A nurse suctioning a client through a tracheostomy tube was careful not to occlude the Y port when inserting the suction catheter because this would do which of the following?

Oxygen cylinders are high-pressure vessels containing compressed medicinal gas that require strict regulatory compliance and safety protocols to prevent catastrophic failure or fire. The maintenance of adequate volume is a clinical priority to ensure that oxygen delivery is not interrupted during patient transport or in emergency settings. Proper management involves assessing the pressure gauge to verify that the remaining gas is sufficient for the intended duration of use based on the flow rate.

Rationale for correct answer

1. Verifying the available pressure on the regulator is a fundamental safety action to ensure the cylinder will not run out during use. A full cylinder typically registers 2,000 psi, and the nurse must calculate if the remaining amount is adequate for the patient's needs. This prevents the life-threatening cessation of oxygen therapy during transport.

Rationale for incorrect answers

2. A cylinder containing only 500 psi is generally considered near empty and should not be used for patient transfers. Standard safety protocols require replacing the tank when it reaches 500 psi to provide a safety margin against total depletion. Using such a low-pressure tank increases the risk of the patient losing their oxygen supply mid-transport.

3. Placing an unsecure cylinder directly on a stretcher next to a patient is a significant safety hazard because the tank could fall or the valve could shear. If a pressurized valve is damaged, the cylinder can become a dangerous projectile. Tanks must be secured in a designated rack or the specific holder on the transport vehicle.

4. Turning the key counterclockwise actually opens the valve further rather than closing it. To discontinue flow and secure the cylinder, the key must be turned clockwise until the valve is completely seated. Operating the valve in the wrong direction can lead to rapid gas loss and depletion of the resource.

Test-taking strategy

• Identify the priority: In oxygen tank questions, safety and resource availability are the main goals.
• Analyze the pressure: Remember the 500 psi rule. In many facilities, 500 psi is the minimum threshold where a tank is replaced. Therefore, starting a transfer with only 500 psi is risky.
• Determine mechanical direction: For almost all medical and industrial valves, turning the handle clockwise closes the system. Choice 4 is a technical error.
• Select the most reliable step: Choice 1 is the only option that represents a universal, standardized pre-procedure safety check for oxygen administration.

Take home points

• Oxygen is an oxidizer and must be kept away from oils, greases, and open flames to prevent combustion.
• The duration of flow for a cylinder can be calculated by multiplying the psi by the tank factor and dividing by the flow rate.

High-concentration oxygen delivery systems utilize a reservoir bag and one-way valves to achieve a high fractional inspired oxygen (FiO2) concentration. This configuration prevents the entrainment of ambient air and the rebreathing of exhaled carbon dioxide, ensuring the patient inspires almost pure oxygen. In a spontaneously breathing patient with severe hypoxemia, this device is the final step in non-invasive respiratory support before progressing to positive pressure ventilation or endotracheal intubation.

Rationale for correct answer

2. Nonrebreather mask is equipped with a reservoir and two one-way valves that allow for the delivery of an FiO2 between 60% and 90%. It is the only non-invasive system capable of providing the highest concentration of oxygen to a patient who is still breathing on their own. It is used in acute emergencies to rapidly stabilize saturation levels.

Rationale for incorrect answers

1. A partial rebreather allows the first third of exhaled air to enter the reservoir, resulting in a maximum oxygen concentration of approximately 60%. It lacks the one-way valve system required to prevent the dilution of inspired oxygen with exhaled gases and room air. It provides significantly less oxygen than a nonrebreather.

3. The simple face mask delivers oxygen concentrations ranging from 35% to 50% at flow rates of 6 to 12 L/min. It depends heavily on the fit of the mask and the patient's inspiratory flow rate, making it a low-to-moderate delivery device. It cannot achieve the high concentrations needed in critical respiratory distress.

4. Venturi mask is designed for precision rather than high concentration, using different-sized orifices to provide a fixed FiO2. While it is excellent for patients requiring controlled oxygen levels, its maximum output is typically capped at 50%. It is used for accuracy in chronic lung disease, not for maximum oxygenation.

Test-taking strategy

• Identify the objective: The question asks for the highest concentration. This is a superlative that points toward a device with a reservoir and one-way valves.
• Compare percentages:
  • Simple mask: ~40%
  • Venturi mask: ~50%
  • Partial rebreather: ~60%
  • Nonrebreather: ~90%
• Apply logic of design: The “non” in nonrebreather means the patient is not rebreathing anything but the oxygen from the bag, which logically leads to the highest concentration.
• Eliminate low-flow: Rule out 3 and 4 immediately as they are designed for routine or precise delivery rather than emergency hyperoxygenation.

Take home points

• The reservoir bag on a nonrebreather mask must be kept at least one-third to one-half full during inhalation to ensure adequate delivery.
• One-way valves on the mask's side ports prevent room air from entering during inspiration.