Mechanical Ventilation

A — Airway

• Is the patient's airway patent?
• Can the patient protect their airway neurologically?

O — Oxygenate

• Can they generate spontaneous breaths?
• Are they strong enough to maintain a respiratory rate and tidal volume to support oxygenation?

V — Ventilation

• Is the V/Q ratio balanced?
• Are oxygenation and CO₂ clearance occurring without excessive work of breathing?

• Three main reasons for intubation:*

1. Respiratory failure — inability to oxygenate or eliminate CO₂
2. Neurological — inability to protect airway
3. Mechanical — loss of airway anatomy (injury, edema)

Standard Modes

• Assist Control Ventilation (AC)*
• Ventilator-programmed breaths and patient-requested breaths are delivered in the same way by the ventilator
• Fully supported breaths regardless of origin

• Intermittent Mandatory Ventilation (IMV)*
• Only ventilator-programmed breaths are fully supported
• Patient-initiated breaths receive only the ordered pressure support level

• Pressure Support Ventilation (PSV)*
• Used in patients who initiate adequate minute ventilation
• No ventilator-programmed breaths
• Assistance determined by ordered pressure support

Advanced Modes

• APRV (Airway Pressure Release Ventilation)
• PRVC (Pressure Regulated Volume Control)

When using advanced modes, ICU Attending should be primarily involved in all ventilator management decisions. Consider comfort level of respiratory therapist and bedside nurses.

Initial Parameters

Initial ABG should be obtained 15–45 minutes from start of ventilation.

Ventilator Synchrony ("Dysynchrony")

"Fighting the ventilator" can result from:

• Anxiety
• Pain
• Chest wall rigidity
• Positioning

Management: adequate sedation and analgesia plus mode adjustment.

SAT Exclusion Criteria (Do NOT perform SAT if):

• Fresh open abdomen (< 72 hours)
• Active seizures
• Escalating sedation for ongoing agitation
• Neuromuscular blockade
• Hemodynamic instability
• Evidence of increased ICP / Moderate-Severe Head Injury
• Critical airway (as indicated by MD)
• Major chest injury (e. g., flail chest)
• Significant arrhythmias

SAT Process

1. Hold enteral feedings; adjust insulin if receiving
2. Allow analgesia for active pain
3. For benzodiazepine drips > 7 days: decrease by 50% and assess for restraint need
4. Monitor for up to 4 hours

• SAT Failure* (restart sedation at ½ previous dose if):
• Sustained anxiety
• Agitation / delirium
• Uncontrolled pain
• RR > 35 for 5 min
• SpO₂ < 88% for 2 min
• Acute cardiac dysrhythmia
• Hemodynamic instability

• SAT Pass:*
• Opens eyes to verbal stimuli
• Follows simple commands
• No evidence of agitation

→ Proceed to Weaning Pathway

• SpO₂ > 90%
• PEEP < 8 cm H₂O
• FiO₂ < 50%
• Minute ventilation < 12 L/min
• Hemodynamically stable (HR 50–120, SBP 90–180)
• Patient initiates spontaneous inspiratory efforts
• Able to follow simple commands (opens eyes, coughs, lifts head)

Extubation Risk Factors (Have re-intubation equipment ready):

• Morbid obesity
• Short neck
• Immobile neck
• Anterior mandibular space < 6 cm
• Large tongue
• Facial fractures (wired mandible, oropharyngeal edema)
• Previous failed intubations
• History of tracheotomy

Post-Extubation Protocol

• Stop continuous sedation/opiates post-extubation
• Consider replacing analgesic drip with PCA if unable to take PO
• Consider swallow study if intubated > 5 days or neurologically compromised
• Monitor closely in ICU for at least 4 hours before any disposition

Respiratory Failure

• Usually requires full positive pressure support with mandatory breaths
• Optimize mode, rate, volume, PEEP, and pressure support
• Goal: minimize V/Q mismatch

Neurological — Unable to Protect Airway

• If generating own breaths: pressure support may suffice
• Severe TBI: mandatory mode for tight CO₂ control
• Hypercarbia → cerebral vasodilation → ↑ ICP
• Neurologic prognosis drives tracheostomy timing (early discussion with neurosurgery/neurology)

Mechanical Airway Loss

• If generating own breaths: pressure support mode
• Prognosis for regaining airway anatomy determines tracheostomy timing

• Ideal Body Weight
• Tidal Volume
• P/F Ratio

• Adapted from SurgCritCare. org ventilator content and Highland Hospital Adult Respiratory Ventilator Protocol. Verify against current institutional ventilator protocols, respiratory therapy standards, and attending guidance.*