Which of the following describes a patient unsupported breath in APRV?

• A. Patient triggers and fully relies on machine support
• B. Patient controls T, L, and C without added pressure support
• C. Ventilator delivers a fixed volume regardless of patient effort
• D. Ventilator provides support only during expiration

Answer: (B)

In APRV (Airway Pressure Release Ventilation), a patient unsupported breath is characterized by the patient controlling the timing (T), level (L), and compliance (C) of their own breath without receiving any additional pressure support from the ventilator. This mode allows for spontaneous breathing while maintaining certain pressure levels set by the clinician, enabling the patient to take breaths based on their needs and comfort.

By facilitating a breath that the patient actively initiates and controls, this mode promotes the use of their own respiratory muscles and encourages more natural breathing patterns. The absence of supplementary pressure support during these breaths means that the patient relies solely on their own effort and lung mechanics to achieve ventilation, which can be important for preserving respiratory muscle function and optimizing gas exchange.

In this context, the other options do not accurately describe an unsupported breath in APRV. For example, if the patient fully relies on machine support, then they are not unsupported. Similarly, if the ventilator is delivering a fixed volume regardless of patient effort, or if support is only provided during expiration, these do not align with the definition of an unsupported breath, where the patient is fully in control of their spontaneous inspirations.