mechanical ventilation

purpose of mechanical ventilation

Maintain homeostasis between gas concentrations Oxygen and CO2

Indications for mechanical ventilation

• Airway protection: Preventive measure
• Cardiac arrest: Life saving measure
• Management of ICP: Creation of alkalosis ->vasoconstriction ->dec cerebral blood flow/dec ICP
• Airway obstruction: Maintenance of patent airway
• Surgery or trauma: General anesthesia

invasive MV

• Intubation of artificial airway into trachea

• Endotracheal tube

• Nasotracheal tube

• Tracheostomy

tidal volume

normal amount of air ventilated at rest (mL)

flow

L/min

non invasive (NIV)

• BiPAP or CPAP (bilevel positive airway pressure, continuous positive airway pressure)

• Last step before intubation

tracheostomy

• Unable to be weaned from ventilator
• Difficult intubation
• Severe morbid obesity
• Airway blocked or obstructed
• Tumor, traumatic injury

volume controlled ventilator modes

• Preset tidal volume
• Can be constant flow (square wave) or decelerating flow (sloped wave)
• Volume drops with stiff (less compliant lungs)
• Volume increases with less stiff lungs

pressure controlled ventilator modes

• Preset pressure
• Inspiratory flow always decelerating
• Stiff lungs can lead to high pressure
• Compliant lungs can lead to low pressure

Continuous Mandatory Ventilation (CMV)

• Patient is not spontaneously breathing
• Ventilator doing all of the work

• breathing muscle atrophy

Intermittent Mandatory Ventilation (IMV)

• Anytime patient triggers vent to get a breath, vent will
• deliver breath with preset volume (VC)
• deliver breath with preset pressure (PC)
• Patient can spontaneously breath between mandatory breath
• deliver breath with preset volume (VC)
• deliver breath with preset pressure (PC)

Positive End Expiratory Pressure (PEEP)

• Can be added to any of the four approaches
• Exhalation ended early to keep positive pressure in airway
• Increases functional residual capacity (FRC)
• Keeps alveoli open
• Aids oxygenation
• Reduces work of breathing

Pressure Support Ventilation (PSV)

• Can be added to IMV options (with or without PEEP)
• Provides extra boost of flow to all spontaneous breaths to reach preset pressure
• Helps to:
• increase spontaneous tidal volume
• overcome resistance of artificial airway
• reduce work of breathing

RED Alarms

• High pressure
• Circuit disconnected
• Apnea

YELLOW Alarms

• Low tidal volume
• High respiratory rate
• Low minute ventilation
• Low inspiratory pressure

Mechanical Ventilation: Weaning/Liberation

• Process of decreasing or discontinuing mechanical ventilation
• Physical therapy will work with patients during this process
• Patients begin process at rest and then slowly increase activities with decreasing vent support
• Condition that lead to vent support needs to be resolved
• Spontaneous breathing trial (SBT)

Five major factors to consider during weaning

• Respiratory demand and ability of neuromuscular system to cope with O2 demand
• Consider types of activity that promotes mobility without over-exerting the
patient
• Oxygenation
• Be sure patient receiving adequate O2 supply during activity
• Cardiovascular performance
• Know patient’s medical history, level of endurance, and closely and continuously monitor patient’s response
• Psychological factors
• Important to remain cool, calm, and collected throughout process
• Adequate rest and nutrition
• Never try SBTs when a patient is fatigued or malnourished

Weaning/Liberation signs of distress

• Tachypnea > 30 breaths/min
• Decreased pH < 7.25-7.30 with increased PaCO2
• Paradoxical breathing patterns
• O2 saturation < 90%
• HR change of > 20 bpm
• BP change > 20 mm Hg
• Agitation, panic, diaphoresis, cyanosis, angina, or arrhythmias

PT contraindications

• Comatose, unresponsive, does not follow commands
• Severe agitation/combativeness
• PEEP > 10cm H2O or FiO2 > 0.60 (60%)
• Uncontrolled active bleeding

Prolonged vent support may lead to

• Skin breakdown (decubitus ulcers)
• Joint contractures
• Deconditioning