What is the main responsibility of erythrocytes (RBCs) in the body?

Rationale:

A. The rule of nines is a method for calculating gestational age during pregnancy is incorrect. Gestational age is determined using methods such as the last menstrual period, early ultrasound measurements, or fetal biometry, which assess fetal growth and development. The rule of nines has no role in obstetrics and does not provide any information about pregnancy duration or fetal maturity.

B. The rule of nines is used to determine the ideal body weight based on height and weight calculations is incorrect. Ideal body weight calculations rely on formulas like the Devine or Hamwi equations, which consider height, sex, and sometimes body frame size. The rule of nines does not involve body weight, body mass index, or nutritional assessment, so it cannot be used for this purpose.

C. The rule of nines is used to estimate burn depth and healing potential of a burn wound is partially incorrect. While assessing burn depth and healing potential is important in burn care, the rule of nines specifically addresses only the total body surface area (TBSA) affected by burns. Burn depth is evaluated separately by examining skin layers involved, color, sensation, and tissue viability. Therefore, this statement inaccurately conflates burn depth assessment with the TBSA estimation function of the rule of nines.

D. The rule of nines divides the body into multiples of nine to estimate the percentage of total body surface area burned is correct. In adults, the body is divided into regions representing roughly 9% or multiples of 9% of TBSA, including the head and neck (9%), each arm (9%), each leg (18%), anterior torso (18%), posterior torso (18%), and perineum (1%). This method allows rapid, standardized estimation of burn size, which is critical for fluid resuscitation, monitoring for complications, and treatment planning in burn patients.

Rationale:

A. Joint pain is not a symptom of asthma. Asthma is a chronic inflammatory airway disease and does not directly affect joints. Joint pain may indicate other conditions such as arthritis or autoimmune disorders, but it is unrelated to asthma.

B. Chest tightness is a common symptom of asthma. Airway inflammation and bronchoconstriction reduce airflow, leading to a sensation of pressure or tightness in the chest, often accompanied by difficulty breathing. This is particularly noticeable during an asthma exacerbation or after exposure to triggers.

C. Increased appetite is not associated with asthma. Appetite changes are unrelated to the pathophysiology of airway inflammation and bronchospasm.

D. Wheezing is a hallmark sign of asthma. It occurs due to turbulent airflow through narrowed bronchi and bronchioles caused by bronchospasm, mucus accumulation, and airway edema. Wheezing is often expiratory and may be audible without a stethoscope in severe cases.

E. Coughing is another key symptom of asthma. It can be dry or productive and is often worse at night or early morning. Coughing results from airway irritation and inflammation and may be the only presenting symptom in some patients, known as cough-variant asthma.