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What is the difference between a normal mask and a venturi inner mask? You have to know about it

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Author : Joe Wong
Update time : 2021-04-16 11:08:22
What is the difference between a normal oxygen mask and a venturi mask? You have to know about it

Ordinary oxygen masks are generally made of medical grade PVC. They are light in weight and have no one-way valve or air reservior. The mask has small holes on both sides for gas discharge, so that even if the oxygen supply is stopped, air can pass through the small holes on the mask and around the mask. The mask needs to be close to the mouth and nose and fixed to the pillow by straps. Compared with nasal cannula oxygen inhalation, PVC mask oxygen inhalation affects the patient's speech and eating. It is easy to shift when the patient is agitated and sleep, and it is easy to cause aspiration when vomiting.

The dead space of the mask and the "pocket effect" affect the relationship between oxygen flow and oxygen concentration. The oxygen flow rate needs to be above 5~6L/min to "wash out" the exhaled air in the mask, which of course also includes carbon dioxide. The oxygen concentration of an ordinary mask is between 50% and 60%. When the oxygen flow rate>8L/min, the oxygen concentration will not increase further as the oxygen flow rate increases. If the oxygen flow is too low when using the mask, not only the concentration of inhaled oxygen decreases, but also the exhaled carbon dioxide accumulates in the mask, causing repeated inhalation of carbon dioxide.

The greater the tidal volume or the faster the inspiratory flow rate, the more the oxygen will be diluted by air. Therefore, ordinary masks are not suitable for patients with acute onset of chronic obstructive pulmonary disease accompanied by severe hypoxemia or acute restrictive ventilatory difficulties (such as acute pulmonary edema).

The mask can increase the oxygen concentration of the patient under certain circumstances by increasing the "oral and nasal dead space". But the same exhaled carbon dioxide may also stay in the mask and cause carbon dioxide retention. When the patient has no COPD or restrictive ventilatory disorder in the past, if the nasal catheter cannot meet the needs of the patient, ordinary masks can be used.

The venturi mask is an oxygen therapy device that uses the Venturi principle to mix a certain flow of air with oxygen to form a high-speed airflow and then deliver it to the patient. The oxygen concentration provided can reach up to 50%, and the flow rate is above 40L/min. As one of the high-flow oxygen supply devices, it has the characteristics of high flow rate and relatively accurate oxygen concentration, and has been widely used in clinical practice.

The change of the patient's breathing state does not affect the inhaled oxygen concentration. The high flow rate gas can promote the discharge of carbon dioxide in the mask, so there is basically no repeated inhalation of carbon dioxide. It is suitable for patients with hypoxia and carbon dioxide retention.