Effects of tidal volume, ventilatory frequency, and oxygen insufflation flow on the fraction of inspired oxygen in cadaveric horse heads attached to a lung model.

The research focuses on understanding the impact of varying tidal volume, ventilatory frequency, and oxygen insufflation flow on the fraction of oxygen breathed in by cadaveric horse heads connected to a lung model.

Study Methodology

The researchers used the following methods for their study:

• Eight equine cadaver heads were prepared for the test. Each horse head was intubated with a nasotracheal tube that was inserted up to the proximal portion of the trachea. In this way, they could simulate breathing by delivering oxygen through a catheter placed within the nasotracheal tube.
• The trachea of the cadaver horse head was connected to a lung model using a spiral-wound hose equipped with a sampling adapter. An artificial lung model is used to simulate the respiratory system’s function in the body.
• The researchers applied eight different treatment combinations to each head. These consisted of two tidal volumes (5 and 8 L), two ventilatory frequencies (6 and 12 breaths/min), and two insufflation rates (10 and 15 L/min).
• To measure the fraction of inspired oxygen, hand-drawn inspired gas samples were collected from the middle of the trachea. These samples were then analyzed to measure the oxygen concentrations.

Research Findings

The study yielded these key findings:

• The fraction of inspired oxygen, as measured in the middle of the trachea, ranged from 26.8% to 39.4% in the horse heads.
• It was found that the fraction of inspired oxygen was significantly higher when the tidal volume was smaller, the ventilatory frequency was lesser, and the insufflation rate was higher.

Implications of the Study

The research findings have important implications:

• The measured fraction of inspired oxygen varied with ventilatory pattern as well as the rate of oxygen insufflation, highlighting the need to consider these parameters when ventilating.
• From a clinical perspective, this information could aid in the interpretation of data regarding arterial blood gases and hemoglobin saturation. It could be particularly beneficial in making appropriate decisions about oxygen insufflation for anesthetized horses, especially those that are breathing room air.