Macintosh indicator is used for ?

Ans. is 'b' i.e., Localization of extradural space Various methods have been used to locate the epidural (extra dural space), most of which rely on subatmospheric pressure. These are :- Loss of resistance to air or saline (most common technique). Gutierrez's method : A hanging drop of saline on the hub of needle is drawn in as the epidural space is entered (more reliable in thorocic than lumbar region). Odom 's indicator : A fine-bore glass tube filled with saline and a bubble that moves in response to a drop in pressure. Macintosh's indicator : A small rubber balloon filled with air connected to an adaptor causing it to deflate on entering the epidural space. Macintosh's spring-loaded needle. Ultrasonic localization. Oxford epidular space detector.