Supplemental oxygen therapy requires the addition of moisture to the gas before it reaches the patient’s airways, a process known as oxygen humidification. This is achieved using a humidifier bottle attached to the oxygen source, which contains a reservoir of water. Distilled water is universally recommended because it serves the dual purpose of protecting the specialized equipment and safeguarding the patient’s respiratory health. The necessity for using distilled water directly addresses the mechanical longevity of the device and the biological purity of the moisture being inhaled.
Why Oxygen Requires Humidification
The oxygen delivered by a concentrator or tank is highly concentrated and lacks natural moisture, making it extremely dry. When this dry gas flows directly into the nasal passages and throat, it can strip the delicate mucous membranes of their natural hydration. This rapid drying effect can lead to significant irritation, discomfort, and inflammation in the upper airway.
Un-humidified oxygen can cause the lining of the nose to dry out, resulting in symptoms like nasal congestion, dryness of the throat, and painful cracking of the membranes. In some cases, this irritation can progress to epistaxis, or nosebleeds. The body’s natural defense mechanisms are compromised when the mucous membranes are desiccated, which can impair the natural clearance of foreign particles. The primary function of the humidifier is to infuse the oxygen with water vapor, ensuring the gas delivered to the patient is moist and comfortable to breathe.
Preventing Mineral Scaling in Equipment
The initial reason for using distilled water is mechanical, focusing on the preservation and efficiency of the oxygen delivery system. Tap water, even soft water, contains dissolved inorganic minerals, most notably calcium and magnesium ions.
As the oxygen gas bubbles through the water or as the water is heated in the humidifier chamber, the pure water molecules vaporize and are carried with the oxygen flow. The dissolved minerals, however, do not evaporate and are left behind in the reservoir. This continuous process concentrates the minerals until they precipitate out of the solution, forming a hard, chalky residue known as scale or limescale. This mineral buildup quickly adheres to the internal surfaces of the humidifier, including the heating element and tubing.
Scaling is detrimental because it reduces the thermal efficiency of the heater and can clog the small orifices and tubing through which the oxygen flows. A scaled-up unit operates less effectively, delivers less humidified oxygen, and requires more frequent, intensive cleaning, ultimately shortening the overall lifespan of the medical equipment. Distillation is a purification process that removes these non-volatile minerals, ensuring the only substance that evaporates is pure water.
Ensuring Respiratory Safety
The second reason for choosing distilled water concerns the patient’s respiratory safety. Tap water, while safe for drinking, is not sterile and may contain a range of biological contaminants, including bacteria, mold spores, and even endotoxins. Endotoxins are toxic compounds released from the cell walls of certain bacteria.
When non-distilled water is used in a humidifier, the warm, moist environment of the reservoir can become an ideal breeding ground for these microorganisms. As the humidifier operates, it can aerosolize these biological contaminants, creating a fine mist that is then delivered directly into the patient’s lungs. For individuals requiring supplemental oxygen due to a compromised respiratory system, inhaling these pathogens poses a significant risk of developing a serious respiratory infection.
The distillation process involves boiling the water to create steam, which separates the pure water vapor from biological contaminants. The steam is then condensed back into liquid form, resulting in water that is virtually free of minerals and microorganisms. This level of purity is necessary to ensure that the moisture inhaled by the patient is clean and does not introduce a risk of infection into the delicate lung tissue.
Distinguishing Distilled Water from Other Sources
Understanding the specific purification of distilled water helps explain why other common water sources are unsuitable for oxygen humidifiers. Tap water is the least appropriate choice due to its high and variable content of both dissolved minerals and potential microbial load. Using it rapidly compromises both the equipment and patient safety.
Filtered water, which may pass through carbon filters or reverse osmosis systems, is better than tap water because it removes some particles and contaminants. However, filtration systems are inconsistent and may not reliably remove all dissolved minerals or eliminate all bacteria and viruses. Bottled water, including spring or mineral water, is also not recommended, as it often contains naturally occurring minerals that will still cause scaling and residue in the device.
Distilled water addresses both major concerns by simultaneously removing minerals to protect the equipment and eliminating biological contaminants to protect the patient. Sterile water, which is water guaranteed to be free of viable microorganisms, is also acceptable and often used in clinical settings. Distilled water is the consumer standard because it meets the stringent requirements for both mineral and microbial purity necessary for safe and efficient oxygen humidification.