Endotracheal tube
The endotracheal tube or ventilation tube is an aid for securing the airways in the area of anesthesia and emergency medicine , which is introduced by means of endotracheal intubation . Such a tube usually consists of a thin tube that is open at both ends. Just above the lower opening is located in endotracheal tubes for adults a block cuff ( cuff ). This device can be inflated via a thin tube that runs in the wall of the tube. It then seals the windpipe (trachea) and thus reduces the risk of aspiration . The thin tube also carries a control cuff, which allows an assessment of the filling of the cuff when the endotracheal tube is inserted. At the upper end, the endotracheal tube is equipped with a standardized connector that enables connection to a ventilator or a resuscitation bag .
Today, endotracheal tubes are made of transparent plastic, especially PVC , which is soft and compatible with tissues. The cuffs for endotracheal tubes are made of silicone , which are inflated with low air pressure (low-pressure cuffs ). This reduces the risk of pressure-related damage to the mucous membrane in the area of the windpipe. From rubber -made Hochdruckcuffs be used only rarely. You only need a small amount of air but high pressure to block. For operations in which lasers are used, tubes are used that cannot be damaged as a result.
When intubating infants and children up to the age of about 10 years, tubes that do not require an inflatable cuff are also used, since in children the seal over the mucous membrane of the windpipe is sufficient.
Endotracheal tubes have X-ray contrast strips to enable detection during radiological examinations.
Sizes
The inside diameter is given in millimeters, the outside circumference in Charrière . In the clinic, the mm designation is predominantly used; sometimes, especially in the older literature, Charrière information is still found. Endotracheal tubes are available with an inner diameter of 2 to 11 mm. It is important to select the correct tube diameter before intubation. The tube should not be too large to prevent injuries from strong pressure on the mucous membrane or parts of the larynx. However, a small diameter leads to an increased airway resistance, what is the end of a ventilation therapy at weaning ( Weaning is important). The increased resistance results from the Hagen-Poiseuille law .
Especially with children, in whom the tube is not sealed with a block cuff but with the mucous membrane, the right size is important, whereby a small air leak is tolerated in order to prevent damage to the mucous membrane. The size of the little finger can be used as a rough guideline (for older children the formula "4 + years of age / 4" for the inner diameter in millimeters), but a smaller and a larger tube should still be available during intubation.
Types
Different types of endotracheal tubes are used depending on the application.
For his endotracheal tubes, Magill used a red, commercially available rubber tube, which, due to the storage on rollers, retained a curve, and cut it at an angle. This curvature is also called the Magill curve . Nowadays tubes are no longer made of this material, but these are often made of PVC. This model is often provided with a protection against the obstruction of the actual tube opening, with the Murphy-eye according to Peter M. Murphy. By incorporating a lateral opening below the cuff, adequate ventilation is possible even when the actual end is closed. This tube is called the Murphy tube , while the tubes without a side opening are also known as the Magill tube . These models are suitable for both nasal and oral intubation.
The EDGAR tube is very similar to the Magill tube . The only difference is an additional small tube that can be used to inject liquid-based drugs directly into the trachea and large bronchi . The acronym EDGAR stands for Endobronchial-Drug and Gas Application during Resuscitation , which means as much as endobronchial drug and oxygen administration during resuscitation .
In order to prevent the tube from kinking, a flexible metal spiral is worked into the wall of the spiral tube (Woodbridge tube). They are mainly used for anesthesia in the respiratory tract, such as B. in interventions on the larynx, jaw or thyroid gland , since this flexible tube does not slip out of its position in the trachea so easily during movements and creates space for the intervention due to its flexible shape. These tubes are more expensive than the standard tubes, in hospital use these are often sterilized and reused. Spiral tubes require a guide rod (mandrin or stylet) to insert into the windpipe and are therefore more difficult to handle. In general, a bite guard should be inserted during shallow anesthesia (e.g. diagnostic procedures) to prevent biting and thus narrowing of the lumen. This is independent of the type of tube.
The Oxford tube is a relatively short, right-angled tube that can only be used for oral intubation. Since the insertion length is determined by the bend, it is almost impossible to insert it too deeply and thus only ventilate one half of the lung. This tube is particularly suitable for difficult intubation in which only the lower part of the glottis can be seen.
The Kuhn tube is specially adapted to the shape of the airways, the lower part is straight, the upper part bent several times. Therefore, this type is very difficult to use (inserting until the tip has passed the glottis, then turning through 180 ° and inserting it into the final position) and is therefore not used.
Tubes for side-separated ventilation , double-lumen tubes : For extensive interventions on the esophagus or thoracic organs , it may be necessary to ventilate one of the lungs in order to make room for the operation. In this case, only the corresponding other side of the lung is ventilated. To ensure this, there are various tubes that are designed for side-separated ventilation. A distinction is made between different types (Carlens tubes, White tubes, Bryce-Smith tubes and Robertshaw tubes). An alternative is to use a conventional tube with a bronchial blocker .
Individual evidence
- ^ A b Hans Walter Striebel: Anesthesia, Intensive Care Medicine, Emergency Medicine for Study and Training Schattauer, 2009, ISBN 9783794526352 , p. 83.
- ↑ a b c Hans Walter Striebel: Anesthesia, intensive care medicine, emergency medicine for study and training Schattauer, 2009, ISBN 9783794526352 , p. 84.
- ↑ Harald Genzwürker, Jochen Hinkebein: Case book anesthesia, intensive care medicine and emergency medicine. Georg Thieme, Stuttgart / New York 2005, ISBN 3-13-139311-4 , p. 175.
- ^ P. Murphy: A fiber-optic endoscope used for nasal intubation. In: Anaesthesia. Volume 22, Number 3, July 1967, ISSN 0003-2409 , pp. 489-491, doi : 10.1111 / j.1365-2044.1967.tb02771.x . PMID 4951601 .
- ↑ Reinhard Larsen: Anesthesia and intensive medicine in cardiac, thoracic and vascular surgery. (1st edition 1986) 5th edition. Springer, Berlin / Heidelberg / New York et al. 1999, ISBN 3-540-65024-5 , pp. 491-496.
