Chapter 76 Emergency Oxygen Administration
O2 is required for cellular metabolism, and is thus essential for life. It is a colorless, odorless, and tasteless gas that makes up 21% of the earth’s atmosphere and is obtained commercially by the fractional distillation of air.3,4 In the case of hypoxia, convenient delivery mechanisms can enable uncomplicated administration of supplemental O2 in both the pre-hospital and hospital settings. Oxygen storage and administration must be controlled, because oxygen will also support and accelerate combustion, even though oxygen is not itself flammable.
Indications
Indications for the use of supplemental O2 include but are not limited to:2,5
Oxygen should be administered by providers trained in its use. According to an FDA statement “The Food and Drug Administration generally regards oxygen to be a prescription drug. Nevertheless, FDA recognizes that there are many circumstances under which it would be impractical to insist that oxygen be administered only under the supervision of a physician.”16
Has FDA modified the federal caution statement requirement for medical oxygen?
Yes, on September 19, 1996, FDA informed the Compressed Gas Association that a final decision had been reached on its citizen petition. The label for medical oxygen should bear the statement, “For emergency use only when administered by properly trained personnel for oxygen deficiency and resuscitation. For all other medical applications, Caution: Federal law prohibits dispensing without prescription.”15
Contraindications
In an acutely hypoxic patient there is no absolute contraindication to the administration of supplemental O2. The one potential exception to this is the person with severe chronic obstructive pulmonary disease (COPD), who may be put at risk for respiratory depression. For such patients, treatment guidelines are optimally based on achieving target arterial oxygen tensions (or saturations) rather than on predetermined concentrations or flow rates of inspired oxygen. Evidence suggests that in patients with impending respiratory failure due to an acute exacerbation of COPD, the arterial oxygen saturation should be maintained no higher than 85% to 92% to minimize the rise in PCO2 that can accompany oxygen administration.11
Pulmonary Oxygen Toxicity
In situations in which a high concentration of supplemental O2 is administered for many hours, pulmonary O2 toxicity is possible, particularly if a diver with decompression illness subsequently requires hyperbaric oxygen therapy (HBOT). The first symptoms of pulmonary O2 toxicity are due to tracheobronchitis, which is characterized by substernal burning, chest tightness, and cough. Continued exposure may result in dyspnea and adult respiratory distress syndrome (ARDS). Pulmonary O2 toxicity is usually reversible with cessation of O2 therapy or reduction in the inspired concentration.8
Central Nervous System Oxygen Toxicity
Central nervous system (CNS) O2 toxicity can only occur when a person is exposed to O2 at ambient pressures greater than 1 ATA. The inspired partial pressure of O2 (PIO2) is calculated by multiplying FIO2 by ambient pressure in ATA (PIO2 = FIO2 × ATA). Signs and symptoms are most likely to appear at PIO2 greater than 1.6 and include (but are not limited to) sweating, bradycardia, mood changes, nausea, visual field constriction, twitching, syncope, and seizures. This is possible only in hyperbaric environments while diving or during HBOT in a hyperbaric chamber used to treat injured divers. In the practice of HBOT, attempts are made to reduce the likelihood of CNS O2 toxicity through the implementation of periodic air breaks of 5 minutes’ duration. Although the incidence of oxygen seizures will vary, the frequency of this event is 1.3 : 10,000 for HBOT at 2.4 ATA (0.7 : 10,000 when hypoglycemic seizures were excluded).17 Treatment using 100% oxygen at nearly 3 ATA is possible because of the air breaks and the fact that the patient undergoing treatment is resting. In a diving environment where the diver is swimming, it would not be possible to use oxygen at such high concentrations.
Equipment
Cylinders
Medical O2 cylinders are made of aluminum or steel and come in a variety of sizes (Table 76-1; Figures 76-1 and 76-2). The working pressure of steel medical O2 cylinders is 2015 psi. The working pressure of aluminum O2 cylinders is either 2015 psi or 2216 psi, depending on the type.
In the United States, any pressure vessel that is transported on public roads is subject to U.S. Department of Transportation (U.S. DOT) regulations. The U.S. DOT requires that cylinders undergo visual and hydrostatic testing every 5 years. Cylinders that do not pass are destroyed, and those that pass are appropriately stamped and labeled.13 Gas suppliers will not fill cylinders that have not been appropriately tested and stamped.
Regulators
The device that mounts directly to the cylinder is the regulator. Its function is to regulate the pressure of delivered O2 by reducing the pressure of the O2 from peak pressures within the tank of either 2015 psi or 2216 psi to a usable flow rate. The extent of pressure reduction depends on the delivery system. The pressure gauge, pressure-reducing valve, and flowmeter combine to create the regulator, which reduces the pressure of the oxygen from that inside the tank to approximately 50 psi. This allows delivery to the victim at flow rates between 1 and 15 L per minute. Regulators are primarily of three types: constant flow only, demand/flow-restricted oxygen-powered ventilator (FROPV) only, or multifunction, which has both constant flow and demand/FROPV capability (Figure 76-3).
Devices for Ventilation of Nonbreathing Patients
Bag-Valve-Mask Device
The bag-valve-mask (BVM) device consists of a mask, bag, and valves that control or direct the flow of air and O2. Like the FROPV, different mask sizes can be used to accommodate different faces or can be attached directly to an endotracheal tube. The volume of the bag is 1600 mL in most commercially available models (Figure 76-4).
An adult BVM device should have the following features: (1) a nonjam inlet valve system allowing a maximum oxygen inlet flow of 30 L/min; (2) either no pressure relief valve or, if a pressure relief valve is present, a pressure relief valve capable of being closed; (3) standard 15-mm/22-mm fittings; (4) an oxygen reservoir to allow delivery of high concentrations of oxygen; (5) a nonrebreathing outlet valve that cannot be obstructed by foreign material; and (6) ability to function satisfactorily under common environmental conditions and extremes of temperature.10
The primary disadvantage is that it requires training and practice to use effectively. In addition, many find it is difficult to maintain adequate mask seal and ventilate sufficient volumes when only one rescuer is available. Even with proper training, few individuals can maintain adequate mask seal and a patent airway with one hand while squeezing the bag fully to achieve the 700 to 1000 mL standard volume. The U.S. DOT National Standard Curricula for first responders, EMTs, and paramedics recommend the BVM be used first with two rescuers (one maintaining mask seal and patency of the airway, the other squeezing the bag). The NSC recommends that a BVM with one rescuer be the last choice (after all other devices and techniques) in ventilating a patient.13
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