Humidification is a very important aspect of tracheostomy tube care. Cilia in the lungs provide a rhythmic pattern of beating that moves mucus upward to be coughed out or swallowed. The average human produces about 10 – 100 mL/day of mucus. Bypassing the upper airway drives dry cold air into the lungs causing the cilia to slow their beating pattern. Accumulation of mucus and mucus plugging may occur as a result of a dry atmosphere in the lungs.
Replacement of humidity to the airway should occur continuously during tracheostomy tube placement. The following methods to replace humidity may be used individually or in some cases an individual may have all methods that may be used a various times.
A Heat Moisture Exchanger (HME) is easy to use and is effective in keeping the airway humidified. The HME used for tracheostomy applications fits directly to the 15 mm adaptor and has an optional oxygen port if oxygen therapy is needed. The efficiency of the HME declines in patients with high respiratory rates, tidal volumes, or high FiO2 delivery. The device that is used with tracheostomy tubes may be called a variety of terms. Note that is may be referred to as an artificial nose, trach nose, or Swedish nose.
The HME has a membrane that collects the exhaled moisture and heat from the patient. When the patient exhales through the device moisture and heat are collected in the hydrophilic material. The subsequent breath passes by the material containing the trapped moisture and humidifies the breath. A HME is contraindicated for patients in the following situations: copious secretions, bloody secretions, and those who have a high need for oxygen. Note that the HME may cause some resistance to flow which may cause unnecessary work of breathing in patients who may be weak.
Bubble humidifier (Low flow use)
A bubble humidifier works by passing oxygen or medical air through sterile water to create humidified air. The gas passes through a porous material to create the bubbles which pick up humidity which is carried to the patient. This humidification device may be used with nasal cannulas.
Aerosol Generator (High flow use)
An aerosol generator typically is used for someone that needs a higher flow of gas. The aerosol generator works by a process called air entrainment. A gas (either oxygen or compressed medical gas) flows past a specially designed air entrainment port which pulls extra molecules of air into the gas flow stream and boosts the total flow that exits the device. As the gas passes through the device water is drawn upward and is aerosolized by a baffle.
The gas flow for an aerosol generator is at least 8 lpm which can increase to the patient via the special device to up to 20 – 30 lpm. It is a good device to deliver oxygen as it can meet the oxygen demand for a patient experiencing shortness of breath.
(Low or High flow use)
A heated humidifier has an electric heating element that heats a reservoir of water and causes the surrounding air to hold a larger amount of water vapor. As the gas travels through the tubing it cools looses it’s ability to hold water vapor. Condensation occurs leaving water inside the corrugated tubing for the care giver to drain.
The heating element of the heated humidifier set up can be turned to higher than 37 degrees Centigrade to offset the cooling that occurs as the gas travels to the patient. Monitoring the temperature so as not to burn the airway is important.