Mechanical Ventilator Management in Clinical Simulations

Mechanical Ventilator Management in Clinical Simulations

Mechanical ventilation is one of the most critical skills a respiratory therapist performs. In the ICU, the ventilator substitutes for or assists the patient's own breathing effort. Your ability to initiate settings correctly, recognize alarms promptly, and assess readiness to wean directly affects patient survival and recovery.

Initiating Ventilation: Selecting the Right Settings

Before touching the ventilator, read the clinical data carefully. The three factors that guide your initial settings are the patient's diagnosis, body weight (used to calculate ideal body weight, or IBW), and arterial blood gas (ABG) values if available.

Mode selection depends on the patient's condition and breathing effort. Volume-controlled assist-control (AC/VC) is a common starting mode because it guarantees a set tidal volume with every breath. Pressure support ventilation (PSV) is often used during weaning because it requires patient effort. Synchronized intermittent mandatory ventilation (SIMV) delivers a set rate of mandatory breaths while allowing spontaneous efforts between them.

Tidal volume (VT) should be set at 6–8 mL per kg of IBW for most adults. For ARDS patients, lung-protective ventilation mandates 6 mL/kg IBW or less to prevent ventilator-induced lung injury (VILI). Never set tidal volume by actual body weight in an obese patient—doing so risks overdistension.

Respiratory rate (RR) is typically set at 12–16 breaths per minute for most adults, adjusted by the target PaCO2 and minute ventilation.

PEEP (positive end-expiratory pressure) keeps alveoli open at the end of exhalation. A starting PEEP of 5 cmH2O is standard; ARDS protocols often require higher PEEP titrated to oxygenation.

FiO2 starts at 1.0 (100%) when oxygenation status is unknown, then is weaned to the lowest level that maintains SpO2 of 92–98% (88–92% for COPD patients to avoid suppressing hypoxic drive considerations and to follow prescribed targets).

Diagnosis-Specific Considerations

ARDS: Use lung-protective ventilation—VT 6 mL/kg IBW, plateau pressure below 30 cmH2O, higher PEEP as tolerated. Permissive hypercapnia (allowing PaCO2 to rise above normal) is acceptable to avoid high pressures.

COPD exacerbation: These patients are at risk for air trapping (auto-PEEP). Use a slower rate, longer expiratory time (lower I:E ratio toward 1:3 or 1:4), and moderate VT. Watch for elevated peak and plateau pressures.

Post-operative patients: Generally healthier lungs. Standard settings apply. Focus on comfort, early weaning, and pain management that allows adequate ventilation.

Alarm Management: Recognize and Respond

Alarms are safety devices—never silence an alarm without first identifying and correcting the cause. For each alarm, follow this sequence: assess the patient first, then troubleshoot the ventilator.

• High-pressure alarm: Causes include secretions, biting the tube, bronchospasm, pneumothorax, or circuit kink. Suction, reposition, or call for immediate physician evaluation if pneumothorax is suspected.
• Low-pressure alarm: Suggests a circuit leak, cuff leak, or disconnection. Check all connections and cuff pressure immediately.
• Apnea alarm: The patient has stopped triggering breaths for the set apnea interval. Assess responsiveness, check for sedation over-effect, and ensure backup rate is active.
• Low minute volume: Total ventilation is insufficient—check for leaks, decreased rate, or decreasing tidal volumes.
• High respiratory rate: Patient is tachypneic—assess for pain, anxiety, worsening hypoxemia, or agitation; do not simply silence the alarm.
• Low SpO2: Verify probe placement first, then check FiO2, PEEP, patient position, and circuit integrity; obtain ABG if indicated.

Weaning and Spontaneous Breathing Trial (SBT)

Weaning is the gradual process of reducing ventilator support before extubation. Before conducting an SBT, confirm that the patient meets standard readiness criteria: the underlying cause of respiratory failure is improving, the patient is awake and able to follow commands, hemodynamics are stable without high-dose vasopressors, FiO2 is at or below 0.40–0.50 with PEEP at or below 5–8 cmH2O, and secretion management is adequate.

A standard SBT places the patient on low-level pressure support (typically 5–8 cmH2O) or a T-piece for 30–120 minutes. Monitor closely for signs of failure: RR greater than 35, SpO2 below 90%, use of accessory muscles, diaphoresis, agitation, or hemodynamic instability. If the patient tolerates the SBT without these signs, extubation readiness should be communicated to the physician.

Safety Points

• Always verify ventilator settings against the physician's order before connecting to the patient.
• Confirm endotracheal tube position before initiating ventilation.
• Perform manual ventilation with a bag-valve-mask if the ventilator malfunctions—never leave the patient without ventilation.
• Document all settings, alarms, and changes on the ventilator flow sheet.
• Work within your scope of practice: adjustments outside standard protocols require physician or advanced-practitioner orders.
• Infection control: use standard precautions and circuit management per facility policy to prevent ventilator-associated pneumonia (VAP).