Mechanical Ventilation
<105
RSBI
Rapid Shallow Breathing Index for weaning
≤-20
NIF
cmH2O minimum for extubation
30-45°
HOB Elevation
Ventilator bundle standard
Ventilator Modes
know the key difference between each modeAC/VC
Assist-Control Volume
Delivers set tidal volume with every breath (patient or machine triggered). Most common initial mode.
AC/PC
Assist-Control Pressure
Delivers set pressure with every breath. Tidal volume varies. Useful when plateau pressures are high.
SIMV
Synchronized Intermittent
Set number of mandatory breaths, patient can take spontaneous breaths between. Used for weaning.
PSV
Pressure Support
Patient triggers every breath, machine provides pressure boost. Used for weaning and SBT.
APRV
Airway Pressure Release
Keeps lungs inflated at high pressure with brief releases. Used in severe ARDS for recruitment.
Ventilator Alarms
High Pressure (Obstruction)
- Secretions in airway
- Patient biting ETT
- Bronchospasm
- Pneumothorax
- Patient-ventilator dyssynchrony
Low Pressure (Leak/Disconnect)
- Circuit disconnection
- ETT cuff leak
- Loose connections
- Chest tube air leak
Weaning and Extubation
RSBI = RR divided by TV. Under 105 predicts successful extubation. Over 105 predicts failure. Calculate it during a spontaneous breathing trial on minimal support.
Spontaneous breathing trial (SBT) on PSV 5-8 or T-piece for 30-120 minutes
RSBI <105 (respiratory rate / tidal volume in liters)
NIF ≤ -20 cmH₂O (adequate inspiratory strength)
PaO2/FiO2 >150-200 on FiO2 ≤40% and PEEP ≤5-8
Hemodynamically stable without high-dose vasopressors
Intact cough, gag reflex, and ability to manage secretions
Key Values to Memorize
RSBI <105 = success
NIF ≤-20 cmH₂O
HOB 30-45° always
Cuff pressure 20-30 cmH₂O
SBT 30-120 min
VAE bundle = HOB + oral care + DVT ppx + sedation vacation
vent questions are everywhere on the CCRN, get ready
Practice CCRN exam-style questions with instant feedback
Practice CCRN QuestionsExam Traps
High pressure alarm means check the PATIENT first
Secretions, biting the tube, bronchospasm, pneumothorax, and patient-ventilator dyssynchrony all cause high pressure alarms. Always assess the patient before troubleshooting the circuit. The exam will present a high alarm scenario and expect you to assess the patient, not disconnect tubing.
Auto-PEEP requires end-expiratory hold to detect
Auto-PEEP (intrinsic PEEP) occurs when air gets trapped. It is invisible on the ventilator display unless you perform an end-expiratory hold maneuver. Common in COPD and asthma. Treatment is reducing rate and increasing expiratory time.
RSBI under 105 predicts successful extubation
RSBI = respiratory rate divided by tidal volume (in liters). Under 105 suggests the patient can sustain spontaneous breathing. Over 105 predicts weaning failure. The exam expects you to calculate and interpret this.
Never extubate without meeting all weaning criteria
Adequate oxygenation, hemodynamic stability, ability to protect airway, minimal secretions, intact cough and gag, and passing a spontaneous breathing trial are all required. Skipping criteria leads to reintubation.
Alarm Priority
High pressure alarm? Check the PATIENT first (secretions, biting, bronchospasm). Then check the circuit. Patient always comes first.
Auto-PEEP in COPD
Auto-PEEP = air trapping. Common in COPD/asthma. Reduce rate, increase expiratory time. Perform end-expiratory hold to detect it.
Think of the ventilator as a machine inflating a balloon (the lungs) over and over. Different modes control whether the machine decides the volume of air, the pressure of air, or lets the patient help.
High pressure alarm = something is making it harder to inflate the balloon (mucus plug, patient coughing, kinked tube). Low pressure alarm = air is escaping somewhere (disconnection, cuff leak). High = obstruction. Low = leak.
Imagine not fully deflating the balloon before pumping more air in. Each breath traps a little more air. The balloon gets stretched tighter and tighter. That is auto-PEEP, and it is dangerous in patients who cannot exhale fully.
Weaning is slowly letting the patient inflate their own balloon. RSBI measures whether they can do it without getting exhausted. Under 105 means they are strong enough. Over 105 means they are struggling.
Ready to test your CCRN knowledge?
1,200+ practice questions written by certified professionals.
Start Practicing CCRN