Oxygen Therapy and Delivery Systems

Overview and Fundamentals of Oxygen (O2) Therapy

Oxygen therapy, commonly referred to as supplemental oxygen, is defined as the use of oxygen as a medical treatment. This therapy is primarily prescribed by a physician who is responsible for specifying the oxygen concentration, the specific method of delivery, and the liter flow per minute. While it is a prescription-based treatment, nurses have the authority to initiate oxygen therapy independently in emergency situations. The primary indication for oxygen therapy is for patients who are unable to obtain sufficient oxygen naturally, which often involves low blood oxygen levels, breathing disorders, or conditions that cause impaired gas exchange. Diagnostic indications include Chronic Obstructive Pulmonary Disease (COPD), Pneumonia, Asthma, Bronchopulmonary Dysplasia (BPD), Congestive Heart Failure (CHF), Cystic Fibrosis, Sleep Apnea, various other lung diseases, and trauma sustained by the respiratory system.

Patients suffering from low oxygen levels may exhibit a variety of clinical symptoms. These symptoms include rapid breathing, coughing, wheezing, shortness of breath, and sweating. Furthermore, patients may present with a fast heart rate, confusion, and observable changes in skin color. Oxygen itself is characterized as a colorless, odorless, and tasteless gas. It is typically supplied from high-pressure cylinders or through a wall-mounted outlet system in clinical settings. Because oxygen from these sources is dry, a humidifier must be utilized to provide moisture, preventing the drying out of the patient's mucous membranes.

Monitoring Oxygen Levels and Diagnostics

The efficacy of oxygen therapy and the patient's respiratory status are monitored through various testing methods. Oxygen saturation ($SpO_2$) is a key metric, with a normal level being defined as $95\%$ or greater. Another critical measure is the partial pressure of oxygen ($pO_2$). A normal $pO_2$ level ranges between $75 - 100\,mmHg$. If a patient's $pO_2$ drops to $60\,mmHg$, it serves as a definitive indicator that supplemental oxygen is required. Conversely, oxygen levels reaching $100\,mmHg$ or above are dangerous, as they may cause significant damage to the lungs and associated structures.

Two common diagnostic tools are pulse oximetry and Arterial Blood Gas (ABG) analysis. A pulse oximeter is the standard device for measuring oxygen saturation; the transcript notes that if a patient lacks hands or feet, the oximeter probe should be placed on the earlobe for an accurate reading.

Components of an Oxygen Cylinder

An oxygen cylinder consists of several specific parts designed to regulate and deliver the gas safely. The Oxygen Input Plug is the component that connects to the oxygen tank; it is screwed onto the port to secure the cylinder. The Pressure Adjuster is linked directly to the Pressure Gauge, which allows clinicians to determine the exact amount of oxygen remaining inside the tank. The Flow Adjuster is connected to the Flow Meter and facilitates the adjustment of the oxygen flow in liters per minute. The Flow Meter itself provides a visual indication of the level of flow. The Humidifying Bottle contains sterile water and is used to humidify the dry oxygen as it leaves the tank. The system also includes an Oxygen Input Pipe and an Oxygen Output, which is the point where the specific administration device is connected for the patient.

Safety Precautions During Oxygen Therapy

Strict compliance with safety protocols is vital when dealing with oxygen in pressurized tanks. One fundamental rule is that the gas inside the tank must not be agitated; if the gases are agitated and a leak occurs, it can lead to combustion. To ensure a safe environment, several precautions must be strictly followed. A "NO SMOKING" sign must be prominently displayed whenever oxygen is in use. All electrical devices in the vicinity must be confirmed to be in good working order and must be properly grounded. Healthcare providers must avoid the use of materials that generate static electricity and prohibit the use of volatile or flammable substances near the oxygen source. Finally, the exact location of fire extinguishers must be known to all staff in the area.

Low-Flow and Standard Oxygen Delivery Systems

Oxygen delivery systems are specialized devices used to administer, supplement, and regulate oxygen. The most common and inexpensive device is the Nasal Cannula, also known as nasal prongs. It is easy to apply and allows the patient freedom of movement. It delivers a low concentration of $24 - 45\%$ at a flow rate of $2 - 6\,L/min$. Clinical practice includes placing gauze behind the patient's ears to prevent the development of pressure wounds from the cannula tubing.

Face masks are another category of delivery device, designed to cover both the nose and mouth. These masks feature exhalation ports on the sides to allow exhaled $CO_2$ to escape. The Simple Mask delivers an oxygen concentration of $40 - 60\%$ at flow rates of $5 - 8\,L/min$. The Partial Rebreather Mask delivers a higher concentration, between $60 - 90\%$ at $6 - 10\,L/min$. This mask includes an oxygen reservoir bag that allows the patient to rebreathe approximately $1/3$ of their exhaled air in conjunction with fresh oxygen. This process increases the Fraction of Inspired Oxygen ($FiO_2$) by recycling expired oxygen. It is critical that the reservoir bag does not totally deflate during inspiration to prevent the buildup of $CO_2$.

High-Concentration and Precise Delivery Systems

For patients requiring the highest possible oxygen levels, the Non Rebreather Mask is used. It can deliver concentrations of $95 - 100\%$ at flow rates of $10 - 15\,L/min$. This mask is equipped with one-way valves located on the mask itself and between the reservoir bag and the mask. These valves prevent room air and the patient's exhaled air from entering the bag, ensuring the patient only inhales gas directly from the oxygen source.

The Venturi Mask, also known as an air entrainment mask, is utilized when precise oxygen concentrations are required. It delivers concentrations ranging from $24 - 60\%$ at $4 - 10\,L/min$. The system uses wide-bore tubing and color-coded jet adapters that correspond to specific, precise oxygen concentrations and liter flows, removing the need for manual regulation beyond selecting the correct adapter. The color-coded standards are as follows: Blue adapters provide $24\%$ concentration at $2\,L/min$; White adapters provide $28\%$ at $4\,L/min$; Orange adapters provide $31\%$ at $6\,L/min$; Yellow adapters provide $35\%$ at $8\,L/min$; Red adapters provide $40\%$ at $10\,L/min$; and Green adapters provide $60\%$ at $15\,L/min$.

Alternative and Surgical Oxygen Delivery

When standard masks are poorly tolerated by a patient, a Face Tent may be used. These provide varying concentrations between $30 - 60\%$ at a flow rate of $4 - 5\,L/min$. For patients who are chronically oxygen-dependent, Transtracheal Oxygen Delivery is an option. This involves a small, narrow plastic cannula that is surgically inserted through the skin directly into the trachea and held in place by a chain around the neck. Because oxygen is delivered directly into the lungs, the client generally requires less oxygen overall. A specific Nursing Alert for this method involves keeping the catheter patent by using $1.5\,mL$ of Normal Saline Solution (NSS). The clinician should clean the rod inside and out and then inject another $1.5\,mL$ of NSS. This maintenance procedure must be performed $2 - 3$ times per day.

Pediatric Oxygen Delivery Systems

Infants require specialized delivery systems to ensure safety and appropriate concentration levels. The Oxygen Hood is a rigid plastic dome that encloses the infant's head. It is designed so that gas does not blow directly into the infant's face. This is preferred for infants because nasal cannulas and traditional facemasks can deliver oxygen concentrations that are excessively high for their needs.

Another pediatric option is the Oxygen Tent, which consists of a rectangular clear plastic canopy. This canopy has outlets connecting to an oxygen source and a humidifier to moisturize the air. It delivers approximately $30\%$ oxygen concentration. The protocol for using an oxygen tent involves initially flooding the tent with $15\,L/min$ for a duration of $5$ minutes, after which the flow is adjusted to a maintenance level of $10 - 15\,L/min$. It is also necessary to cover the patient with a gown or cotton blanket while inside the tent to prevent chilling.