Final answer:
Ejection fraction, derived from stroke volume and end-diastolic volume, indicates the percentage of blood ejected from the heart with each beat. Normal values range from 55-70%. Stroke volume is affected by factors like heart size and condition, and normal values range from 55-100 mL.
Step-by-step explanation:
The student appears to be confused between the concepts of ventilation-perfusion ratio (VD/VT) and stroke volume (SV) related to cardiac function. The question initially seems to inquire about VD/VT, which refers to dead space volume over tidal volume, a parameter used in pulmonary medicine. However, the provided information primarily discusses stroke volume and ejection fraction relating to cardiology. Therefore, a direct answer related to the provided information would be: Ejection fraction is calculated by dividing stroke volume (SV) by end-diastolic volume (EDV), expressed as a percentage with normal values ranging between approximately 55-70 percent.
The stroke volume used in this equation is the volume of blood pumped out of the left ventricle of the heart with each beat, and is measured as EDV minus end-systolic volume (ESV). Deviations from the normal range can indicate cardiac dysfunction or disease. The measurements are often obtained using an echocardiogram. Stroke volume can vary significantly depending on factors such as the individual's size, physical condition, gender, and heart mechanics. The normal SV range is 55-100 mL, with an average resting heart rate (HR) of approximately 75 beats per minute (bpm). As such, this assessment can reveal important insights into a patient's cardiovascular health.