Measurements of electromagnetic fields radiated from communication equipment and of environmental electromagnetic noise: impact on the use of communication equipment within the hospital.

The increasing use of all types of cellular telephones requires the formulation of new standards to ensure the immunity of electronic medical equipment to electromagnetic radiation. It will be many years before all hospital medical equipment conforms to new and higher standards. Until that time, the medical, security, maintenance, and other staff will need to be ever vigilant regarding restrictions on the use of wireless equipment within the hospital, to prevent potential danger to the lives of the patients. A comprehensive hospital policy must be formulated to reduce risks to patients from equipment susceptible to electromagnetic interference (EMI). Such an aim should address the following needs: To devise a uniform policy for the instruction of hospital staff, visitors, and patients, thereby reducing confusion regarding the use of cellular telephones, beepers, and portable transceivers. To implement a policy that avoids unwarranted restrictions but does not ignore statistical evidence regarding potential EMI problems. To allow comparison, with other clinical facilities, of the benefits derived from such a policy.

[Cellular phone interference with medical instruments].

Cellular telephones and other telecommunication equipment occasionally cause malfunctioning of medical equipment, including life-support equipment. We review such malfunctioning and relate it to Israeli and Worldwide standards, analyzing the characteristics of the interference in terms of amplitude and frequency. The results of a controlled study of interference by cellular telephones and portable 2-way radios with medical devices in our clinical departments are also presented. The levels of background environmental electromagnetic noise at several sites in both Hadassah hospitals (Ein Karem and Mount Scopus) were measured, as well as signal levels of cellular telephones and other communication equipment at various distances and in various areas. We recommend 2 different levels of restrictions on the use of this equipment within the hospital. These include prohibition of the use of wireless telecommunication equipment in intensive care areas and operating theaters. In all other areas it is recommended to turn off the cellular telephone within 1 meter of medical devices and not to transmit (but only to receive) calls with a portable 2-way radio within a 5 meter distance of medical devices.

Irradiation induced blood flow changes in the breast during radiotherapy--a pilot study.

Skin blood flow and underskin temperature were measured in breasts during the complementary radiotherapy following lumpectomy, using the noninvasive transient thermal clearance method. On average, blood flow and tissue temperature increased at the start of the irradiation then slightly decreased. The response varied significantly among the patients. The increase in blood flow is associated with the vasodilatation which accompanies irradiation-induced inflammation and the method enables the assessment of this vasodilatation during the irradiation treatment. The decrease of blood flow after the initial increase is attributed to vascular damage. The method provides a noninvasive means for the evaluation of radiation effects on individual patients during radiotherapy.

Monitoring of erythrocyte aggregate morphology under flow by computerized image analysis.

The morphology of red blood cell (RBC) aggregates was studied by direct visualization of RBC aggregation at different flow conditions in a computerized image analyzer. The aggregate morphology is expressed by an Aggregate Shape Parameter (ASP), defined as the ratio of the aggregate projected area to its square perimeter. Aggregation was induced by either dextran-70 (m.w. 70,000) or dextran-500 (m.w. 500,000), and compared to that in plasma. It was found that the aggregate morphology is a characteristic of the aggregating agent--in dextran-500, the RBC form rouleau aggregates as in plasma, while in dextran-70, they form clusters. In each system, while maintaining the overall typical morphology, the ASP decreases (i.e., the aggregate becomes longer) as the aggregate size is increased. The distribution of the ASP as a function of the aggregate size remains unchanged when the aggregate size is changed by modulation of the dextran concentration or the shear stress. Stretching of a rouleau aggregate by application of shear stress is reflected by a corresponding change in the ASP. It is suggested that the ASP is a characteristic of intercellular interactions. A theoretical model is proposed for evaluation of the deviation of aggregate shape from that of rouleau structure.

Skin blood flow measurements on the breast areola.

Blood flow and thermally insulated skin temperature were measured in the aerolae of normal breasts by means of the non-invasive transient thermal clearance method. Both parameters showed high variability among different women, but also showed typical dependence on the subject's age: the two parameters were constant up to age 50, and then showed a decrease at higher ages. The decrease can be attributed to the normal decrease of tissue blood flow at higher age and to atrophy of the breast glandular tissue after menopause. Statistically significant higher values of blood flow and insulated skin temperature were found for the left breast relative to the right breast.

A measurement of pulmonary blood volume increase during systole in humans.

Pulmonary blood volume increase during systole was measured in patients by analysing chest images obtained during ECG gated radionuclide angiography examination. The difference in the total radiation counts between systole and diastole in regions of interest, which included the lungs and the left ventricle, was measured and the relative pulmonary systolic blood volume increase (SBVI)-the ratio between the pulmonary SBVI and the cardiac stroke volume-was calculated. The relative pulmonary SBVI, which is a measure for the compliance of the pulmonary blood vessels, was found to be 0.26-0.85, and the average value was 0.57 +/- 0.15. The relative pulmonary SBVI was inversely correlated with the patient age (r = 0.27, p < 0.05) and with the left ventricular ejection fraction and stroke volume (r = 0.36, p < 0.01) due to decreased arterial compliance for older patients and for increased pulmonary blood volume respectively. The correlation coefficients were not high, indicating that the compliance of the patients is determined mainly by other individual factors. Radionuclide plethysmography enables qualitative assessment of pulmonary arterial compliance.

Red blood cell aggregability is enhanced by physiological levels of hydrostatic pressure.

The effect of hydrostatic pressure of up to 15 bars on the aggregability of rat and human red blood cells (RBC), i.e., their capability to form aggregates, was studied using computerized image analysis. The aggregate size distribution was determined under ambient pressure, following application of hydrostatic pressure for various durations up to 2 h. It was found that RBC aggregability markedly increases, up to three-fold, as the pressure which had been applied was increased. Accordingly, higher shear stress is required for dispersing the aggregates of pressure-treated RBC than those of untreated cells. The median size of human RBC aggregates was about three times higher than that of rat RBC, and this ratio was maintained following pressure treatment. RBC aggregability is a major determinant in blood flow, especially in the microcirculation. Pressure at the levels used in this study occurs in physiological states such as hyperbaric treatment or diving. The enhanced aggregability induced by application of such pressure implies that blood flow in microvessels might be altered under conditions associated with elevated hydrostatic pressure.

Faster procedure for deriving regional blood flow by the noninvasive transient thermal clearance method.

The noninvasive transient clearance method provides absolute quantitative measurement of skin blood flow. It is based on thermally insulating the skin under investigation and measuring the time constant of the resultant exponential skin temperature increase. Conventional assessment of the time constant, by measuring the temperature increase until final equilibrium skin temperature is achieved, has the disadvantage of long time of measurement. A procedure shortening the measurement time is presented. The time constant of the exponential temperature increase is calculated without obtaining the final equilibrium temperature. The method can be used for calculating the time constant of an exponential change of any variable, even though the asymptotic value of that variable is not known.

Intra-articular pressure measurements in patients with suddenly developing, severely limited mouth opening.

A condition of sudden, severe, and persistent limited mouth opening, which readily responds to arthrocentesis, is postulated to be the effect of a vacuum between disc and fossa in the upper compartment of the temporomandibular joint. In 16 patients with this condition, the negative intra-articular pressure was found to be significantly lower (mean, -82.6 +/- 25.4 mm Hg) than in the control group (mean, -7.7 +/- 2.5 mm Hg) (P less than .0001). It is suggested that the process underlying the vacuum effect starts with persistent pressure (eg, clenching) resulting in the viscoelastic disc being pressed flat against the fossa. Immediately on cessation of the pressure, the disc resumes its natural biconcave shape, but its rims remain fastened to the fossa. The consequent increased negative pressure in the closed space created firmly anchors the disc to the fossa and any attempt to elicit condyle and disc sliding will only stretch the joint capsule and cause pain. This, in turn, will reflexly prevent the pterygoid muscle from exerting sufficient force to pull the disc and thus release the vacuum. This chain of events may account for the severe and persistent limitation in jaw movement and for the easy reversal of the condition by simple nonsurgical treatment.

Computer processing of artifact and arrhythmias in heart rate variability analysis.

Analysis of heart rate variability (HRV) with Holter monitoring is often difficult due to excessive artifacts and arrhythmias. While short sudden surges are treated successfully by most methods, slow heart rate (HR) variations, nocturnal trapezoidally-shaped HR increases and special types of arrhythmias which are similar to normal HRV fluctuations may distort further time domain and spectral analysis. This paper examines the advantages and disadvantages of different methods for preprocessing of HR data. We have developed the following approach to the analysis of HRV. (1) A combination method based on the absolute difference between HR values and both the last normal HR value and an updated mean is used for removal of artifacts and arrhythmias. This method can detect both sudden surges in HR values as well as longer periods of noise combined with slow normal variations. An additional stage of wild point removal is then optionally applied. (2) Certain special problems such as large T-waves, bigeminal rhythm, slow HR variations and nocturnal trapezoidally-shaped HR increases are also identified. Although none of the algorithms can be applied successfully to all cases, the final computer analysis for preprocessing described in the present study has proved to be superior to the simplified methods which are usually used and provides more suitable data for HRV analysis.

Day vs night ECG and heart rate variability patterns in patients without obvious heart disease.

The day vs night values of variables that may be related to the autonomic nervous system were compared in 50 individuals without obvious heart disease. Using ambulatory electrocardiographic monitoring and heart rate variability analysis, it was found that in contrast to daytime, nocturnal heart rate and total heart rate variability were reduced and low (0-0.05 Hz) and high (0.2-0.35 Hz) frequency power of nocturnal heart rate variability were increased, whereas mid-frequency (0.05-0.2 Hz) power was reduced. In addition, nocturnal episodes of trapezoidal-shaped waveforms of heart rate increase were present primarily at night and ST was elevated to a greater extent at night. Many of these factors were related to age and tentatively, despite the small sample size, reflect an age-related diminished autonomic nervous system response. These results serve to establish a circadian basis for comparison when evaluating disease states such as ischemic heart disease and its prognosis.

The relationship between systolic blood pressure and microvascular resistance in non-diabetic and diabetic subjects.

Skin blood flow and microvascular resistance were measured in the feet of hypertensive and normotensive subjects by the non-invasive transient thermal clearance method. Skin blood flow decreased and microvascular resistance increased as a function of systolic brachial blood pressure for the non-diabetic subjects who were not treated by vasoactive medication. The relationship between blood flow and systolic blood pressure for diabetic patients and for patients who were treated by enalapril was poor. The average resistance for non-diabetic patients treated by enalapril was lower than that of untreated non-diabetic subjects. For diabetic patients no significant difference in resistance between enalapril treated and untreated patients was found. The results demonstrate that for non-diabetic patients the role of microvascular resistance in hypertension is significant while it is less important in diabetic patients.

Diagnostic value of computer analysis of multipeaked EMG spikes.

Computer analysis of absolute number of peaks per second and the number of peaks in the multipeaked spikes/sec was carried out in the EMG interference recordings of 5 healthy, 6 myopathic and 8 neuropathic subjects. The purpose of the study was to detect diagnostically different patterns. A spike was considered multipeaked if it had 6 or more peaks. The amplitude of elimination (baseline) was examined at 1: 5, 1: 10 and 1: 15 of the average amplitude per second. Both the number of peaks and the number of peaks in multipeaked spikes in the neuropathic and myopathic muscles showed statistically significant differences when compared to healthy muscles. This technique could give an indication for the differential diagnosis of myopathic, neuropathic or healthy state of the muscle.

ECG gated radionuclide plethysmography--a method for the assessment of pulmonary systolic blood volume increase.

During cardiac systole the stroke volume of blood which is ejected from the right ventricle increases the pulmonary blood volume. This systolic pulmonary blood volume increase is measured by using ECG gated chest scintigrams obtained with 99Tcm-labelled red blood cells. The total radiation counts in a region of interest that includes either the right or the left lung increases during systole. On the average, the increase of the total pulmonary systolic radiation was found to be 62% of the systolic radiation decrease in the left ventricle region of interest. The discrepancy between the value of the systolic pulmonary blood volume increase and that of stroke volume is attributed to blood flow from the lungs into the left atrium during the cardiac systole period.

Fourier series analysis of the electrophysiological pattern of fatigue in healthy human beings, after curare administration.

Real time computer analysis of the electrophysiological development of muscular fatigue after small doses of d-tubocurarine (TC), has been examined in anesthetized human beings. As compared to a decrease of frequency in the control measurements, previous studies have shown an increase of the frequency of spikes after TC administration. The present experiments were carried out on the biceps brachii of 8 healthy human volunteers maintained in isometric contraction against a constant counter load until complete fatigue occurred. The Fourier spectrum analysis showed a statistically significant shift to lower frequencies before, and a milder statistically non significant shift after TC. These results may indicate that under mild curarization the early phase of muscular contraction requires a higher number of large motor units and thus, at a later stage of the contraction the pool of available large motor units becomes smaller. This conclusion supports the hypothesis that mild curarization causes a state of initial muscular fatigue.

The effect of swimming exercise on spontaneous ventricular defibrillation and ventricular fibrillation threshold in the isolated perfused rat heart.

Effects of swimming exercise training on left ventricular contraction and relaxation, the incidence of spontaneous defibrillation and the ventricular fibrillation threshold were studied in the isolated, perfused rat heart. The heart/body weight ratio was 4.8 +/- 0.4 x 10(-3) in swimmers compared with 3.9 +/- 0.6 x 10(-3) in sedentary controls (p less than 0.0005). The spontaneous heart rate was lower in isolated hearts of trained animals (222 +/- 18 bpm compared with 244 +/- 28, p less than 0.05). Left ventricular systolic pressure was higher in trained hearts and the rate of ventricular relaxation enhanced (p less than 0.05). The ventricular fibrillation threshold was 7.2 +/- 5.2 and 10.8 +/- 6.1 mamp in hearts of swimmers and controls, respectively, the difference not being significant. The incidence of spontaneous defibrillation was not significantly different between the two groups. It is concluded that, while swimming induces cardiac hypertrophy and hemodynamic changes, it neither protects against the induction of ventricular fibrillation nor facilitates spontaneous defibrillation in the isolated, non-ischemic rat heart.

Comparison of the electrophysiological pattern of fatigue between athletes required to perform explosive and endurance sports.

The electrophysiological behavior of an isometric contraction sustained to fatigue, was examined in 6 long distance runners and 9 athletes involved in explosive (burst) sports, by on line computer analysis of the electrical activity of vastus medialis, rectus femoris and vastus lateralis. The experiments were carried out with a counterload of 50% of the maximal strength of the muscle. The duration of spike increased and the frequency decreased in the 3 examined muscles, in both types of sport. In the burst sports the changes of value of both parameters were statistically significant in the 3 muscles. In endurance sports the variations of duration were not significant and the changes of frequency were statistically significant only in the vastus lateralis. These results could be explained by the gradual activation of motor units of more strikingly different sizes in burst sports. Thus it may be speculated that prolonged training in burst sports may result in the automatic mobilization of higher number of small motor units, for the initiation of contraction while in endurance sports the onset of contraction is more gradual and carried out by large motor units.

Detection of breast cancer by measuring areolar blood flow--a pilot study.

Regional blood flow in the areola was measured by using the non-invasive transient thermal clearance method in normal breasts and in breasts involved with cancer. Areolar blood flow (ABF) in normal breasts was almost constant for women in the age range 20-60y, but decreased at higher ages. ABF in breasts involved with cancer was higher than that in the contralateral breast, and higher than the average normal ABF in the corresponding age group. The effect was more prominent in the left breast. The transient thermal clearance method provides a potential non-invasive means for detection of breast cancer.