mechanical ventilation: the basics and beyond
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Mechanical Ventilation: The Basics and Beyond. Presented By: Diana Gedamke, BSN, RN, CCRN Marion College - Fond du Lac Masters of Nursing Student . Module 3. Ventilator Wave Forms. Positive Pressure Ventilation. Two Main Types of Ventilators with Positive Pressure - PowerPoint PPT PresentationTRANSCRIPT
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Mechanical Ventilation: The Basics and Beyond
Presented By:Diana Gedamke, BSN, RN, CCRN
Marion College - Fond du LacMasters of Nursing Student
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Module 3Ventilator Wave Forms
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Two Main Types of Ventilators with Positive Pressure
Volume-cycled ventilation – With a set volume of air delivered per breath; Pressure to deliver breath will vary
Pressure-preset ventilation – With a set volume of pressure to open airways; Volume delivered will vary
Positive Pressure Ventilation
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Delivers a preset volume of gas with each machine breath—airway pressures increase in response to the delivered breath
Airway pressures are higher in patients with low compliance or high resistance—high pressures indicate risk of ventilator-induced lung injury
Volume-cycled Ventilation
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Spontaneous Breathing vs. Positive Pressure Ventilation
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Assist Control (AC) Synchronized Intermittent Mandatory
Ventilation (SIMV)
Volume-cycled Ventilation
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Most widely used mode of MV Delivers a minimum number of fixed-
volume breaths Patients can initiate extra assisted
breaths (will get full set volume with each effort)
Assist-control (AC)
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Pressure-time TracingsAssist Control Mode
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Delivers preset number of fixed-volume breaths
Patient can breathe spontaneously between breaths (rate and depth determined by patient)
Patients often have trouble adapting to intermittent nature of ventilatory assistance
Synchronized Intermittent Mandatory Ventilation (SIMV)
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Pressure-time TracingsSIMV Mode
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Delivers a predefined target pressure to the airway during inspiration
Resulting tidal volume (VT) and inspiratory flow profile vary with the impedance of the respiratory system and the strength of the patient’s inspiratory efforts
Includes pressure-control (PC) and Pressure support (PS)
Pressure-preset Ventilation
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Delivers a preset gas pressure to the airway for a set time and at a guaranteed minimum rate
Patient can breathe in excess of set rate Tidal volume achieved depends on pressure
level, lung mechanics, and patient effort Inspiratory flow rate variable
Pressure-control (PC) Ventilation
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Delivers preset airway pressure for each breath
Variable parameters: Inspiratory and expiratory times (respiratory rate), flow rate, and tidal volume (VT)
Pressure Support (PS)
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A set number of Mandatory breaths are delivered per minute.
Remainder of patients breath are at his own rate and volume
Spontaneous breaths allowed in SIMV are assisted by PS
Synchronized Intermittent Mandatory Ventilation (SIMV) + Pressure Support (PS)
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New modes often introduced Involves nothing more than a modification
of the manner in which positive pressure is delivered to the airway and of the interplay between mechanical assistance and patient’s respiratory effort
Goals: enhance respiratory muscle rest, prevent deconditioning, improve gas exchange, prevent lung damage, improve synchrony, foster lung healing
New Modes of MV
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Respiratory rate Tidal volume FiO2 Inspiratory:Expiratory (I:E) ratio Pressure limit Flow rate Sensitivity/trigger Flow waveform
Ventilator Settings
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Inspiratory Flow (V) Waveform
Square waveform Decelerating Waveform (constant flow) (decelerating flow)
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Square waveform: volume of gas is evenly distributed across inspiratory time. Has highest peak pressure and lowest mean airway pressure. Ideal for those at risk for autopeeping due to short inspiration time
Inspiratory Flow (V) Waveform
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Decelerating waveform: Volume of gas flow is high at the beginning of inspiration then tapers off toward the end of the breath. Has lowest peak pressure and highest mean airway pressure. Increased inspiratory time; useful in ARDS.
Inspiratory Flow (V) Waveform
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Check for: ◦ Symmetric chest inflation◦ Regular breathing pattern◦ Respiratory rate < 30 bpm◦ Synchrony between patient effort and machine
breath◦ Paradoxical breathing
Patient-Ventilator Synchrony
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Inspiratory effort expended by patients with acute respiratory failure is 4 - 6 x normal
Don’t eliminate respiratory effort: causes deconditioning and atrophy
Patient-Ventilator Synchrony
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Possible causes:◦ Anxiety or pain◦ Ventilator settings may not be appropriate: check
ABG and alert individual responsible for ventilator orders
◦ Auto-PEEP◦ Pneumothorax
Patient-Ventilator Asynchrony
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Ventilator Alarms and Common Causes
High Pressure Low Pressure Low Exhaled Volume
Kink in tubingPatient biting ETT
Ventilator disconnected from ETT
Pressures exceeding high pressure limit
Secretions Cuff leak Cuff leak
Coughing Extubation Ventilator disconnected
Bronchospasm
Foreign body
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PEEP – positive-end-expiratory pressure applied during mechanical ventilation
CPAP - continuous positive airway pressure applied during spontaneous breathing
Definitions
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Improves oxygenation - increases functional residual capacity (FRC) above closing volume to prevent alveolar collapse◦ permits reduction in FIO2
Reduces work of breathing Increases intrathoracic pressure -
decreases venous return to right heart - decreases CO
Titrate to least amt. necessary to achieve O2 sat > 90% or PO2 > 60 mm Hg with FiO2 < 0.6
PEEP
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Auto-PEEP/intrinsic PEEP (PEEPi)/inadvertent PEEP/occult PEEP - positive end expiratory alveolar pressure occurring in the absence of set PEEP. Occurs when expiratory time is inadequate.
Auto-PEEP
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Assessing Flow Waveform for Presence of Auto-PEEP
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Resistance and Compliance
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Peak Airway Pressure (Ppk)◦ An increase in Ppk indicates either an increase
in airway resistance or a decrease in compliance (or both).
Plateau Pressure (Ppl) - end-inspiratory alveolar pressure
Definitions
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Airway Pressure Analysis
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High volumes and pressures can injure the lung, causing increased permeability pulmonary edema in the uninjured lung and enhanced edema in the injured lung
Alveolar overdistention + repeated collapse and re-opening of alveoli
Ventilator-Induced Lung Injury
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resistance to expired flow results in air trapping/hyperinflation hyperinflation may result in
cardiopulmonary compromise Goal: meet minimal requirements for gas
exchange while minimizing hyperinflation Allow increased time for expiratory flow
Mechanical Ventilation in Obstructive Lung Disease
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Decrease inspiratory time◦ Increase flow rate◦ Square waveform
Decrease minute ventilation (VE)◦ RR x TV
Increasing Time for Exhalation
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Monitor plateau pressure: in general, Pplat < 30 cm H20 to decrease risk of hyperinflation and alveolar overdistension
Permissive hypercapnia
Monitoring Patients with Obstructive Lung Disease Requiring Mechanical Ventilation
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Watch for overventilation post intubation High Ppk common May require sedation to establish
synchronous breathing with ventilator Avoid paralytics Ventilate as stated above (Increase
exhalation time by decreasing RR and TV, increasing inspiratory flow rate, and using square waveform)
May want to use SIMV
Respiratory Failure Due to Asthma
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Ppk typically not as elevated as in asthma; when it is, think other pathologic processes
Many patients with COPD have chronic hypercapnia; ventilatory support titrated to normalize pH and not PCO2
Small levels of set PEEP may decrease WOB
May try NIPPV
Respiratory Failure Due to COPD
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Cooperative patient Functionally intact upper airway Minimal amount of secretions Done by full face or nasal mask Watch for gastric distension; may
increase risk of aspiration May use standard ventilators Monitor patients closely for
decompensation and need for intubation
Noninvasive Positive Pressure Ventilation (NIPPV)
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Non-recruitable
Recruitable
Normal
ARDS: A Three Lung Unit Model
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Refractory hypoxemia Avoid ventilator induced lung injury
◦ pressure-limited approach keep Pplat < 30 cm H20 small tidal volumes (6 ml/kg)
◦ permissive hypercapnia Avoid O2 toxicity; apply moderate levels
of PEEP
Respiratory Failure Due to ARDS
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May need to increase inspiratory time Inverse ratio ventilation (IRV)
◦ I:E > 1:1◦ May require sedation/paralysis◦ Use as second-line strategy if PEEP fails to
improve oxygenation
ARDS
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Present with acute or subacute respiratory failure, usually with hypercapnia
progressive neurologic dysfunction (amyotrophic lateral sclerosis, muscular dystrophies, Guillain-Barre, CNS dysfunction due to head injury or drug ingestion)◦ usually ventilated without difficulty unless RF is
complicated by secondary conditions (atelectasis or pneumonia)
◦ lung compliance and gas exchange remain relatively normal
Mechanical Ventilation in Patients with Neuromuscular Weakness