The decrease in altitude would affect a person who already has low blood pressure, (or high blood pressure if traveling to a significantly higher altitude).

At higher altitudes, the blood oxygen levels decrease. The human body compensates for this change by increasing blood pressure. By living and working in a high altitude region, your body has become acclimated to the environment. The sudden, substantial decrease in altitude would have a more noticeable adverse effect on persons with existing low blood pressure.

A researcher studied the affects on homeowners who lived at sea level and had a second home at high altitude regions. Thirty percent of these people experienced an increase in their arterial blood pressure. It would be reasonable to conclude that persons with low blood pressure would have to acclimate to sea level conditions. .

A physical adjustment will occur if the person relocates to a different elevation, however this takes several weeks to do so. Your ten day vacation was not sufficient for your body to acclimate to the change in elevation. That is the likely cause of your temporary "illness" which was quickly resolved by returning to your home environment, (the "normal"elevation to which your body is accustomed).