Walkie talkies cause more electromagnetic interference to medical equipment than mobile phones.

It is generally realised that mobile phones can interfere with medical electrical equipment and many hospitals have policies which aim to minimise the risk to their patients from this cause. Walkie talkies are also used in hospitals, but very little information is available concerning their ability to interfere with hospital equipment. Two walkie talkies and three mobile phones have been used to study and compare interference in 29 items of patient-connected equipment in a large hospital. Test results show that with some equipment there will be signal distortion and/or false alarms, and a Power off/on Reset may be necessary. In rare cases, when equipment is subjected to extreme signal strengths, it is possible to observe equipment failure requiring the replacement of failed components. For these tests the walkie talkies were set at 4W of output power and they caused significantly more interference than the mobile phones. The observed effects have been classified according to the maximum distance at which they were observed and according to the criticality of the possible outcome for the patient. It is concluded that, except for emergency services, the use of walkie talkies should be restricted in hospital buildings.

Body composition changes following laparoscopic gastric banding for morbid obesity.

Most reports of outcome following obesity surgery report weight and co-morbidity changes only. We studied body composition changes in 17 adult patients (15 F, 2 M, age 43+/-2 years, range 28-58 years), with morbid obesity (initial BMI 40.4+/-4.9 kg/m(2), range 34.7-48.8) who were managed surgically by laparoscopically inserting an adjustable gastric band. Body composition was studied before and after surgery (mean interval of 909+/-51 days, range 441-1155 days) using anthropometry (abdominal circumference, AC, sum of four skinfold thicknesses, SFSUM), whole-body potassium counting (TBK), in vivo neutron activation analysis total body nitrogen (TBProtein) and whole-body dual-energy ray absorptiometry (total body percent fat TBF%, and total body bone mineral density TBBMD). Weight loss over the study period was 23.4+/-2.5 kg. ( p<0.0003) with an AC reduction of 20.0+/-4.5 cm ( p<0.008). Both SFSUM and TBF% were significantly reduced ( p<0.02 and p<0.0005 respectively). Both TBK and TBProtein after normalization for sex and height, were significantly ( p<0.0054 and p<0.001 respectively) reduced, but the ratio of loss of fat mass to fat-free mass, at 4.4:1 was usual for weight loss, and there was no significant changes in the ratio of potassium to protein. TBBMD, after normalization relative to a young same sex adult, was not significantly changed. In this group of patients, most of the substantial weight loss over a 2- to 3-year period was due to loss of fat mass, with relatively less reduction in the components of fat-free mass. Adjustable laparoscopic gastric banding induces fat loss without significant other deleterious effects on body composition.

Correlates of prepubertal bone mineral density in cystic fibrosis.

AIM: To examine early factors in bone mineral accretion in cystic fibrosis (CF). METHODS: In 22 prepubertal children with CF and mild lung disease, the relation between total body bone mineral density (BMD) and measures of body composition, biochemistry, lung function, and physical activity was studied. RESULTS: There was a non-significant mild reduction in mean total body BMD. No relation was found between BMD and anthropometric indices, fat free soft tissue, degree of lung disease, degree of fat malabsorption, dietary energy intake, or level of physical activity. Significant impairments in physical growth were apparent in this population and were found to correlate with degree of lung disease. CONCLUSION: A CF specific factor appears unlikely to be associated with the osteopenia commonly found in CF. Careful attention to general aspects of lifestyle and nutrition is recommended to maximise bone mineral accretion in this population.

Total body dual X-ray absorptiometry is a good measure of both fat mass and fat-free mass in liver cirrhosis compared to "gold-standard" techniques. Melbourne Liver Group.

Liver cirrhosis is a condition in which overnutrition, edema, and undernutrition can coexist simultaneously, or successively, over a period of time, giving rise to alterations in body composition, as well as systemic and multiorgan manifestations. We undertook a cross-sectional study of body composition in 198 adult patients with liver cirrhosis (140 males, mean age 53.6, range 31-85 years; and 58 females, mean age 58.4, range 36-79 years). The patients had cirrhosis of differing etiology and different stages of severity. They were gathered from seven different hospital clinics in the city of Melbourne, Australia, but all the body composition measurements were performed in one body composition laboratory. A variety of body composition techniques were used to identify which commonly available ones could best assess both fat-free mass and fat mass relative to a criterion "gold-standard" method available in a specialist laboratory. A gold-standard fat-free mass (FFMGS) was defined as the sum of total body protein, measured by in vivo neutron activation analysis (IVNA), plus total body water, measured by D2O dilution, plus bone mineral content, measured by dual X-ray absorptiometry (DXA). A gold-standard fat mass (FATGS) was defined as the difference between body weight and FFMGS. "Usual" fat mass and fat-free mass were defined by different techniques including DXA, anthropometry (ANT), single-frequency bioelectrical impedance (SFBIA), multiple-frequency bioelectrical impedance spectroscopy (MFBIA), and whole body gamma counting (TBK). The FFMGS was overhydrated in both sexes, relative to the usual value of 0.73, but women were significantly overhydrated compared to men. Relative to the gold-standard deuterium oxide dilution method for measuring total body water, SFBIA slightly overestimated TBW, whereas MFBIA slightly underestimated TBW, with both methods having wide limits of agreement for any single estimate. In comparing FFM to FFMGS, only DXA showed a small negative bias, in both males and females, with modest limits of agreement for any single estimate. All other methods showed a large negative bias (ANT, SFBIA, and MFBIA) or a large positive bias (TBK) relative to FFMGS, with wide limits of agreement. In comparing FAT with the FATGS, only DXA showed a small positive bias, in both males and females, with modest limits of agreement for any single estimate. All other methods showed a large positive bias (ANT, SFBIA, and MFBIA) or a large negative bias (TBK) relative to FATGS, with wide limits of agreement. In cirrhosis, DXA is a good and widely available method to assess both fat mass and fat-free mass. However, it cannot give information about the quality of the FFM, particularly its water content. The bedside methods of anthropometry and bioelectrical impedance, both SFBIA and MFBIA, are poor methods of measuring body composition in patients with liver cirrhosis, whereas whole body gamma counting, although not widely available, also significantly differs from the gold-standard method of assessment of fat-free mass and fat mass in liver cirrhosis.

Comparison of total body chlorine, potassium, and water measurements in children with cystic fibrosis.

BACKGROUND: Symptoms of cystic fibrosis (CF) may limit the utility of total body chlorine (TBCl) and total body potassium (TBK) measurements for assessing body fluid compartments of children. OBJECTIVE: This study assessed relations among independent measurements of TBCl, TBK, and total body water (TBW) in children with CF. DESIGN: We compared cross-sectional measurements of TBCl by in vivo neutron activation analysis, TBK by whole-body counting of (40)K, TBW by D(2)O dilution [TBW(D(2)O)], and TBW from TBCl and TBK [TBW(Cl + K)] in 19 prepubertal children (13 boys) aged 7.6-12.5 y who had mild symptoms of CF. Body-composition measurements were compared with data from previous studies of healthy children. RESULTS: Subjects with CF had deficits in TBCl, TBK, TBW, and body weight compared with control reference data (P < 0.05). The ratios (TBCl + TBK)/TBW and TBCl/TBK were not significantly different from control reference values, and plasma chlorine and potassium concentrations were within control reference ranges. The sum of TBCl and TBK correlated with TBW(D(2)O) (r(2) = 0.79, P < 0.001), and TBW(Cl + K) correlated with TBW(D(2)O) (r(2) = 0.78, P < 0.001). TBW(Cl + K) was similar to TBW(D(2)O) (mean +/- SEM: 19.0 +/- 0.5 compared with 19.4 +/- 0.5 L; NS). CONCLUSIONS: Prepubertal children with mild symptoms of CF can develop deficits in TBCl, TBK, and TBW that reflect chronic energy malnutrition. Mild symptoms of CF do not appear to affect normal relations among TBCl, TBK, and TBW. Measurements of TBCl and TBK may be used to assess body fluid compartments in these patients.

Agreement of skinfold measurement and bioelectrical impedance analysis (BIA) methods with dual energy X-ray absorptiometry (DEXA) in estimating total body fat in Anglo-Celtic Australians.

OBJECTIVE: To compare percentage total body fat (%BF) estimated by the four skinfold thickness measurement (SKF) and single-frequency bioelectrical impedance analysis (BIA) methods using three different sets of equations, to that assessed by the dual energy X-ray absorptiometric (DEXA) method using a Lunar DPX densitometer. DESIGN: Cross-sectional study. SUBJECTS: An Anglo-Celtic Australian population of 66 males and 130 females (age: 26-86 y). MEASUREMENTS: %BF by anthropometry, BIA using three different sets of equations and DEXA. RESULTS: Mean %BF assessed by DEXA (%BF(DEXA)) was similar to that estimated by SKF (%BF(SKF)) in males, while %BF(DEXA) was slightly higher in females. %BF estimated by BIA (%BF(BIA)) was significantly lower than %BF(DEXA) in females, regardless of equations used for calculation, while the level of agreement between BIA and DEXA in estimating %BF in males was dependent on prediction equations used for calculation of %BF(BIA). A better agreement was obtained from the use on the prediction equations of Segal et al (1988), compared to other two sets of equations. The agreement between SKF or BIA and DEXA declined with increasing %BF. CONCLUSIONS: There was a good agreement between DEXA and SKF, and slightly less so between DEXA and BIA, in estimating %BF in an Anglo-Celtic adult population. The agreement in most cases, however, was dependent on the degree of body fatness. In comparison to DEXA, both SKF and BIA, with the use of the equations of Segal et al (1988), are applicable to estimate %BF in an Anglo-Celtic Australian population.

A neutron activation analysis facility for in vivo measurement of nitrogen and chlorine in children.

The construction, calibration and evaluation of a prompt- gamma in vivo neutron activation analysis (IVNAA) facility for the simultaneous measurement of total body nitrogen (TBN) and chlorine (TBCl) in children is described. Subjects are irradiated unilaterally by a 0.2 GBq 252Cf neutron source from shoulder to mid thigh in both supine and prone positions. Prompt gamma-ray spectra are measured with two pairs of NaI(TI) crystals (each crystal: 10 cm x 10 cm x 15 cm) positioned on both sides of the subject. TBN and TBCl are estimated from the ratios of nitrogen-to-hydrogen (Nc/Hc) and chlorine-to-hydrogen (Clc/Hc) counts as determined from the measurement of 10.83 MeV, 8.57 MeV and 2.22 MeV prompt gamma-rays from the respective reactions 14N(n, gamma)15N, 36Cl(n, gamma)35Cl, and 1H(n, gamma)D. Nc/Hc and Clc/Hc are corrected for the effect of body width and thickness on background and gamma-ray attenuation. Total body hydrogen (TBH) is used as an internal standard which is independently determined using a four compartment model of body weight defined as the sum of total body water (TBW) measured by the D2O dilution technique, total body protein (TBPr) (i.e. 6.25 x TBN) measured by IVNAA, total body bone mineral (TBBM) measured by dual energy x-ray absorptiometry and total body fat (TBF) estimated as body weight less the sum of TBW, TBPr and TBBM. The effective dose equivalent to a small child is 0.25 mSv (Q = 20) per measurement scan. Repeated measurements of a child-size bottle phantom containing tissue-equivalent concentrations of nitrogen and chlorine yield respective intra- and inter-assay precision values of 2.8% (CV) and 2.3% for TBN measurements, and 7.9% and 10.0% for TBCl measurements. Similarly, intra- and inter-assay accuracy is determined to be respectively +0.1% +/- 1.0% (mean, 95% confidence interval) and +1.4% +/- 1.4% for TBN measurements, and +2.3% +/- 4.3% and +3.9% +/- 6.0% for TBCl measurements.

Total body protein status assessed by different estimates of fat-free mass in adult peritoneal dialysis patients.

OBJECTIVE: To assess the usefulness of fat-free mass (FFM) as an index of total body protein (TBPr) status in continuous ambulatory peritoneal dialysis (CAPD) patients. DESIGN: TBPr was measured by in vivo neutron activation analysis (IVNAA) and expressed as a standardised protein index (PI). FFM was estimated by dual energy X-ray absorptiometry (DXA), whole body counting of total body potassium (TBK), and creatinine kinetics (CK), and expressed as a standardised FFM index (FFMI). FFM was also determined by a criterion method based on four compartment model (4CM) which is defined as the sum of total body water determined by D2O dilution, TBPr determined by IVNAA, bone mineral determined by DXA, and glycogen estimated to be 4.4% of TBPr. Each patient was measured within a four hour period by all methods. SETTING: Body Composition Laboratory, Monash Medical Centre. SUBJECTS: Six male and twelve female CAPD patients (33-77 years). RESULTS: FFMI assessed by DXA and by TBK agreed with measurements of PI on identifying the mean TBPr status of the CAPD group as significantly below a comparable normal reference population (mean Z score: PI = -1.01 (P < 0.05); FFMI by DXA = -0.50 (P < 0.05); FFMI by TBK = -1.24 (P < 0.05)). In contrast, FFMI assessed by CK did not reveal a significantly reduced TBPr status (mean Z score: -0.70 (NS)). Furthermore, significant linear correlations were noted between PI and FFMI estimated by DXA and by TBK (r = 0.57 (P < 0.05) vs r = 0.69 (P < 0.05)) however no significant correlation was observed between PI and FFMI estimated by CK (r = 0.36 (NS)). Moderate variation in FFM hydration did not compromise the ability of DXA, TBK or CK to differentiate between protein deleted, normal and enriched patients. Comparison of FFM estimates between the criterion method and either DXA, TBK or CK revealed no significant bias (+ 1.8 kg vs -2.0 kg vs +0.8 kg) and respective SEE values of 3.8 kg (8.3%), 5.9 kg (14.3%) and 9.6 kg (21.7%). CONCLUSION: The findings of this study indicate that FFM estimated by either DXA or the whole body counting of TBK is a useful index of TBPr status in CAPD patients. However, FFM assessed by CK does not appear to be an appropriate index of TBPr status in CAPD patients.

The use of Cole-Cole plots to compare two multifrequency bioimpedance instruments.

Two commercially available multifrequency bioimpedance spectrometers (Xitron 4000B and SEAC SFB3) were compared by performing measurements on a set of electronic circuits and by studying 14 healthy volunteers. Output data were plotted as reactance versus resistance and fitted with a semi-circle using a least squares fitting program. In tests with six electronic circuits both instruments produced impedance loci that were well described by semicircular Cole-Cole plots, though there were some minor discrepancies using the Xitron instrument at frequencies above 150 kHz. When tested on the volunteers the SEAC instrument gave very good fits (RMSE = 1.5 Omega) to a semi-circle from 5-600 kHz on all volunteers. The Xitron instrument gave excellent fits to the semi-circle between 5 and 55 kHz (RMSE = 0.7 Omega) but above 55 kHz the phase measurements stayed constant or even increased, confirming the anomalous behaviour reported by other authors. The conclusions to be drawn are that the semicircular plots predicted by the Cole-Cole theory give a very good description of multifrequency impedance data recorded by the SEAC SFB3 instrument, on human subjects, for frequencies between 5 and 600 kHz. The Xitron 4000B is not able to reproduce the theoretically expected results in humans above 55 kHz.

Kt/V in CAPD by different estimations of V.

This study compared the measurements of total body water (TBW) by 58% body weight (TBW58%), the Watson equation (TBWWV) and bioelectric impedance (TBWBIA) with the gold standard, Deuterium oxide (TBWD2O) dilution method in twenty continuous ambulatory peritoneal dialysis (CAPD) patients. TBW volumes were highest when calculated as TBW58% (42.6 +/- 9.4 liter) and lowest when calculated from TBWWV (34.6 +/- 6.8 liter). TBWBIA underestimated TBW when compared to TBWD2O, although the difference was not statistically significant (37.1 +/- 9.8 liter and 38.8 +/- 9.3 liter, respectively). In fact, TBWBIA correlated strongly with TBWD2O (r = 0.8, P < 0.0001). These discrepancies resulted in significant differences when Kt/V week-1 derived from the four methods were compared. To determine the effect of percent fat mass on the estimation of TBW by each method, we compared TBW and Kt/V week-1 derived from the four methods in nine CAPD patients who had normal percent fat mass (Non-Obese) and 11 CAPD patients who had greater than normal % fat mass (Obese). In the Non-Obese group, there was close correlation of TBWBIA, TBWWV and TBW58% when compared with TBWD2O (r = 0.93, P < 0.001, r = 0.89, P < 0.01 and R = 0.86, P < 0.01, respectively. Also, Kt/V week-1 derived from TBWBIA, TBWWV and TBW58% correlated strongly with Kt/V week-1 from TBWD2O (r = 0.93, P < 0.0005, r = 0.83, P < 0.01 and r = 0.8, P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Can total body nitrogen be measured in newborn infants?

The feasibility of using prompt in vivo neutron activation Analysis (IVNAA) of nitrogen to measure the total body nitrogen (TBN) of newborn infants has been investigated by redesigning and recalibrating an existing IVNAA facility used for the measurement of TBN in adults. Repeated 1000 sec measurements of an infant phantom (4kg wt: 80g N) yielded an average measured value that is within 0.2± 1.8% (1xSD) of the actual value and a precision of 7.9% (CV) for a single measurement. Preliminary investigations indicate that the whole body radiation dose is no greater than 1 mSv (Q=20) for a 1000 s irradiation. It is proposed, and in part demonstrated, that measurement precision can be reduced to ≒5% by (i) using a graphite neutron reflector positioned over the infant to increase the in vivo thermal neutron flux, and (ii) doubling the number of NaI(TI) detectors.

Quality control in body composition measurements.

The principles of quality control (QC) are not new; they have always been with mankind. At the most fundamental level QC can be defined as a state of mind in which we continually strive to analyse what we are doing in order to produce a 'product' which our peers will judge to be 'better' . Paradoxically, this simple concept is expressed in many different ways within the multi-disciplinary team that makes up a body composition laboratory and very careful discussion is needed to ensure uniformity of technique and results. The situation is made even more difficult by the large range of equipment and techniques that are now available for the measurement of body composition. It is necessary to have a detailed understanding of the equipment and techniques and to have good communication within the group of workers. Good communication is essential to ensure that all members of the group have a clear understanding of the relevant guidelines and principles of QC and measurements, and to ensure that they are applied consistently throughout all the work of the laboratory. A detailed understanding of the equipment is necessary in order to define and implement simple tests that will monitor the most sensitive or troublesome features without imposing an undue burden upon the operator. There is a need for such tests to be automated as much as possible and, in general, there is a need for a more professional approach to the analysis of error and its propagation throughout an experiment. Inter comparisons of results between centres is a logical, but generally difficult requirement and some of the problems that arise would be simplified if equipment designs were more standardized. Finally, all these requirements need to be achieved within an environment that is continually changing with respect to the aims of the laboratory and the funding bodies.

Mobile telephones interfere with medical electrical equipment.

Electromagnetic interference in medical electrical equipment has not been a serious problem in recent years even with the proliferation of analogue mobile phones and two-way handheld radios. With the introduction of GSM digital mobile phones into Australia we have conducted measurements and found that, within 2m, the electric fields from digital mobile phones can exceed the immunity level of 7 V/m recommended by the US Food and Drug Administration (FDA) for medical electrical equipment. Current analogue mobile phones were shown to produce electric fields that exceed the 7 V/m level only at relatively shorter distances. In another test, both analogue and digital mobile phones were operated close to a range of typical medical electrical equipment. It was found that existing equipment generally meets the FDA standard, but digital mobile phones caused a variety of artefacts and alarm conditions. This problem must be addressed by the medical engineering profession; in the meantime, nursing and other staff should be educated to recognise these problems and restrictions must be placed upon the use of mobile phones in hospitals.

Early detection of protein depletion in alcoholic cirrhosis: role of body composition analysis.

BACKGROUND: Malnutrition is common in alcoholic cirrhosis. Bedside nutritional assessment techniques may be unreliable in patients with chronic liver disease. The aim of this study was to quantify changes in body composition and compare methods for measuring body composition in alcoholic cirrhosis. METHODS: Thirty-eight men with alcoholic cirrhosis were compared with 16 age-matched healthy men. Body composition was assessed using anthropometry and bioelectrical impedance to determine fat-free mass and body fat, deuterium oxide dilution to measure total body water, in vivo neutron activation analysis to measure total body protein, and dual energy x-ray absorptiometry to measure bone mineral content and total body fat mass. RESULTS: With increasing severity of cirrhosis, total body water increased, whereas total body protein decreased with a significant decrease in serum albumin levels. Total body protein levels, expressed as an index, were a more sensitive indicator of protein depletion than serum albumin levels. When patients were assessed by anthropometry and bioelectrical impedance for fat-free mass, there was no reduction compared with controls. CONCLUSIONS: Anthropometry and bioelectrical impedance do not accurately reflect changes in body composition associated with chronic liver disease. Quantification of body composition changes in alcoholic cirrhosis requires the use of direct methods such as in vivo neutron activation analysis, dual energy x-ray absorptiometry, or deuterium oxide dilution.

Spatial sensitivity measurements of a prompt gamma IVNAA facility.

A technique has been developed for measuring the spatial sensitivity of a prompt gamma in vivo neutron activation analysis facility as used for determining total body nitrogen (i.e. protein). A water filled perspex phantom was used to simulate a patient. Relative spatial sensitivity of the system was measured at various positions in the tank by observing the prompt gamma rays from thermal neutron capture in the 35Cl of a carbon tetrachloride sample contained in a small glass phial.

Anthropometry underestimates body protein depletion in haemodialysis patients.

The body composition of 62 haemodialysis patients (41 males) and 63 controls (30 males) was assessed using anthropometry and in vivo neutron activation analysis of body nitrogen. There was no significant difference between patients and controls in body mass index (BMI) and percentage body fat. Arm muscle circumference was significantly reduced in males. Lean body mass was strongly correlated with body nitrogen in controls (r = 0.951) but less so in patients (r = 0.876). The mean standardised body nitrogen index (NI) was reduced in male patients by 13% (95% confidence interval -9 to -17%) and in females by 4% (95% confidence interval +4 to -12%). Of the 16 patients with a NI below the control range, arm muscle circumference was below the control range in only 3 and BMI less than 18 kg/m2 in 2. NI was correlated negatively with the duration of renal replacement therapy, duration of haemodialysis, the number of previous failed transplants and the total dose of steroids received but not with current energy or protein intakes. Steroid dose was the only significant independent variable. Anthropometry underestimates body protein depletion in haemodialysis patients and the degree of protein loss is related to the cumulative dose of corticosteroids previously received.