E. Katie Mozader, RRT-NPS, LRT. Lead Respiratory Therapist, St. Joseph Mercy Oakland Hospital

Transcription

1 E. Katie Mozader, RRT-NPS, LRT Lead Respiratory Therapist, St. Joseph Mercy Oakland Hospital

2 Objectives Indications for mechanical ventilation Orders required to initiate mechanical ventilation Initial ventilator settings Mechanical breath delivery Volume ventilation basics Understanding settings to adjust to meet patient needs

3 Indications for Ventilator Initia Decreased ventilatory drive eg.. Drugs, ph changes Ventilation abnormalities hypercapnea/ hypoventilation Increased airway resistance and/or obstruction eg.. Reactive airway disease, upper airway obstruction Oxygenation difficulties/hypoxemia Increased/excessive work of breathing Metabolic acidosis compensation

4 Mechanical Ventilation Orders Ventilator mode Respiratory rate (frequency) Tidal volume 6 to 10 ml/kg IBW FIO2 21 to 100% PEEP level 5 to 20 cmh2o Inspiratory pressure 5 to 40 cmh2o * for PCV Inspiratory time *for PCV

5 Volume Cycled Ventilation Volume Breath breath ends when tidal volume is reached Set tidal volume is delivered at whatever pressure is required Most common method of mechanical ventilation Requires ordered volume based on ideal body weight: - generally 6 to 10 ml/kg depending on lung mechanics - stiff/noncompliant lungs require smaller volumes to avoid injury (often 5 to 7 ml/kg) Advantages Stable, consistent tidal volume delivery and minute ventilation Tidal volume is constant even with variable compliance and resistance

6 Volume Cycled Ventilation Disadvantages Fixed flow that may not meet the patient s inspiratory flow demand An increased respiratory rate can cause patient/ventilator asynchrony ( increased WOB with fatigue) Increased airway pressures can lead to barotrauma & adverse hemodynamic effects Auto PEEP(air trapping) due to insufficient expiratory time (e.g. COPD)

7 Pressure A. Start Mechanical Breath Delivery (Volume) Trigger - What starts the breath? (e.g. pressure drop below baseline or patient inspired rate of flow) B. Limit What is controlled and what is variable? (gas flow delivery/airway pressure) C. End Cycle mechanism - What causes the breath to end? (predetermined volume) A. B. C.

8 Assist/Control Ventilation (AC) Set tidal volume with a machine set respiratory rate Sensitivity (pressure or flow trigger) responds to each patient inspiratory effort (assisted ventilation) The ventilator delivers an automatic back up respiratory rate if the patient fails to initiate a breath (controlled ventilation) Advantages : Guaranteed minimum Ve Patient can adjust respiratory rate according to demand Disadvantages Positive pressure breaths may reduce cardiac output in some patients Possible respiratory alkalosis

9 Pressure, cm H2O Assist/Control Ventilation Note that the first breath is provided by the ventilator without any patient trigger (controlled breath) The second and third breaths are triggered by the patient (assisted breaths) Controlled Breath Assisted Breath No patient effort Patient effort 8

10 Flow Waveform (Volume) Peak flow - how fast the gas is delivered Results in a determined inspiratory time Higher flow = shorter inspiratory time (longer expiratory time) In volume ventilation, flow rate and tidal volume do not change in response to lung changes or patient demand 60 (Inspiratory time) A B C. V LPM (Expiratory time) D (Peak Flow) INSP EXH 60 10

11 Auto PEEP Inadvertently enhanced PEEP levels (air trapping) Caused by flow limitation and inadequate emptying of the lungs during exhalation The higher lung volume at the end of exhalation leads to an increased end-exhalation base line pressure..auto-peep

12 Synchronized Intermittent Mandatory Ventilation (SIMV) Set Vt is given with each mandatory ventilator breath Patient is able to take spontaneous breaths at variable rates and volumes between mandatory breaths The ventilator will not stack a mandatory breath on top of a spontaneous breath (synchronized feature) Pressure Support can be added to assist the patients work of breathing during spontaneous breaths Commonly used for post-surgery patients waiting to wake from anesthesia

13 Volume, ml Pressure, cm H2O Synchronized Intermittent Mandatory Ventilation Mandatory breath Spontaneous Breath

14 PEEP PEEP and CPAP Adjusting Resting Lung Volumes (Positive End Expiratory Pressure) Lung pressurization during the expiratory phase of mechanical delivered breaths PEEP is the most common method to elevate mean airway pressure and improve oxygenation Recruits collapsed alveoli to help improve ventilation/perfusion mismatch 5 cmh2o routinely used to splint open alveoli (2-5 cmh20 is physiologic) CPAP (Continuous Positive Airway Pressure) Lung pressurization during the inspiratory and expiratory phases of spontaneous breathing

15 Ventilation / Oxygenation Ventilation the movement of gas in and out of the lungs, effectiveness measured by PaCO2 - manage PaCO2 by adjusting minute ventilation (Ve) Oxygenation the movement of gas across membranes, effectiveness measured by PaO2 - manage oxygenation by adjusting PEEP or FIO2

16 Calculations - YAAAY! (to take away some of the guesswork involved with managing ventilation) Minute ventilation (Ve) = RR x Vt ex. 12 x.5 = 6.0 CHANGING PCO2 (ventilator patient) Desired Ve = actual PaCO2 x actual Ve desired PaCO2 ex. 53 x = 7.95 Desired PaCO2 = 1.5 x (current HCO3) + 8 *used for metabolic acidosis ex. 16 x = 32 Desired PaCO2 = 0.9 x (current HCO3) + 9 *used for metabolic alkalosis

17 Compliance Compliance is measured as: Tidal volume Plateau PEEP The willingness of lungs to increase volume when pressure is applied Typical for vent patient = ml/cmh2o Critical = < 20 ml/cmh2o - A significant increase in compliance corresponds to an increase V P in elastance (alveolar septal destruction COPD) Ventilation the movement of gas in and out of the lungs, effectiveness measured by PaCO2 - A decrease in compliance results in an decrease in elastance (pulmonary edema, pulmonary fibrosis, ARDS, airway obstruction, etc )

18 Pressure and Lung Injury Peak Airway Pressure (PIP) Total force required to deliver a breath Includes pressure needed to generate flow through airways, which is not transmitted to alveolar wall Plateau Pressure (Pplat) Force required to distend the lung - reflects alveolar distending pressure Measured in static condition (breath hold) at end inspiration Values > 30 cmh2o suggest increased risk of barotrauma

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