What percentage of total body surface area (TBSA) is represented by the head of an adult according to the rule of nines?

Rationale:

A. Decreased heart rate and blood pressure is incorrect. Pulmonary embolism (PE) typically causes tachycardia as a compensatory mechanism to maintain cardiac output in the face of impaired pulmonary circulation. Hypotension may occur in massive PE, but bradycardia is not a typical manifestation.

B. Chest pain that worsens with deep breaths is correct. Pleuritic chest pain is a hallmark symptom of PE. It occurs because the embolus obstructs pulmonary blood flow, leading to infarction or irritation of the pleura. The pain often intensifies with deep inspiration or coughing, and is frequently accompanied by dyspnea, tachypnea, tachycardia, and sometimes hemoptysis. These signs reflect the acute pulmonary vascular obstruction and resultant ventilation-perfusion mismatch.

C. Increased appetite and weight gain is incorrect. These are nonspecific and unrelated to PE. Pulmonary embolism affects respiratory and cardiovascular function, not metabolic appetite regulation or short-term weight gain.

D. Fatigue and weakness is incorrect. While clients may feel general fatigue after prolonged hypoxia or illness, the acute, prominent manifestations of PE are respiratory distress, chest pain, and cardiovascular changes. Fatigue is not the most notable symptom in the acute setting.

Rationale:

A. Destruction of melanocytes occurs in conditions such as vitiligo, where the pigment-producing cells are lost, leading to depigmented patches. Psoriasis does not primarily affect melanocytes or pigmentation.

B. While secondary bacterial infections can occur in psoriatic lesions due to skin barrier disruption, bacterial overgrowth is not the underlying cause or pathophysiology of psoriasis.

C. Allergic reactions, such as contact dermatitis, involve hypersensitivity mechanisms, but psoriasis is not triggered by allergens in this manner.

D. Psoriasis is a chronic autoimmune-mediated inflammatory condition in which T-cell activation leads to increased cytokine production, resulting in hyperproliferation of keratinocytes. This accelerates the normal skin cell turnover from about 28–30 days to as little as 3–7 days, causing excessive epidermal shedding, thickened plaques, and silvery scales. The accelerated turnover and abnormal differentiation of epidermal cells are hallmarks of psoriasis pathophysiology, making this the most accurate description.