A patient is undergoing oxygen therapy through a nasal cannula.If the patient inquires about the reason for having oxygen tubing in their nose, what explanation about the cannula should the nurse provide?

Choice A rationale

Mycoplasmal pneumonia, also known as walking pneumonia, is typically not an airborne disease. Standard precautions, including the use of a surgical mask, are usually sufficient when caring for these patients.
Choice B rationale
Scarlet fever is caused by group A Streptococcus bacteria, which are spread through respiratory droplets. Standard precautions, including the use of a surgical mask, are usually sufficient when caring for these patients.
Choice C rationale
Tuberculosis is an airborne disease. Healthcare providers should wear an N95 respirator when caring for a client with tuberculosis to protect themselves from inhaling the bacteria.
Therefore, Choice C is the correct answer.
Choice D rationale
Scabies is caused by a mite and is spread through direct skin-to-skin contact. It is not an airborne disease, so an N95 respirator is not necessary when caring for a client with scabies.

The correct answer is Choice D

Choice A rationale: A 1-inch needle is typically used for intramuscular injections, not intradermal administration. Intradermal injections require a short, fine-gauge needle—usually ¼ to ⅝ inch in length and 25 to 27 gauge—to ensure accurate placement within the dermis. Using a longer needle increases the risk of injecting into subcutaneous tissue, which alters absorption and invalidates the test. Scientific technique demands precise needle selection based on anatomical depth and pharmacokinetics of the test substance.

Choice B rationale: A 20° angle is inappropriate for intradermal injections, which require a shallow angle of 5° to 15° to ensure deposition within the dermal layer. Angles greater than 15° risk penetrating into subcutaneous tissue, compromising test accuracy and absorption kinetics. The dermis is a narrow layer between the epidermis and subcutaneous fat, and precise angulation is critical for forming the characteristic wheal and ensuring localized immune response. Scientific technique mandates strict adherence to angle parameters.

Choice C rationale: The standard volume for a tuberculin skin test using purified protein derivative (PPD) is 0.1 mL, not 0.5 mL. Administering 0.5 mL would exceed the recommended dose, potentially causing excessive local reaction, invalid test results, and patient discomfort. The Mantoux method requires exact dosing to elicit a controlled immune response for accurate interpretation. Scientific protocol emphasizes precision in volume to maintain test validity and minimize adverse effects. Overdosing violates established guidelines.

Choice D rationale: Pinching or gently pulling the skin taut at the injection site stabilizes the dermal layer and facilitates correct needle placement. This technique ensures the needle enters at the proper angle and depth, allowing formation of a visible wheal, which confirms intradermal delivery. It also minimizes patient discomfort and prevents misplacement into deeper tissues. Scientific technique for intradermal injections prioritizes anatomical control and tactile feedback to optimize accuracy and diagnostic reliability.