Acceleration Atelectasis in the F-22

Return of an ‘old friend’

Lt Col Jay Flottman,

USAF F-22 Pilot-Physician

Disclosure Information

I have no financial relationships to disclose.

I will not discuss off-label use and/or investigational use in my presentation

This presentation contains the opinion of the author and does not the reflect the view of the U.S. Air Force or Department of Defense.

Overview

• Historical literature review• Acceleration Atelectasis – definition• F-22 OBOGS Review• Upper Pressure Garment Review• Personal History

Historical Literature Review (sample)

• Ernsting, J. Some Effects of Oxygen Breathing, Proceeding of the Royal Society of Medicine, 1960• Langdon, D.E. and G.E. Reynolds, Post-Flight Respiratory Symptoms Associated with 100% Oxygen

and G Forces: Aerospace Medicine, 1961• Green I.D., and B.F. Burgen, An Investigation into the major factors contributing to post-flight chest

pain in fighter pilots: Flying Personnel Research Committee, Air Ministry, 1962• Levy, P.M., et al, Aeroatelectasis: A Respiratory Syndrome in Aviators, Aerospace Medicine, 1962• Glaister, D.H., Pulmonary gas exchange during positive acceleration, Flying Personnel Research

Committee, Air Ministry, 1963• Ernsting, J., The ideal relationship between inspired oxygen concentration , Aerospace Med. 34,

1963 • York, E., et al, Post-Flight Chest Discomfort in Aviators: Aero-Atelectasis: Bureau of Medicine and

Surgery, 1965• Glaister, D.H., The Effects of Gravity and Acceleration on the Lung: The Advisory Group for

Aerospace Research and Development. NATO, 1970• Tacker, W.A., et al, Induction and Prevention of Acceleration Atelectasis: Aviation, Space

Environmental Medicine, 1987• Glaister, D.H., Effect of Acceleration on the Distribution of Ventilation in Man: RAF Institute of

Aviation Medicine, 1994• Balldin UI. Pressure Breathing and Acceleration Atelectasis. Raising the operational ceiling. A

workshop on the life support and physiological issues of flight at 60,000 and above, June 1995

Acceleration Atelectasis• Collapse of alveoli in the dependent lung due to

increased accelerative forces• Symptoms – cough, inability to take a deep

breath, pain in the chest (Keefe, 1958)– May last minutes to several hours (Balldin, 1995)

Atelectasis Cont.• Glaister reported three conditions required for

development of Atelectasis (AGARD, 1970): – Acceleration, elevation of the diaphragm

(Anti-G Suit), 100% Oxygen• Reduction of incidence recommended 40%

Nitrogen for air mixtures up to 25,000 ft cabin altitude (Ernsting, 1963)

Atelectasis Cont.• Life Support System

Task Force (LSS) further identified specific factors in the F-22 (see flow diagram) that may have been contributing factors

Atelectasis Cont.• “We believe there

is a certain amount of atelectasis. If we conduct the study that Dr. Balldin is suggesting relating to assisted PBG, I think the fit and tightness of the Jerkin will be critical,” (Ackles, 1995)

F-22 OBOGS Review

F-15 LO

X

F-15E MSOGS

F-16 OBOGS

F-22 OBOGS MAX

F-22 OBOGS AUTO

Transition to MAX at 11K Cabin Altitude

• UPG is designed to inflate during Positive Pressure Breathing (PPB) only• During non-PPB operation, UPG should not inflate

• Test results show UPG fills and retains BRAG safety pressure at all times• UPG pressure is often above mask pressure • Pilots are forced to breathe against UPG restriction

-6

-4

-2

0

2

4

6

230 235 240 245

InWg

Seconds

Mask Pressure

UPG Pressure

Delta Pressure

Altitude: 8K

F-22 Baseline Configuration (w/ UPG), Mask-UPG Differential Pressure

Non-PPB Designed UPG Pressure

Deep Breath #1 Deep Breath #2

Altitude Chamber – Typical of 12 of 12 pilots

Upper Pressure Garment Operation

Upper Pressure Garment Breathing Changes

• UPG causes pilots to adjust their breathing patterns• F-22 Baseline w/o UPG had higher peak flows than F-22 Baseline (w/UPG) for

similar inhalation cycles • UPG restricts pilot peak flow rate by one third

• UPG restricts thoracic expansion• To maintain a similar tidal volume, the pilot must inhale longer

F-22 Baseline (w/ UPG) vs. F-22 Baseline w/o UPG, Pressure – Flow Comparison

0

20

40

60

80

100

120

140

160

180

200

-6

-5

-4

-3

-2

-1

0

1

2

3

4

230 232 234 236 238 240 242 244

lpmInWg

seconds

Deep Breath #1

F-22 Baseline w/o UPG Mask Pressure

F-22 Baseline (w/UPG) Delta Pressure

F-22 Baseline w/o UPG Flow

F-22 Baseline (w/UPG) Flow

Altitude: 8K

Deep Breath #2

Personal Testimony

• April 2012 – “Red-Air” F-22 Sortie, Elmendorf– Cold WX gear including

undergarments, ATAGS, UPG, C2A1 canister, finger-mounted pulse oximeter, survival vest, MAX OBOGS selection with mask up from start to shutdown

Personal Testimony• April 2012 – “Red-Air” F-22 Sortie, Elmendorf

– Cold WX gear including undergarments, ATAGS, UPG, C2A1 canister, finger-mounted pulse oximeter, survival vest, MAX OBOGS selection with mask up from start to shutdown

– Relatively low G; 2-3 x high G turns (+6-7G) lasting only few seconds

– Less than 1.5hr mission– Post flight: inability to breathe deeply without substernal chest

pain (pain lasted 3-4 hours), pulse ox drop to 94-95% immediately post-flight that lasted 2-3 minutes, minor cough

• Classic symptoms per original literature reviews (60’s and 70’s) – discussed with Boeing Led Physiology Team during Physiologic Event Investigation

Take Away

• Need to further explore AFE fitting procedures• Placement of AFE on the torso (i.e. survival

vest)• AFE in general – was it contributing to the

symptoms that had been reported by pilots in the field?

• Importance of HSI in life support equipment development