You cannot see what is happening inside the patient that has a tracheostomy and sometimes this can be confusing. In this section you will learn about normal functions of the upper airway including the following:
- Indications for tracheostomy
The first thing to understand with tracheostomy tubes is where they are placed in the neck. The trachea is approximately 11 cm in length, with a range of 10 – 13 cm in the average adult. The tracheostomy tube is placed between the 2nd and 3rd, or the 3rd and 4th cartilage rings of the trachea.
The trachea is 2.3 cm in width and 1.8 cm from front to back. (trach tubes are measured in mm – A common outer diameter size of about 8mm. This trach tube would take up about 50% of the inside of the trachea.)
There are two tracheostomy tube placement techniques. Percutaneous dilatation technique (PDT) and open surgical technique (OST). The PDT is usually done at the patient’s bedside. A needle is inserted into the trachea through the front of the neck. The incision is opened up slightly and dilators are used that increase in size to open up the trachea. A bronchoscope is used to assist with the placement and to ensure safety when the needle and dilators are used.
The OST is done under sterile conditions in the operating room. A lengthwise or horizontal incision is made exposing the trachea. The tracheostomy tube is placed and is sutured into place. Sometimes the flaps of the trachea are sutured with long pieces of suture that are left loose. They are done this way in case of accidental displacement. The sutures can be used to pull open the trachea.
Learning about airflow through the upper airway is important to understanding the differences between someone with a tracheostomy tube and someone without a tracheostomy tube.
Compare the two graphics showing the airflow in a normal airway and one with a tracheostomy tube in place.
The individual without a tracheostomy tube in place has a normal flow of air into and out of the lungs. Air is warmed and humidified by the nasal passage. The body is very well adapted at making sure that by the time the air gets to the lungs it will not dry out or cool down the lungs. Airflow resistance is low unless the patient has an abnormal airway shape, or a tumor in the airway.
The individual with a tracheostomy tube can have two different airflow paths.
(Cuff up) This shows the airflow when the tracheostomy tube cuff is inflated. Note that the airflow path is exclusively in and out of the tracheostomy tube. The tracheostomy tube has a much small diameter than the natural airway and so the resistance is increased. This can cause some increased work of breathing for the patient. The inflated cuff will provide some airway protection from aspiration and is the state whereby we can mechanically ventilate.
(Cuff down) The situation with the cuff down provides two pathways for air to flow both into and out of the lungs. On inhalation, air enters into both the mouth and tracheostomy tube. On exhalation, air will exit past the tracheostomy tube and through the tracheostomy tube. The path that has the least amount of resistance will experience the greater flow of air both into and out of the lungs. The cuff must always be deflated when capping the trach or using a speaking valve.
Speech occurs when air passes through the vocal cords in the larynx. As you have seen previously the airflow when an individual has a tracheostomy tube is altered. Speech is completely stopped or impaired because the flow is directed around the vocal cords. Special equipment can be used to facilitate speech. Allow for alternative ways for an individual to communicate with caregivers such as ABC cards or a pen and paper.
One of the benefits of the use of a tracheostomy tube over an endotracheal tube is that it allows the patient to take nutrition orally. Normally the swallowing function is a coordinated series of steps that is driven by both mechanical movement and pressure. The swallowing mechanism is dominant to respiration in normal individuals. At the start of a swallow a person exhales slightly, respiration pauses while the epiglottis and vocal chords close (protecting the airway), finally an exhalation follows.
The tracheostomy tube “anchors” the larynx in position and alters the swallowing mechanism by not allowing the free movement of the mechanical steps and may cause the airway to not close during the swallow. Aspiration is common.
The upper airway is efficient at heating and humidifying inspired air. By the time inspired air reaches the lung tissue it has been fully saturated with water vapor and heated to body temperature. On exhalation the warm air reaches cooler airways and condenses, leaving moisture in the airways which will be ready for the next inhaled breath to add warmth and humidity. The placement of a tracheostomy tube or other ratification airway bypasses this natural heating and humidifying.
Airway anatomy includes cilia which protect and clear the airway. The cilia are constantly moving to bring foreign material and mucus up the airway to be coughed and either swallowed or expectorated. Cilia activity can be impaired within 10 minutes if exposed to cold dry air. The impaired cilia can take weeks to recover. The effects are thicker secretions, contributing to mucus plugging, and inability to maintain pulmonary hygiene. Humidification equipment supports normal physiologic functions and should always be used with an individual with an artificial airway such as a tracheostomy tube.
Compare the two interactive models by clicking on the various airway anatomy locations.
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Anatomy With a Trach:
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Three main reasons for the placement of a tracheostomy tube:
- To bypass an upper airway obstruction
- To aid in removal of secretions from the airway
- To provide long-term mechanical ventilation