Effect of Head UP and Head Down Tilt on Heart Rate Variability in Females

Cardiovascular autonomic function can be assesed by the orthostatic stress. This is done mainly by Head Up Tilt (HUT) testing and Head Down Tilt (HDT)Testing. The parameters which represent the cardiovascular autonomic function involved the Heart Rate (HR), Systolic Blood Pressure (SBP), Diastolic Blood Pressure (DBP), Mean Arterial Pressure (MAP) and Pulse Pressure (PP). Heart Rate Variability (HRV) indices provide non-invasive assessment of cardiovascular control mechanisms. Low Frequency (LF) is an indicator of sympathetic system. High Frequency (HF), an index of parasympathetic and the ratio LF/HF is the specific and quantitative index of sympathovagal balance.

Hundred healthy females in the age group of 18–45 years were selected to evaluate the effect of HUT and HDT on Heart Rate Variability(HRV). LF, HF and LF/HF were recorded at supine, 30⁰, 60⁰, 80⁰HUT and 30⁰, 60⁰ 80⁰ HDT. In each position the HR was determined by recording the ECG for 5 min in lead II. Niviquire software was used to measure the LF, HF and the LF/HF ratio.

On HUT LF and the LF/HF ratio increased and HF decreased. On HDT the LF,HFand the LF/HF ratio decreased in females.

During HUT there is increase in sympathetic activity (increase in LF and LF/HF ratio). On HDT there is decrease in the sympathetic activity which is indicated by decrease in the LF and the LF/HF ratio. Postural stress test is useful for medical students, physiologists and clinicians to understand cardiovascular reflex response in healthy or diseased individuals.