Clinical Implications of VC and AC-VC

Ventilator Modes

• Assist-control ventilation (A/C) is a mode that delivers a preset number of breaths per minute and assists any additional breaths initiated by the patient.
• There are two types of A/C ventilation: assist-control volume control (AC-VC) and assist-control pressure control (AC-PC).
• The main challenge with A/C ventilation is that patient-initiated breaths are not proportional to effort, which can lead to hyperventilation, air trapping, and poor ventilator synchrony.
• Synchronized intermittent mandatory ventilation (SIMV) is a mode that delivers mandatory breaths at a preset rate but synchronizes them with patient effort, allowing spontaneous breaths in between.

Positive End-Expiratory Pressure (PEEP)

• PEEP is the maintenance of positive airway pressure after passive exhalation during mechanical ventilation.
• Benefits of PEEP include increased functional residual capacity (FRC), improved oxygenation, prevention of alveolar collapse, and reduced ventilator-induced lung injury (VILI).
• Risks of PEEP include reduced venous return, decreased cardiac output, and lung overdistention or pneumothorax.
• Intrinsic PEEP (iPEEP) is PEEP that results from incomplete exhalation between breaths, often due to improper ventilator settings.

Pressure Control (PC) Ventilation

• The key parameters for PC ventilation are pressure target, inspiratory time, respiratory rate (RR), and positive end-expiratory pressure (PEEP).
• The variable parameters in PC ventilation are tidal volume and inspiratory flow rate.
• Clinical implications of PC ventilation include controlling airway pressure but not guaranteeing tidal volume, making it suitable for patients with high respiratory drive.
• PC ventilation is best suited for patients with severe asthma, COPD, and salicylate toxicity.

Volume Control (VC) Ventilation

• The key parameters for VC ventilation are tidal volume, inspiratory rate (RR), inspiratory flow pattern, and inspiratory time.
• The variable parameters in VC ventilation are peak inspiratory pressure (PIP) and end-inspiratory alveolar pressure.
• Clinical implications of VC ventilation include guaranteeing tidal volume but risks high or injurious lung pressures, making it suitable for ARDS or obesity.
• VC ventilation is best suited for patients with ARDS, obesity, and severe burns.

Pressure Support Ventilation (PSV)

• The key feature of PSV is the level of pressure support.
• PSV is best suited for spontaneously breathing patients with good respiratory effort requiring minimal ventilator support.

Continuous Positive Airway Pressure (CPAP)

• The key feature of CPAP is the level of continuous positive airway pressure.
• CPAP is best suited for alert, spontaneously breathing patients with reversible respiratory distress (e.g., COPD, ACPE).

Bilevel Positive Airway Pressure (BiPAP)

• BiPAP is characterized by IPAP and EPAP.
• BiPAP is used for patients similar to CPAP, but with alternating pressures during inspiration and expiration.

Explore the clinical implications of volume control (VC) and assist-control volume control (AC-VC) in medical practice. This quiz will cover the best conditions for management, key features, and practical scenarios associated with these ventilation strategies. Enhance your understanding of critical care settings with focused questions.