Certified Respiratory Therapist Practice Exam

What could be a reason for a patient not receiving the expected volume while being manually ventilated with a bag-valve mask?

1. Incorrect tidal volume settings

2. Fatigue of the bag user

3. Absence of the inlet valve

4. Inadequate oxygen supply

The correct answer is: Absence of the inlet valve

A primary reason that a patient may not receive the expected volume during manual ventilation with a bag-valve mask is the absence of the inlet valve. The inlet valve is crucial for maintaining the one-way flow of oxygen or air into the patient’s lungs. If this valve is missing or malfunctioning, it can lead to the loss of positive pressure, preventing adequate volume delivery and consequently resulting in hypoventilation or ineffective ventilation. When the inlet valve does not function correctly, the bag does not maintain sufficient pressure during the squeeze, allowing air to escape rather than forcing it into the patient's airway. This can manifest as low tidal volumes during ventilation efforts. Understanding the role of the inlet valve highlights the importance of checking equipment integrity before use. Considering the other options provides insights into various challenges encountered in bag-valve mask ventilation. Incorrect tidal volume settings could limit the volume delivered, but in manual ventilation, settings typically allow for adjustments through user technique rather than fixed settings. Fatigue of the bag user can impact the operator’s ability to ventilate effectively over time, but this usually affects the technique rather than directly changing the volume. Inadequate oxygen supply could lead to hypoxemia but wouldn’t necessarily affect the volume delivered; it primarily affects the quality of the