the lower pressure at altitude, is at lower pressure than the  external ear canal. This results in the higher outside pressure,  causing the eardrum to bulge inward. This condition can be more difficult to relieve due to the  fact that the partial vacuum tends to constrict the walls of  the eustachian tube. To remedy this often painful condition,  which also causes a temporary reduction in hearing  sensitivity, pinch the nostrils shut, close the mouth and lips,  and blow slowly and gently in the mouth and nose. This is  commonly referred to as the Valsalva procedure. The Valsalva procedure forces air through the eustachian tube  into the middle ear. It may not be possible to equalize the  pressure in the ears if a pilot has a cold, an ear infection, or  sore throat. A flight in this condition can be extremely painful,  as well as damaging to the eardrums. If a pilot experiences  minor congestion, nose drops or nasal sprays may reduce the  risk of a painful ear blockage.  but open during chewing, yawning, or swallowing to equalize  pressure. Even a slight difference between external pressure  and middle ear pressure can cause discomfort.  In a similar way, air pressure in the sinuses equalizes with  the ambient or outside pressure through small openings  that connect the sinuses to the nasal passages. An upper  respiratory infection, such as a cold or sinusitis, or a nasal  allergic condition can produce enough congestion around an  opening to slow equalization. As the difference in pressure  between the sinus and the ambient atmosphere increases,  congestion may plug the opening. This “sinus block” occurs  most frequently during descent. Slow descent rates can reduce  the associated pain. A sinus block can occur in the frontal  sinuses, located above each eyebrow, or in the maxillary  sinuses, located in each upper cheek. It will usually produce  excruciating pain over the sinus area. A maxillary sinus  block can also make the upper teeth ache. Bloody mucus  may discharge from the nasal passages. Balloon pilots rarely experience issues with spatial  disorientation while in flight, as virtually all balloon  operations are conducted under visual flight rules (VFR)  conditions. Knowledge of these conditions, however, is  important in the event of unusual circumstances or situations,  such as inadvertently being caught in fog, or perhaps in areas  of low visibility. The balloon pilot should have an awareness  of these issues, so that appropriate actions may be taken as  necessary. Sinus block can be avoided by not flying with an upper  respiratory infection or nasal allergic condition. Adequate  protection is usually not provided by decongestant sprays  or drops to reduce congestion around the sinus openings.  Oral decongestants have side effects that can impair pilot  performance. If a sinus block does not clear shortly after  landing, a physician should be consulted.  [Figure 9-1]  Spatial disorientation specifically refers to the lack of  orientation with regard to the position, attitude, or movement  of an aircraft in space. The body uses three integrated systems  working together to ascertain orientation and movement in  space. The eye is by far the largest source of information.  Kinesthesia refers to the sensation of position, movement, and  tension perceived through the nerves, muscles, and tendons.  The vestibular system is a very sensitive motion-sensing  system located in the inner ears. It reports head position,  orientation, and movement in three-dimensional space. All this information comes together in the brain and, most  of the time, the three streams of information agree, giving  a clear idea of where and how the body is moving. Flying  can sometimes cause these systems to supply conflicting  information to the brain, which can lead to disorientation.  During flight in visual meteorological conditions (VMC),  the eyes are the major orientation source and usually prevail  over false sensations from other sensory systems. When  these visual cues are removed, as they are in instrument  meteorological conditions (IMC), false sensations can cause  a pilot to become quickly disoriented. During a climb, middle ear air pressure may exceed the  pressure of the air in the external ear canal, causing the  eardrum to bulge outward. Pilots become aware of this  pressure change when they experience alternate sensations  of “fullness” and “clearing.” During descent, the reverse  happens. While the pressure of the air in the external ear  canal increases, the middle ear cavity, which equalized with  9-4 $_{Figure 9-1.}$  The eustachian tube allows air pressure to equalize in  the middle ear. Spatial Disorientation and Illusions Opening to Throat Middle Ear Outer Ear Auditory Canal Eustachian Tube Eardrum