Certified Respiratory Therapist Practice Exam

What is a common consequence of high supplemental O2 flows when using NPPV ventilators?

1. A decreased tidal volume

2. An increased inspiratory force

3. Interference with triggering or cycling

4. A more comfortable patient experience

The correct answer is: Interference with triggering or cycling

High supplemental oxygen flows utilized in non-invasive positive pressure ventilation (NPPV) can create an environment where the flow of gas interferes with the device's ability to effectively trigger and cycle the breaths. NPPV relies on detecting patient effort to either initiate or terminate mechanical breaths based on their own respiratory mechanics. When high levels of supplemental oxygen are delivered, the flow dynamics change significantly. This can overwhelm the sensitivity settings of the ventilator, leading to issues where the ventilator cannot accurately sense the patient's inspiratory efforts. Consequently, it might fail to provide assistance during inhalation or may not appropriately cycle off during exhalation. This can result in ineffective ventilation, patient discomfort, and increased work of breathing. Understanding this concept emphasizes the importance of ensuring that oxygen flow settings are appropriate to support patient triggering and the efficient cycling of breaths in the use of NPPV. The comfort of a patient, tidal volume, or inspiratory force are less directly affected by high flow settings compared to the interaction between the ventilator and the patient's respiratory effort.