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PubMed2003

[Incidence and clinical characteristics of perioperative pulmonary thromboembolism under the use of intermittent pneumatic compression as a preventive measure].

Pulmonary thromboembolism (PTE) is a crucial complication characterized by rapid onset and a high mortality rate. There are few reports concerning perioperative incidence of PTE and deep vein thrombosis (DVT) among Japanese population. All surgical patients excluding young patients for minor surgery were equipped with calf- or thigh-length intermittent pneumatic compression (IPC) device as a DVT preventive method during the period of immobility. Incidence and clinical characteristics of perioperative PTE and DVT under the use of IPC device were analyzed at Kobe University Hospital. One patient developed DVT and four patients developed PTE among the 6500 surgical cases. All patients with DVT or PTE were 66 years or older, and all patients were diagnosed by computer tomography, venography and pulmonary angiography between 7 to 14 days after each operation. One patient was surgically treated by embolectomy and removal of intraarterial thrombus, and others were treated with thrombolysis, anticoagulants and placement of vena cava filters. For prevention of DVT and PTE, other preventive methods such as anticoagulants and prolonged application of IPC should be necessary.

Age Factors↗
PubMed2004

Graduated compression stockings reduce the venous velocity augmentation of foot pumps.

The use of the A-V Impulse System of foot pumps and graduated compression stockings to reduce the incidence of thrombo-embolic disease after total hip arthroplasty is well recognised. It is not known if they have a synergistic effect as all clinical trials have used them in combination. We examined the effect compression stockings had on the ability of the A-V Impulse System to accelerate peak venous velocities in the common femoral vein in ten healthy volunteers using a duplex scanner. The use of foot pumps without stockings produced the greatest increase in peak venous velocity and this was 34% greater than using a foot pump with stockings. It is not known if this difference could account for a reduction in thrombo-embolic episodes and so we propose a randomised clinical trial.

Arthroplasty, Replacement, Hip↗
PubMed2005

Mechanical counter-pressure vs. gas-pressurized spacesuit gloves: grip and sensitivity.

INTRODUCTION: An elastic mechanical counter pressure (MCP) glove for spacesuits is under development. In this study we compared handgrip and pinch grip strength levels for the MCP glove and the current extravehicular mobility unit (EMU) gas-pressurized glove. METHODS: We employed handgrip and pinch grip dynamometers to assess strength levels and von Frey monofilaments to evaluate hand sensitivity. Tests were conducted with the gloved hand inserted in an evacuation chamber at 200 mmHg below atmospheric pressure to simulate conditions in space. RESULTS: Average bare hand strength was 463 N and decreased to 240 N for EMU and 250 N for MCP. Pinch grip and key grip testing showed no difference among conditions. However, there was a significant decrease in palmar grip strength from 111 N barehanded to 67 N in both gloves. Barehanded endurance time was 160 s and dropped to 63 and 69 s for EMU and MCP, respectively. Sensitivity was significantly better for MCP compared with the EMU. DISCUSSION: The MCP glove improved hand sensitivity when compared with the EMU glove and performed as well as the EMU glove in terms of overall handgrip strength, endurance at 25% of maximum handgrip strength, pinch grip, palmar grip, and key grip tests. Improvements in fabric composition and glove design may further improve ergonomic and other functional parameters of the MCP glove.

Adult↗
PubMed1992

Comparison of warfarin and external pneumatic compression in prevention of venous thrombosis after total hip replacement.

OBJECTIVE: To compare the effectiveness and safety of warfarin and external pneumatic compression (EPC) in prevention of venous thrombosis after total hip replacement. DESIGN: Prospective, randomized trial in consecutive patients, with blinded assessment of the primary end point. SETTING: University medical center and large community hospital. PATIENTS: Patients over age 18 years scheduled for elective primary total hip replacement were eligible. Of 254 patients interviewed, 232 were randomized, 220 patients had surgery and received prophylaxis, and 201 had venography. INTERVENTIONS: Patients were randomly assigned to prophylaxis with a device providing bilateral sequential EPC to both the calf and thigh or to receive warfarin in a low-intensity regimen beginning 10 to 14 days preoperatively. Prophylaxis was continued until venography. MAIN OUTCOME MEASURES: Venous thrombosis was diagnosed by venography between postoperative days 6 and 8. Bleeding was assessed by surgical blood loss, transfusion requirements, changes in hematocrit, and clinically identified bleeding complications. RESULTS: The total incidence of venous thrombosis was virtually the same in the warfarin and EPC groups (31% vs 27%), but the distribution of thrombi was different. Proximal thrombosis occurred in 12% of patients in the EPC group compared with only 3% in the warfarin group (P = .012, 95% confidence interval for difference, 2% to 18%). In contrast, calf vein thrombosis was more frequent in the warfarin group (21%) than in the EPC group (12%) (P = .021, 95% confidence interval for difference, 0% to 18%). Most proximal thrombi in EPC-treated patients were located within 15 cm of the femoral head and were not continuous with thrombi in deep calf veins. The high incidence of proximal thrombosis in the EPC group resulted in termination of the study by the safety monitoring committee. Blood loss and bleeding complications were similar in the two groups. CONCLUSION: Warfarin therapy is significantly more effective than EPC in preventing serious proximal vein thrombosis after total hip replacement. The greater effectiveness of warfarin therapy in preventing proximal vein thrombi and of EPC in preventing thrombosis in the calf suggests that there are differences in the pathogenesis of thrombosis in these two locations.

Aged↗
PubMed2005

Pressure breathing without a counter-pressure vest does not impair acceleration tolerance up to 9 G.

INTRODUCTION: This study was to determine whether safe and adequate G-protection by pressure breathing during G (PBG) could be maintained if the COMBAT EDGE counter-pressure vest were eliminated to ensure aircrew do not unnecessarily endure a possible in-flight discomfort or distraction. METHODS: Centrifuge exposures up to +9 Gz were completed by 11 subjects, including 5 F-15 aircrew, using PBG at 60 mmHg pressure with and without the counter-pressure vest. Additional G-exposures using pressures of 0, 30, and 45 mmHg were performed without the vest. RESULTS: Elimination of the COMBAT EDGE counter-pressure vest did not significantly reduce G-tolerance. During gradual onset G exposure, the mean G level reached with PBG was 8.4 G without the vest and 8.2 G with the vest. In comparison, 6.7 G was reached without PBG. Mean times at G with rapid onset G exposure were 59 and 60 s, respectively, compared with 49 s without PBG. PBG, with or without the vest, was preferred by all test subjects. PBG at 60 mmHg produced the highest G protection and was preferred by the test subjects over lesser pressures. Subjects reported no adverse effects from the use of PBG without chest counter-pressure. CONCLUSION: The use of PBG and the anti-G straining manuever (AGSM) together enhances G tolerance and comfort more than AGSM alone. Elimination of the counter-pressure vest during use of PBG does not hinder an individual's ability to reach +9 Gz or complete a short duration simulated aerial combat maneuver G exposure. Further research is needed to determine if use of PBG without chest counter-pressure increases fatigue during multiple sorties or produces other aeromedical problems in operational environments.

Acceleration↗
PubMed2005

G-induced visual and cognitive disturbances in a survey of 65 operational fighter pilots.

INTRODUCTION: Only one previous study has assessed almost loss of consciousness (A-LOC) in operational fighter pilots, reporting an incidence rate of 14%. Research also indicates that 8-13% of pilots have experienced G-induced loss of consciousness (G-LOC). A-LOC can be as insidious as G-LOC due to the associated altered state of awareness and relative incapacitation time, making it a significant risk factor in the high +Gz environment. Royal Australian Air Force (RAAF) pilots currently fly the F/A-18 and Hawk 127, producing +Gz accelerations up to +7.5 Gz, which places these pilots at risk of both A-LOC and G-LOC. METHODS: A survey was administered to 100 active RAAF fighter pilots requesting information on G-induced visual and cognitive disturbances, A-LOC symptoms, and G-LOC. Details regarding type of aircraft, flying maneuvers performed and mission outcome were also sought. RESULTS: There were 65 RAAF fighter pilots who completed the survey (age 20-53 yr, height 168-193 cm, weight 64-110 kg, jet hours 30-5700 h). Of these pilots, 98% indicated they had experienced at least one visual or cognitive disturbance in the high G environment: gray-out 98%; black-out 29%; and A-LOC symptoms 52%, including abnormal sensation in limbs, disorientation, and confusion. There were 9% who indicated they had experienced G-LOC (50% were the pilot flying the aircraft). DISCUSSION: These findings indicate that RAAF fighter pilots are experiencing a similar rate of visual disturbances and G-LOC when compared with other air forces. However, RAAF pilots reported a much higher incidence of A-LOC compared with the only other study of operational fighter pilots.

Adult↗
PubMed2005

Computer modeling of acceleration effects on cerebral oxygen saturation.

INTRODUCTION: Failure to effectively regulate BP and cerebral perfusion during high-G aircraft maneuvering may contribute to reduced performance in pilots due to the fact that perfusion to the peripheral cerebral tissues may not be adequate to support the mental demands of flight. Therefore, a critical area of investigation is the study of cortical tissue oxygenation responses to +Gz acceleration. METHODS: Two experiments were used to build two sections of a cerebral oxygen saturation (rSo2) model. Experiment 1: Six subjects participated in the study. A cerebral oximeter (gold standard) provided rSo2. Acceleration profiles (subjects relaxed) included a 0.1 G x s(-1) G onset to central light loss (CLL) and a 3 G x s(-1) onset to a G level that was 1 Gz above CLL to an endpoint of G-LOC. Experiment 2: There were 12 subjects (with G protection) who participated in this study. The rSo2 data were collected during five different simulated aerial combat maneuvers. A model was created that read the Gz profile as input and calculated changes in rSo2. The correlation coefficient, linear best-fit slope, and mean percent error were calculated to determine agreement. RESULTS: The average value for the correlation coefficients, linear best-fit slopes, and mean percent errors for the unprotected subjects were 0.79, 0.87, and 6.08, respectively. These values for the protected subjects were 5 G (0.994, 1.011, 0.384), 6 G (0.994, 0.909, 0.811), 7 G (0.986, 1.061, 0.692), 8 G (0.969, 1.016, 1.300), and 9 G (0.994, 0.979, 0.558), respectively. DISCUSSION: The model is a good predictor of rSo2 values for protected and unprotected subjects under +Gz stress.

Adult↗
PubMed2006

Physical conditioning to enhance +Gz tolerance: issues and current understanding.

INTRODUCTION: Although Canadian Forces (CF) efforts directed at developing new G-protection strategies have often raised the question of potential benefits of physical conditioning (PC) on G tolerance (GT), a fatality in a CF fighter aircraft accident, in which it was suggested the pilot may have had 'sub-optimal GT,' sparked renewed interest in this topic. METHODS: A two-part review was conducted: 1) a survey of the literature on the effects of PC on GT; and 2) a determination of further research required to resolve uncertainties on the subject. RESULTS: Five key themes surfaced: 1) GT as a concept is complex, and has different connotations for different users; 2) the term 'PC' likewise has a variety of meanings, and precise definitions are necessary to compare research results; 3) in examining the relationship between PC and GT, the roles of strength training, muscle fatigue, and aerobic fitness are not as clear as some studies seem to suggest; 4) in designing PC programs to enhance GT, issues such as palatability, efficacy, and intended target population must be addressed for the program to be operationally useful; and 5) there is a requirement for investigations that have controlled important influences such as intercurrent +Gz-stress exposure, proficiency in performing the anti-G straining maneuver, and the wide inter- and intra-individual variation for PC and GT measurements. DISCUSSION: The effects of PC on GT are not well established. Further research with more robust experimental designs and/or analyses than those used to date must be conducted (on new or existing data) to clarify this relationship. Conducting such work with sound experimental design and controls is more complex and time-consuming than some may appreciate.

Aerospace Medicine↗