV, Spontaneous, NPPV Breath types volume or pressure Modes of Ventilation Assist/Control Ventilation (A/C) Synchronized Intermittent Mandatory Ventilation (SIMV) or IMV Pressure Controlled Ventilation (PCV) Spontaneous Modes Pressure Support Ventilation (PSV) Continuous Positive Airway Pressure (CPAP) BiPAP Assist/Control Breaths delivered at clinician-set parameters: Tidal volume Flow rate and pattern Back-up respiratory rate Machine-initiated initiated and/or patient-initiated initiated breaths are all delivered at these set parameters Pressure Time
Assist/Control Can provide full ventilatory support Patient controls rate of breathing Disadvantages Settings may not match patient s s ventilatory demands As spontaneous breaths increase, minute ventilation increases proportionately can result in hyperventilation need to set high respiratory rate and minute ventilation alarms SIMV Combination of machine and spontaneous breaths Mandatory breaths typically delivered when patient effort is sensed (synchronized) Patient determines tidal volume and rate of spontaneous breaths Pressure Time Synchronized machine breath Patient effort SIMV Synchronized breaths may improve patient comfort Reduces competition between patient and ventilator Hyperventilation less of a concern compared to A/C SIMV Disadvantages May not be enough support if set rate or V T too low May increase work of breathing (WOB) lag time between patient effort and delivered flow resistance of ET tube and circuit NPPV Non-Invasive Positive Pressure Ventilation Ventilation mode delivered by face mask and not ET tube or trach Patient ventilator synchrony is essential Brackets settings that will facilitate success BiPap in a critical care ventilator Low Volume Alarms are usually allowed to be shut off Volume vs. Pressure Control Ventilation Volume Ventilation Pressure Ventilation Volume delivery Volume delivery varies constant Inspiratory pressure Inspiratory pressure constant varies Inspiratory flow varies Inspiratory flow Inspiratory time set by constant clinician Inspiratory time determined by set flow and V T
Pressure Control Ventilation Pressure Control Ventilation Definition The application of clinician-set inspiratory pressure and inspiratory time. Flow delivery varies according to patient demand. The clinician sets the inspiratory pressure, I-I time or I:E ratio, and RR Tidal volume varies with changes in compliance and resistance Flow delivery is decelerating Limits risk of barotrauma May recruit collapsed and flooded alveoli Improved gas distribution Disadvantages Tidal volumes vary when patient compliance changes (i.e. ARDS, pulmonary edema) With increases in I-time, I patient may require sedation and/or chemical paralysis Indications for PCV Enhance patient/ventilatory synchrony Patient determines flow Lung protection strategy Lower inspiratory pressure with decelerating flow can improve V/Q matching Adjusting I-time I can improve oxygenation by increasing mean airway pressure (MAP) Alveolar diseases that produce varying time constants Can recruit alveoli by lengthening I-time I Pressure Support Ventilation Goals Overcome resistive work associated with moving inspiratory flow through the artificial airway and circuit Improve patient/ventilator synchrony Augment spontaneous tidal volume 10 cm Pressure Time Pressure Support Ventilation MV as a Drug: Dosing Patient controls rate, volume and duration of breaths Patient comfort May overcome WOB Disadvantages May not be enough ventilatory support if patient condition changes fatigue or changes in compliance/resistance Support level remains constant regardless of patient drive Full Ventilatory Support: May be provided with any mode Except CPAP (No PSV) Partial Ventilatory Support: May be provided with any mode Except CMV and A/C
MV as a Drug: Dosing MV as a Drug: Dosing How to determine Dose of each parameter: Primary Effect Secondary Effect Must consider effect on hemodynamics and respiratory pump Every time your finger touches a control knob, you should make a risk/benefit analysis Follow-up with appropriate monitoring to support continued benefit ABG ETCO2 Pulse Ox Review of MV Effects Dosing V T Ventilation Oxygenation Mechanics WOB/Comfort Hemodynamic Knowledge of airway and physiologic deadspace is helpful Important for mandatory and spontaneous breaths With Rate, determines mandatory V E With IP, determines spontaneous V E Respiratory Rate (f) Dosing Respiratory Rate Primary Effect: Ventilation Secondary Effect: Oxygenation, Mechanics Hemodynamics: Neg. Effect Control versus Safety Net Determination of mandatory V E Will influence: Total WOB Paw Recruitment Auto PEEP
Flow/Insp Time Dosing Flow rate Primary Effect: Mechanics Secondary Effect: Oxygenation, Ventilation Hemodynamics: Neg. Effect Must match or exceed patient demand Monitor Pressure/Time curve during VCV Must set flow waveform during VCV Allow vent to determine flow during PCV Rise time setting must be optimized Dosing Inspiratory Time PEEP/CPAP May be dependant or independent variable Must allow adequate time for equilibration and distribution Influences Paw and recruitment Primary Effect: Mechanics Secondary Effect: Oxygenation, Ventilation Hemodynamics: Neg. Effect Dosing PEEP/CPAP Historical PEEP Titration Primary effect is on expiratory lung volume Monitor response with regard to: Mechanics P/V curve, Breathing Pattern Gas Exchange ETCO2, VCO 2, PaO2,PaCO2 Hemodynamics CO, BP, etc. PEEP has been traditionally set to a gas exchange end-point PaO 2, SpO 2 Optimal PEEP studies were an early attempt to determine PEEP based on measured lung mechanics Optimal PEEP versus Best PEEP
Recent PEEP Titration SbCO 2 Waveform Use of a PEEP/FiO 2 table Used in ARDS Net trial 20 cm H 2 O FiO 2 0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0 PEEP 5 5 8 8 10 10 10 12 14 14 14 16 18 18 18-24 PEEP of 22 cm H 2 O What caused the bottom SbCO 2 waveform to drop? Pressure Support (PSV) Pressure Support (PSV) Primary Effect: Mechanics Secondary Effect: Oxygenation, Ventilation Hemodynamics: Neg. Effect Modifies WOB Partial Ventilatory Support Full Ventilatory Support Modifies breathing pattern May have negative effect on gas exchange FiO 2 Ventilator Alarms Primary Effect: Oxygenation Secondary Effect: None Hemodynamics: No Effect High airway pressure Low airway pressure High respiratory rate High minute volume Low minute volume Low exhaled tidal volume Apnea
Weaning Protocols Weaning Readiness Numerous studies have shown the utility of weaning protocols in expediting weaning and improving success Reduces prolonged ventilation and premature extubation, each which carry additional risks and costs Foster CCM 1984;12:994, Cohen CCM 1991;19:1278, Wood Respir Care 1995;40:219, Ely NEJM 1996;335:1864, Kollef CCM 1997;25:567, Horst Arch Surg 1998;133:483 Daily Screen 5 Criteria Patient coughs when suctioned No continuous vasopressor or sedative infusions ABG s s are appropriate for Pt. PEEP < 6 cm H 2O f/v T < 105 for one minute Ely NEJM 1996;335:1864 Spontaneous Breathing Trials Conclusion All pts who pass the daily screen SBT 30 mins Termination of the SBT Resp rate > 35 for > 5 mins SpO2 < 90% for > 30 secs 20% increase or decrease in heart rate for > 5 mins Agitation, anxiety, diaphoresis > baseline for > 5 minutes Ely NEJM 1996;335:1864 The Mechanical Ventilator provides support of respiratory pump. PEEP/CPAP is the most important physiologic setting we may determine. Choice of appropriate end-points will have dramatic effect on MV use and duration. Don t t forget the importance of quality general care. Contact Information jalaging@hotmail.com 773-573 573-9155 Thank you