The effect of temperature, humidity and peak inspiratory nasal flow on olfactory thresholds

An automated contact model for transmission of dry surface biofilms of Acinetobacter baumannii in healthcare

BACKGROUND

Dry surface biofilms (DSBs) have been recognized across environmental and equipment surfaces in hospitals and could explain how microbial contamination can survive for an extended period and may play a key role in the transmission of hospital-acquired infections. Despite little being known on how they form and proliferate in clinical settings, DSB models for disinfectant efficacy testing exist.

AIM

In this study we develop a novel biofilm model to represent formation within hospitals, by emulating patient to surface interactions.

METHODS

The model generates a DSB through the transmission of artificial human sweat (AHS) and clinically relevant pathogens using a synthetic thumb capable of emulating human contact. The DNA, glycoconjugates and protein composition of the model biofilm, along with structural features of the micro-colonies was determined using fluorescent stains visualized by epifluorescence microscopy and compared with published clinical data.

RESULTS

Micrographs revealed the heterogeneity of the biofilm across the surface; and reveal protein as the principal component within the matrix, followed by glycoconjugates and DNA. The model repeatably transferred trace amounts of micro-organisms and AHS, every 5 min for up to 120 h on to stainless-steel coupons to generate a biofilm model averaging 1.16 × 103 cfu/cm2 falling within the reported range for clinical DSB (4.20 × 102 to 1.60 × 107 bacteria/cm2).

CONCLUSION

Our in vitro DSB model exhibits many phenotypical characteristics and traits to those reported in situ. The model highlights key features often overlooked and the potential for downstream applications such as antibiofilm claims using more realistic microbial challenges.

Association between ambient temperature and chronic rhinosinusitis

BACKGROUND

Chronic exposure to particulate matter air pollution (PM2.5 ) is associated with chronic rhinosinusitis (CRS). Elevated ambient temperature may increase PM2.5 levels and thereby exacerbate sinonasal symptoms. This study investigates the association between high ambient temperature and the risk of CRS diagnosis.

METHODS

Patients with CRS were diagnosed at Johns Hopkins hospitals from May to October 2013-2022, and controls were matched patients without CRS meanwhile. A total of 4752 patients (2376 cases and 2376 controls) were identified with a mean (SD) age of 51.8 (16.8) years. The effect of maximum ambient temperature on symptoms was estimated with a distributed lag nonlinear model (DLNM). Extreme heat was defined as 35.0°C (95th percentile of the maximum temperature distribution). Conditional logistic regression models estimated the association between extreme heat and the risk of CRS diagnosis.

RESULTS

Exposure to extreme heat was associated with increased odds of exacerbation of CRS symptoms (odds ratio [OR] 1.11, 95% confidence interval [CI] 1.03-1.19). The cumulative effect of extreme heat during 0-21 lag days was significant (OR 2.37, 95% CI 1.60-3.50) compared with the minimum morbidity temperature (MMT) at 25.3°C. Associations were more pronounced among young and middle-aged patients and patients with abnormal weight.

CONCLUSIONS

We found that short-term exposure to high ambient temperature is associated with increased CRS diagnosis, suggesting a cascading effect of meteorological phenomena. These results highlight climate change's potentially deleterious health effects on upper airway diseases, which could have a significant public health impact.

Orientation in the European common frogs Rana temporaria Linnaeus, 1758 during their first wintering migration

The orientation of naive animals during their first migration is extensively studied in birds and sea turtles, whereas the data for other groups such as amphibians are still scarce. To date, it is unknown whether young-of-the-year anurans perform a random or directional search for the hibernation sites, and what cues (global or local) do they use. We conducted a series of field experiments to study the orientation behavior of juvenile common frogs during their first wintering migration. We captured 1614 froglets from two subpopulations with different directions of migration and assessed their orientation in large circular outdoor arenas (20 m in diameter) on the opposite sides of the river. Before the migration, froglets used local cues and moved back towards the forest (summer habitat). At the start of migration, the froglets do not move randomly: they navigate towards the river using local cues; later, however, before approaching the hibernation site, they memorize the compass direction of migration and follow it using global cues. Orientation along a memorized compass heading begins to dominate in the hierarchy of orientation mechanisms, and this predominance is maintained even after reaching the hibernation site. Unlike in birds, no innate direction of migration was found.

Principles of odor coding in vertebrates and artificial chemosensory systems

The biological olfactory system is the sensory system responsible for the detection of the chemical composition of the environment. Several attempts to mimic biological olfactory systems have led to various artificial olfactory systems using different technical approaches. Here we provide a parallel description of biological olfactory systems and their technical counterparts. We start with a presentation of the input to the systems, the stimuli, and treat the interface between the external world and the environment where receptor neurons or artificial chemosensors reside. We then delineate the functions of receptor neurons and chemosensors as well as their overall I-O relationships. Up to this point, our account of the systems goes along similar lines. The next processing steps differ considerably: while in biology the processing step following the receptor neurons is the "integration" and "processing" of receptor neuron outputs in the olfactory bulb, this step has various realizations in electronic noses. For a long period of time, the signal processing stages beyond the olfactory bulb, i.e., the higher olfactory centers were little studied. Only recently there has been a marked growth of studies tackling the information processing in these centers. In electronic noses, a third stage of processing has virtually never been considered. In this review, we provide an up-to-date overview of the current knowledge of both fields and, for the first time, attempt to tie them together. We hope it will be a breeding ground for better information, communication, and data exchange between very related but so far little connected fields.

Clinical assessment of olfactory function

Approximately 5% of the general population is affected by functional anosmia with approximately additional 15% exhibiting decreased olfactory function. Many of these individuals ask for help. Because the subjective rating of olfactory function is biased, assessment of olfactory function is important. Olfactory measurements are needed for patient counseling and the tracking of changes in the sense of smell over time. The present review provides an overview of frequently used psychophysical tests for olfactory function, discusses differences between threshold and suprathreshold aspects of olfactory function, and gives examples on how to apply psychophysical tests.

The sense of smell is not strongly affected by ambient temperature and humidity: a prospective study in a controlled environment

INTRODUCTION

The sense of smell is dependent on environmental conditions. In this study, we analysed the effect of temperature and humidity on the ability to smell.

METHODS

Using the controlled setting of a hypobaric climate chamber 50 healthy participants (40 men, 10 women; mean age of 33 years) completed repeated testing in 4 different settings-cold/dry, cold/humid, warm/dry, warm/humid. The temperatures were 20-35 °C, respectively, and the humidity was set at 30-75%. Testing was performed using the "Sniffin' Sticks" test battery (odour threshold, discrimination and identification) in a semi-randomised order and in controlled atmospheric pressure conditions.

RESULTS

The analysis showed that neither temperature nor humidity had a significant effect on olfactory test results. This indicates that olfactory functions in healthy, young subjects with an excellent sense of smell are not strongly affected by temporary changes in environmental conditions.

Factors affecting flavor perception in space: Does the spacecraft environment influence food intake by astronauts?

The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that astronauts typically consume only 80% of their daily calorie requirements when in space. This is despite daily exercise regimes that keep energy usage at very similar levels to those found on Earth. This calorie deficit seems to have little effect on astronauts who spend up to 12 months on the ISS, but given that a mission to Mars would take 30 to 36 months to complete, there is concern that a calorie deficit over this period may lead to adverse effects in crew members. The key question is why astronauts undereat when they have a supply of food designed to fully deliver their nutritional needs. This review focuses on evidence from astronauts that foods taste different in space, compared to on Earth. The underlying hypothesis is that conditions in space may change the perceived flavor of the food, and this flavor change may, in turn, lead to underconsumption by astronauts. The key areas investigated in this review for their potential impact on food intake are the effects of food shelf life, physiological changes, noise, air and water quality on the perception of food flavor, as well as the link between food flavor and food intake.

When the Nose Doesn't Know: Canine Olfactory Function Associated With Health, Management, and Potential Links to Microbiota

The impact of health, management, and microbiota on olfactory function in canines has not been examined in review. The most important characteristic of the detection canine is its sense of smell. Olfactory receptors are primarily located on the ethmoturbinates of the nasal cavity. The vomeronasal organ is an additional site of odor detection that detects chemical signals that stimulate behavioral and/or physiological changes. Recent advances in the genetics of olfaction suggest that genetic changes, along with the unique anatomy and airflow of the canine nose, are responsible for the macrosmia of the species. Inflammation, alterations in blood flow and hydration, and systemic diseases alter olfaction and may impact working efficiency of detection canines. The scientific literature contains abundant information on the potential impact of pharmaceuticals on olfaction in humans, but only steroids, antibiotics, and anesthetic agents have been studied in the canine. Physical stressors including exercise, lack of conditioning, and high ambient temperature impact olfaction directly or indirectly in the canine. Dietary fat content, amount of food per meal, and timing of meals have been demonstrated to impact olfaction in mice and dogs. Gastrointestinal (GI) microbiota likely impacts olfaction via bidirectional communication between the GI tract and brain, and the microbiota is impacted by exercise, diet, and stress. The objective of this literature review is to discuss the specific effects of health, management, and microbiota shifts on olfactory performance in working canines.

Effects of diversity in olfactory environment on children's sense of smell

Diversity in children's everyday olfactory environment may affect the development of their olfactory abilities and odor awareness. To test this, we collected data on olfactory abilities using the Sniffin' Sticks and odor awareness with Children's Olfactory Behaviors in Everyday Life Questionnaire in 153 preschool children and retested them one and a half year later. Parents completed an inventory on children's exposure to a variety of odors and on their own odor awareness using the Odor Awareness Scale. We controlled for the effects of age and verbal fluency on the children's performance. We found that the children's odor identification and discrimination scores differed as a function of parental odor awareness. Although these effects were rather small, they were commensurate in size with those of gender and age. To the best of our knowledge, this study is the first to present evidence that diversity in children's olfactory environment affects variation in their olfactory abilities and odor awareness. We suggest that future studies consider the long-term impact of perceptual learning out of the laboratory and its consequences for olfactory development.

Reduction of olfactory sensitivity during normobaric hypoxia

OBJECTIVE

Acute mountain sickness (AMS) is caused by a low partial pressure of oxygen and may occur above 2500m. The aim of this research was to evaluate olfactory and gustatory abilities of healthy subjects during baseline conditions and after seven hours of normobaric hypoxia.

METHODS

Sixteen healthy subjects were assessed using the Sniffin' Sticks, as well as intensity and pleasantness ratings. Gustatory function was evaluated utilizing the Taste Strips. Experiments were carried out under baseline conditions (518m altitude) followed by a second testing session after seven hours of normobaric hypoxia exposure (comparable to 4000m altitude).

RESULTS

During normobaric hypoxia olfactory sensitivity and intensity estimates were significantly reduced.

CONCLUSIONS

We conclude that normobaric hypoxia leads to a significant decrease of olfactory sensitivity and intensity ratings.

Quantifying Search Dog Effectiveness in a Terrestrial Search and Rescue Environment

OBJECTIVE

There is widespread and longstanding use of dogs in land search and rescue (SAR) operations, and their effectiveness is well accepted within the SAR community. However, very little published research exists that quantifies that effectiveness within a realistic SAR environment.

METHODS

This study included 25 experiments, conducted between October 2013 and February 2014 with 10 dog/handler pairs, using randomized target placement to calculate the ratio of hits, misses, and false positives per dog. Each dog was fitted with a GPS receiver to record their paths and ambient temperature. Wind strength and humidity were recorded throughout each run.

RESULTS

There was no identifiable correlation between humidity, temperature, or wind speed and effectiveness, but the age of the dog has a small positive correlation. Using a standard effectiveness formula, basic descriptive statistics were generated, which showed that the dogs tested were 76.4% successful overall, with an effectiveness of 62.9%. Dogs covered a mean distance 2.4 times greater than their human handlers but travelled at roughly average human walking speed.

CONCLUSIONS

This work represents a first attempt to quantify and understand levels of performance in lowland search dogs, and these results need to be understood within that context. A repeatable experimental framework has been demonstrated and provides a foundation for further work in this area.

A brief history of olfaction and olfactometry

The sense of smell has been a cause for speculation and fascination over the centuries. An appreciation of odours has been deeply rooted in many cultures, including ancient civilisations such as the Egyptians. The level of understanding of the anatomy and physiology of olfaction which our ancestors had was slight, and much remains to be discovered. This paper explores the progression of knowledge over the years to the present day. Particular emphasis is placed on odour classification and olfactometry, and on the techniques whereby great scientific minds have sought to quantify that human sense which is arguably least quantifiable. A review of some of the current methods of olfactometry is included within this remit.

The superosmic phenomenon

BACKGROUND

Olfaction studies in the institution of Department of Otorhinolaryngology at Leicester Royal Infirmary have detected a previously unreported, variable phenomenon--'superosmia'--in which subjects' olfaction threshold concentrations are up to 100,000 smaller than the average value.

OBJECTIVES

The aim of this report is to define and quantify this phenomenon.

METHODS

Two hundred and thirty subjects, who had been screened for active nasal pathology (age range 20-60 years), underwent individual olfactory threshold tests for phenylethyl alcohol or eucalyptol, using a computer-driven olfactometer in a controlled laboratory setting. Some tests were single tests and others were repeated on a small cohort.

RESULTS

Two per cent of subjects demonstrated the superosmic phenomenon on single testing, and 10 per cent demonstrated this phenomenon on variable occasions during repeated testing. The superosmic phenomenon was defined by: (1) confident olfactory perception of a threshold at least equal to if not greater than three threshold levels below the subject's average threshold; (2) repeated perception of the odour at this level for at least 10 responses (1:1024 probability of chance finding); and (3) (where time permitted) a sudden, rapid loss of superosmia.

CONCLUSIONS

Superosmia is a distinct phenomenon, the stimulus or mechanism of which is currently the subject of further research. The enhancement of olfactory ability may be possible through activation of an accessory pathway or modulation of the existing olfactory apparatus.

Olfactory clearance: what time is needed in clinical practice?

Objective:

To determine olfactory adaptation and clearance times for healthy individuals, and to assess the effect of common variables upon these parameters.

Study design and setting:

Fourteen healthy volunteers were recruited for a series of tests. Their initial olfactory threshold levels for phenethyl alcohol were determined. After olfactory exposure to a saturated solution of phenethyl alcohol (i.e. olfactory adaptation), the time taken for subjects to return to their initial olfactory threshold was then recorded (i.e. olfactory clearance). Visual analogue scale scores for subjective variables were also recorded.

Results:

The 14 subjects performed 120 tests in total. Despite consistent linear trends within individuals, olfactory clearance times varied widely within and between individuals. The mean olfactory clearance time for phenethyl alcohol was 170 seconds (range 81–750). Univariate analysis showed a relationship between olfactory clearance times and age (p = 0.031), symptoms (p = 0.029) and mood (p = 0.048).

Conclusions:

When testing a person's sense of smell in a clinical setting, recent exposure to similar smells should be noted, and a period of 15 minutes needs to be allowed before retesting if using phenethyl alcohol. Other variables need not be controlled, but greater clearance time may be needed for older patients.

Changes of pressure and humidity affect olfactory function

The present study aimed at investigating the question whether olfactory function changes in relation to barometric pressure and humidity. Using climate chambers, odor threshold and discrimination for butanol were tested in 75 healthy volunteers under hypobaric and hyperbaric, and different humidity conditions. Among other effects, olfactory sensitivity at threshold level, but not suprathreshold odor discrimination, was impaired in a hypobaric compared to a hyperbaric milieu, and thresholds were lower in humid, compared to relatively dry conditions. In conclusion, environmental conditions modulate the sense of smell, and may, consecutively, influence results from olfactory tests.

What is the short term effect of perfumes on olfactory thresholds?

OBJECTIVES

Body sprays and perfumes are commonly worn by patients attending ENT out-patients clinics. Their effect on performance in olfactory testing is unknown. The aim of this study was to determine whether olfactory thresholds are altered by the presence of such fragrances.

MATERIALS AND METHODS

One hundred and sixty healthy volunteers, aged 18 to 65 years, underwent olfactory thresholds testing. Each was then exposed to one of four strong perfumes, applied in a facemask for two minutes, and the thresholds were retested.

RESULTS AND ANALYSIS

All olfactory thresholds worsened after being exposed to the strong perfumes of Lynx and Impulse body sprays, with the strongest effect being on olfactory detection of phenylethyl alcohol (p<0.001).

CONCLUSIONS

Strong perfumes can have a negative effect on olfactory thresholds.

SIGNIFICANCE

Patients attending olfactory threshold testing need to be advised not to wear body sprays or perfumes.

Normative Values of Olfactory Function Testing Using the ???Sniffin??? Sticks???

OBJECTIVES

Quantitative olfactory assessment is often neglected in clinical practice, although olfactory loss can assist to diagnosis and may lead to significant morbidity. "Sniffin' Sticks" is a modern test of nasal chemosensory performance that is based on penlike odor-dispensing devices. It consists of three tests of olfactory function: odor threshold, odor discrimination, and odor identification. The results of this test may be presented as a composite threshold-discrimination-identification (TDI) score. The aim of this study was first to develop normative data of olfactory function for the Greek population using this test and second to relate olfactory performance to age, sex, and side examined.

STUDY DESIGN

The authors conducted a prospective clinical trial.

METHODS

A total of 93 healthy subjects were included in the study, 48 males and 45 females, mean age of 44.5 years (range, 6-84 years).

RESULTS

A database of normal values for olfactory testing was established for the Greek population. Females performed better than males and older subjects performed less efficiently in all tests. We also found a right nostril advantage compared with the left. Additionally, scores obtained from bilateral presentation were similar with scores obtained from the nostril with the better performance.

CONCLUSIONS

The "Sniffin' Sticks" can be used effectively in the Greek population to evaluate olfactory performance. Mean values of olfactory tests obtained were better in comparison with data from settings located in central and northern Europe.

Which solvent for olfactory testing?

The physical properties of any carrier can deteriorate over time and thus alter the results in any olfactory test. The aim of this study was to evaluate clinically potential solvents as a clean odourless carrier for olfactory testing. Sweet almond oil, pure coconut oil, pure peach kernel oil, dipropylene glycol, monopropylene glycol, mineral oil and silicone oil were studied. The experimentation was conducted in two parts. First, an olfactory device was used to conduct air through the solvents on a weekly basis using a cohort of six volunteers to assess the perceived odour of each solvent at weekly intervals. Secondly a cross-reference test was performed using small bottled solutions of phenylethyl-alcohol and 1-butanol in 10-fold dilutions to compare any perceived difference in concentrations over a period of 8 weeks. We concluded that mineral oil is the most suitable carrier for the purpose of olfactory testing, possessing many desirable characteristics of an olfactory solvent, and that silicone oil may provide a suitable alternative for odorants with which it is miscible.