Predicted Body Weight Calculation

Predicted Body Weight Formula:

\[ \text{PBW (kg)} = \begin{cases} 50 + 0.91 \times (\text{height (cm)} - 152.4) & \text{for males} \\ 45.5 + 0.91 \times (\text{height (cm)} - 152.4) & \text{for females} \end{cases} \]

Predicted Body Weight (PBW):

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1. What is Predicted Body Weight?

Predicted Body Weight (PBW) is an estimation of ideal body weight based on height and sex. It is commonly used in medical settings for drug dosing, ventilator settings, and nutritional assessments.

2. How Does the Calculator Work?

The calculator uses the PBW formula:

\[ \text{PBW (kg)} = \begin{cases} 50 + 0.91 \times (\text{height (cm)} - 152.4) & \text{for males} \\ 45.5 + 0.91 \times (\text{height (cm)} - 152.4) & \text{for females} \end{cases} \]

Where:

\( height \) — Height in centimeters (cm)
50 — Base weight for males (kg)
45.5 — Base weight for females (kg)
0.91 — Weight increment per cm above 152.4 cm
152.4 — Reference height in cm (5 feet)

Explanation: The equation calculates ideal body weight based on the assumption that for each inch (2.54 cm) over 5 feet, add 2.3 kg for males and 2.1 kg for females.

3. Importance of PBW Calculation

Details: PBW is crucial for accurate medication dosing (especially for drugs with narrow therapeutic windows), setting appropriate tidal volumes in mechanical ventilation, and determining nutritional requirements.

4. Using the Calculator

Tips: Enter height in centimeters, select sex. Height must be a positive value. The calculator will provide the predicted body weight in kilograms.

5. Frequently Asked Questions (FAQ)

Q1: Why use predicted body weight instead of actual weight?
A: PBW is used because it estimates lean body mass, which is more relevant for drug distribution and ventilator settings than total body weight, especially in obese patients.

Q2: What is the clinical significance of PBW?
A: PBW is used to calculate tidal volumes in ARDS patients (6 mL/kg PBW), dose certain medications, and assess nutritional status.

Q3: How accurate is the PBW calculation?
A: PBW provides a reasonable estimate for most adults, but may be less accurate in extremes of height, athletes with high muscle mass, or elderly patients with sarcopenia.

Q4: Are there different formulas for PBW?
A: Yes, there are several formulas (Devine, Robinson, Miller) with slight variations. This calculator uses one of the most commonly accepted formulas.

Q5: Should PBW be used for all medication dosing?
A: No, PBW is primarily used for drugs that distribute mainly in lean body tissue. Always follow specific medication guidelines and consult pharmacokinetic references.