The term “oxygen therapy” refers to the giving of oxygen to a patient at a concentration higher than that found in ambient air. Oxygen therapy is a critical component of hypoxemia treatment and is frequently utilized across a broad variety of disciplines. Oxygen is a narcotic. It should not be self-administered; rather, it should be prescribed. Thus, it requires caution when administered, but no patient should be without it when necessary and warranted. This needs a grasp of the oxygen delivery devices themselves, as well as the proper use of the different gadgets included in the oxygen treatment arsenal.
OXYGEN DISTRIBUTION DEVICES
There are several oxygen delivery devices, which are essentially classified as low flow oxygen devices and high flow oxygen devices. 1st Table The nasal cannula, basic face mask, partial rebreathing mask, and non-rebreathing mask are all examples of low flow devices. Venturi masks, oxygen tents, and oxygen hoods are examples of high flow oxygen delivery equipment.
Nasal cannulas are the most often utilized kind in our daily practice. Patients are often more comfortable with the nasal cannula, but it is important to consider if the fraction of inspired oxygen (FiO2) given by the nasal cannula is adequate for the patient. At a flow rate of 6 L/min, the nasal cannula provides the highest fraction of inspired oxygen (FiO2). There is no additional rise in FiO2 with increasing flow. Appropriate devices and flow rates should be utilized to ensure that the patient’s oxygen saturation is maintained within the specified range. Prolonged use of a nasal cannula may result in mucosal dryness and secretory crusting, which may result in epistaxis.
A simple face mask adds another reservoir of 100-200mL of oxygen to the system. It may supply the patient with a FiO2 of up to 0.6. A minimum flow rate of 5 L/min is required to avoid rebreathing and carbon dioxide (CO2) buildup. Although it is lightweight and easy to use, it must be removed when eating and conversing. It might be challenging to get a suitable seal in patients using Ryle’s tube. It is contraindicated in people with face injuries or burns. If the face mask mistakenly creeps up towards the eyes, it may cause irritation and dryness of the eyes.
Reservoir bags are fitted to both partial rebreathing and non-rebreathing masks to give extra reservoir content. As the name implies, partial rebreathing masks permit some level of rebreathing. The reservoir bag collects exhaled oxygen from the anatomic dead space that is not involved in gas exchange. This is particularly beneficial in circumstances when oxygen supply is limited and oxygen conservation is desirable. A partial rebreathing mask produces a FiO2 concentration of between 0.6 and 0.8. The reservoir bag must be inflated throughout to ensure that the maximum amount of FiO2 is delivered while also allowing for proper CO2 evacuation. This requires fresh gas fluxes greater than 8 L/min. In comparison to partial rebreathing masks, nonrebreathing masks contain extra valves. Gases may flow in just one direction via the valves. Flutter valves on the side ports prevent entrainment of room air. By adding a valve between the mask and the reservoir bag, the exhaled gases are stopped from entering the reservoir bag. It is capable of providing the greatest FiO2 values of 0.9 to 1.0 without intubation at 12 – 15 L/min of fresh gas flow. Prolonged usage might be painful for the patient due to the need for a tight seal and the overall weight of the device. Equipment failure may result in CO2 buildup and asphyxia.
Venture masks, which are frequently used, are included in the high flow oxygen device. The benefit of this kind of equipment is that the precise amount of FiO2 given by the gadget is known. FiO2 is dependent on the device’s structure and the flow of new gas. The mechanism of action is often misquoted due to the venturi effect. The mechanism of action is based on the air entrainment theory. Air entrainment happens as a result of the viscosity of the fluid. The viscous shearing force between the flowing and static layers of fluid drags the non-moving fluid into the moving stream. There are two models available: a fixed FiO2 model that needs color-coded and labeled inspiratory attachments that generate a known FiO2 at a particular flow rate. Green has the highest FiO2 content at 60%, followed by red, yellow, orange, white, and blue with 40%, 35%, 31%, 28%, and 24%, respectively. A variable FiO2 model has a graduated adjustment of the air entrainment inlet that may be adjusted to accommodate variations in supplied FiO2. These are not color coordinated in any way.
Oxygen hoods are high-flow devices that are used to provide oxygen to newborns. It is a plastic hood that fits over the baby’s head and has a neck hole. This gadget is beneficial for newborns who need more than 40% oxygen. This technique of oxygen delivery should be warmed and humidified. To avoid CO2 buildup, the overall flow rate must be more than 10 L/min. By mixing the flow of oxygen and air, the desired oxygen concentration may be attained. The given oxygen must be humidified and warmed. Hypoxemia, hyperoxia, hyperthermia, hypothermia, discomfort, and soreness in the neck are all possible problems of oxygen hood use.
An air/oxygen blender, an active heated humidifier, a single heated circuit, and a nasal cannula are used in high flow nasal oxygen treatment. The inspiratory fraction of oxygen (FIO2) is regulated between 0.21 and 1.0 on the air/oxygen blender. A high-flow nasal cannula (HFNC) can supply up to 8 liters per minute (L/min) in babies and 60 liters per minute (L/min) in adults. The active humidifier heats and humidifies the gas before it is supplied via the heated circuit. It is thought to have a variety of physiological consequences, including decreased anatomical dead space, the PEEP effect, a consistent proportion of inspired oxygen, and adequate humidification. It has established the gold standard of treatment for babies, children, and preterm neonates in a variety of clinical circumstances. Due to a number of physiological advantages over conventional oxygen therapy, including increased comfort and tolerance, more effective oxygenation in certain circumstances, and an improved breathing pattern with increased tidal volume and decreased respiratory rate and dyspnea, we are now seeing an increase in adult use.
SELECTION OF SUITABLE OXYGEN DISTRIBUTION DEVICES
To select the best oxygen delivery decision, a few fundamental concepts must be grasped, followed by the prescription of oxygen through an appropriate delivery system. The very first consideration should be the patient’s state. When patients are reasonably stable but at risk of developing type 2 respiratory failure as a result of underlying lung or systemic disease, the goal oxygen saturation should be 88-92 percent and the oxygen dose should be titrated accordingly. Inappropriately high flow and saturation levels may be detrimental in these patients, increasing mortality and morbidity, while titrated oxygen supply has been shown to dramatically lower mortality, hypercapnia, and respiratory acidosis. These patients are best treated by initiating treatment with a fixed flow oxygen delivery device capable of providing consistent and predictable FiO2, such as a blue or white venturi, while maintaining patient arterial oxygen saturation (SpO2) of 88-92 percent. And then titrating the oxygen to get the lowest possible dosage of FiO2 while retaining the desired SpO2 level. The goal should be to maintain a SpO2 of 94-98 percent in patients who are not at risk of type 2 respiratory failure and who need oxygen treatment due to hypoxemia. Patients with initial severe hypoxemia (SpO2 less than 85%) should be started on high flow oxygen at a rate of 10-15 L/min through reservoir mask. Others who have a pretty normal SpO2 of 85-94 percent may begin with a low flow device such as a nasal cannula at 2-6 L/min or a simple face mask at 5-10 L/min and gradually increase to 2L/min to maintain the goal SpO2. Apart from the goal SpO2 mentioned for different illnesses, permissive hypoxia is a relatively recent method for maintaining SpO2 between 82 and 88 percent in critically sick patients in order to enhance outcomes.
Oxygen should be viewed as a medication, and caution should be used while giving it. To minimize the risks associated with excessive and insufficient oxygenation, clear objectives should be kept in mind while selecting suitable oxygen treatment and delivery equipment.. Regardless of the aim, the principles for selecting delivery devices and titrating the flow rate remain the same.