Abstract: A narrow seating device or chair including a support caddy having lockable ground engaging caster wheels and a seat portion for a patient undergoing a medical test. The seat portion is detachably mounted on the support caddy and tiltable to a plurality of tilt positions. The seat portion has a convexly curved surface which rests on spaced apart rollers on the upper side of the support caddy to enable tilting. A safety mechanism detachably secures the seat portion to the support caddy, while still allowing for tilting. The safety mechanism includes a flexible steel cable which is reeved around a pulley attached to the curved surface. The ends of the cable are secured to the support caddy. A tension spring and a turnbuckle to adjust spring tension are connected each to a respective one of the ends of the cable. A locking mechanism releasably locks the seat portion in a selected tilt position.