Which pulse best estimates a systolic blood pressure of approximately 70 mmHg?

The femoral pulse is the most appropriate choice for estimating a systolic blood pressure of approximately 70 mmHg. This is because the femoral pulse is closer to the heart and reflective of central circulation. When systolic blood pressure is low, such as at 70 mmHg, peripheral pulses may become difficult to palpate or may not be present due to reduced perfusion. In such cases, the femoral pulse often remains palpable, making it a better indicator of systemic blood pressure in severely compromised patients.

While the carotid pulse is also central and can correspond to systemic blood pressure, it can sometimes be affected by factors such as positioning or neck compression. The radial pulse, on the other hand, is indicative of more stable blood pressure levels, often requiring a systolic range above approximately 80 mmHg to be consistently palpable. The brachial pulse, similarly, is less reliable at lower blood pressures due to its peripheral location and the fact it may not be well-palpated when perfusion is compromised. Thus, the femoral pulse stands out as the best indicator of a systolic blood pressure around 70 mmHg.