Using a simplified pre-hospital 'MET' score to predict in-hospital care and outcomes.

BACKGROUND: Medical emergency team (MET) activation criteria serve as a predictor of serious adverse events on hospital wards and in the emergency department (ED). We aimed to determine whether in-hospital MET activation criteria would be useful in identifying patients at risk in pre-hospital care. METHODS: The data were collected retrospectively from 610 adult patients treated by physician-staffed helicopter emergency medical services. Pre-hospital vital signs were compared with MET activation criteria and scored accordingly to receive a simplified pre-hospital 'MET' score. The primary outcome measure was hospital mortality. The secondary outcome measures were admission to intensive care unit and the length of ED stay, intensive care unit (ICU) stay and hospital stay. The simplified pre-hospital 'MET' score was also compared with Emergency Severity Index (ESI) used as a triage tool in ED. RESULTS: Higher simplified pre-hospital 'MET' scores were associated with hospital mortality (P<0.001), the need for ICU treatment (P<0.001) and a more urgent ESI class in the ED (P<0.001). Higher simplified pre-hospital 'MET' scores were associated with shorter stay in the ED (P<0.001), longer stay in the ICU (P<0.001) and longer hospital stay (P<0.001). A simplified pre-hospital 'MET' score was an independent predictor for hospital mortality (odds ratio 2.42, confidence interval 1.84 3.18, P<0.001), regardless of age or patient's previous overall physical health classified by American Society of Anesthesiologists physical status classification system. CONCLUSION: A simplified pre-hospital 'MET' score is a predictor for patient outcome and could serve as a risk assessment tool for the health care provider on-scene.

Effects of Arctic ozone depletion and snow on UV exposure in Finland.

The increase in the UV exposure of the Finnish population associated with the combined effects of ozone depletion and snow reflection was studied with the aid of theoretical calculations based on Green's clear sky UV model. A simple formula was utilized to transform horizontal irradiances to vertical irradiances averaged over 360 degrees azimuth angle. The model was verified with spectral and broadband measurements. The difference between the theoretical and measured UV radiation falling to horizontal surfaces was in most cases less than +/- 10%, and the additional error to theoretical vertical irradiances was less than +/- 10%. The calculations show that the annual horizontal doses in Helsinki (60.2 degrees N, 25 degrees E) are about 35% higher than in Saariselkä (68.4 degrees N, 27.5 degrees E), but the difference is only 16% for vertical doses owing to the stronger contribution to vertical (facial) surfaces of the reflection of UV from snow. At Saariselkä, the maximum vertical irradiance at the end of April approaches the midsummer values. The ozone depletions up to 40% in February and March 1992 had no significant effect on the annual doses because the total ozone returned to normal before the UV increased to biologically significant levels.

Increased UV exposure in Finland in 1993.

Exceptionally low total ozone, up to 40% below the normal level, was measured over Northern Europe during winter and spring in 1992 and 1993. In 1993 the depletion persisted up to the end of May, resulting in a significant increase of biologically effective UV radiation. The increases were significantly smaller in 1992 and 1993 than in 1993. The UV exposure of the Finnish population was evaluated through measurements and theoretical calculations. The increase in measured erythemal (International Lighting Commission) UV falling onto horizontal surfaces on clear day was determined relative to model calculations for an average ozone amount. The increase was on average 10% from April to May 1993, and the maximal measured increase was 34%. Theoretical calculations for both erythemal and carcinogenic (Skin Cancer Utrecht--Philadelphia) UV indicated that in 1993 the theoretical annual increase to a vertical (cylinder) surface ranged from 8 to 13% in Finland. The reflection of UV from snow considerably increases facial UV doses in Northern Finland.

Ultraviolet erythema sensitivity in anamnestic (I-IV) and phototested (1-4) Caucasian skin phototypes: the need for a new classification system.

The anamnestic skin phototypes (ASP) I-IV of 22 Caucasian volunteers wee compared with their phototested skin phototypes (PSP) using solar simulating, broadband UV radiation. The Commission Internationale de l'Eclairage (CIE)-weighted (i.e. erythemally effective) minimal erythema doses (MED) for solar simulating radiation varied from 20 mJ/cm2 (PSP type 1) to 57 mJ/cm2 (PSP type 4). In only 11 of 21 volunteers did the ASP (I-IV) and PSP (1-4) classifications coincide, and the MED values of the volunteers within the different ASP groups (I-IV) overlapped considerably. To compare the reactivity to erythematogenic radiation of different wavelengths, narrowband monochromator irradiations were performed at 298 nm, 310 nm and 330 nm. The CIE-weighted MED values at these wavelengths (20-80 mJ/cm2) corresponded well with those obtained in the broadband testing. Our results indicate that, with classification by interrogation, Caucasian skin can reliably be classified into only two subtypes, corresponding to Fitzpatrick phototypes I-III and phototype IV, respectively. A classification into four sensitivity types can be achieved by phototesting, only. We propose that the concept of ASP should be used with caution. The concept of PSP 1-4 should be favored.

Theoretical and measured power density in front of VHF/UHF broadcasting antennas.

A simple and easy-to-use model based on more rigorous computations was formulated for the prediction of power density levels in front of dipole array-type VHF (very high frequency) and UHF (ultra high frequency) broadcasting antennas. Measurements on site verified the usefulness of the model. The distance at which the power density begins to exceed 10 W.m-2--the value established by standards as a limit--is roughly 40 m for UHF-TV antennas, 30 m for FM (frequency modulated) radio antennas and 15 m for VHF-TV antennas. Typical average input powers of antennas are 20 kW, 4 kW and 10 kW for FM radio, VHF-TV and UHF transmissions, respectively.

Electrophysiological considerations relevant to the limiting of pulsed electric and magnetic fields.

The objective of the study was to theoretically examine the stimulation threshold of large myelinated axons and to use the results to formulate criteria for exposure limits of pulsed magnetic fields. The induced electric fields were calculated with a homogeneous tissue equivalent prolate spheroid. The stimulation level of the field was computed with the SENN model by using a folded axon with 2 mm separation for the Ranvier nodes. In the case of rectangular induced electric field pulses, the asymptotic stimulation level for electric field strength was 10 Vm(-1) with pulse durations greater than 100 micro(s) and for integrated electric field strength 1 x 10(-3) V m(-1)s with pulse durations less than 100 micro(s). The latter threshold level was exceeded in the surface of the prolate spheroid when the magnetic flux density changed by more than 7.4 mT within 100 micro(s). For sinusoidal bursts, the threshold amplitude of the magnetic field decreased asymptotically to a minimum value 2.5 mT when the carrier frequency and burst duration exceeded 5 kHz and 100 micro(s), respectively. If the same safety criteria are applied for pulsed and continuous exposure, the peak limits for induced current densities and magnetic field can exceed the amplitude values of the limits for continuous exposure only by a factor varying from 3 to 10.

Restricting exposure to pulsed and broadband magnetic fields.

A general procedure is described for application of the new ICNIRP exposure guidelines to pulsed and broadband magnetic fields below 100 kHz. The procedure involves weighting of the spectral components with a function that takes into account the basic restrictions and reference levels. A simple first-order RC response or its piecewise linear equivalent is proposed for the weighting function. The weighting can be performed either on the Fourier transformed sample of the measured signal or in real time by processing the signal with an analog or digital filter circuit. The cut-off frequency of the filter is 820 Hz. The occupational exposure criteria are exceeded when the weighted peak magnetic flux density exceeds 43 microT or equivalently the weighted peak dB/dt exceeds 0.22 T s(-1). The maximal peak exposures allowed by the proposed approach are compared with the stimulation thresholds computed with a stimulation model. The results strongly suggest that the safety margin to the stimulation is greater for non-sinusoidal than for sinusoidal waveforms, and at low frequencies it is higher than at high frequencies. The increase of the low-frequency safety margin is desirable to avoid magnetophosphenes and possible CNS effects that may occur below the level predicted by the classical nerve models. Measurement techniques and examples of measured magnetic fields are presented. Particularly high exposures were measured inside MRI equipment and anti-theft gates.

Measurements of electromagnetic emissions from video display terminals at the frequency range from 30 Hz to 1 MHz.

Electric (E) and magnetic field (B) strengths or flux densities were measured at distances of 30 and 50 cm from the screen of video displays at a frequency range from 30 Hz to 1 MHz. The measurement system consisted of an optically coupled active dipole for E-fields, a magnetic field meter, a digital oscilloscope, a portable computer for data storage and a laboratory computer for Fourier analysis of the recorded signals. Comparison of measurement results with available broadband exposure standards or proposed standards indicated that magnetic flux density should be measured at both the (ELF) frequency range from 30 Hz to 300 Hz and at the (RF) frequency range from 10 kHz to 500 kHz. Alternatively, time derivative of magnetic flux density may be measured. Nor should the measurement of the electric field strength at the RF range be neglected. These conclusions, however, are valid only in relative terms. In all cases the exposure is at least one decade below the most stringent exposure limit. The maximum relative exposure 0.077 was obtained by applying the ACGIH standard for magnetic fields at a distance of 30 cm from the screen. The field strengths decrease by a factor varying from 2.5 to 3.5 at a distance of 50 cm, which is a more realistic distance when considering actual working conditions.

Radio frequency currents induced in the human body for medium-frequency/high-frequency broadcast antennas.

Radio frequency currents in the human body, induced by high-frequency and medium-frequency high-power broadcast antennas, were studied theoretically and experimentally. An analytical formula was derived to calculate the foot currents in a grounded semispheroidal model of the human body. The model agrees within 30% with the results given by the standard formula presented by Gandhi on the basis of measurements with humans. Near 100 kHz, the model predicts a decrease of 14% of the current dissipated in the human body, which is due to the beta relaxation of the cells. The effect of the body and foot-contact impedances were studied with the aid of a simplified equivalent circuit which showed that the body impedance does not considerably affect the foot current below 10 MHz. The normalized foot currents measured in front of the broadcast antennas were within 30% agreement of the currents calculated with the Gandhi formula from the electric fields measured at a height of 1 m. The foot currents are induced by vertical electric fields for both medium-frequency and high-frequency antennas in spite of a strong horizontal component in the latter case. The distance at which the occupational exposure limit of 200 mA was exceeded in the worst (maximum coupling) case was 50 m for the high-frequency antenna and < 14 m for the medium-frequency antenna. In the latter case, the radio frequency shocks resulting from touching ungrounded metallic bodies impose a practical limit to about 40 m.

Radiation hazard assessment of pulsed microwave radars.

Observed biological effects of pulsed microwave radiation are reviewed and the exposure standards for microwave radiation are summarized. The review indicates that the microwave auditory effect is the only well-established specific effect in realistic exposure situations. The threshold for the effect depends on the energy density per pulse and may be as low as 20 mJ/m2 for people with low hearing threshold. Energy density limits have been included in the most recent exposure standards. A new battery-operated, hand-held meter developed for measurements of pulse power densities around scanning radar antennas is described, and a simple new model for the calculation of power density in the main beam of radar antennas is presented. In the near field measured values differed from the calculated values by 2-3 dB.

Continuous recording instrument for RF-exposure measurements in FM/TV broadcasting towers.

A continuously recording exposure meter has been developed for radio-frequency (RF) hazard measurements in FM/TV broadcasting towers for the frequency range 47-790 MHz. The instrument consists of an electrically-small dipole, loop probes and recording electronics. The dipole and loop are attached to the safety helmet; their distance from the head is approximately 7 cm. The dipole and loop respond to the tangential E field and radial H field, respectively. The error due to body proximity and one-dimensionality is 1 to 2 dB at 100 MHz and 2 to 3 dB at 200 MHz (for average power density measurements) if the probes move continuously and the measurement period is sufficiently long. Measurements in Finnish FM/TV towers showed that the average power density inside the tower increases with increasing power and decreasing antenna surface area. The highest levels have been found near UHF and FM antennas. For the FM band (100 MHz) the average H field exposures exceed the new ANSI standard value 10 W/m2, but remain in most cases below 100 W/m2. Local maxima may exceed 300 W/m2.