Sweat Sodium Concentration Research Articles

Effects of training intensity and environmental condition on the hydration status of elite football players

ABSTRACT Objective: To examine the effects of training intensity and environmental condition on the hydration status of Elite football players. Methods: Eleven elite football players completed three training sessions of varying intensity in cool (12°C) and warm (23°C) environments. Training demands was measured by Global Positioning System, sweat rate and sweat sodium concentration were measured using dermal patches and body mass change. Results: Warm condition increased sweat rate (0.9 ± 0.3 vs 1.7 ± 0.3 L.h-1, P<0.001), fluid intake (0.7 ± 0.1 vs 1.5 ± 0.2 L, P<0.001), total sodium loss (1405 ± 340 vs 2946 ± 958 mg, P<0.001) and total sweat loss (1.4 ± 0.5 vs 2.5 ± 0.4 L, P<0.001) compared to cool. Training intensity increased sweat sodium concentration (16.1 ± 6.6 vs 54.6 ± 22.2 mmol.L-1, P<0.001) and sodium loss (779 ± 231 vs 1405 ± 340 mg) in both environmental conditions. Total sweat loss and sodium loss were positively correlated with total distance covered (r=0.48, P=0.005 and r=0.4, P=0.023, respectively), meanwhile sodium loss was also positively correlated with the total number of high-intensity efforts (r=0.35, P=0.045). Conclusions: The results show that training load and environmental condition have a major impact on the hydration status of elite football players, hence hydration strategies should be developed accordingly.

Sweat Characteristics of Cramp-Prone and Cramp-Resistant Athletes.

Exercise-associated muscle cramps (EAMCs) are thought to be caused by dehydration and/or electrolyte losses. In this multicenter, cross-sectional study, the authors determined whether sweat rates (SRs), sweat electrolyte concentrations, or sweat electrolyte content differed in athletes with (i.e.,crampers) and without (i.e.,noncrampers) a history of EAMCs and whether these variables could predict EAMC-prone athletes. Male and female collegiate athletes (N = 350) from 11 sports with (n = 245) and without (n = 105) a self-reported history of EAMCs completed a typical exercise or conditioning session. SRs, calculated from body mass, and posterior forearm sweat were analyzed for sweat sodium concentration ([Na+]sw), sweat potassium concentration ([K+]sw), and sweat chloride concentration ([Cl-]sw). The authors used SRs and sweat electrolyte concentrations to calculate sweat electrolyte content lost. Within each gender, no differences in SRs (204 males, p = .92; 146 females, p = .24); [Na+]sw (191 males, p = .55; 126 females, p = .55); Na+sw content (191 males, p = .59; 126 females, p = .20); [K+]sw (192 males, p = .57; 126 females, p = .87); K+sw content (192 males, p = .49; 126 females, p = .03); [Cl-]sw (192 males, p = .94; 77 females, p = .57); and Cl-sw content (192 males, p = .55; 77 females, p = .34) occurred between crampers and noncrampers. Receiver operating characteristic curve analysis revealed that sweat electrolyte content and SRs were predictive of EAMC-prone athletes in American football (area under curve = 0.65-0.72, p ≤ .005), but not in any other sport. EAMCs may not be solely caused by fluid or electrolyte losses in most athletes. Fluid and electrolyte replacement may help American footballers. Clinicians should individualize fluid and electrolyte replacement and understand different etiologies for EAMCs.

Permanent tattooing has no impact on local sweat rate, sweat sodium concentration and skin temperature or prediction of whole-body sweat sodium concentration during moderate-intensity cycling in a warm environment.

This study investigated the impact of permanently tattooed skin on local sweat rate, sweat sodium concentration and skin temperature and determined whether tattoos alter the relationship between local and whole-body sweat sodium concentration. Thirteen tattooed men (27 ± 6years) completed a 1h (66 ± 4% of [Formula: see text]) cycling trial at 32°C, 35% relative humidity. Sweat rate and sweat sodium concentration were measured using the whole-body washdown and local absorbent patch techniques. Patches and skin-temperature probes were applied over the right/left thighs and tattooed/non-tattooed (contralateral) regions. Local sweat rates did not differ (p > 0.05) between the right (1.11 ± 0.38) and left (1.21 ± 0.37) thighs and the permanently tattooed (1.93 ± 0.82) and non-tattooed (1.72 ± 0.81mgcm-2min-1) regions. There were no differences in local sweat sodium concentration between the right (58.2 ± 19.4) and left (55.4 ± 20.3) thighs and the permanently tattooed (73.0 ± 22.9) and non-tattooed (70.2 ± 18.9mmolL-1) regions. Difference in local skin temperature between the right and left thighs (- 0.043) was similar to that between the permanently tattooed and non-tattooed (- 0.023°C) regions. Prediction of whole-body sweat sodium concentration for the permanently tattooed (41.0 ± 6.7) and the non-tattooed (40.2 ± 5.3mmolL-1) regions did not differ. Permanent tattoos do not alter local sweat rate, sweat sodium concentration or local skin temperature during moderate-intensity cycling exercise in a warm environment. Results from a patch placed over a tattooed surface correctly predicts whole-body sweat sodium concentration from an equation developed from a non-tattooed region.

The Impact of Dietary Sodium Intake on Sweat Sodium Concentration in Response to Endurance Exercise: A Systematic Review

The collection, processing, and analysis of sweat samples to determine sodium losses during endurance exercise is common amongst sports and exercise nutrition practitioners, and necessary for researchers investigating sodium losses and replacement strategies. Several factors influence sweat sodium concentration ([Na+]) that need to be controlled or considered when interpreting results. Dietary sodium intake in the days preceding exercise is one factor that may influence sweat [Na+]. A systematic review was undertaking using six databases (CINAHL, Embase, Medline Ovid, Scopus, SPORTDiscus, and Web of Science) to determine the impact of dietary sodium intake on sweat [Na+] in response to endurance exercise. Six papers met the inclusion criteria. They varied in the level of sodium intake (<196 to 9177 mg/d), intervention timeframe (3 to 42 days), exercise modality (cycling ergometry, treadmill walking and running), and sweat collection method (whole body washdown and regional patch techniques). Two studies showed significant differences in sweat [Na+] due to diet, two showed no significant difference, and two were not analysed statistically. No relationship was found across studies comparing the difference in sodium intake between interventions and sweat [Na+]. Several limitations were identified, including lack of validation of the intervention, collecting regional sweat samples from limited sites or averaging results across sites or collection days, and lack of statistical analysis. It is concluded that the impact of dietary sodium intake on sweat [Na+] in response to endurance exercise remains uncertain, however the review provides useful insights into the optimal study design for future research in this area.

Impact of 3-day high and low dietary sodium intake on sodium status in response to exertional-heat stress: a double-blind randomized control trial.

To determine the impact of altering dietary sodium intake for 3days preceding exercise on sweat sodium concentration [Na+], and cardiovascular and thermoregulatory variables. Fifteen male endurance athletes (runners n = 8, cyclists n = 7) consumed a low (LNa, 15mgkg-1day-1) or high (HNa, 100mgkg-1day-1) sodium diet, or their usual free-living diet [UDiet, 46 (37-56) mgkg-1day-1] for 3days in a double-blind, randomized cross-over design, collecting excreted urine (UNa) and refraining from exercise. On day 4, they completed 2h running at 55% [Formula: see text]O2max or cycling at 55% maximum aerobic power in Tamb 35°C. Pre- and post-exercise blood samples were collected, and sweat from five sites using absorbent patches along the exercise protocol. UNa on days 2-3 pre-exercise [mean (95% CI) LNa 16 (12-19) mgkg-1day-1, UDiet 46 (37-56) mgkg-1day-1, HNa 79 (72-85) mgkg-1day-1; p < 0.001] and pre-exercise aldosterone [LNa 240 (193-286) mgkg-1day-1, UDiet 170 (116-224) mg kg-1day-1, HNa 141 (111-171) mg kg-1day-1; p = 0.001] reflected sodium intake as expected. Pre-exercise total body water was greater following HNa compared to LNa (p < 0.05), but not UDiet. Estimated whole-body sweat [Na+] following UDiet was 10-11% higher than LNa and 10-12% lower than HNa (p < 0.001), and correlated with pre-exercise aldosterone (1st h r = - 0.568, 2nd h r = - 0.675; p < 0.01). Rectal temperature rose more quickly in LNa vs HNa (40-70min; p < 0.05), but was similar at the conclusion of exercise, and no significant differences in heart rate or perceived exertion were observed. Three day altered sodium intake influenced urinary sodium excretion and sweat [Na+], and the rise in rectal temperature, but had no effect on perceived exertion during moderate-intensity exercise in hot ambient conditions.

SHORT-TERM CHANGES IN DIETARY SODIUM INTAKE INFLUENCE SWEAT SODIUM CONCENTRATION AND MUSCLE SODIUM CONTENT IN HEALTHY SUBJECTS

Objective: There is increasing evidence that sodium can be stored in the skin and muscles without being osmotically active, yet whether acute changes in dietary sodium intake alter sweat and muscle sodium content has not been investigated previously. Design and method: In a cross-over design, we assessed muscle sodium content by 23Na magnetic resonance imaging (MRI) in 38 healthy normotensive volunteers (aged 33.5 ± 11.1 years, 76.3% female) after 5 days of high sodium diet (HS) (6 g of salt added to their normal diet) and 5 days of a low-sodium diet (LS). Women performed each study visit during the same phase of the menstrual cycle. In a sub-group of 18 participants (72.2% female) we conducted quantitative pilocarpine iontophoretic sweat collections and measured the sodium concentration in sweat. Office blood pressure, electrolytes, creatinine and circulating aldosterone levels were measured in all participants, and 24 h urine was collected Results: Under HS conditions urinary sodium excretion, muscle sodium content and sweat sodium concentration all increased significantly (see Figure). Muscle sodium content by MRI (rm = 0.47, p = 0.03) and sodium sweat concentration (rm = 0.72, p < 0.001) correlated positively with salt intake as estimated by 24-hour urine sodium excretion. Age, gender or the phase of the menstrual cycle did not influence muscle or sweat sodium concentrations or their changes. In contrast, plasma aldosterone levels were strongly and negatively associated with both muscle sodium content (rs = −0.42, p = 0.0001) and sweat sodium (rs = −0.52, p = 0.002). Sweat and muscle sodium content were not different in participants with a salt-sensitive blood pressure compared to non-sensitives. Conclusions: Muscle and sweat sodium concentrations are significantly higher under high salt conditions in healthy male and female subjects, suggesting that muscle and sweat play a role in the dietary sodium balance in humans.

Chloride and sodium ion concentrations in saliva and sweat as a method to diagnose cystic fibrosis

ObjectiveCystic fibrosis diagnosis is dependent on the chloride ion concentration in the sweat test (≥60mEq/mL – recognized as the gold standard indicator for cystic fibrosis diagnosis). Moreover, the salivary glands express the CFTR protein in the same manner as sweat glands. Given this context, the objective was to verify the correlation of saliva chloride concentration and sweat chloride concentration, and between saliva sodium concentration and sweat sodium concentration, in patients with cystic fibrosis and healthy control subjects, as a tool for cystic fibrosis diagnosis. MethodsThere were 160 subjects enrolled: 57/160 (35.70%) patients with cystic fibrosis and two known CFTR mutations and 103/160 (64.40%) healthy controls subjects. Saliva ion concentration was analyzed by ABL 835 Radiometer® equipment and, sweat chloride concentration and sweat sodium concentration, respectively, by manual titration using the mercurimetric procedure of Schales & Schales and flame photometry. Statistical analysis was performed by the chi‐squared test, the Mann–Whitney test, and Spearman's correlation. Alpha=0.05. ResultsPatients with cystic fibrosis showed higher values of sweat chloride concentration, sweat sodium concentration, saliva chloride concentration, and saliva sodium concentration than healthy controls subjects (p‐value<0.001). The correlation between saliva chloride concentration and sweat chloride concentration showed a positive Spearman's Rho (correlation coefficient)=0.475 (95% CI=0.346 to 0.587). Also, the correlation between saliva sodium concentration and sweat sodium concentration showed a positive Spearman's Rho=0.306 (95% CI=0.158 to 0.440). ConclusionsSaliva chloride concentration and saliva sodium concentration are candidates to be used in cystic fibrosis diagnosis, mainly in cases where it is difficult to achieve the correct sweat amount, and/or CFTR mutation screening is difficult, and/or reference methods for sweat test are unavailable to implement or are not easily accessible by the general population.

Normative data for sweating rate, sweat sodium concentration, and sweat sodium loss in athletes: An update and analysis by sport

ABSTRACTThe purpose of this study was to expand our previously published sweat normative data/analysis (n = 506) to establish sport-specific normative data for whole-body sweating rate (WBSR), sweat [Na+], and rate of sweat Na+ loss (RSSL). Data from 1303 athletes were compiled from observational testing (2000–2017) using a standardized absorbent sweat patch technique to determine local sweat [Na+] and normalized to whole-body sweat [Na+]. WBSR was determined from change in exercise body mass, corrected for food/fluid intake and urine/stool loss. RSSL was the product of sweat [Na+] and WBSR. There were significant differences between sports for WBSR, with highest losses in American football (1.51 ± 0.70 L/h), then endurance (1.28 ± 0.57 L/h), followed by basketball (0.95 ± 0.42 L/h), soccer (0.94 ± 0.38 L/h) and baseball (0.83 ± 0.34 L/h). For RSSL, American football (55.9 ± 36.8 mmol/h) and endurance (51.7 ± 27.8 mmol/h) were greater than soccer (34.6 ± 19.2 mmol/h), basketball (34.5 ± 21.2 mmol/h), and baseball (27.2 ± 14.7 mmol/h). After ANCOVA, significant between-sport differences in adjusted means for WBSR and RSSL remained. In summary, due to the significant sport-specific variation in WBSR and RSSL, American football and endurance have the greatest need for deliberate hydration strategies.Abbreviations: WBSR: whole body sweating rate; SR: sweating rate; Na+: sodium; RSSL: rate of sweat sodium loss

Tattoos do not affect exercise-induced localised sweat rate or sodium concentration

ObjectivesSkin tattoos have been shown to reduce localised sweat rate and increase sweat sodium concentration ([Na+]) when sweating is artificially stimulated. This study investigated whether similar responses are observed with exercise-induced sweating. DesignUnblinded, within-participant control, single trial. MethodsTwenty-two healthy individuals (25.1±4.8 y (Mean±SD), 14 males) with a unilateral tattoo ≥11.4cm2 in size, ≥2 months in age, and shaded ≥50% participated in this investigation. Participants undertook 20min of intermittent cycling (4×5min intervals) on a stationary ergometer in a controlled environment (24.6±1.1°C; 64±6% RH). Resultant sweat was collected into absorbent patches applied at two pairs of contralateral skin sites (pair 1: Tattoo vs. Non-Tattoo; pair 2: Control 1 vs. Control 2 (both non-tattooed)), for determination of sweat rate and sweat [Na+]. Paired samples t-tests were used to determine differences between contralateral sites. ResultsTattoo vs. Non-Tattoo: Neither sweat rate (Mean±SD: 0.92±0.37 vs. 0.94±0.43mg·cm−2·min−1, respectively; p=0.693) nor sweat [Na+] (Median(IQR): 37(32–52) vs. 37(31–45) mM·L−1, respectively; p=0.827) differed. Control 1 vs. Control 2: Neither sweat rate (Mean±SD: 1.19±0.53 vs. 1.19±0.53mg·cm−2·min−1, respectively; p=0.917) nor sweat [Na+] (Median(IQR): 29(26–41) vs. 31(25–43)mM·L−1, respectively; p=0.147) differed. The non-significant differences for sweat rate and [Na+] between Tattoo vs. Non-Tattoo were inside the range of the within participant variability (sweat rate CVi=5.4%; sweat [Na+] CVi=4.4%). ConclusionsSkin tattoos do not appear to alter the rate or [Na+] of exercise-induced sweating. The influence of skin tattoos on localised sweat responses may have previously been over-estimated.

Skin Tattoos Do Not Affect Exercise-induced Sweat Rate Or Sodium Concentration.

PURPOSE: Skin tattoos have been shown to reduce sweat rate and increase sweat sodium concentration when sweating is artificially stimulated. This study investigated whether similar responses are observed with exercise-induced sweating. METHODS: Twenty-two healthy individuals (25.1±4.8 y (Mean±SD), 14 males) with a unilateral tattoo ≥11.4 cm2 in size, >2 months in age, and shaded ≥50% participated in this investigation. Participants undertook 20 min of intermittent cycling (4 x 5 min intervals) on a stationary ergometer in a controlled environment (24.6±1.1°C, RH 64±6%). Resultant sweat was collected into absorbent patches applied at two pairs of contralateral skin sites (pair 1: Tattoo vs. Non-Tattoo; pair 2: Control 1 vs. Control 2 (both non-tattooed)), for determination of sweat rate and sweat [Na+]. Paired samples t tests were employed to determine differences between contralateral sites. RESULTS:Tattoo vs. Non-Tattoo: Neither sweat rate (Mean±SD: 0.92±0.37 vs. 0.94±0.43 mg.cm-2.min-1, respectively; p=1.000) nor sweat [Na+] (Median(IQR): 36(32-53) vs. 37(31-45) mM.L-1, respectively; p=0.827) differed. Control 1 vs. Control 2: Neither sweat rate (Mean±SD: 1.19±0.53 vs. 1.19±0.53 mg.cm-2.min-1, respectively; p=0.917) nor sweat [Na+] (Median(IQR): 29(26-41) vs. 31(25-43) mM.L-1, respectively; p=0.147) differed. The non-significant differences for Tattoo vs. Non-Tattoo were within the range of normal variability (sweat rate CV=5.4%; sweat [Na+] CV=4.4%). CONCLUSIONS: Skin tattoos do not appear to alter rate or [Na+] of exercise-induced sweat. The influence of skin tattoos on thermoregulatory responses to exercise may have been over-estimated.

Impaired Heat Adaptation From Combined Heat Training and "Live High, Train Low" Hypoxia.

Purpose: To determine whether combining training in heat with "Live High, Train Low" hypoxia (LHTL) further improves thermoregulatory and cardiovascular responses to a heat-tolerance test compared with independent heat training. Methods: A total of 25 trained runners (peak oxygen uptake = 64.1 [8.0]mL·min-1·kg-1) completed 3-wk training in 1 of 3 conditions: (1)heat training combined with "LHTL" hypoxia (H+H; FiO2 = 14.4% [3000m], 13 h·d-1; train at <600m, 33°C, 55% relative humidity [RH]), (2)heat training (HOT; live and train <600m, 33°C, 55% RH), and (3)temperate training (CONT; live and train <600m, 13°C, 55% RH). Heat adaptations were determined from a 45-min heat-response test (33°C, 55% RH, 65% velocity corresponding to the peak oxygen uptake) at baseline and immediately and 1 and 3 wk postexposure (baseline, post, 1wkP, and 3wkP, respectively). Core temperature, heart rate, sweat rate, sodium concentration, plasma volume, and perceptual responses were analyzed using magnitude-based inferences. Results: Submaximal heart rate (effect size [ES] = -0.60 [-0.89; -0.32]) and core temperature (ES = -0.55 [-0.99; -0.10]) were reduced in HOT until 1wkP. Sweat rate (ES = 0.36 [0.12; 0.59]) and sweat sodium concentration (ES = -0.82 [-1.48; -0.16]) were, respectively, increased and decreased until 3wkP in HOT. Submaximal heart rate (ES = -0.38 [-0.85; 0.08]) was likely reduced in H+H at 3wkP, whereas CONT had unclear physiological changes. Perceived exertion and thermal sensation were reduced across all groups. Conclusions: Despite greater physiological stress from combined heat training and "LHTL" hypoxia, thermoregulatory adaptations are limited in comparison with independent heat training. The combined stimuli provide no additional physiological benefit during exercise in hot environments.

SAT-LB093 Salty Relationships with Bone: Not Calcium nor Vitamin D

Previous studies demonstrated a positive relationship between blood sodium concentration and bone mineral density (BMD) in ultramarathon runners following a 100-mile race (1) and a negative relationship in walkers (treadmill walking for 45-minutes) following an oral sodium load (2). However, accurate assessment of sweat sodium concentration ([Na+]) was absent in those exercise studies. Therefore, the primary aim of these pilot data were to assess potential relationships between sweat [Na+] versus bone mineral content (BMC) at rest. We hypothesized that higher sweat [Na+] would be associated with lower BMC in athletes participating in a larger vitamin D supplementation trial. The current data represent a cross-sectional baseline assessment whereas: sweat [Na+] was obtained via pilocarpine iontophoresis (Wescor), total body BMC, fat and lean mass obtained via dual energy x-ray absorptiometry scan (Hologic), serum 25-OH vitamin D (25-OH-D) obtained via venipuncture (Cobas E Immunoassay), and dietary intake assessed via 3-month Food Frequency questionnaire (NutritionQuest). Twenty-two male (n=13) and female (n=9) collegiate basketball players completed baseline testing (20±2years). Significant relationships between total body BMC vs. sweat [Na+] (r=0.54;p=0.01) and total lean mass (r=0.93;p<0.01) were documented, but not between total BMC vs. 25-OH-D (r=-0.30;NS), vitamin D intake (r=-0.17;NS), calcium intake (r=0.16;NS), or sodium intake (r=0.22;NS). African-American athletes (n=14) had significantly lower 25-OH-D levels vs. Caucasian athletes (28±11 vs. 44±15ng/mL;p=0.01), respectively. Male vs. female differences noted in: sweat [Na+] (51±15 vs. 33±11mmol/L;p=0.006), total body BMD (1.35±0.11 vs. 1.19±0.06g/cm2;p=0.001), fat mass (14.9±0.45 vs. 19.8±4.5kg;p=0.009) and lean mass (71.7±8.0 vs. 55.9±6.0kg;p<0.001). Total body BMC was positively related to sweat [Na+], and not calcium intake nor 25-OH-D in this small cohort of healthy collegiate athletes. However, the direction of this relationship was opposite of expected (i.e. higher sweat sodium losses would be associated with lower, not higher, bone mineral). These data cautiously suggest sweat sodium output may represent an extrarenal mechanism to excrete excess sodium ingested. We believe these pilot data are worthy of expansion, involving rigorous endocrine evaluation, and of particular relevance to African-Americans with paradoxically low 25-OH-D and high BMD.

Chloride and sodium ion concentrations in saliva and sweat as a method to diagnose cystic fibrosis

ObjectiveCystic fibrosis diagnosis is dependent on the chloride ion concentration in the sweat test (≥60mEq/mL – recognized as the gold standard indicator for cystic fibrosis diagnosis). Moreover, the salivary glands express the CFTR protein in the same manner as sweat glands. Given this context, the objective was to verify the correlation of saliva chloride concentration and sweat chloride concentration, and between saliva sodium concentration and sweat sodium concentration, in patients with cystic fibrosis and healthy control subjects, as a tool for cystic fibrosis diagnosis. MethodsThere were 160 subjects enrolled: 57/160 (35.70%) patients with cystic fibrosis and two known CFTR mutations and 103/160 (64.40%) healthy controls subjects. Saliva ion concentration was analyzed by ABL 835 Radiometer® equipment and, sweat chloride concentration and sweat sodium concentration, respectively, by manual titration using the mercurimetric procedure of Schales & Schales and flame photometry. Statistical analysis was performed by the chi-squared test, the Mann–Whitney test, and Spearman's correlation. Alpha=0.05. ResultsPatients with cystic fibrosis showed higher values of sweat chloride concentration, sweat sodium concentration, saliva chloride concentration, and saliva sodium concentration than healthy controls subjects (p-value<0.001). The correlation between saliva chloride concentration and sweat chloride concentration showed a positive Spearman's Rho (correlation coefficient)=0.475 (95% CI=0.346 to 0.587). Also, the correlation between saliva sodium concentration and sweat sodium concentration showed a positive Spearman's Rho=0.306 (95% CI=0.158 to 0.440). ConclusionsSaliva chloride concentration and saliva sodium concentration are candidates to be used in cystic fibrosis diagnosis, mainly in cases where it is difficult to achieve the correct sweat amount, and/or CFTR mutation screening is difficult, and/or reference methods for sweat test are unavailable to implement or are not easily accessible by the general population.

Relation between Regional and Whole Body Sweat Sodium Concentration and the Effect of Exercise Intensity

Relation between Regional and Whole Body Sweat Sodium Concentration and the Effect of Exercise Intensity

Wearable Platform for Real-time Monitoring of Sodium in Sweat.

A fully integrated and wearable platform for harvesting and analysing sweat sodium concentration in real time during exercise has been developed and tested. The platform was largely produced using 3D printing, which greatly simplifies fabrication and operation compared to previous versions generated with traditional production techniques. The 3D printed platform doubles the capacity of the sample storage reservoir to about 1.3 ml, reduces the assembly time and provides simple and precise component alignment and contact of the integrated solid-state ion-selective and reference electrodes with the sorbent material. The sampling flowrate in the device can be controlled by introducing threads to enhance wicking of sweat from the skin, across the electrodes to the storage area. The platform was characterised in the lab and in exercise trials over a period of about 60 minutes continuous monitoring. Sweat sodium concentration was found to rise initially to approximately 17 mM and decline gradually over the period of the trial to about 11-12 mM.

Is sweat testing for cystic fibrosis feasible in patients with down syndrome?

BackgroundRecurrent airway infections are common in patients with Down’s syndrome (DS). Hence, ruling out Cystic Fibrosis (CF) in these patients is often required. In the past, the value of sweat testing – the gold standard to diagnose CF – has been questioned in DS as false positive results have been reported. However, these reports are based on measurements of sweat osmolality or sodium concentrations, not chloride concentrations. This study analyses sweat secretion rate and chloride concentration in sweat samples of patients with DS in comparison to healthy controls.MethodsWe assessed sweat samples in 16 patients with DS and 16 healthy controls regarding sweat secretion rate (SSR) and sweat chloride concentration.ResultsAll measured chloride concentrations were within the normal range. The chloride concentrations were slightly, but not significantly lower in patients with DS (15,54 mmol/l (±4,47)) compared to healthy controls (18,31 mmol/l (±10,12)). While no gender gap in chloride concentration could be found, chloride concentration increased with age in both groups.Insufficient sweat was collected in 2 females with DS (12.5% of the study group) but not in an individual of the control group. A significant lower sweat secretion rate was found in the DS group (27,6 μl/30 min (± 12,18)) compared to the control group (42,7 μl/30 min (± 21,22)). In a sub-analysis, female patients produced significantly less sweat (20,8 ± 10,6 μl/30 min) than male patients with DS (36,4 ± 7,8 μl/30 min), which accounts for the difference between patients and controls. Furthermore, while the sweating secretion rate increased with age in the control group, it did not do so in the DS group. Once again this was due to female patients with DS, who did not show a significant increase of sweat secretion rate with age.ConclusionsSweat chloride concentrations were within the normal range in patients with DS and therefore seem to be a reliable tool for testing for CF in these patients. Interestingly, we found a reduced sweat secretion rate in the DS group. Whether the last one has a functional and clinical counterpart, possibly due to a disturbed thermoregulation in DS patients, requires further investigation.

Sweat Sodium, Potassium, and Chloride Concentrations Analyzed Same Day as Collection Versus After 7 Days Storage in a Range of Temperatures.

The purpose of this study was to determine the effect of storage temperature on sodium ([Na+]), potassium ([K+]), and chloride ([Cl-]) concentrations of sweat samples analyzed 7 days after collection. Using the absorbent patch technique, 845 sweat samples were collected from 39 subjects (32 ± 7 years, 72.9 ± 10.5kg) during exercise. On the same day as collection (PRESTORAGE), 609 samples were analyzed for [Na+], [Cl-], and [K+] by ion chromatography (IC) and 236 samples were analyzed for [Na+] using a compact ion-selective electrode (ISE). Samples were stored at one of the four conditions: -20 °C (IC, n = 138; ISE, n = 60), 8 °C (IC, n = 144; ISE, n = 59), 23 °C (IC, n = 159; ISE, n = 59), or alternating between 8 °C and 23 °C (IC, n = 168; ISE, n = 58). After 7 days in storage (POSTSTORAGE), samples were reanalyzed using the same technique as PRESTORAGE. PRESTORAGE sweat electrolyte concentrations were highly related to that of POSTSTORAGE (intraclass correlation coefficient: .945-.989, p < .001). Mean differences (95% confidence intervals) between PRESTORAGE and POSTSTORAGE were statistically, but not practically, significant for most comparisons: IC [Na+]: -0.5(0.9) to -2.1(0.9) mmol/L; IC [K+]: -0.1(0.1) to -0.2(0.1) mmol/L; IC [Cl-]: -0.4(1.4) to -1.3(1.3) mmol/L; ISE [Na+]: -2.0(1.1) to 1.3(1.1) mmol/L. Based on typical error of measurement results, 95% of the time PRESTORAGE and POSTSTORAGE sweat [Na+], [K+], and [Cl-] by IC analysis fell within ±7-9, ±0.6-0.7, and ±9-13mmol/L, respectively, while sweat [Na+] by ISE was ±6 mmol/L. All conditions produced high reliability and acceptable levels of agreement in electrolyte concentrations of sweat samples analyzed on the day of collection versus after 7 days in storage.

Thirty Years of Sweat Chloride Testing at One Referral Center.

To conduct a descriptive analysis of the sweat test (ST), associating ST results with epidemiological data, CFTR (cystic fibrosis transmembrane conductance regulator) mutations and reasons to indicate the ST, as well as correlating sweat sodium and sweat chloride concentrations in subjects. Retrospective survey and descriptive analysis of 5,721 ST at a university referral center. The inclusion of the subjects was based on clinical data related with cystic fibrosis (CF) phenotype. The samples were grouped by (i) sweat chloride concentrations (mEq/L): <30: 3,249/5,277 (61.6%); ≥30 to <60: 1,326/5,277 (25.1%); ≥60: 702/5,277 (13.3%) and (ii) age: (Group A--GA) 0 to <6 months; (Group B--GB) ≥6 months to <18 years; (Group C--GC) ≥18 years. Digestive symptoms showed higher prevalence ratio for the CF diagnosis as well as association between younger age and higher values of sweat chloride, sweat sodium, and chloride/sodium ratio. The indication of ST due to respiratory symptoms was higher in GB and associated with greater age, lower values of sweat chloride, sweat sodium, and chloride/sodium ratio. There was higher prevalence of ST with sweat chloride levels <30 mEq/L in GB, ≥60 mEq/L in GC, and with borderline level in GB. There was positive correlation between sweat sodium and sweat chloride. Sweat chloride/sweat sodium and sweat sodium-sweat chloride indexes showed association with sex, reason for ST indication, and CFTR mutations. Sex alters some values presented in the ST. The number of ST/year performed before and after the newborn screening implementation was the same; however, we observed a higher number of borderlines values. A wide spectrum of CFTR mutation was found. Severe CFTR mutations and F508del/F508del genotype were associated with highest probability of ST chloride levels ≥60 mEq/L, and the absence of CFTR mutations identified was associated with borderline ST and respiratory symptoms. ST data showed wide variability dependent on age, sex, reason for examination indication, CFTR mutations, and weight of the collected sweat sample. Sweat sodium concentration is directly correlated with sweat chloride levels and it could be used as a quality parameter.

Sweat Sodium Concentration: Inter-Unit Variability of a Low Cost, Portable, and Battery Operated Sodium Analyzer.

The B-722 Laqua Twin is a low cost, portable, and battery operated sodium analyzer, which can be used for the assessment of sweat sodium concentration. The Laqua Twin is reliable and provides a degree of accuracy similar to more expensive analyzers; however, its interunit measurement error remains unknown. The purpose of this study was to compare the sodium concentration values of 70 sweat samples measured using three different Laqua Twin units. Mean absolute errors, random errors and constant errors among the different Laqua Twins ranged respectively between 1.7 mmol/L to 3.5 mmol/L, 2.5 mmol/L to 3.7 mmol/L and -0.6 mmol/L to 3.9 mmol/L. Proportional errors among Laqua Twins were all < 2%. Based on a within-subject biological variability in sweat sodium concentration of ± 12%, the maximal allowable imprecision among instruments was considered to be £ 6%. In that respect, the within (2.9%), between (4.5%), and total (5.4%) measurement error coefficient of variations were all < 6%. For a given sweat sodium concentration value, the largest observed difference in mean and lower and upper bound error of measurements among instruments were, respectively, 4.7 mmol/L, 2.3 mmol/L, and 7.0 mmol/L. In conclusion, our findings show that the interunit measurement error of the B-722 Laqua Twin is low and methodologically acceptable.

An Endurance Athlete's Self-Report of a Novel Method for Sweat Sodium Measurement in the Field

Hypovolemia and reduced blood sodium levels have been reported in some athletes. Sweat sodium concentration has been shown to be directly proportional to percent plasma volume loss and, therefore, may serve as useful proxy indicator of hypovolemia. This case, a 44-year old male physician with ten years of experience in long distance triathlons and endurance racing, reports himself to be a salty, heavy sweater; has noted significant weight loss during some competitions; and, occasionally, encounters symptoms that could be attributed to hypovolemia, despite drinking to thirst. This case relates his attempts to measure sweat sodium concentration using regional patches and two tools, the Horiba LAQUA twin B-721 Compact Salt Meter and the AquaChek strip (from the swimming pool industry) as compared to a pilocarpine test using a standard approved by the Cystic Fibrosis Foundation. Both tools yielded comparable results, with wide variation in sweat sodium concentration across the samples. The AquaChek showed a consistent bias of -4.16 sodium mEq/L compared to the Horiba. Both are comparable to a pilocarpine standard and validity and reliability of each method was robust when later tested against standard saline solutions. In this case, ease of application, sufficient sweat volume, and potentially reduced contamination from body hair suggest this site for further evaluation of sweat sodium in the field. Additionally, compared to laboratory testing, each method is cost efficient.