"Proximate cause", when used with respect to Dr. Davis, means that cause which, in a natural and continuous sequence, produces en event, and without which cause such event would not have occurred. In order to be a proximate cause, the act or omission complained of must be such that a physician using ordinary care would have foreseen that the event, or some similar event, might reasonably result therefrom. There may be more than one proximate cause of an event.