These are classified as high flow Oxygen Delivery Devices and low flow Oxygen Delivery Devices.
Classification of Oxygen Delivery Devices in non intubated patient :
1. High flow (fixed performance) delivery systems.
2. Low flow (variable performance) delivery systems.
As the high flow oxygen delivery devices have already been discussed, let us see what the low flow ones are.
Low Flow Oxygen Delivery Devices :
These include:
i. Nasal cannula.
ii. Simple mask also called as Mary Carterall mask.
iii. Oxygen tents.
iv. Non rebreathing mask.
v. Rebreathing mask.
vi. Polymask.
The advantage is that these are very cheap and can be used in wards, preoperative and postoperative rooms and these are better tolerated by patients as compared to high flow systems.
The disadvantage is that the delivered oxygen (F102) accuracy can not be predicted (compared to venturi mask which delivers accurate concentration).
These low flow Oxygen Delivery Devices are variable performance devices i.e., their performance is effected by changes in patient’s tidal volume and respiratory rate.
Oxygen Mask
Very commonly used among the Oxygen Delivery Devices in wards. Also known as Mary Carterall mask.
| Oxygen flow ratelminute | Delivered oxygen (Fl02) |
| 5-6 litres | 40% |
| 6-7 litres | 50% |
| 7-8 litres | 60% |
So the maximum concentration of oxygen that can be delivered by oxygen mask is 60%. Increasing flow rate beyond 8 litres will not increase the (F102) to more than 60%.
Attaching reservoir bag can increase F102 to 80%.
Nasal Cannula
The tip of nasal cannula should lie in nasopharynx.
| Flow rate (litre/mm) | Fl02 |
| 1 | 24% |
| 2 | 28% |
| 3 | 32% |
| 4 | 36% |
| 5 | 40% |
| 6 | 44% |
So the maximum oxygen which can be delivered by nasal cannula is 44%.
These are another type of Oxygen Delivery Devices can deliver up to 80% of oxygen.
Rebreathing Mask :
When tightly fitted they can provide approximately 100% oxygen.
Oxygen Tents (Hoods) :
Used for children. A lot of wastage of oxygen do occur and accurate concentration can not he predicted.
Oxygen Delivery Devices In Intubated Patient :
It is through ventilators which deliver accurate concentration of oxygen from 21% to 100%.
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