The Small Animal Ventilator

Did you know that a person could be breathing just fine but not getting enough oxygen into the body as needed? While breathing is simply taking air in and out of the lungs, ventilation takes into account the exchange of gasses.

For adequate ventilation to occur, sufficient oxygen must enter into the bloodstream while the carbon dioxide produced must be expelled from the lungs properly. The small animal ventilator necessary when this exchange is not happening properly. Risk factors that predispose anesthetized patients to inefficient ventilation include diaphragmatic impairment, surgical positioning, analgesics and decreased body temperature. Patients who are obese, have pneumonia, head trauma, are debilitated or are undergoing thoracotomy or diaphragmatic hernia repair will benefit from the anesthetic ventilator.

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The problems that the anesthetic ventilator solves

The small animal ventilator solves two main problems: hypoxemia and carbon dioxide expulsion. Let’s look at them in depth. Now we all know that for the body to function properly, enough oxygen must reach the tissues from the lungs. This oxygen is transported to the tissues through the blood. When sufficient amounts of oxygen do not reach the tissues, a condition known as hypoxemia occurs. This should not be confused with cyanosis that affects the mucous membranes and is caused by inadequate amounts of oxygenated hemoglobin. Hypoxemia is caused by low inspired oxygen, ventilation and blood perfusion mismatch, hypoventilation, low perfusion and blood shunting past the lungs.

When carbon dioxide is not sufficiently being expelled from the lungs, proper ventilation is obviously not taking place. Carbon dioxide is a by-product of the cellular activities. The cells release this carbon dioxide into the blood which in turn takes it to the lungs for expulsion. The exchange site is the lungs where efficient ventilation is highly relied on. The amount of arterial carbon dioxide concentration is known as PaCO2. Patients who are under an anesthesia are prone to elevated levels of PaCO2. This is as a result of the improper elimination of carbon dioxide due to; hypoventilation, muscle weakness or impaired diffusion of carbon dioxide due to lung disease. The elevated levels of carbon dioxide can also be due to re-breathing carbon dioxide. This can occur if the patient has excessive dead space in their lungs, they have a one-way valve on their anesthesia machine is misbehaving, and their endotracheal tube is too long and exhausted soda lime among others. A rare cause of high concentrations of PaCO2 is excessive production of carbon dioxide by the body when it is in a hypermetabolic state for instance due to hyperthermia.

Setting up the anesthetic ventilator

It takes some time for the small animal ventilators to kick in once you have set it up well. It takes about 12-16 breaths per minute for about 3-5 minutes by the patient before the ventilator takes over the breathing function.

The small animal ventilator is designed by for use on intubated animals of a small weight mostly up to 10kg in weight. With the help of the incoming gas from your machine, the machine controls the gas sent to the patient in the inspiratory system until the set airway pressure is noted, and at this point, the patient is can exhale. A user-defined can then elapses before inspiration starts again and the process repeats.

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