What are the different ventilation modes used in the Cardiovascular Intensive Care Unit (CVICU) and their significance?

Ventilation Modes in the Cardiovascular Intensive Care Unit (CVICU) and Their Significance

Assist-control ventilation (ACV) should be used at night over pressure support ventilation (PSV) in CVICU patients to improve sleep quality, reduce central apneas, and optimize patient-ventilator synchrony. 1

Common Ventilation Modes in CVICU

Controlled Modes

• Assist-Control Ventilation (ACV): Delivers a preset tidal volume or pressure when triggered by patient effort or time. Provides backup ventilation and improves sleep efficiency by preventing central apneas due to its backup rate 1
• Volume-Controlled Ventilation (VCV): Delivers a preset tidal volume regardless of pressure required, offering consistent minute ventilation but may lead to higher peak pressures in patients with changing compliance 2
• Pressure-Controlled Ventilation (PCV): Delivers a preset pressure with variable tidal volumes, limiting maximum airway pressure and potentially reducing ventilator-induced lung injury 2

Assisted/Spontaneous Modes

• Pressure Support Ventilation (PSV): Augments spontaneous breathing with preset pressure support. May cause central apneas during sleep if set too high, leading to hyperventilation and hypocapnia, particularly problematic in cardiac patients 1
• Proportional Assist Ventilation (PAV): Delivers pressure proportional to patient effort based on respiratory mechanics, improving patient-ventilator synchrony and potentially enhancing sleep quality 1
• Neurally Adjusted Ventilatory Assist (NAVA): Uses diaphragmatic electrical activity to proportionally assist breathing, minimizing asynchrony but requires specialized equipment 1

Advanced/Hybrid Modes

• Airway Pressure Release Ventilation (APRV): Maintains high continuous positive airway pressure with intermittent releases, promoting alveolar recruitment over time and potentially improving oxygenation 3
• Adaptive Support Ventilation (ASV)/INTELLiVENT-ASV: Closed-loop ventilation that automatically adjusts settings based on patient physiology and respiratory mechanics 4
• Adaptive Pressure Control (APC): Combines volume targeting with pressure-limited delivery, potentially offering benefits of both volume and pressure modes 5

Clinical Significance and Selection Criteria

Sleep Quality Considerations

• ACV is superior to PSV for sleep quality: ACV prevents central apneas during sleep, improves total sleep time and reduces sleep fragmentation compared to PSV 1
• PSV can worsen sleep: 54% of patients develop central apneas during PSV, leading to arousals and sleep fragmentation, particularly problematic in heart failure patients 1
• Adding dead space to PSV: Can reduce central apneas (from 53±8 to 4±2 events/h) if PSV must be used 1

Patient-Ventilator Synchrony

• Proportional modes (PAV, NAVA): Improve patient-ventilator interaction by proportionally unloading patient effort, reducing asynchrony which is associated with prolonged ventilation and increased mortality 1
• Asynchrony impact: Patient-ventilator asynchrony is associated with prolonged mechanical ventilation, increased morbidity, mortality, and poorer sleep quality 1
• Mode selection for synchrony: In spontaneously breathing patients with variable respiratory demand, pressure-based modes may offer lower work of breathing and improved comfort 2

Cardiac Considerations in CVICU

• Heart failure patients: More susceptible to central apneas during PSV due to decreased cardiac output, increased left ventricular filling pressure, prolonged circulation time, and increased chemoreceptor sensitivity 1
• Avoiding hyperventilation: Critical in cardiac patients as it may worsen central apneas; adjust ventilator settings to prevent PaCO2 from falling below the apneic threshold 1
• PEEP considerations: For cardiac patients, appropriate PEEP (4-8 cmH2O) can offset intrinsic PEEP and improve triggering 6

Practical Recommendations for CVICU

Optimizing Nighttime Ventilation

• Use ACV at night: Switch from PSV to ACV during nighttime to improve sleep quality and prevent central apneas 1
• If using PSV: Carefully adjust the level of assistance to prevent hyperventilation and central apneas, particularly in patients with heart failure 1
• Consider proportional modes: PAV or NAVA may improve patient-ventilator synchrony and potentially sleep quality, though evidence for sleep improvement is mixed 1

Ventilator Setting Adjustments

• Tidal volume: Target 4-8 ml/kg predicted body weight to minimize complications 6
• PEEP setting: Use 4-8 cmH2O to offset intrinsic PEEP and improve triggering 6
• Oxygen titration: Maintain SpO2 between 88-92% to avoid worsening hypercapnia 6, 7
• Respiratory rate: Set between 10-14 breaths/min initially 6
• I:E ratio: Allow adequate expiratory time (I:E ratio of 1:2 or 1:3) to prevent air trapping, especially important in COPD patients 6, 7

Common Pitfalls to Avoid

• Excessive PSV levels: Can cause hyperventilation, hypocapnia, and central apneas 1
• Inadequate expiratory time: Can cause dynamic hyperinflation and auto-PEEP, particularly in patients with obstructive lung disease 6
• Excessive oxygen therapy: Can worsen hypercapnia; maintain target saturation of 88-92% 6, 7
• Delayed recognition of asynchrony: Monitor for patient-ventilator asynchrony and adjust settings or consider alternative modes accordingly 1

By selecting appropriate ventilation modes and optimizing settings based on patient characteristics and time of day, clinicians can improve patient-ventilator synchrony, sleep quality, and potentially clinical outcomes in the CVICU setting.