A patient arrived in the emergency room with a fever of 38.5 °C. Change the temperature to Fahrenheit.

Choice A rationale

Dullness upon percussion indicates increased tissue density, such as in consolidation (e.g., pneumonia), pleural effusion, or a tumor. This occurs because the sound waves are attenuated and dampened by the solid or fluid-filled structures, resulting in a short, high-pitched, thudding sound.

Choice B rationale

Tympany is a drum-like, high-pitched, loud sound typically heard over air-filled organs like the stomach or intestines. When percussing the lungs, tympany suggests a large pneumothorax or a distended abdomen impinging on the thoracic cavity, indicating abnormal air accumulation.

Choice C rationale

Resonance is the expected percussive sound over healthy, air-filled lung tissue. It is a low-pitched, clear, hollow sound produced by the vibration of air within the alveoli and bronchi. This sound indicates normal lung aeration and the absence of significant pathology.

Choice D rationale

Hyperresonance is a louder, lower-pitched sound than normal resonance and suggests an increased amount of air in the lung or pleural cavity, such as in emphysema or pneumothorax. This hyperinflation causes greater vibration and a more boomy quality to the sound.

Choice A rationale

The abdomen, specifically 2 inches from the umbilicus, is a common site for subcutaneous injections due to the presence of ample adipose tissue, which allows for slower absorption of medications like insulin or heparin. Intradermal injections require a site with a thin epidermis and minimal subcutaneous tissue to ensure the medication remains within the dermal layer, making the abdomen unsuitable.

Choice B rationale

The anterior thigh is a common site for intramuscular injections, particularly in infants, due to the large muscle mass (vastus lateralis). While it can be used for subcutaneous injections, its muscularity and varying skin thickness make it less ideal for the precise shallow angle required for an intradermal injection, where the goal is to deposit the medication into the dermis.

Choice C rationale

The posterior upper arm, specifically the triceps area, is frequently utilized for subcutaneous injections, such as insulin or certain vaccines, because it offers sufficient subcutaneous tissue. However, similar to the anterior thigh, its anatomical characteristics with thicker skin and subcutaneous fat layers make it less optimal for the very superficial intradermal injection technique.

Choice D rationale

The upper chest, particularly below the clavicle and above the breasts, is an appropriate site for intradermal injections. This area, along with the inner forearm and upper back, has a thin epidermis and less subcutaneous tissue, which facilitates the proper placement of the medication within the dermis, allowing for the formation of a visible wheal, a key indicator of a successful intradermal injection.