In field care, which vital sign may be unavailable but is useful when possible to monitor?

• A. Temperature
• B. Oxygen saturation
• C. Blood pressure
• D. Heart rate

Answer: (B)

Oxygen saturation tells you how well the blood is carrying oxygen, and a pulse oximeter gives that quick, noninvasive readout. In field care, you don’t always have access to a pulse oximeter or the device may be out of power or not carried at the moment. When you can monitor it, it adds crucial information that other vitals don’t directly provide: it shows whether tissues are being oxygenated adequately and helps you judge whether to supplement oxygen, escalate care, or reassess after interventions. Normal values are roughly in the mid‑90s to 100%, and dips below about 92% raise concern for hypoxemia. Remember its limitations: it requires good perfusion and a properly placed sensor, and readings can be affected by motion, poor sensor contact, nail polish, or ambient light, and it doesn’t measure ventilation or explain why hypoxemia is occurring. Because heart rate, blood pressure, and temperature are more routinely obtainable in the field, oxygen saturation stands out as the sign that may be unavailable but is especially useful when you can obtain it.