An experimental study on the ergonomics indices of partial pressure suits.

Partial pressure suits (PPSs) are used under high altitude, low-pressure conditions to protect the pilots. However, the suit often limits pilot's mobility and work efficiency. The lack of ergonomic data on the effects of PPSs on mobility and performance creates difficulties for human factor engineers and cockpit layout specialists. This study investigated the effects of PPSs on different ergonomic mobility and performance indices in order to evaluate the suit's impact on pilot's body mobility and work efficiency. Three types of ergonomics indices were studied: the manipulative mission, operational reach and operational strength. Research results indicated that a PPS significantly affects the mobility and operational performance of the wearers. The results may provide mission planners and human factors engineers with better insight into the understanding of pilots' operational function, mobility and strength capabilities when wearing PPS.

Designing pressure garments capable of exerting specific pressures on limbs.

Pressure garments have been used prophylactically and to treat hypertrophic scars, resulting from serious burns, since the early 1970s. They are custom-made from elastic fabrics by commercial producers and hospital staff. However, no clear scientifically established method has ever been published for their design and manufacture. Previous work [2] identified the most commonly used fabrics and construction methods for the production of pressure garments by hospital staff in UK burn units. These methods were evaluated by measuring pressures delivered to both cylinder models and to human limbs using I-scan pressure sensors. A new calibration method was developed for the I-scan system to enable measurement of low interface pressures to an accuracy of +/-2.5 mmHg. The effects of cylinder/limb circumference and pressure garment design on the pressures exerted were established. These measurements confirm the limitations of current pressure garment construction methods used in UK hospitals. A new method for designing pressure garments that will exert specific known pressures is proposed and evaluated for human thighs. Evaluation of the proposed design method is ongoing for other body parts.

Reproducibility of repeated measurements with the Kikuhime pressure sensor under pressure garments in burn scar treatment.

This study investigated the reproducibility of repeated measurements with the Kikuhime pressure sensor under two different types of pressure garments used in the treatment and prevention of scars after burns. Also efficiency of garments was assessed in clinical circumstances by assessing pressure loss and residual pressure after 1 month. Intra- and inter-observer reproducibility and repeated measurements with 1-month time lapse were examined on 55 sites in 26 subjects by means of intra-class correlation coefficients and standard error of measurements. Results showed good to excellent ICC and low SEMs in the two conditions. There was a significant difference in pressure after 1 month between elastic tricot and weft knit garments, although evolution of pressure loss after 1 month was similar. Concerning different locations, there was a significant difference in pressure loss after 1 month between gloves and sleeves with the largest pressure loss for sleeves. Considering these results we concluded that the Kikuhime pressure sensor provides valid and reliable information and can be used in comparative clinical trials to evaluate pressure garments used in burn scar treatment. Secondly, elastic tricot garments in our study tended to have higher clinical pressures but both types of garments had similar pressure loss over time.

A novel technique to determine pressure in pressure garments for hypertrophic burn scars and comfort properties.

Current recommendations state that pressure garments should be worn for up to 2 years for hypertrophic burn scars. Thermo-physiological properties of pressure garments were assessed by the thermo-physiological tests and a comparison of the fabric with a sportwool which is a single-jersey knitted fabric was performed. In this novel technique, it was aimed to determine the exact pressure of pressure garments on the applied body part. For the theoretical part of this study, the Laplace equation was used with an optimum pressure of 20 mmHg and a relationship between change in length versus circumference was calculated. To determine the change in length a ruler was prepared for each predetermined circumference value using this relationship. Grid printed fabric samples were prepared with an interval of 2 cm in width direction to be used for the calculation of mean pressure on a Mannequin Leg. The resultant mean pressure calculated experimentally on Mannequin Leg as 24 mmHg was compared to the optimum pressure of 20 mmHg. It was observed that the two values were not statistically significantly different.

A new hydrostatic anti-G suit vs. a pneumatic anti-G system: preliminary comparison.

HYPOTHESIS: A newly developed hydrostatic anti-G suit is now commercially available. The suit is said to offer a high level of protection against +Gz acceleration. However, past experience shows that it is difficult to produce a hydrostatic suit with effective high-G protection. Careful testing is, therefore, needed to verify its efficacy. METHODS: The G-protective properties of the hydrostatic anti-G suit (Libelle; L) were compared with those of a pneumatic anti-G ensemble (AGE-39) used in the Swedish JAS 39 Cripen aircraft. Three pilots were studied during vertical (+Gz) acceleration in a centrifuge using the following: 1) the L-suit with varied straining maneuvers; 2) the AGE-39 in combination with full anti-G straining maneuvers (AGSM) throughout each high-G exposure (full maneuver; FM); and 3) the AGE-39 in combination with AGSM during the initial part of each high-G exposure (reduced maneuver; RM). G-intensity tolerance was established during exposures to rapid onset rate (ROR) profiles with G-plateau levels ranging from +6.0 to +9.0 Gz. G-endurance was studied during simulated aerial combat maneuvers (SACM) consisting of 10 cycles of 5.5 to 7.5 G. RESULTS: All three pilots tolerated 9.0 G with the pneumatic system both in the RM and FM conditions; their tolerances averaged 6.3 G (range 6.0 to 7.0 G) for the L suit. Thus, during the ROR exposures only the 6.0 G profile was completed by all subjects in all three conditions. At this G-load both muscle straining (as indicated by electromyographic activity in thigh and abdomen) and heart rate were higher in the L than in the RM condition. Mean arterial pressure at eye level was higher in the FM than in the L and RM conditions. Only one subject was able to complete the SACM profile in the L condition. In the RM condition all subjects completed the SACM profile and in the FM condition two subjects completed the SACM. CONCLUSIONS: Whether the AGE-39 was used in combination with maximal AGSM throughout the duration of each high-G exposure or with AGSM only during the initial part of the high-G exposure, G-intensity tolerance was 9.0 G. While wearing the L-suit, G-tolerance was 6.3 G. Thus, under the conditions tested, the G-protection afforded by the L-suit is not adequate for use in a 9-G aircraft.

Cognitive performance and physiological changes in females at high G while protected with COMBAT EDGE and ATAGS.

BACKGROUND: Female fighter pilots are flying the F-16 and F-15 with COMBAT EDGE, the positive pressure breathing under G (PBG) protection system. The standard CSU 13 B/P anti-G suit may soon be replaced with the Advanced Technology Anti-G suit. The purpose of this research was to compare human performance and physiological changes between the subjects protected by COMBAT EDGE with the standard anti-G suit (STD) and with the Advanced Technology Anti-G Suit (ATAGS). METHODS: Six female centrifuge subjects completed this experiment. Performance of the 3-min simulated aerial combat sorties on the Dynamic Environment Simulator. Heart rate, %SaO2 (percent arterial oxygen saturation), %rSO2 (percent regional cerebral tissue oxygen saturation) and electromyography (EMG) were compared between the two suit conditions. Subjective evaluations of the two suit conditions were also collected. RESULTS: No significant performance differences or EMG differences were found between the STD and ATAGS suits. In the ATAGS suit, %rSO2 and %SaO2 were significantly less and heart rate was significantly lower during the last minute of G exposure compared with the STD condition. Subjects rated the ATAGS suit as having provided better G tolerance, but more uncomfortable. The ATAGS were prototype suits, however, and were not custom fit to the women. CONCLUSIONS: Physiological changes did occur significantly during the last minute of G exposure, even though no significant performance differences were found between two suit conditions. Subjective comments supported the finding that the more G protection and body coverage afforded by the anti-G suit, the less comfortable the suit may be.

[Technical consideration of setting up a specification for human centrifuge evaluation of anti-G equipment].

Anti-G equipment needs to be evaluated using human centrifuge before further developed. However, there isn't a general specification for human centrifuge evaluation of anti-G equipment. From related literature and from our over thirty years experience in this area, we sum up to five aspect technical consideration below: human centrifuge, medical specification for using human in +Gz stress experiment, anti-G equipment experimental assembly, principle should be abided by during human centrifuge evaluation of anti-G equipment. We hope that the technical considerations mentioned in the paper should be helpful to the work of setting up a specification for human centrifuge evaluation anti-G equipment. After we have a specification, the research will be conducted orderly and the anti-G [correction of an-G] equipment will be developed sequentially.

Male/female SACM endurance comparison: support for the Armstrong Laboratory modifications to the CSU-13B/P anti-G suit.

BACKGROUND: The standard anti-G suit (CSU-13B/P) was designed based on male body structure. Females differ from males with respect to body proportionality. In Armstrong Laboratory (AL) studies, females have terminated centrifuge simulated air combat maneuvers (SACM) because of anti-G suit (CSU-13B/P modified according to original T.O. 14P3-6-121)(OTO) discomfort. AL modifications to the suit have since been adopted in the OTO in an attempt to provide females a best-fit suit (AL Mod). The study examined male/female SACM endurance with females wearing both the OTO and the AL Mod suits. METHODS: There were 6 females and 8 males who performed a +5.0 to +9.0 Gz SACM to fatigue using the anti-G straining maneuver with anti-G suit inflation. The females performed in both the OTO and AL Mod suits while the males performed in the OTO suit only (OTO was their best-fit suit). RESULTS: Wearing the OTO, males performed the SACM significantly longer than the females, three of whom reported severe suit discomfort. However, when the females wore the AL Mod suit, their SACM endurance almost doubled over their OTO performance and none reported suit discomfort. When wearing their best-fit suits, there was no significant gender difference in SACM endurance. CONCLUSIONS: These data support the efficacy of the AL modifications to the CSU-13B/P anti-G suit through greatly improved performance during the +5.0 to +9.0 SACM in females. These data also suggest that, in the small sample examined, when fitted with a best-fit anti-G suit, females can endure the +5.0 to +9.0 SACM to the same degree as males.

Comparison of the characteristics and features of pressure garments used in the management of burn scars.

Two companies provide custom-made pressure garments to clients with burn scars at Westmead Hospital. This prospective study was completed in order to make objective decisions about which garments were most appropriate and cost effective to provide to clients. Issues such as cost, durability, fit and client preferences were investigated. Data were collected from 43 clients; at the time of initial fitting, at a follow-up appointment 4-6 weeks later, and at the time one of the garments required replacement. One Second Skin and one Jobst garment were provided to each client and the garments were compared using therapists' evaluation and clients' perspectives on a number of variables. Second Skin garments had significantly more favourable results on the variables of time for delivery, fit at follow-up, garment design, quality of fabric and seams, overall satisfaction and garment preference for ongoing wear. On all other variables there was no significant difference between the garments. Second Skin provided the most optimal and appropriate option for pressure garments in the management of burn scars for our clients.

[Human tolerance of +Gx loads in anti-G suits during deorbiting of the "Soiuz" space vehicles]. / Perenosimost' chelovekom peregruzok napravleniia +Gx na uchastke spuska s orbity kosmicheskikh korablei tipa "Soiuz" pri ispol'zovanii protivoperegruzochnykh kostiumov.

Reported are results of the study of tolerance of the "thorax-back" g-loads (+Gx) during deorbiting of 83 total suited and unsuited cosmonauts in the period of 1997-1997. G-loads averaged 3.7 +/- 0.058 units (from 3.1 up to 5.1 units). Pneumatic gradient G-suits (PGS) Karkas and Centaur had a positive effect on the +Gx tolerance of humans following microgravity. As compared with unsuited crews returning from missions of similar duration, wearing PGS has proven to improve the general health of cosmonauts and to reduce the strain of the leg and abdominal muscles. Tight fitting of PGS abolished visual disorders due to the longitudinal component of G-loads that were registered in 6.6% of observations of unsuited cosmonauts. Sinus tachycardia was significantly weaker (P < 0.05). The authors recommend the use of the standard antiblackout Centaur suit as the efficacy of this PGS was equal to that of Karkas while its ergonomic characteristics were superior.

Do custom-fitted pressure garments provide adequate pressure?

Pressure garment therapy has become the worldwide standard of care for the prevention and treatment of hypertrophic scars. There are many reports in the literature on pressure garment therapy but few studies state the amount of pressure actually provided. The purpose of our study was to determine the amount of pressure applied to the scar/garment interface by custom-fitted pressure garments. The Iscan (Tekscan, Inc.) system was used to document scar/garment interface pressures of 144 new custom-fitted pressure garments. Average pressure readings for garments for the anterior thigh, anterior trunk, abdomen, buttocks, posterior trunk, posterior thigh, and arm were less than 22 mm Hg. Average pressure readings for the dorsal hand, leg, forearm, and dorsal foot were more than 28 mm Hg, with smaller relative standard deviations. The pressure readings varied greatly between garments in this group, frequently resulting in standard deviations that were higher than the pressure readings. The data show that despite precise fitting techniques, pressure garments do not provide a consistent amount of pressure at the scar/garment interface. This means that studies that report results of pressure therapy, but do not verify the amount of pressure applied, are of limited value. Precise determination of pressure "dose" must be made before the efficacy of pressure garment therapy can be determined objectively.

Influence of a reduced G-suit pressure schedule on G-duration tolerance using enhanced G-protection ensembles.

BACKGROUND: Reducing pressure to enhanced G-protection ensembles may diminish potential undesirable physiologic effects, as well as improve wear comfort and garment durability. HYPOTHESIS: G-duration tolerance will not be affected by reducing pressure to the Swedish tactical flight combat suit (TFCS). A second objective tested the similarity in G-duration tolerance between the TFCS and Combined Advanced Technology Enhanced Design G-Ensemble (COMBAT EDGE) combined with a prototype enhanced coverage G-suit. METHODS: There were 12 Swedish pilots (mean = 30 yr) who experienced gradual onset (+0.1 G.s-1) runs (GOR) to +9 Gz, rapid (+6 G.s-1) onset runs (ROR) and simulated aerial combat maneuvers (SACM) with +5 to +9 Gz cycles. The GOR and ROR profiles had a sustained times of 60 s after reaching +9 Gz. RESULTS: GOR duration tolerance was statistically decreased (p < 0.01) by the lower pressure (1.1 psig.G-1) when compared to standard pressure (1.5 psig.G-1). No statistical difference between TFCS and COMBAT EDGE was observed during the GOR trials. For all conditions, during the RORs, 90% of the subjects completed at least 30 s at +9 Gz. Many technical or medical difficulties during SACM trials limited statistical treatment of these data. However, no obvious among-condition differences were observed. Noteworthy among SACM trials were those of 3 subjects enduring more than 9 min before stopping; one completing 12.5 min (35 cycles). Neither heart rate, blood pressure, nor perceived exertion data revealed a condition-effect difference. CONCLUSION: Moderately reduced pressure to the extended coverage anti-G suit, combined with positive pressure breathing, may yield decreased G-tolerance results during laboratory evaluation; however, observed differences are sufficiently small they are likely operationally insignificant.

A new tool to measure pressure under burn garments.

This article introduces a new tool to measure the pressure that is under pressure garments. The Iscan (Tekscan, Inc.) system uses a patented ultra-thin (0.007 inch) sensor with multiple sensing locations that sample continuously at 100 times per second. It is noninvasive, convenient, and quick. The study had two parts. First, we established the validity and reliability of the device. Next, garment/scar interface pressures were measured on new garments with use of the Iscan system. Four garment types were studied, with 10 measurements made in each group: Isotoner gloves (Smith & Nephew Roylan, Inc.); custom-fit pressure gloves; Tubigrip forearm sleeves (Seton Health Care Group); and custom-fit pressure forearm sleeves. Mean garment/scar interface pressures were 18 +/- 2 mm Hg for the Isotoner glove, 34 +/- 5 mm Hg for the custom-fit pressure glove, 20 +/- 7 mm Hg for the Tubigrip sleeve, and 35 +/- 6 mm Hg for the custom-fit sleeve. We concluded that the Iscan system can be used to measure pressure under pressure garments accurately and reliably, and that custom-fit hand and forearm garments provide more pressure than Isotoner gloves or Tubigrip sleeves.

Overhead and forward reach capability during exposure to +1 to +6 Gx loads.

The lack of reach performance data obtained under space-flight conditions has led to questions regarding the operational impact of higher G loads on crew performance. This investigation studied the effect of increasing G loads on reach capability. Ten subjects were exposed in a stepwise fashion to increasing accelerations resulting in G loads of from +1 to +6 Gx in the Brooks AFB centrifuge. Four subjects wore the pre-Challenger Launch Entry Helmet (LEH) ensemble and six the current Launch Entry Suit (LES). The subjects performed standardized reach sweeps at each G level. These sweeps were recorded on videotape and subsequently analyzed using a 3-dimensional motion analysis system. Significant differences in forward and overhead reach were determined using the General Linear Models (GLM) procedure of the Statistical Analysis System (SAS) program. The results from this study suggest that purposeful movement can be realistically performed in the LEH at the 5 G level and in the LES up to the 4 G level.