Mechanical Ventilation – Study Notes

Basics

• Mechanical ventilation = machine delivers breaths (positive pressure ventilation, PPV).

• Normal breathing = negative pressure (diaphragm pulls air in).

• PPV dangers:

  • Barotrauma (lung damage from overinflation).

  • Can cause pneumothorax (popped lung).

Suctioning (most tested NCLEX topic)

1. Suction OUT only – never on insertion.

2. <10 seconds per pass.

3. Pre-oxygenate 100% O₂ for 30 seconds before suction.

4. Avoid suctioning before ABGs – wait ≥20 min.

5. Never suction routinely – only when needed (risk of trauma).

Key terms: acute lung injury, assess before intervention.

Oral Care & VAP (Ventilator-Associated Pneumonia)

• Prevention measures:

  1. Reposition q2h.

  2. Oral care with chlorhexidine q2h.

• Best indicators of VAP: sputum culture (+), fever >100.3°F, new infiltrates on CXR.

• Prevention protocols:

  • Daily sedation vacations & weaning trials.

  • HOB ≥30–45°.

  • Oral care.

  • Strict hand hygiene.

NG Tube & Stress Ulcers

• No bolus feedings → aspiration risk. Use continuous feedings.

• Stress ulcers (from gastric secretions). Prevent with PPIs or H₂ blockers.

Complications

• Dropping O₂ sat → always assess first.

  • Auscultate lungs, check for mucus plugs/secretions → suction.

  • If unresolved → manual ventilation (ambu bag).

• Pneumothorax: from high PEEP/barotrauma.

• Hypotension: PPV compresses thoracic vessels → ↓ cardiac output.

Extubation

• Risks: airway obstruction, respiratory distress.

• Post-extubation care:

  • Humidified O₂ mask.

  • Oral care with sponges (no ice chips).

  • NPO initially.

  • High Fowler’s.

• Watch for:

  • Atelectasis → encourage IS, turn/cough/deep breathe.

  • Stridor (squeak) = airway emergency → report immediately.

Tracheostomy Care

• New trach (<7 days): check tie tightness (1 finger under tie). Priority = maintain airway.

• If dislodged:

  • Mature trach (>7 days) → reinsert with obturator/hemostat.

  • New trach (<7 days) → cover with sterile occlusive dressing + bag-mask ventilation.

Ventilator Alarms

• Low pressure alarm (low tidal volume) = disconnection, cuff leak, tube displacement.

• High pressure alarm (high blockage) = secretions, kinked tube, biting tube, coughing, pulmonary edema, pneumothorax.

Ventilator Modes

• AC (Assist Control) = full machine control (life support, post-CPR).

• SIMV (Synchronized Intermittent Mandatory Ventilation) = weaning mode, pt initiates some breaths.

Ventilator Settings

• VT (tidal volume): 500–800 mL (air per breath).

• RR (respiratory rate): 12–20/min.

• FiO₂: 35–100% (“feed me O₂”).

• PEEP: keeps alveoli open; watch for barotrauma/pneumothorax.

• PS (pressure support): helps spontaneous breaths.

Monitoring

• VE (minute ventilation) = air delivered per minute.

• PIP (peak inspiratory pressure) = max pressure during inspiration.

• Plateau pressure (Pplat) = measures lung compliance (↑ in ARDS/stiff lungs).

Key NCLEX Traps

• Always assess before intervening.

• Priority is airway, not infection prevention/dressing changes.

• High PEEP → barotrauma/pneumothorax.

• Stridor after extubation = emergency.

• No bolus feeds in intubated patients.

Mechanical Ventilation – Ventilator Settings & Initial Setup

Definition

• Ventilator settings = controls on a ventilator that determine how much ventilation (removing CO₂) and oxygenation (O₂ delivery) a patient receives.

• Adjusting settings = more or less support depending on patient need.

Core Ventilator Settings

1. Ventilator Modes

• Defines how the ventilator assists with inspiration (full vs partial support).

• Common modes:

  • Assist Control (AC) → full support.

  • SIMV → partial support, weaning.

  • Pressure Support Ventilation (PSV) → assists spontaneous breaths.

  • CPAP → continuous positive airway pressure.

  • Other advanced modes: Volume Support, Control Mode Ventilation (CMV), APRV, MMV, IRV, HFOV.

2. Tidal Volume (VT)

• Amount of air delivered per breath.

• Normal breathing: air inhaled/exhaled each cycle.

• Volume-controlled mode: set VT directly.

• Pressure-controlled mode: VT depends on pressure applied.

• Initial setting: 5–10 mL/kg IBW (commonly 6–8 mL/kg).

3. Respiratory Rate (Frequency, f)

• of breaths delivered per minute.

• Normal range: 10–20/min.

• Sets overall minute ventilation when combined with VT.

4. FiO₂ (Fraction of Inspired Oxygen)

• % O₂ delivered (21% = room air).

• Initial setting: 30–60%, unless patient was already on higher O₂.

• Severe hypoxemia: may start at 100%, but must wean to <60% ASAP (to avoid oxygen toxicity).

5. Inspiratory Flow Rate

• Speed of gas delivery.

• Normal: 40–60 L/min (up to 120 L/min if needed).

• If too low → ventilator dyssynchrony, ↑ work of breathing.

• If too high → ↓ mean airway pressure.

6. I:E Ratio (Inspiratory:Expiratory)

• Normal: 1:2 to 1:4.

• Longer expiratory times needed in obstructive disease (prevent air trapping).

• Adjusted by: flow rate, inspiratory/expiratory time, VT, and frequency.

7. Sensitivity (Trigger)

• Determines how much negative pressure patient must generate to trigger a breath.

• Normal: –1 to –2 cmH₂O.

• If too high → auto-triggering (extra breaths).

• If too low → patient struggles to trigger breaths.

8. PEEP (Positive End-Expiratory Pressure)

• Positive pressure left in lungs at end of expiration.

• Prevents alveolar collapse → improves oxygenation.

• Common use: refractory hypoxemia unresponsive to FiO₂.

• Initial: 4–6 cmH₂O.

• Caution: excessive PEEP → barotrauma, hypotension, pneumothorax.

9. Ventilator Alarms

• High pressure: obstruction (secretions, biting, kinks, coughing, pulmonary edema, pneumothorax).

• Low pressure/volume: disconnection, leak, tube displacement.

• Other alarms: low expired volume, apnea, high/low PEEP.

Initial Ventilator Settings (General Guidelines)

1. Mode:

   • AC (full support) or SIMV (partial support).

2. Tidal Volume (VT): 5–10 mL/kg IBW (6–8 mL/kg preferred for lung protection).

3. Rate (f): 10–20/min.

4. FiO₂: 30–60% (100% if severe hypoxemia).

5. Flow Rate: 40–60 L/min.

6. I:E Ratio: 1:2 to 1:4.

7. Sensitivity: –1 to –2 cmH₂O.

8. PEEP: 4–6 cmH₂O.

Key Takeaways for Exams:

• Always use lowest FiO₂ possible to maintain O₂ sat.

• High PEEP → pneumothorax/barotrauma risk.

• Assess alarms before intervening.

• Modes: AC = full support, SIMV = weaning.

• Sensitivity too high/low → dyssynchrony.