scholarly journals High-altitude decompression strain can be reduced by an early excursion to moderate altitude while breathing oxygen

2021 ◽  
Vol 121 (11) ◽  
pp. 3225-3232
Author(s):  
Rickard Ånell ◽  
Mikael Grönkvist ◽  
Mikael Gennser ◽  
Ola Eiken
Keyword(s):  
Gas Exchange ◽  
High Altitude ◽  
Decompression Sickness ◽  
Continuous Exposure ◽  
Moderate Altitude ◽  
Cardiac Ultrasound ◽  
Healthy Men ◽  
Hypobaric Chamber ◽  
Long Duration ◽  
Peak Value

AbstractRecent observations suggest that development of venous gas emboli (VGE) during high-altitude flying whilst breathing hyperoxic gas will be reduced by intermittent excursions to moderate altitude. The present study aimed to investigate if an early, single excursion from high to moderate altitude can be used as an in-flight means to reduce high-altitude decompression strain. Ten healthy men were investigated whilst breathing oxygen in a hypobaric chamber under two conditions, once during a 90-min continuous exposure to a simulated cabin altitude of 24,000 ft (High; H) and once during 10 min at 24,000 ft, followed by 30 min at 15,000 ft and by 80 min at 24,000 ft (high–low–high; H–L–H). VGE scores were assessed by cardiac ultrasound, using a 6-graded scale. In H, VGE increased throughout the course of the sojourn at 24,000 ft to attain peak value [median (range)] of 3 (2–4) at min 90, just prior to descent. In H–L–H, median VGE scores were 0 throughout the trial, except for at min 10, just prior to the excursion to 15,000 ft, whence the VGE score was 1.5 (0–3). Thus, an early, single excursion from high to moderate cabin altitude holds promise as an in-flight means to reduce the risk of altitude decompression sickness during long-duration high-altitude flying in aircraft with limited cabin pressurization. Presumably, such excursion acts by facilitating the gas exchange in decompression bubbles from a predomination of nitrogen to that of oxygen.

Hyperoxic Effects on Decompression Strain During Alternating High and Moderate Altitude Exposures

2021 ◽  
Vol 92 (4) ◽  
pp. 223-230
Author(s):  
Rickard nell ◽  
Mikael Grnkvist ◽  
Mikael Gennser ◽  
Ola Eiken
Keyword(s):  
Gas Exchange ◽  
Decompression Sickness ◽  
The Other ◽  
Moderate Altitude ◽  
Cardiac Ultrasound ◽  
Fighter Aircraft ◽  
Lower Altitude ◽  
Healthy Men ◽  
Altitude Exposure ◽  
Long Duration

INTRODUCTION: In fighter aircraft, long-duration high-altitude sorties are typically interrupted by refueling excursions to lower altitude. In normoxia, excursions to moderate cabin altitude may increase the occurrence of venous gas emboli (VGE) at high cabin altitude. The aim was to investigate the effect of hyperoxia on VGE and decompression sickness (DCS) during alternating high and moderate altitude exposure.METHODS: In an altitude chamber, 13 healthy men were exposed to three different conditions: A) 90 min at 24,000 ft (7315 m) breathing normoxic gas (54% O2; H-NOR); B) 90 min at 24,000 ft breathing hyperoxic gas (90% O2; H-HYP); and C) three 30-min exposures to 24,000 ft interspersed by two 30-min exposures to 18,000 ft (5486 m) breathing 90% O2 (ALT-HYP). VGE occurrence was evaluated from cardiac ultrasound imaging. DCS symptoms were rated using a scale.RESULTS: DCS occurred in all conditions and altogether in 6 of the 39 exposures. The prevalence of VGE was similar in H-NOR and H-HYP throughout the exposures. During the initial 30 min at 24,000 ft, the prevalence of VGE was similar in ALT-HYP as in the other two conditions, whereas, after the first excursion to 18,000 ft, the VGE score was lower in ALT-HYP than in H-NOR and H-HYP.DISCUSSION: Hyperoxic excursions from 24,000 to 18,000 ft reduces VGE occurrence, presumably by facilitating diffusive gas exchange across the bubble surfaces, increasing the share of bubble content contributed by oxygen. Still, the excursions did not abolish the DCS risk.nell R, Grnkvist M, Gennser M, Eiken O. Hyperoxic effects on decompression strain during alternating high and moderate altitude exposures. Aerosp Med Hum Perform. 2021; 92(4):223230.

Adrenocortical responses to maximal exercise in moderate-altitude natives at 447 Torr

1984 ◽  
Vol 56 (2) ◽  
pp. 482-488 ◽  
Author(s):  
C. M. Maresh ◽  
B. J. Noble ◽  
K. L. Robertson ◽  
R. L. Seip
Keyword(s):  
High Altitude ◽  
Fluid Intake ◽  
Maximal Exercise ◽  
Bicycle Ergometer ◽  
Moderate Altitude ◽  
Simulated Altitude ◽  
Maximum Exercise ◽  
Hypobaric Chamber ◽  
Low Altitude ◽  
Adrenocortical Responses

Serum hydrocortisone and aldosterone (Aldo) responses to maximal exercise were examined in six low-altitude natives (LAN) (373 m or less, aged 19–25 yr) and eight moderate-altitude natives (MAN) (1,830–2,200 m, aged 19–23 yr) at their residence (home) altitudes (740 and 587 Torr, respectively) and later in a hypobaric chamber at a simulated altitude of 4,270 m (447 Torr). After 2 days at their respective residence altitude and in the chamber, each subject exercised to voluntary exhaustion on the bicycle ergometer. Fluid intake was similar in both groups at all testing locations. Preexercise 24-h urinary Aldo was lower in both groups at 447 Torr but only significantly reduced in the LAN group. In general, the changes in maximum exercise cardiorespiratory variables were twice as large in LAN as in MAN subjects going from residence altitude to 447 Torr. Both serum hydrocortisone and Aldo concentrations were increased (P less than 0.01) after exercise in both groups at residence altitude and 447 Torr. Aldo was lower (P less than 0.05) postexercise at 447 Torr than at residence altitude in both groups, but this decrease was more pronounced (P less than 0.01) in the LAN group. Thus it appears that high-altitude Aldo concentrations are more like resident altitude values in MAN than in LAN subjects.

Evolution and Preservation of Venous Gas Emboli at Alternating High and Moderate Altitude Exposures

2020 ◽  
Vol 91 (1) ◽  
pp. 11-17
Author(s):  
Rickard Ånell ◽  
Mikael Grönkvist ◽  
Mikael Gennser ◽  
Ola Eiken
Keyword(s):  
Ground Level ◽  
Moderate Altitude ◽  
Cardiac Ultrasound ◽  
Simulated Altitude ◽  
Fighter Aircraft ◽  
Long Duration ◽  
Grade Scale ◽  
Nitrogen Exchange ◽  
Decompression Stress ◽  
Low Nitrogen

INTRODUCTION: The evolution and preservation of venous gas emboli (VGE), as markers of decompression stress, were investigated during alternating high- and moderate altitude exposures, thus, simulating a fighter aircraft high-altitude flight, interrupted by refueling excursions to lower altitudes.METHODS: Eight men served as subjects during three normoxic simulated altitude exposures: High = 90 min at 24,000 ft; High-Low = three × 30 min at 24,000 ft, interspersed by two 30-min intervals at 15,000 ft; Low = 90 min at 15,000 ft. VGE scores were assessed by cardiac ultrasound, using a 5-grade scale. Respiratory nitrogen exchange was measured continuously using a modified closed-circuit electronic rebreather.RESULTS: Both High and High-Low induced persistent VGE, with no inter-condition difference either at rest [median (range): High: 1 (0-3), High-Low: 2 (0-3)] or during unloaded knee-bends [High: 3 (1-4), High-Low: 3 (0-4)], whereas VGE was considerably less in Low, both at rest [0 (0-1)] and during knee-bends [0 (0-2)]. In High-Low, VGE decreased temporarily during the 15,000-ft excursions, but resumed pre-excursion values upon return to 24,000 ft. During the final descent to ground level, VGE were more persistent following High-Low than High. In both High and Low, nitrogen was continuously washed out at altitude, whereas in High-Low, the washout at 24,000 ft was interrupted by nitrogen uptake at 15,000 ft.DISCUSSION: In normoxic conditions, long-duration flying at a cabin altitude of 24,000 ft is associated with substantial VGE occurrence, which is not abolished by intermittent excursions to a cabin altitude of 15,000 ft.Ånell R, Grönkvist M, Gennser M, Eiken O. Evolution and preservation of venous gas emboli at alternating high and moderate altitude exposures. Aerosp Med Hum Perform. 2020; 91(1):11–17.

scholarly journals Simultaneous generalized and low-layer SCIDAR turbulence profiles at san pedro mártir observatory

2019 ◽  
Vol 490 (1) ◽  
pp. 1397-1405 ◽  
Author(s):  
R Avila ◽  
O Valdés-Hernández ◽  
L J Sánchez ◽  
I Cruz-González ◽  
J L Avilés ◽  
...  
Keyword(s):  
High Altitude ◽  
Wind Direction ◽  
Close Agreement ◽  
Baja California ◽  
Ground Level ◽  
Combined Effect ◽  
Moderate Altitude ◽  
San Pedro ◽  
Simultaneous Measurements

ABSTRACT We present optical turbulence profiles obtained with a Generalized SCIDAR (G-SCIDAR) and a low-layer SCIDAR (LOLAS) at the Observatorio Astronómico Nacional in San Pedro Mártir (OAN-SPM), Baja California, Mexico, during three observing campaigns in 2013, 2014, and 2015. The G-SCIDAR delivers profiles with moderate altitude-resolution (a few hundred metres) along the entire turbulent section of the atmosphere, while the LOLAS gives high altitude resolution (on the order of tens of metres) but only within the first few hundred metres. Simultaneous measurements were obtained on 2014 and allowed us to characterize in detail the combined effect of the local orography and wind direction on the turbulence distribution close to the ground. At the beginning of several nights, the LOLAS profiles show that turbulence peaks between 25 and 50 m above the ground, not at ground level as was expected. The G-SCIDAR profiles exhibit a peak within the first kilometre. In 55 per cent and 36 per cent of the nights stable layers are detected between 10 and 15 km and at 3 km, respectively. This distribution is consistent with the results obtained with a G-SCIDAR in 1997 and 2000 observing campaigns. Statistics computed with the 7891 profiles that have been measured at the OAN-SPM with a G-SCIDAR in 1997, 2000, 2014, and 2015 campaigns are presented. The seeing values calculated with each of those profiles have a median of 0.79, first and third quartiles of 0.51 and 1.08 arcsec, which are in close agreement with other long term seeing monitoring performed at the OAN-SPM.

Decompression Sickness in Women Recreational Scuba Divers

1999 ◽  
Vol 8 (1) ◽  
pp. 47-54
Author(s):  
Jacalyn J. Robert
Keyword(s):  
High Altitude ◽  
Decompression Sickness ◽  
Scuba Diving ◽  
Training Center ◽  
Men And Women ◽  
Recreational Sport ◽  
Scuba Divers ◽  
Hyperbaric Environment ◽  
Recreational Scuba

Recreational sport diving is becoming an increasingly popular sport for women. Women now comprise approximately 25% of the diving community according to Divers Alert Network statistics. In the diving literature it has been stated that women are at a greater risk for decompression sickness than men. Most of these statements were derived from high-altitude (hypobaric environment) studies rather than from a scuba diving (hyperbaric) environment. Data from the naval diving and salvage training center were analyzed, and it was found that women are not more susceptible to decompression sickness than men during dives between 4 and 10 atmospheres. More specific studies on sport diving should be completed on factors contributing to underwater decompression sickness in both men and women.

Recent changes in hypoxia training at the Royal Air Force Centre of Aviation Medicine

2015 ◽  
Vol 101 (2) ◽  
pp. 186-187
Author(s):  
A Wrigley
Keyword(s):  
Air Force ◽  
Decompression Sickness ◽  
Student Experience ◽  
Training Method ◽  
Royal Air Force ◽  
Aviation Medicine ◽  
Oxygen Breathing ◽  
Hypobaric Chamber ◽  
The Subject ◽  
New System

AbstractHypoxia training at the Royal Air Force Centre of Aviation Medicine (RAF CAM) has traditionally involved the use of a hypobaric chamber to induce hypoxia. While giving the student experience of both hypoxia and decompression, hypobaric chamber training is not without risks such as decompression sickness and barotrauma. This article describes the new system for hypoxia training known as Scenario-Based Hypoxia Training (SBHT), which involves the subject sitting in an aircraft simulator and wearing a mask linked by hose to a Reduced Oxygen Breathing Device (ROBD). The occupational requirements to be declared fit for this new training method are also discussed.

An echo from the past: Building a Doppler repository for big data in diving research

2021 ◽  
pp. 57-58
Author(s):  
Virginie Papadopoulou ◽  
◽  
Peter Lindholm ◽  
Keyword(s):  
Big Data ◽  
High Altitude ◽  
Decompression Sickness ◽  
Non Invasive ◽  
The Past ◽  
Subject Variability ◽  
Decompression Stress

Decompression sickness (DCS) remains a major operational concern for diving operations, submarine escape and high-altitude jumps. Aside from DCS symptoms, venous gas emboli (VGE) detected with ultrasound post-dive are often used as a marker of decompression stress in humans, with a specificity of 100% even though the sensitivity is poor [1]. Being non-invasive, portable and non-ionizing, ultrasound is particularly suited to regular and repeated monitoring. It could help elucidate inter- and intra-subject variability in VGE and DCS susceptibility, but analyzing these recordings remains a cumbersome task [2].

Neurologic Decompression Sickness Following Cabin Pressure Fluctuations at High Altitude

2010 ◽  
Vol 81 (4) ◽  
pp. 427-430 ◽  
Author(s):  
Jonathan D. Auten ◽  
Michael A. Kuhne ◽  
Harlan M. Walker ◽  
Henry O. Porter
Keyword(s):  
High Altitude ◽  
Decompression Sickness ◽  
Pressure Fluctuations

When Is It Safe to Fly or Travel to High Altitude?

2019 ◽  
pp. 175-175
Author(s):  
David L. Brody
Keyword(s):  
Cognitive Function ◽  
High Altitude ◽  
Cognitive Performance ◽  
Air Force ◽  
Moderate Altitude ◽  
Impaired Balance

Most commercial airplanes are pressurized to the equivalent of about 7000 to 8000 feet. U.S. Air Force researchers have shown that uninjured people experience very little change in cognitive function or symptoms at this altitude, but that this is not the case after concussion. Symptoms and deficits that had resolved can come back at altitude, most notably headaches, slowing of cognitive performance, and impaired balance. Inform the patient and family about this risk and then let them make their own decisions about whether it is worth it. No evidence of permanent harm from flying or traveling to moderate altitude in concussion patients exists, but it has not been carefully studied.

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