ENT problems in aviation

ENT problems in aviation
Jason Goodwin
Aircraft accident statistics
• CY 2013 to date from NTSB database
• 1164 Aviation accidents logged with NTSB
• 252 of those involved a fatality (almost 500
deaths)
• Estimated that human error to blame for
up to 80% of aircraft mishaps
• Perfectly good airplanes are flown into the
ground routinely. Why?
Overview
• History
• ENT-related aviation problems
– Trapped gas
– Vestibular
Historical ties between ENT and
aviation
• Early aviation was very dangerous
– Still learning, new aircraft, no instumentation
• Need for proper pilot selection and training
recognized by two military
otolaryngologists
– Revised the medical selection criteria
– Incorporated vestibular training
• Recognized need for specialized physician
dealing with flight issues
– Coined “flight surgeon”
• Specialized flight surgeon course began
1918.
• Has evolved to a specialty. There is an
aerospace medicine residency
• Specialized pilot training has evolved
– Barany chair
– Simulators
– Altitude chamber
Flight Stresses
•
•
•
•
•
Hypoxia
Barometric Pressure
Thermal
Gravitational Forces
Noise
• Vibration
• Decreased Humidity
• Fatigue
Time of Useful
Consciousness (TUC)
Altitude in Feet / Flight Level
TUC
12,000 to 20,000 feet (FL 200) 20 to 30 minutes
25,000 feet (FL 250)
3 to 5 minutes
30,000 feet (FL 300)
1 to 2 minutes
35,000 feet (FL 350)
30 to 60 seconds
40,000 feet (FL 400)
15 to 20 seconds
50,000 feet (FL 500)
9 to 12 seconds
Average Barometric Pressures
Altitude
(1000 feet)
Barometric Pressure
mm Hg
Psi
Temperature Cº
Temperature Fº
0
760
14.70
+ 15.0
+ 59.0
1
733
14.17
+ 13.0
+ 55.4
2
706
13.87
+ 11.0
+ 51.8
3
681
13.67
+ 9.1
+ 48.38
4
656
12.69
+ 7.1
+ 44.78
5
632
12.23
+ 5.1
+ 41.18
6
609
11.78
+ 3.1
+ 37.58
7
586
11.34
+ 1.1
+ 33.98
8
565
10.92
- 0.9
+ 33.67
9
542
10.51
- 2.8
+26.96
10
523
10.11
- 4.8
+ 23.36
12
483
9.35
- 8.8
+ 16.6
14
447
8.63
- 12.7
+9.4
16
412
7.97
- 16.7
+1.94
18
380
7.34
- 20.7
- 5.26
20
349
6.75
- 24.6
- 12.28
24
295
5.70
- 32.6
- 26.68
28
247
4.78
- 40.5
- 40.9
30
228
4.36
- 44.4
- 47.92
32
206
3.98
- 48.4
- 55.12
36
171
3.30
- 55.0
-67
42
128
2.47
- 55.0
-67
48
96
1.86
- 55.0
-67
ENT problems in aviation
• Trapped gas disorders
• Vestibular problems/Spatial disorientation
Trapped gas disorders
• Ear block
• Sinus block
• Tooth block
• Boyles law – pressure of gas is inversely
proportional to the volume
• Charles law – Volume of gas directly
proportional to the temperature
• Daltons Law – total pressure of a gas is
sum of partial pressures of individual
gases
Gas Expansion
43,000
6.0X
4.0X
2.5X
34,000
9.5X
5.0X
3.0X
25,000
1.8X
16,000
2.0X
Barometric Pressure
• Body cavities most often affected
–
–
–
–
–
Gastrointestinal tract
Middle ear
Paranasal sinuses
Teeth
Respiratory tract
• Clinical Significance
– The amount of volume expansion is limited by the
pliability of the structure or membrane which encloses
the gas
The Middle Ear
• Ascent to altitude
– As barometric pressure decreases with
ascent, gas expands within the middle ear
– Air escapes through the eustachian tubes to
equalize pressure
– As pressure increases, the eardrum bulges
outward until a differential pressure is
achieved and a small amount of gas is forced
out through eustachian tube and the eardrum
relaxes
The Middle Ear
• Descent to altitude
– Equalization of pressure does not occur automatically
– Eustachian tube performs as a flutter valve and
allows gas to pass outward easily, but resists the
reverse
– During descent the ambient pressure rises above that
inside and the eardrum is forced inward
– If pressure is not equalized
• Ear block may occur and it is extremely difficult to reopen the
eustachian tube
• The eardrum may not vibrate normally and decreased
hearing results
Pressure Effect
Tympanic
Membrane
Middle Ear Cavity
External Ear
Atmospheric
Pressure
Clear
Eustachian Tube
Middle Ear Cavity
Tympanic
Membrane
External Ear
Eustachian Tube
Blocked / Infected
Atmospheric
Pressure
Ear Block
Ear Block (Barotitis Media)
• Symptoms
–
–
–
–
–
“Ear congestion”
Inflammation
Discomfort
Pain
Temporary impairment
of hearing
– TM rupture
– Bleeding
– Vertigo
• Contributing Factors
– Flying with head cold
– Flying with a sore
throat
– Otitis media
– Sinusitis
– Tonsillitis
Ear Block (Barotitis Media)
• Treatment
– Yawning or swallowing
– Valsalva maneuver
– Nasal sprays – best used prior to descent
although evidence conflicting
– Pain medications
– For infants / children – provide a bottle / straw
to suck
– Ascend to safe altitude where symptoms
subside and then slowly descend
Ear Block (Barotitis Media)
• Prevention
– DO NOT FLY WITH A HEAD COLD
– “Stay ahead of your ears”
• Valsalva during descent
– Use self-medications with vasoconstrictors
with caution
• Rebound effects of nasal sprays may not allow
swelling to subside
Delayed Ear Block
• Occurs in situations where crew members
breath 100% oxygen at altitude or in an altitude
chamber, especially if oxygen was maintained
during descent to ground level
• Symptoms occur 2 to 6 hours after descent
• Oxygen in the middle ear is absorbed and
creates a decreased pressure
• Prevention – valsalva numerous times after
altitude exposure to prevent absorption
Sinus problems
The Sinuses
• Most often involves frontal sinuses and
maxillary sinuses
• Gas vented upon ascent most often
without problems
• With descent, air moves back out through
the ducts if they are open
• If the openings are swollen or are
malformed, a blockage may occur
The Sinuses
• Symptoms
– Severe pain
– Possible epistaxis
– Possible referred pain
to teeth
– Blow-out fractures
have been described
• Treatment
– Equalize pressure as
quickly as possible
– Valsalva is sometimes
effective
– Ascent to safe altitude
then slow descent
– Nasal sprays may help
The Sinuses
• Prevention
– DO NOT FLY WITH A COLD
– Try to maintain an equalized pressure
– “Keep ahead of your ears”
The Teeth (Barodontalgia)
• Incidence reported at ~8% military aircrew
• Pain is excruciating
• Altitude of occurrence varies greatly with
individuals
• Air trapped within teeth expands with ascent
• Confirmed barodontalgia is experienced in
previously restored defective teeth
• Untreated caries may cause pain at altitude
• Rarely caused by a root abscess with a small
pocket of trapped gas
The Teeth (Barodontalgia)
• Treatment / Prevention
– Descent
– Pain medications
– Good dental hygiene
Vestibular problems in flight
• Seat of the pants flying
– 1. to pilot a plane by feel and instinct rather
than by instruments
– 2. to proceed or work by feel or instinct
without formal guidelines or experience.
The Human Inner Ear
THE VESTIBULAR APPARATUS
Vestibular System
•
•
•
•
•
The vestibular system is
located in the inner ear
Consists of vestibular
organs that measure
accelerations
Each vestibular has what
is referred to as the
semicircular canals and
the otolith organs
The semicircular canals
measure acceleration and
deceleration in three
rotational axes.
The otolith organs
measure linear
acceleration/dceleration
by virtue of sensory hairs
that are in contact with an
overlaying gelatenous
membrane
Mapping of Semicircular Canals
• Depends on head position
HAIR CELLS
Acceleration versus Velocity
Otolith Organs (Macula)
Orientation systems
Vestibular
Apparatus
Vision
Orientation
Proprioceptive
Spatial disorientation
• Spatial disorientation is a condition in
which an aircraft pilot's perception of
direction does not agree with reality
• Human vestibular system is easily tricked
when visual cues are lost
Spatial disorientation
• 50-80% of accidents caused by human
error
• 10-15% of all accidents caused by spatial
disorientation
– Of these accidents >90% fatal
• USAF estimates $200 million per year
losses due to SD
Spatial Disorientation
• Type I: Unrecognized SD
– Most dangerous type of SD because the aviator is unaware of the
deviation in perceived and actual aircraft state
– Outcome of type I SD is usually fatal
– May be induced by a gradually failing gyroscope, a situation for which
pilots receive little or no training.
• Type II SD
– Pilot actually perceives problem related to orientation or attitude
– Pilot may not be able to generate the correct control response, because
the vestibular cues of perceived straight and level flight are so strong
– E.g. graveyard spiral is a type of unusual attitude, where the plane is in
a steep banking descending turn with decreasing radius and increasing
angle of bank
• Type III SD:
– Pilot overwhelmed by the sensation of movement induced by the
vestibular system that aircraft control cannot be regained, unless a
second crew member can take over the controls.
The Leans
• Most common illusion
• Plane is in small turn,
below threshold of
angular acceleration
pickup (<2°/sec)
• Plane then returns to
level flight but pilot thinks
it is in an opposite
direction turn
• Body tries to assume
posture of when it was in
turn
Coriolis effect
• Simultaneous activation of multiple canals
• Mostly when in a turn and quickly tilt head
up or down
• Simultaneous activation stimulates vertigolike feeling
– Feels like plane is rolling, yawing, pitching at
same time
– Described as tumbling down a hill
• Easy to lose control of aircraft
Graveyard spiral
• Set by prolonged turn. Body adjusts to
turn after ~20 secs and thinks level
• Any turning to level flight will produce
strong sensation that plane is banking
hard to right
• Pilot over-corrects to the original turn side,
continuing the turn
•
•
•
•
•
•
•
•
•
•
AFMAN 11-217
AFMAN 11-202v3
FAA Spatial Disorientation Course
http://www.faa.gov/pilots/safety/pilotsafetybrochures/
Nadeau et al. Medical Neuroscience, 1st ed.
In-flight barodontalgia: analysis of 29 cases in military aircrew. Aviation,
Space and Environmental Medicine. 2007 Jun;78(6):593-6.
Bortolami SB, Pierobon A, DiZio P, Lackner JR. Localization of the
subjective vertical during roll, pitch, and recumbent yaw body tilt. Exp Brain
Res. 2006 Aug;173(3):364-73
Spatial Disorientation. Air Force School of Aerospace Medicine course
Love JT Jr, Caruso VG. Civilian air travel and the otolaryngologist.
Laryngoscope. 1978 Nov;88(11):1732-42.
Mirza S, Richardson H. Otic barotrauma from air travel.
J Laryngol Otol. 2005 May;119(5):366-70.