Biomedical subjects

I Shochat

Publications and source records attributed to I Shochat.

13 recordsLinked to original sources

PubMed1993

Heat stress and helicopter pilot errors.

Helicopter pilots are subjected to degrees of heat stress that under laboratory conditions result in decreased performance. However, the effect of heat stress on the frequency of helicopter pilot errors is uncertain. The purpose of this study is to determine whether there is an association between ambient heat stress and pilot error. The records of 500 helicopter accidents and incidents due to pilot error during the months May through October were selected at random. On the day of the event, ambient dry bulb and wet bulb temperatures were recorded and compared to temperature and humidity readings on 1000 days chosen at random over the same time period, after eliminating days where events occurred. There was a significant difference between the dry temperature distributions of the days with pilot error compared with the control group (chi 2 = 47.54, P < .0001). A dose-response relationship was found, with a significantly lower risk when ambient dry bulb temperatures were 25 to 29 degrees C (odds ratio, 0.6; 95% confidence interval, 0.5 to 0.8, P < .0001), an increased risk of 1.6 (1.3 to 2.0, P < .0001) at 30 to 34 degrees C, and the highest risk at 35 degrees C or more (6.2, 95% confidence interval, 2.1 to 21.8, P < .0002). There is a dose-response relationship between ambient heat stress and pilot error in Israel military helicopter pilots. This is the first study outside the laboratory showing a connection between heat stress and accidents due to human error. Further studies are required to substantiate our findings and to determine whether extrapolation to other settings is warranted.

Accidents, Aviation↗

PubMed1992

The incidence of myopia in the Israel Air Force rated population: a 10-year prospective study.

It is important to define the risk in pilots of becoming myopic in order to determine the need for yearly screening, and to predict pilot eligibility in environments where the use of corrective lenses may present problems. We conducted a prospective study of 1400 air force personnel followed for 10 years, who could be divided into three major groups; those with 20/20 vision in both eyes, those with 20/25 in one eye only and whose vision was 20/20 using both eyes together, and those who were accepted despite the fact that they required corrective lenses. Over the 10-year period, 23.1% of those with 20/25 visual acuity in one eye needed corrective lenses, significantly more than the 7.4% observed in those with 20/20 vision in both eyes (relative risk 3.1, 95% confidence interval 2.2-4.3, p less than 0.0000). The prevalence of corrective lenses increased until age 26. We conclude that 7.4% of pilots will become myopic over a 10-year period if accepted with 20/20 vision in both eyes. The risk, however, is much higher in those with incipient growth myopia starting in one eye at entry. Therefore, the annual screening of visual acuity in air force personnel is essential.

Adolescent↗

PubMed1991

Intraocular lens in a fighter aircraft pilot.

A pseudophakic pilot of the Israeli air force flying an F-15 (Eagle) aircraft was followed up for three years. He experienced about 100 flying hours, 5% of the time under high g stress. The intraocular lens did not dislocate and no complications were observed. It seems that flying high performance fighter aircraft is not contraindicated in pseudophakic pilots.

Adult↗

PubMed1991

Heat stress on helicopter pilots during ground standby.

We attempted to use measurements of ambient thermal conditions to characterize and then predict thermal conditions in the cockpit before takeoff and during an hour standby period in Bell 206 and Bell 212 helicopters with a crew of two and with the cockpit doors opened. Dry bulb, wet bulb, and globe temperatures were measured on 28 separate summer days. The wet bulb globe temperature index (WBGT) was used to estimate heat stress. Ambient WBGT at time 0 ranged from 13 degrees C to 31 degrees C. There was a 2.9 +/- 3.7 degree difference in WBGT between ambient and cockpit conditions at time 0 which increased to 7.2 +/- 3.5 degrees after 1 h. Because of the cooling effect of opening the helicopter cockpit doors, the cockpit WBGT actually decreased over the standby period when cockpit WBGT values were 30 degrees C or more at time 0. Thus, there was an inverse correlation between cockpit WBGT at time 0 and the change in cockpit WBGT over the 1-h period (r = -0.767, p less than 0.001). The mean WBGT in the cockpit over the 1-h standby period was positively correlated with the ambient WBGT at time 0 (r = 0.783, p less than 0.001). We conclude that the greenhouse effect results in a cockpit WBGT which is significantly higher than ambient conditions. Subsequent changes in cockpit WBGT depend on the balance between heat transfer from the pilot's bodies to the cockpit and the loss of heat after the doors of the helicopters are opened. Ambient thermal conditions can be used to predict heat stress during the ground standby period.

Aerospace Medicine↗

PubMed1991

Factors associated with leukocyturia in asymptomatic pilots.

We attempted to relate the prevalence of leukocyturia during annual examinations to recent activities and history data in 923 pilots. Urinary analysis was done and the results cross-tabulated with answers from a questionnaire and with a past history of leukocyturia obtained from the pilot's chart. The prevalence of 4 to 6 or more white blood cells (WBCs) in the urinary sediment was 5.3%. Leukocyturia was 35.7 times more common (odds ratio) in those with a previous history of leukocyturia and a concomitant history of urethritis (p less than 0.0001). Yet, a history of leukocyturia accounted for only 18.1% of the cases of leukocyturia. There was a trend for an association between jogging and leukocyturia. The prevalence of leukocyturia was not affected by smoking, other physical exercise, a history of nephrolithiasis, air duty in the preceding 24 h or a history of transient illness during the last 2 weeks. We conclude that there is an association between a history of both leukocyturia and urethritis and leukocyturia. In most cases, however none of the variables tested were found to be associated with leukocyturia.

Aerospace Medicine↗

PubMed1990

The effect of repeated doses of 30 mg pyridostigmine bromide on pilot performance in an A-4 flight simulator.

The effect of repeated doses of 30 mg pyridostigmine bromide every 8 h on flight skills in an A-4 simulator was tested in this crossover double-blind placebo-controlled study on 10 pilots experienced in actual and simulated A-4 flights. The pilots flew two test simulator flights 2 h after the fourth dose of pyridostigmine or placebo. The flight profile included navigation, rapid ascent, 360 degrees turns, and instrument landing. Each flight lasted approximately 20 min. Flight parameters measured included indicated air speed, true heading, barometric altitude, vertical velocity, and bank. The mean whole blood cholinesterase inhibition level was 29%. There was no decrement in performance under treatment with pyridostigmine in the percent of deviation time from the prescribed limits or in the average duration or magnitude of the deviation in each of the flight parameters. We conclude that pyridostigmine bromide in repeated doses of 30 mg every 8 h does not appear to influence pilot performance during short A-4 missions.

Adult↗

PubMed1990

Blood pressure response to exercise in normotensive and hypertensive young men.

We attempted to determine the optimal cut-off value of blood pressure defining a hypertensive response to exercise testing in 90 asymptomatic Israeli candidates for flight training with casual resting blood pressure of 140/90 mm Hg or more, and 72 age-matched normotensive controls tested in the Israel Air Force Aeromedical Center. Exercise testing (Bruce protocol) was performed using a calibrated Quinton Treadmill and a Hewlett Packard 151711-A three-channel ECG recording system. Recordings were made at 3-min intervals. At 3 min of exercise 12/87 (14%) of the hypertensive subjects had a SBP of greater than or equal to 210, compared to only 1/71 (1%) of the control group (relative risk 14). At 12 min of exercise 27/51 (53%) of the hypertensives and 9/55 (16%) of the controls had similar elevations of SBP (relative risk 3.3). At 6 min of exercise 11/87 (13%) of hypertensives had SBP greater than or equal to 220, whereas none of the normal controls had SBPs elevated to that degree. We concluded that an increase in SBP to 210 mm Hg or more after 3 min or to 220 mm Hg after 6 min of exercise testing by the Bruce protocol best separates the hypertensive group from the control group. This occurs at the expense of sensitivity. Only appropriate longitudinal studies can compare the degree to which various definitions of the hypertensive response to exercise will predict future hypertension.

Adolescent↗

PubMed1989

Mitral leaflet motion: age and implications for the diagnosis of mitral valve prolapse.

The extent of posterior mitral leaflet motion (PMLM) during systole in relation to age was studied in 300 asymptomatic men aged 18-42 years. PMLM of 4 mm or more on two-dimensional directed M-mode echocardiography was found in 8% (16/200) of subjects under age 35 years, but in only 2% (2/100) of those aged 35 years or more (p less than 0.05). On two-dimensional echocardiography, 16% (31/200) of men under 35 years old had PMLM greater than or equal to 0.40 mm2 compared with 1% (1/100) of those 35 years or more (p less than 0.001). The findings were not related to differences in left ventricular cavity dimensions or in the extent of systolic ventricular contraction. Body mass index (BMI) increased with age, but there was a significant and independent negative correlation of age with PMLM after controlling for BMI. The data are compatible with the hypothesis that the aging process is associated with decreased mobility of the mitral valve or annulus with lesser degrees of backward bowing or billowing of the leaflets during systole. Age should be taken into account in determining "normal" values for mitral leaflet motion.

Adolescent↗

PubMed1989

Systolic tricuspid leaflet prolapse in asymptomatic young men.

The degree of systolic movement of the tricuspid valve (TV) leaflets was measured in 100 consecutive apparently healthy men 18-20 years old at the time of maximum posterosuperior motion toward or into the right atrium. Backward bowing of greater than 0.20 mm2 of the anterior leaflet, and greater than 0.15 mm2 of either the posterior or septal leaflets beyond the plane of the tricuspid annulus was found in 5% or less of the cohort irrespective of the echocardiographic view in which it was recorded. The upper 5% of these young men had greater than 0.80 mm2 of backward bowing when the leaflet motion was summed from all three views. The anterior leaflet demonstrated more bowing than either the septal or posterior leaflets. The systolic TV prolapse area correlated highly with the degree of mitral leaflet prolapse (r = 0.654, p less than 0.001). We conclude that there is a wide continuous spectrum of tricuspid valve leaflet prolapse area in healthy young men. This quantitative approach may help standardize the echocardiographic evaluation of tricuspid leaflet motion.

Adolescent↗

PubMed1989

Retirement of fighter pilots with incidentally detected illnesses: a decision analytic model.

Decisions regarding professional fitness after an incidental detection of a clinical disorder are often problematic. The added risk of an occupational error related to the detected disorder may be smaller than the risk of an error due to lack of experience if a veteran is replaced by a novice. In this paper, we examine the choice between grounding or granting a waiver to an experienced fighter pilot with an incidental finding of premature ventricular contractions. The decision considers the probability of sudden incapacitation during flight and of pilot error-related air accidents in novices and veterans. Although deliberately biased in favor of grounding the veteran, the analysis indicates that the risk of sudden death or incapacitation in an experienced fighter pilot with an incidentally detected illness should be increased ten-fold to 46-fold to justify his or her replacement by a novice. In the specific case considered, the analysis suggests that the risk of an air accident due to sudden death or incapacitation of a veteran with incidentally detected premature ventricular contractions is similar to the estimated added risk of an error-related air accident if she or he is grounded and replaced by a novice. When reliable data on the frequency of human error by age and experience become available, the proposed model may be applied to other situations in which trained professionals develop a potentially disabling disease.

Accidents, Aviation↗

PubMed1988

Determination of the "time of useful consciousness" (TUC) in repeated exposures to simulated altitude of 25,000 ft (7,620 m).

Time of useful consciousness (TUC) was determined in 17 subjects exposed twice to 25,000 ft (7,620 m) in an altitude chamber. The criterion for TUC determination was inability to add two-digit numbers correctly. Median values of TUC were 267.5 seconds (s) in the first exposure and 240 s in the second. The intraindividual variability between the two exposures was 40.6 s. The probability of remaining in "useful" consciousness as a function of time at 25,000 ft (7,620 m) was similar in both exposures. The need for a more scientific approach towards the determination of time of useful consciousness in simulated high altitudes is raised.

Adult↗

PubMed1988

Left anterior hemiblock in otherwise healthy pilots.

We studied 15 male pilots with left anterior hemiblock (LAH) and compared them to 15 age-matched controls. Exercise testing was normal in all 15 pilots with LAH. There was no significant difference in the measurements of cardiac geometry in the 15 pilots compared to the controls, with valve thickness, mitral valve posterior motion and septal thickness also being similar in the two groups. The pilots remained asymptomatic and on active flying duty during the mean follow-up period of 52 +/- 8 months. We conclude that LAH is a benign condition in young asymtomatic men.

Adult↗

PubMedDate not supplied

A comparison between partial and complete ligation of the inferior vena cava for the prevention of recurrent pulmonary embolism.

Interruption of the inferior vena cava is the definitive surgical measure for the control of pulmonary emboli. There is, however, some controversy as to whether the preferred treatment is complete or partial interruption. This report summarizes our experience with 49 patients who underwent partial ligation, using a technique developed in our Department, and 66 patients, who underwent complete ligation of the inferior vena cava. The incidence and severity of sequelae due to venous stasis in the legs were less in the group that underwent partial interruption.

Adult↗