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Mechanical Ventilation & Airway Management | 마이메르시 MyMerci
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Mechanical Ventilation & Airway Management

NCLEX Review Guide: Mechanical Ventilation & Airway Management

Mechanical Ventilation Basics

Indications for Mechanical Ventilation

  • Mechanical ventilation is indicated when a patient cannot maintain adequate oxygenation (PaO₂ < 60 mmHg) or ventilation (PaCO₂ > 50 mmHg with pH < 7.25) despite supplemental oxygen therapy and other supportive measures.
  • Common clinical conditions requiring mechanical ventilation include acute respiratory distress syndrome (ARDS), severe pneumonia, neuromuscular disorders affecting respiratory muscles, and post-operative respiratory support.

Key Points

  • Always assess ABGs, vital signs, and work of breathing before initiating mechanical ventilation
  • Mechanical ventilation is a supportive therapy, not a cure for the underlying condition

Ventilator Modes

  • Assist-Control (AC): Delivers a preset tidal volume or pressure with each breath, whether patient-initiated or time-triggered. This mode guarantees a minimum respiratory rate while allowing the patient to trigger additional breaths.
  • Synchronized Intermittent Mandatory Ventilation (SIMV): Delivers a preset number of mandatory breaths while allowing the patient to take spontaneous breaths between mandatory ones. Spontaneous breaths receive only pressure support, not full ventilator support.
  • Pressure Support Ventilation (PSV): Patient triggers all breaths, and the ventilator delivers a preset pressure to assist each breath. Used primarily for weaning or in patients with adequate respiratory drive.
  • Continuous Positive Airway Pressure (CPAP): Maintains positive airway pressure throughout the respiratory cycle during spontaneous breathing. Not a true ventilator mode but supports oxygenation by preventing alveolar collapse.

Ventilator Mode Comparison

Mode Breath Initiation Delivery Control Best For
Assist-Control Patient or timer Volume or pressure Patients with minimal/no respiratory effort
SIMV Patient and timer Volume or pressure for mandatory; pressure support for spontaneous Transitioning patients; weaning
PSV Patient only Pressure Patients with adequate drive; weaning
CPAP Patient only Continuous pressure Spontaneously breathing patients needing oxygenation support

Key Points

  • Mode selection depends on patient's clinical condition, respiratory effort, and ventilation goals
  • Ventilator modes can be volume-controlled or pressure-controlled

Ventilator Settings

  • Tidal Volume (VT): The volume of air delivered with each breath, typically set at 6-8 mL/kg of ideal body weight to prevent ventilator-induced lung injury. Lower tidal volumes (4-6 mL/kg) are used for patients with ARDS.
  • Respiratory Rate (RR): The number of mandatory breaths delivered per minute, typically set between 12-20 breaths/minute based on the patient's metabolic demands and acid-base status.
  • Fraction of Inspired Oxygen (FiO₂): The percentage of oxygen in the delivered gas, ranging from 21% (room air) to 100%. Goal is to maintain SpO₂ > 90% using the lowest possible FiO₂ to prevent oxygen toxicity.
  • Positive End-Expiratory Pressure (PEEP): Pressure maintained at the end of expiration to prevent alveolar collapse, improve oxygenation, and reduce work of breathing. Typically set at 5 cmH₂O and titrated based on oxygenation needs.
  • Pressure Support (PS): The pressure applied during inspiration to augment patient effort during spontaneous breathing. Typically ranges from 5-20 cmH₂O depending on the clinical situation.
Prolonged exposure to FiO₂ > 60% can lead to oxygen toxicity and absorption atelectasis. Aim to reduce FiO₂ to < 60% as soon as clinically feasible by optimizing other ventilator parameters like PEEP.

Key Points

  • Use lung-protective strategies (low tidal volumes) to prevent ventilator-induced lung injury
  • Titrate PEEP to optimize oxygenation while minimizing hemodynamic compromise
  • Calculate settings based on ideal body weight, not actual weight

Airway Management

Endotracheal Intubation

  • Endotracheal intubation involves placing a tube through the mouth or nose into the trachea to establish and maintain a patent airway, facilitate mechanical ventilation, and protect the lungs from aspiration.
  • Confirmation of proper tube placement must be verified through multiple methods including end-tidal CO₂ detection, bilateral breath sounds, chest rise, and chest X-ray.

    Endotracheal Intubation Procedure

  1. Pre-oxygenate patient with 100% oxygen for 3-5 minutes
  2. Administer sedation and/or neuromuscular blocking agents as ordered
  3. Position patient in "sniffing position" (unless contraindicated)
  4. Visualize vocal cords using laryngoscope
  5. Insert endotracheal tube through vocal cords
  6. Inflate cuff to create seal (20-30 cmH₂O pressure)
  7. Confirm placement with end-tidal CO₂ and auscultation
  8. Secure tube and obtain chest X-ray

Clinical Scenario: Failed Intubation

A 68-year-old male with COPD exacerbation requires intubation for respiratory failure. After two failed intubation attempts, the patient's oxygen saturation drops to 82%. The appropriate next steps include:

  1. Resume bag-mask ventilation with 100% oxygen
  2. Call for additional assistance (anesthesia if available)
  3. Consider alternative airway devices (supraglottic airway, video laryngoscope)
  4. Prepare for possible surgical airway if oxygenation cannot be maintained

Key Points

  • Endotracheal tube size: 7.0-8.0 mm for adult females, 8.0-9.0 mm for adult males
  • Position tube 2-3 cm above the carina (typically 21-23 cm at teeth for adults)
  • Maintain cuff pressure between 20-30 cmH₂O to prevent tracheal damage and aspiration

Artificial Airways

  • Endotracheal Tube (ETT): Inserted through the mouth (orotracheal) or nose (nasotracheal) into the trachea. Appropriate for short-term airway management (typically up to 14 days) and allows for positive pressure ventilation.
  • Tracheostomy Tube: Surgical opening created in the anterior trachea below the larynx. Indicated for patients requiring prolonged mechanical ventilation (>14 days), upper airway obstruction, or to facilitate weaning from ventilation.
  • Laryngeal Mask Airway (LMA): Supraglottic device that sits above the larynx creating a seal. Used for short-term airway management or as a rescue device when intubation is difficult; does not fully protect against aspiration.

Artificial Airway Comparison

Feature Endotracheal Tube Tracheostomy LMA
Aspiration Protection Good Good Limited
Duration of Use Short-term (up to 14 days) Long-term Very short-term
Patient Comfort Poor Better Moderate
Ability to Speak No Possible with speaking valve No
Oral Care Access Limited Good Limited

Key Points

  • Consider tracheostomy for patients requiring prolonged ventilation (>14 days)
  • LMAs do not provide definitive airway protection against aspiration
  • Tracheostomy allows for easier weaning, improved patient comfort, and ability to speak with a speaking valve

Airway Suctioning

  • Airway suctioning is performed to remove secretions that obstruct the airway, maintain airway patency, and prevent complications like atelectasis and ventilator-associated pneumonia.
  • Indications include visible or audible secretions, increased peak airway pressures, decreased oxygen saturation, or abnormal breath sounds indicating secretions.

    Endotracheal Suctioning Procedure

  1. Pre-oxygenate with 100% oxygen for 30-60 seconds
  2. Use sterile technique to maintain catheter sterility
  3. Insert catheter without applying suction until resistance is met, then withdraw 1-2 cm
  4. Apply suction (80-120 mmHg) while withdrawing catheter in a rotating motion
  5. Limit suction duration to <10-15 seconds
  6. Re-oxygenate patient between suction attempts
  7. Assess patient response and effectiveness of suctioning
Prolonged suctioning can cause hypoxemia, cardiac dysrhythmias, and increased intracranial pressure. Always limit suction application to less than 15 seconds and ensure adequate pre-oxygenation.

Key Points

  • Catheter size should be no more than half the internal diameter of the artificial airway
  • Closed suction systems reduce risk of healthcare worker exposure and prevent loss of PEEP
  • Monitor for adverse effects: hypoxemia, bradycardia, increased ICP, bronchospasm

Ventilator Complications & Troubleshooting

Ventilator-Associated Complications

  • Ventilator-Associated Pneumonia (VAP): A pneumonia that develops 48 hours or more after endotracheal intubation. Prevention strategies include head-of-bed elevation (30-45°), oral care with chlorhexidine, subglottic suctioning, and daily sedation interruption with spontaneous breathing trials.
  • Ventilator-Induced Lung Injury (VILI): Lung damage caused by mechanical forces during ventilation, including barotrauma (pressure-related), volutrauma (volume-related), and atelectrauma (repeated opening/closing of alveoli). Prevention includes lung-protective ventilation strategies with low tidal volumes (4-6 mL/kg IBW) and appropriate PEEP.
  • Auto-PEEP (Intrinsic PEEP): Occurs when there is incomplete exhalation before the next breath, leading to trapped air and increased intrathoracic pressure. Common in COPD patients and can cause hemodynamic compromise. Management includes increasing expiratory time and treating underlying bronchospasm.
  • Oxygen Toxicity: Prolonged exposure to high FiO₂ (>60%) can cause absorption atelectasis and oxidative damage to lung tissue. Prevention involves using the lowest effective FiO₂ to maintain adequate oxygenation (SpO₂ 88-95%).

VAP Prevention Bundle "WHAP"

  • Weaning trials daily
  • Head of bed elevation (30-45°)
  • Antacid prophylaxis (stress ulcer prevention)
  • Pneumonia prevention (oral care with chlorhexidine)

Key Points

  • Implement VAP prevention bundle for all mechanically ventilated patients
  • Use lung-protective ventilation strategies to prevent VILI
  • Monitor for signs of auto-PEEP, especially in patients with obstructive lung disease

Ventilator Alarms and Troubleshooting

  • Ventilator alarms alert healthcare providers to changes in patient condition or ventilator function that require immediate attention. Prompt assessment and intervention are essential to prevent adverse outcomes.
  • Common alarms include high pressure, low pressure/disconnect, low exhaled volume, apnea, high respiratory rate, and low oxygen alarms. Each requires specific troubleshooting steps based on the underlying cause.

Common Ventilator Alarms and Interventions

Alarm Possible Causes Nursing Interventions
High Pressure Secretions, bronchospasm, coughing, biting ET tube, patient-ventilator asynchrony, pneumothorax Suction airway, assess for tube obstruction, administer bronchodilators if ordered, check for pneumothorax, evaluate need for sedation
Low Pressure/Disconnect Circuit disconnect, ET tube cuff leak, ET tube displacement Check all connections, assess ET tube position, check cuff pressure, manually ventilate if needed
Low Exhaled Volume Circuit leak, ET tube cuff leak, patient-ventilator asynchrony Check for leaks in circuit, check cuff pressure, assess patient-ventilator synchrony
Apnea Sedation effects, neuromuscular weakness, central respiratory depression Assess patient, manually ventilate if needed, review sedation, notify provider
High Respiratory Rate Pain, anxiety, respiratory distress, auto-triggering Assess for pain/anxiety, check ventilator sensitivity, evaluate respiratory status, consider sedation/analgesia

Clinical Scenario: High Pressure Alarm

A 45-year-old intubated patient with pneumonia suddenly triggers high-pressure alarms. The patient appears agitated, SpO₂ drops from 95% to 88%, and breath sounds are diminished on the right. Systematic troubleshooting should include:

  1. Quickly assess patient (vital signs, breath sounds, chest movement)
  2. Disconnect from ventilator and manually ventilate to assess lung compliance
  3. Suction airway to remove potential secretions
  4. Check for tube displacement or obstruction
  5. Evaluate for pneumothorax (diminished breath sounds, tracheal deviation)
  6. In this case, findings suggest possible pneumothorax requiring immediate chest X-ray and potential chest tube placement

Key Points

  • Never silence alarms without addressing the underlying cause
  • High-pressure alarms require immediate attention to rule out life-threatening causes
  • Always have manual resuscitation bag at bedside for emergency ventilation

Weaning from Mechanical Ventilation

  • Weaning is the process of gradually reducing ventilatory support to allow the patient to resume spontaneous breathing. Successful weaning depends on resolution of the underlying condition, adequate respiratory muscle strength, and absence of significant comorbidities.
  • Readiness for weaning is assessed through specific parameters including adequate oxygenation (PaO₂/FiO₂ > 200, PEEP ≤ 5-8 cmH₂O), stable hemodynamics, adequate respiratory drive, and resolution of the condition that necessitated ventilation.

Weaning Parameters "SMART"

  • Spontaneous breathing trial tolerance
  • Minute ventilation < 10 L/min
  • Adequate cough and gag reflexes
  • Respiratory rate < 30 breaths/min
  • Tidal volume > 5 mL/kg

    Spontaneous Breathing Trial (SBT) Procedure

  1. Ensure patient meets readiness criteria
  2. Place on T-piece, CPAP (5 cmH₂O), or low-level PSV (5-8 cmH₂O)
  3. Monitor vital signs, work of breathing, and SpO₂ during trial
  4. SBT duration typically 30-120 minutes
  5. Assess for signs of failure: RR > 35, SpO₂ < 90%, HR increase > 20%, SBP change > 20%, agitation, diaphoresis
  6. If SBT successful, evaluate for extubation
  7. If SBT fails, return to previous ventilator settings and address causes of failure
Post-extubation respiratory failure occurs in 10-20% of patients and is associated with increased mortality. Have equipment for reintubation readily available and consider prophylactic NIV for high-risk patients after extubation.

Key Points

  • Daily assessment of readiness for spontaneous breathing trials improves outcomes
  • Pair daily SBTs with sedation interruption ("wake up and breathe" protocol)
  • Consider tracheostomy for patients failing multiple weaning attempts

Summary of Key Points

  • Mechanical ventilation provides respiratory support when patients cannot maintain adequate oxygenation or ventilation. Common modes include Assist-Control, SIMV, PSV, and CPAP, each with specific indications based on patient condition.
  • Lung-protective ventilation strategies (tidal volumes 4-6 mL/kg IBW, appropriate PEEP) are essential to prevent ventilator-induced lung injury, especially in patients with ARDS.
  • Proper airway management includes confirming endotracheal tube placement with multiple methods (end-tidal CO₂, bilateral breath sounds, chest X-ray) and maintaining appropriate cuff pressures (20-30 cmH₂O).
  • Ventilator-associated complications include VAP, VILI, auto-PEEP, and oxygen toxicity. Prevention strategies include implementing VAP bundles, using lung-protective ventilation, and minimizing FiO₂.
  • Ventilator alarms require prompt assessment and intervention. High-pressure alarms may indicate life-threatening conditions like pneumothorax or tube obstruction.
  • Weaning from mechanical ventilation involves assessing readiness parameters, conducting spontaneous breathing trials, and monitoring for signs of failure. Daily SBTs paired with sedation interruption improve outcomes.

Critical Ventilator Settings to Remember

  • Tidal Volume: 6-8 mL/kg IBW (4-6 mL/kg for ARDS)
  • PEEP: Minimum 5 cmH₂O, titrate based on oxygenation
  • FiO₂: Lowest possible to maintain SpO₂ 88-95%
  • Plateau Pressure: Maintain < 30 cmH₂O to prevent barotrauma
  • ET Tube Cuff Pressure: 20-30 cmH₂O

Commonly Confused Points

Ventilator Modes: AC vs. SIMV

Feature Assist-Control (AC) SIMV
Mandatory Breaths All breaths receive full support Only set number of breaths receive full support
Spontaneous Breaths All spontaneous efforts trigger fully supported breaths Spontaneous efforts between mandatory breaths receive only pressure support
Work of Breathing Lower work of breathing Higher work of breathing
Best Use Patients with minimal respiratory effort or high WOB Weaning; patients with adequate respiratory drive

Volume Control vs. Pressure Control

Feature Volume Control Pressure Control
Set Parameter Tidal volume is set and guaranteed Inspiratory pressure is set and limited
Variable Parameter Pressure varies based on compliance Volume varies based on compliance
Risk of Barotrauma Higher (pressure can increase) Lower (pressure is limited)
Risk of Hypoventilation Lower (volume is guaranteed) Higher (volume may decrease with compliance changes)
Best Use Patients with stable lung compliance Patients at risk for barotrauma; variable compliance

PEEP vs. CPAP

Feature PEEP CPAP
Definition Positive pressure maintained at end of expiration Continuous positive pressure throughout respiratory cycle
Use With Component of mechanical ventilation Used with spontaneous breathing
Ventilatory Support Used with other ventilator settings No additional ventilatory support provided
Primary Purpose Prevent alveolar collapse, improve oxygenation Maintain airway patency, improve oxygenation
A common mistake is confusing pressure support ventilation (PSV) with pressure control ventilation (PCV). PSV applies only to patient-triggered breaths and is often used with CPAP or SIMV, while PCV delivers mandatory breaths at a set pressure and can be used in assist-control mode.

Study Tips

Memory Aids

Indications for Mechanical Ventilation "SOAP-A"

  • Severe hypoxemia (PaO₂ < 60 mmHg on FiO₂ > 60%)
  • Obstructed airway requiring protection

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