What could cause a higher oxygen percentage than the set FIO2 in an air-entrainment device?

A higher oxygen percentage than the set FIO2 in an air-entrainment device can occur due to several factors, and one of the key reasons is the presence of kinked aerosol tubing. When the tubing is kinked, it can limit the airflow and affect the mixing of air and oxygen within the device. This could result in less ambient air being entrained, causing a higher concentration of oxygen in the delivered mixture than intended.

In an air-entrainment device, the set FIO2 is determined based on the specific ratios of oxygen and ambient air that are allowed to mix. A kink in the tubing disrupts this ratio, which can lead to an increased fraction of inspired oxygen being delivered to the patient, as less air is mixed and more oxygen is directed to the patient.

Factors like a depleted reservoir or a clogged down tube might impact the overall performance of a nebulizer or aerosol device, but they do not directly lead to a higher FIO2. Similarly, a leak in the aerosol tubing may reduce the delivery of FIO2 as it allows ambient air to escape, further complicating the mixture. Therefore, the kinked tubing is a more definitive cause of achieving a higher than intended FIO2 in this context.