The pressure difference that can cause atmosphere and middle ear barotrauma is:

(> 90 mmHg): Ref: 349-LT (79-Maqbool 11th)BARQTRAUMATIC OTITIS MEDIA: or otitic barotraumas, when the air pressure within the middle ear is markedly less than that of surrounding atmosphere. It occurs due to rapid descent, whether in an aircraft or while diving. The passage of air down the eustaction tube on ascending in passive, but the passage of air up the tube on descent is always active, being aided by the opening of the mouth of the tube buy the tensor and levator palate muscles. If there is a pressure differential between the nasopharynx and middle ear of 90 mmHg or above, the mouth of the tube 'locks' and the muscular contraction is insufficiently strong to overcome this.* If the eustaction tube lining is oedematous due to URTI, the locking will take place at a lower pressure differential.* They first feal severe pain on ascent in an aircraft and the pain is relieved either by rupture of the drum or by descent