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A*S*Y*S - Sweat Tears

Fifty patients were included in this study. Skin disinfection was done with an alcohol-based solution. Swabs for RT-PCR (real-time reverse transcriptase polymerase chain reaction) were taken from forehead and axilla skin after sweating patients for 30 min. After collection of sweat, swabs were placed into 2 ml of sterile viral transport medium, then transported quickly to the microbiology laboratory.

A*S*Y*S - Sweat Tears

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Disinfection of forehead and axillary skin with an alcohol-based product was done. Patients were asked to walk back and forth in the room until they sweated, and in order to help sweating, we exposed them to a room temperature 30 C. After sweating was seen, samples were taken 5 times from forehead, 5 times from one axilla, and 5 times from other axilla by pressing on the skin. Sterile nylon, dacron, or rayon swabs with flexible plastic shafts were used to collect sweat samples from patients followed up with the diagnosis of COVID-19. After sample collection, swabs were placed into 2 mL of sterile viral transport medium (VTM; various manufacturers). Samples were transported and tested as soon as possible after collection.

All of the patients had positive PCR tests for SARS-CoV-2 and radiologically positive findings in chest CT (computed tomography) for COVID-19. All of the patients had COVID-19-specific symptoms like fever, myalgia, and cough. SARS-CoV-2 was not detected in the sweat of PCR samples which were taken from axilla and forehead in none of the 50 patients.

In this study, we investigated the presence of SARS-CoV-2 virus in the sweat of 50 COVID-19 patients. Sweat samples were taken from forehead and axilla skin after cleaning with alcohol-based solutions. There is no virus detected in any of the samples.

Limitations of our study are the small number of the study sample, but our study has more patients than the first study, and every single PCR test is very valuable during pandemics. There is also no contamination of the sweat samples in our study.

Wearable biosensors are garnering substantial interest due to their potential to provide continuous, real-time physiological information via dynamic, noninvasive measurements of biochemical markers in biofluids, such as sweat, tears, saliva and interstitial fluid. Recent developments have focused on electrochemical and optical biosensors, together with advances in the noninvasive monitoring of biomarkers including metabolites, bacteria and hormones. A combination of multiplexed biosensing, microfluidic sampling and transport systems have been integrated, miniaturized and combined with flexible materials for improved wearability and ease of operation. Although wearable biosensors hold promise, a better understanding of the correlations between analyte concentrations in the blood and noninvasive biofluids is needed to improve reliability. An expanded set of on-body bioaffinity assays and more sensing strategies are needed to make more biomarkers accessible to monitoring. Large-cohort validation studies of wearable biosensor performance will be needed to underpin clinical acceptance. Accurate and reliable real-time sensing of physiological information using wearable biosensor technologies would have a broad impact on our daily lives.

Abstract:Recent advances in microfluidics, microelectronics, and electrochemical sensing methods have steered the way for the development of novel and potential wearable biosensors for healthcare monitoring. Wearable bioelectronics has received tremendous attention worldwide due to its great a potential for predictive medical modeling and allowing for personalized point-of-care-testing (POCT). They possess many appealing characteristics, for example, lightweight, flexibility, good stretchability, conformability, and low cost. These characteristics make wearable bioelectronics a promising platform for personalized devices. In this paper, we review recent progress in flexible and wearable sensors for non-invasive biomonitoring using sweat as the bio-fluid. Real-time and molecular-level monitoring of personal health states can be achieved with sweat-based or perspiration-based wearable biosensors. The suitability of sweat and its potential in healthcare monitoring, sweat extraction, and the challenges encountered in sweat-based analysis are summarized. The paper also discusses challenges that still hinder the full-fledged development of sweat-based wearables and presents the areas of future research.Keywords: point-of-care; biomonitoring; personalized healthcare; sweat; biosensors

Evaluating and testing hydration status is increasingly requested by rehabilitation, sport, military and performance-related activities. Besides commonly used biochemical hydration assessment markers within blood and urine, which have their advantages and limitations in collection and evaluating hydration status, there are other potential markers present within saliva, sweat or tear. This literature review focuses on body fluids saliva, sweat and tear compared to blood and urine regarding practicality and hydration status influenced by fluid restriction and/or physical activity. The selected articles included healthy subjects, biochemical hydration assessment markers and a well-described (de)hydration procedure. The included studies (n=16) revealed that the setting and the method of collecting respectively accessing body fluids are particularly important aspects to choose the optimal hydration marker. To obtain a sample of saliva is one of the simplest ways to collect body fluids. During exercise and heat exposures, saliva composition might be an effective index but seems to be highly variable. The collection of sweat is a more extensive and time-consuming technique making it more difficult to evaluate dehydration and to make a statement about the hydration status at a particular time. The collection procedure of tear fluid is easy to access and causes very little discomfort to the subject. Tear osmolarity increases with dehydration in parallel to alterations in plasma osmolality and urine-specific gravity. But at the individual level, its sensitivity has to be further determined.

Human health and performance can be reduced when the body is dehydrated1, 2 and no gold standard for hydration assessment exists.3, 4 Dehydration is a result of excess total body water (TBW) loss and is often accompanied by abnormalities in electrolyte balance. Heat, exercise-induced sweating or reduced thirst (often found in the elderly population) cause more water than sodium loss from the extracellular fluid (ECF) compartment, that is, hypertonic dehydration. Hypotonic dehydration shows more sodium than water loss and can be induced by diuretics or severely burned skin. Isotonic dehydration is caused by water and sodium loss in equivalent proportions such as during diarrhoea.5 When people exercise for longer periods without fluid replacement, whole-body dehydration is associated with reductions in plasma, interstitial and intracellular volume, that is, hypovolemia.6

The following keywords and combinations were used in Cochrane Library (CENTRAL): dehydration AND saliva, dehydration AND sweat, dehydration AND tear, dehydration AND body weight and dehydration AND axillary moisture.

In the Cochrane Library n=388 studies were recorded: dehydration AND body weight (279 hits), dehydration AND saliva (19 hits), dehydration AND sweat (75 hits), dehydration AND tear (15 hits), and dehydration AND axillary moisture (0 hits). In PubMed n=312 studies were found. After excluding records by duplicates and by not relevant titles, abstracts and full texts, 15 records met our inclusion criteria and one record was included through links of related articles (references). In summary, a total of n=16 studies was included in this review. Figure 1 presents the search strategy and selection process.

In this section the dehydration procedures of the included studies of saliva (Table 1), sweat (Table 2) and tear are listed. To achieve an euhydrated state before testing all studies conducted a well-described hydration protocol. For a controlled dehydrated status, either a stationary cycle ergometer was used in an environmental chamber (saliva,20, 28, 36, 37, 38 sweat19, 39, 40 and tear27, 31) or a treadmill (saliva20, 28, 29, 34, 41 and sweat34). Passive dehydration was either used with fluid restriction42, 43 or extracellular dehydration using a loop diuretic (Furosemide).44 For comparison reasons, the results stand for the control/placebo groups to evaluate (de)hydration status.

For most of the included studies, the measurement equipment to evaluate osmolarity and sodium concentration of saliva and sweat do not differ compared to the evaluation of blood and urine.19, 20, 28, 29, 34, 36, 37, 39, 40, 42, 44

In a hot environment or during exercise, body temperature is controlled by the evaporation of sweat. The deficit in electrolytes can be preserved by means of sodium reabsorption from the duct of sweat glands. Evidence supporting blood osmolality as a hydration assessment marker usually comes from studies that integrate a sweat-loss model of hypertonic-hypovolemia in young, fit and healthy individuals. In this regard, blood osmolality is unsuitable to detect isotonic-hypovolemia often following from illness and medications (for example, diuretics) in a clinical setting.47

Tear fluid is a complex solution intended to sustain the surface of the eye.51 The lacrimal gland secretes tear fluid consisted mainly of water and electrolytes, and human tears have been disclosed to be isotonic with plasma.52

In summary, the setting and the method of collecting respectively accessing body fluids determine the use of a biochemical hydration assessment marker. Compared to other body fluids (for example, blood) obtaining a sample of saliva is one of the simplest ways to collect body fluids. During exercise and heat exposures, saliva might be an effective index to evaluate hydration status but seems to be highly variable and should be carefully used as a substitute marker of other biochemical hydration assessment markers. The lack of a baseline measurement and the time-consuming collection of sweat makes it more difficult to evaluate dehydration and to make a statement about the hydration status at a particular time. The collection procedure of tears shows little discomfort to the participants and is easy to access. TEosm can evalute changes in hydration status and increase with dehydration and recorded changes in BPosm with comparable utility to URsg. But with only two included studies, it has to be further determined whether TEosm is sensitive enough to evaluate dehydration at the individual level as its validity and reliability. 041b061a72


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