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Abstract

It is known that high-altitude trips cause nasal congestion, impaired nasal mucociliary transport rate, and increased nasal resistance, due to decreased partial oxygen pressure and dry air. It is also known that olfactory perception is affected by barometric pressure and humidity. The aim of the present study was to investigate whether olfactory function changes in relation to high altitude in a natural setting. The present study included 41 volunteers with no history of chronic rhinosinusitis or nasal polyposis. The study group consisted of 31 men (76 %) and 10 women (24 %); the mean age of the study population was 38 ± 10 years. Olfactory testing was conducted using "Sniffin' Sticks" at a high altitude (2,200 ms) and at sea level. Odor test scores for threshold and identification were significantly better at sea level than at high altitude (p < 0.001). The major finding of this investigation was that olfactory functions are decreased at high altitudes.

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... The sense of smell was evaluated in all participants by means of the "Sniffin' Sticks" (Sniffin' Sticks, Burghart GmbH, Wedel, Germany) [13,14] test battery, which tests psychological and physical aspects of olfactory function with felttipped pens. The various odours were presented as follows: the examiner took off the cap of each stick and presented it at a distance of around 1-2 cm away from the participant's nostrils. ...
... The participants had control over how long 1 3 they needed to decide on the odour presented. Scoring for the test depended on adding up the number of odours appropriately described by the test subjects [13,14]. ...
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PurposeAt the time of writing, there is a pandemic affecting virtually every country on Earth. There is considerable discussion amongst clinicians as well as lay people about anosmia and ageusia in COVID-19 sufferers. We aimed to report the results from comprehensive olfactory and gustatory testing in a series of hospital in-patients.Methods The prospective study evaluated 81 individuals with a COVID-19 infection, as confirmed by 2019 n-cov Real-Time PCR laboratory testing. The control group consisted of forty individuals with COVID-19 negative. Olfactory and gustatory testings were carried out by an examiner utilizing stringent safety standards and wearing full personal protective equipment. The results obtained in the case group were then compared with those obtained for the controls.ResultsIn the case group, 41(50.6%) of patients were male and 40 (49.4%) were female, mean age of 54.16 ± 16.98 years (18–95). In the control group, 21 (52.5%) of subjects were male and 19 (47.5%) were female, and mean age was 55 ± 15.39 years (18–90). Fifty (61.7%) COVID-19-positive patients had complaints related to olfaction. The distribution of olfactory symptoms in the case group differed at the level of statistical significance from the control group (p < 0.001). Turning to gustatory abnormalities, within the case group, 22 individuals (27.2%) had taste malfunction. A statistically significant difference was found in the distribution of gustatory abnormalities between cases and controls (p < 0.001).Conclusions Olfactory and gustatory dysfunctions are strongly associated with SARS-CoV-2 infection. Hyposmia with or without hypogeusia is potentially a reliable indicator of latent COVID-19.
... In line with these results, Kuehn et al. and Altundag et al. postulated a decrease of olfactory sensitivity under hypobaric conditions (comparable height approx. 2700 m) or at high altitude using the Sniffin' Sticks [8,9]. Reasons for the reduced olfactory sensitivity were seen in the expansion of gases under lower pressure leading to a lower amount of odor molecules in a certain gas volume. ...
... The aim of the current research study was to investigate the influence of normobaric hypoxia on olfactory and gustatory performance scores. In line with the existing literature we found a decrease in olfactory sensitivity under normobaric hypoxia (see Fig. 1) whereas ability to discriminate odors was not impaired [7,9,17]. Further, overall intensity ratings significantly decreased under normobaric hypoxia, whereas pleasantness ratings revealed no differences between the two conditions. ...
Article
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.
... Therefore, we performed genetic and cytologic analyses to examine the effects of CIH exposure on olfaction in mice using our hypoxia model. In line with the existing literature, we observed a decrease in olfactory sensitivity under hypoxia [11][12][13]. ...
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Purpose Obstructive sleep apnea (OSA) is characterized by repetitive upper airway collapse during sleep, which induces chronic intermittent hypoxia (CIH). CIH results in low-grade inflammation, sympathetic overactivity, and oxidative stress. Nevertheless, it remains unclear how exposure to CIH affects olfaction. The purpose of this study was, therefore, to investigate the cytotoxic effects of CIH exposure on mouse olfactory epithelium and the underlying pathophysiology involved. Methods Mice were randomly divided into four groups: Youth mouse (You) + room air (RA), You + intermittent hypoxia (IH), Elderly mouse (Eld) + RA, and Eld + IH (n = 6 mice/group). Mice in the two hypoxia groups were exposed to CIH. The control condition involved exposure to room air (RA) for 4 weeks. Olfactory neuroepithelium was harvested for histologic examination, gene ontology analysis, quantitative real-time polymerase chain reaction (qRT-PCR), and western blotting. Results Based on qRT-PCR analysis, olfactory marker protein (OMP), Olfr1507, ADCY3, and GNAL mRNA levels were lower, whereas NGFR, CNPase, NGFRAP1, NeuN, and MAP-2 mRNA levels were higher in the You + IH group than in the You + RA group. Olfactory receptor-regulated genes, neurogenesis-related genes and immunohistochemical results were altered in nasal neuroepithelium under CIH exposure. Conclusions Based on genetic and cytologic analysis, CIH impacted the olfactory neuroepithelium in an age-dependent manner. Our findings suggest that CIH-induced damage to the olfactory neuroepithelium may induce more severe change in the youth than in the elderly.
... An interesting observation is the improvement in olfactory sensitivity during fasting [60] and, incidentally, 5-HT in fasting state is significantly increased [61]. Another interesting observation is the disruption of olfactory (and also gustatory) functions at high altitude [62,63] and it is known that low oxygen at high altitude lowers 5-HT as the synthesis of 5-HT from tryptophan is hindered because the enzyme tryptophan hydroxylase involved in the synthesis of 5-HT requires molecular oxygen [64,65]. Also, anosmia or hyposmia is more frequent in migraineurs [66] who have chronic low 5-HT level (the 5-HT level only rises during the attack) [67]. ...
Article
Different mechanisms forwarded to understand anosmia and ageusia in coronavirus patients are not adequate to explain reversible anosmia and ageusia, which are resolved quickly. In addition, the reason behind the impaired chemesthetic sensations in some coronavirus patients remains unknown. In the present paper it is proposed that SARS-CoV-2 patients suffer from depletion of tryptophan, as ACE2, a key element in the process of absorption of tryptophan from the food, is significantly reduced in the patients as coronavirus uses ACE2 as the receptor to enter the host cells. The tryptophan depletion leads to a deficit of serotonin (5-HT) in SARS-COV-2 patients because tryptophan is the precursor in the synthesis of 5-HT. Such 5-HT deficiency can explain anosmia, ageusia and dysfunctional chemesthesis in COVID-19, given the fact that 5-HT is an important neuromodulator in the olfactory neurons, taste receptor cells and transient receptor potential channels (TRP channels) involved in chemesthesis. In addition, 5-HT deficiency worsens silent hypoxemia and depresses hypoxic pulmonary vasoconstriction leading to increased severity of the disease. Also, the levels of anti-inflammatory melatonin (synthesized from 5-HT) and nicotinamide adenine dinucleotide (NAD⁺, produced from niacin whose precursor is the tryptophan) might decrease in coronavirus patients resulting in the aggravation of the disease. Interestingly, selective serotonin reuptake inhibitors (SSRIs) may not be of much help in correcting the 5-HT deficiency in COVID-19 patients, as their efficacy goes down significantly when there is depletion of tryptophan in the system. Hence, tryptophan supplementation may herald a radical change in the treatment of COVID-19 and accordingly, clinical trials (therapeutic / prophylactic) should be conducted on coronavirus patients to find out how tryptophan supplementation (oral or parenteral, the latter in severe cases where there is hardly any absorption of tryptophan from the food) helps in curing, relieving or preventing the olfactory, gustatory and chemesthetic dysfunctions and in lessening the severity of the disease.
... At higher altitudes (>3000 m), serious consequences of high-altitude cerebral edema (HACE, at >3000 m) and high-altitude pulmonary edema (HAPE, at >4000 m) would occur. In addition to the respiratory and cardiac outcomes, sustained low barometric oxygen pressure adversely affects body weight, muscle structure, exercise capacity, energy metabolism, mental functioning, and olfactory sensation in low-altitude accustomed people when they are certainly exposed to hypoxia (Leon-Velarde et al. 2005;Naeije 2010;Sargent et al. 2013;Altundag et al. 2014;Ferezou et al. 1993;Ou and Leiter 2004). It has the heaviest impairments during perinatal life, increases the risk of intrauterine growth restriction and pre-eclampsia, and influences neonatal survival (Crocker et al. 2020;Niermeyer et al. 2009;Moore et al. 2004;Julian and Moore 2019). ...
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The natural hypoxic experiments performed on native human populations residing the highlands provide an excellent opportunity to learn how environmental challenges reform human genetic architecture. In this chapter, we give a broad overview of current evidence for physiological and genetic adaptations based on three renowned highland groups from the Qinghai-Tibet Plateau, the Andes Altiplano, and the Ethiopian Plateau. We summarize several well-recognized adaptive signals strongly suggested by early studies and highlight recent findings accumulating rapidly and broadly with whole-genome sequencing and multi-omics approaches. These studies offer a glimpse into the complex driving forces and mechanisms of adaptive evolution and imply the genetic predisposition of relevant diseases and possible therapeutic strategies.
... Previous studies have shown that atmospheric pressure has an effect on the sense of smell. Hypobaric conditions negatively influence olfaction, while hyperbaric conditions seem to be associated with an improvement [3][4][5][6]. Most of these studies were performed in hypobaric and hyperbaric chambers, simulating conditions at high altitude (or below sea level). ...
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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.
... An altered immunopathological characteristic have been demonstrated in CRS patients dwelling at high altitudes, suggesting a possible modulatory role of altitude in immunopathogenesis of CRS [41]. In addition, cold temperatures and dry air related to high altitude regions have been demonstrated to impair olfactory functions [42] which is an established risk factor for CRS [19]. To add to this, altitude also plays a role in vitamin D metabolism and multiple studies have found a lower vitamin D level in apparently healthy population residing at high altitudes [43,44]. ...
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Purpose: To evaluate the association of serum vitamin D levels with chronic rhinosinusitis (CRS) in population residing at high altitudes and to assess its correlation with severity of CRS. Methods: A prospective case-control study comparing vitamin D in 60 cases (30 with nasal polyposis and 30 without) and 31 controls was carried out. Correlation of vitamin D with severity of disease (Lund Mackay CT/LMS and endoscopic Lund Kennedy scores/LKS) was assessed using Spearman's correlation (rs). Logistic regression analysis using vitamin D and confounding factors (Age and gender only, as other variables like smoking, bronchial asthma were exclusion criteria) as dependent and CRS (presence/absence) as independent variable, was also conducted. Results: A significantly lower vitamin D levels were found in CRS (14.60 ± 7.68 ng/ml), CRSwNP (13.70 ± 7.88 ng/ml) and CRSsNP (15.49 ± 7.50 ng/ml), when compared to controls (29.36 ± 7.49 ng/ml). Non allergic cases when compared with controls, showed significantly lower vitamin D levels (13.91 ± 6.78 compared to 29.36 ± 7.49 ng/ml). LMS and LKS in CRS showed a moderate correlation with vitamin D (rs: - 0.604 for LMS, rs: - 0.595 for LKS). Logistic regression analysis showed vitamin D levels (Odds-Ratio 0.783) to be an independent predictive factor of CRS. Conclusion: A significantly lower vitamin D level is associated with CRS, irrespective of presence or absence of nasal polyposis in adults residing at high altitudes. Vitamin D is an independent predictive factor for CRS. There is an inverse moderate correlation of severity of CRS with vitamin D.
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Physiological adaptation of tree shrews (Tupaia belangeri) to changing environmental temperature has been reported in detail. However, the T. belangeri origin (mainland or island), population history, and adaptation to historical climate change remain largely unknown or controversial. Here, for the first time, we sequenced the simplified genome of 134 T. belangeri individuals from 12 populations in China and further resequenced one individual from each population. Using population genomic approaches, we first observed considerable genetic variation in T. belangeri. Moreover, T. belangeri populations formed obvious genetic structure and reflected different demographic histories; they generally exhibited high genetic diversity, although the isolated populations had relatively low genetic diversity. The results presented in this study indicate that T. b. modesta and T. b. tonquinia were separated recently and with a similar population dynamics. Second, physical barriers rather than distance were the driving factors of divergence, and environmental heterogeneity may play an important role in genetic differentiation in T. belangeri. Moreover, our analyses highlight the role of historical global climates in the T. belangeri population dynamics and indicate that the decrease of the T. belangeri population size may be due to the low temperature. Finally, we identified the olfaction-associated adaptive genes between different altitude populations and found that olfactory-related genes of high-altitude populations were selectively eliminated. Our study provides demographic history knowledge of T. belangeri; their adaption history offers new insights into their evolution and adaptation, and provides valuable baseline information for conservation measures. This article is protected by copyright. All rights reserved
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Travel-related illnesses are those which result from travel by a patient. They may be caused by the motion of travel, moving to higher elevations, an alteration in the climate or by infections that are endemic to a particular region.
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Long-term operations carried out at high altitude (HA) by military personnel, pilots, and astronauts may trigger health complications. In particular, chronic exposure to high altitude (CEHA) has been associated with deficits in cognitive function. In this study, we found that mice exposed to chronic HA (5000 m for 12 weeks) exhibited deficits in learning and memory associated with hippocampal function and were linked with changes in the expression of synaptic proteins across various regions of the brain. Specifically, we found decreased levels of synaptophysin (SYP) (p < 0.05) and spinophilin (SPH) (p < 0.05) in the olfactory cortex, post synaptic density−95 (PSD-95) (p < 0.05), growth associated protein 43 (GAP43) (p < 0.05), glial fibrillary acidic protein (GFAP) (p < 0.05) in the cerebellum, and SYP (p < 0.05) and PSD-95 (p < 0.05) in the brainstem. Ultrastructural analyses of synaptic density and morphology in the hippocampus did not reveal any differences in CEHA mice compared to SL mice. Our data are novel and suggest that CEHA exposure leads to cognitive impairment in conjunction with neuroanatomically-based molecular changes in synaptic protein levels and astroglial cell marker in a region specific manner. We hypothesize that these new findings are part of highly complex molecular and neuroplasticity mechanisms underlying neuroadaptation response that occurs in brains when chronically exposed to HA.
Article
This study examined the influence of hypoxic hypoxia on olfactory sensitivity in humans. Olfactory detection thresholds for n-butanol were studied when the subjects (male volunteers aged 18–20 years without ear, nose, or throat diseases and with low tolerance to hypoxia) breathed a hypoxic gas mixture. To mimic hypoxic hypoxia, participants were asked to breathe a gas mixture containing 10.5% oxygen. The oxygen level in the blood was controlled by the degree of hemoglobin oxygenation, as measured using a Nonin 9843 digital portable pulse oximeter (United States). The results of our study show that with a low fraction of inspired oxygen the olfactory detection thresholds for n-butanol increased (p ≤ 0.01). Therefore, a human olfactory receptor becomes less sensitive under hypoxic hypoxia.
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We agree with Dr. Basnyat that dehydration in the mountains is a concern, but no compelling data confirm that dehydration has a role in acute mountain sickness. The report he cites demonstrated a correlation between lower water intake and acute mountain sickness, but causality could not be established; persons with acute mountain sickness are often nauseated and therefore have reduced fluid intake. The only well-controlled investigation found no effect of hydration status on the development of acute mountain sickness.1 As for the rate of ascent, 600 m per day may indeed be too rapid for some, whereas for others, 400 m per day is agonizingly slow. Such is the problem with offering general guidelines. We cited the article by Dumont et al. only to acknowledge the uncertainty regarding the lowest effective dose of acetazolamide. Unlike Dr. Ogilvie, we consider the conclusion by Dumont et al. invalid, for reasons that have already been described elsewhere.2,3 In fact, 500 mg of acetazolamide per day is helpful during rapid ascent.2,3 Only studies directly comparing different doses of acetazolamide will be able to establish the optimal dose; the meta-analysis of Dumont et al. does not. Dr. White highlights the risk of dexamethasone abuse. Dexamethasone should not be used for routine prophylaxis, since it does not enhance acclimatization, as acetazolamide does. However, it is useful for those who have an intolerance to acetazolamide, preferably in the setting of rapid ascent to a high altitude with no further ascent until acclimatization has occurred. We agree that its use as a performance-enhancing agent at high altitude is dangerous. In addition, dexamethasone does not prevent high-altitude pulmonary edema, a deadly risk for those who push their limit of acclimatization. In response to Dr. O’Brien: we did not mention nitric oxide as a therapeutic agent for high-altitude pulmonary edema because no clinical advantage over oxygen has yet been demonstrated, and its use is impractical in the field.Oxygen is remarkably effective for the rapid resolution of high-altitude pulmonary edema. Whether the finding of Anand et al.4 that oxygen combined with nitric oxide is more effective than either alone for decreasing pulmonary vascular resistance will translate into a clinical benefit remains unknown. Perhaps the combination will prove useful for the occasional victim who does not have a prompt response to oxygen. Only a clinical trial can answer this question.
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High altitude changes human physiology and can result in illnesses such as acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema. The physiological impacts of high-altitude illnesses occur secondary to extravasation of fluid from the intravascular space into the extravascular space during a rapid ascent. Headache, hearing disturbances, vestibular disturbances, epistaxis, sleep apnea, coughing, respiratory tract infections, and nasal obstruction are main ear, nose, and throat complaints of individuals travelling to high altitude. These complaints can cause delays or cancelations in a person's climbing plans. In this article, we review the ear, nose, and throat effects of high altitude based on the relevant literature.
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Exposure to cold dry air induces rhinorrhea and other nasal symptoms in many persons. To evaluate whether this response involves a neurogenic component, we delivered a unilateral cold dry air (UniCDA) nasal challenge to volunteers with previously documented reactivity to cold dry air. We measured their nasal secretory responses bilaterally using small filter paper discs to absorb secretions from the nasal mucosa. UniCDA increased nasal secretion both ipsilateral (p < 0.001) and contralateral (p < 0.001) to the challenge when compared with control challenge. Topical atropine (0.225 mg), a muscarinic antagonist, inhibited ipsilateral secretion (p < 0.002) when given ipsilateral to UniCDA. When atropine was given contralateral to UniCDA, there was a trend toward reduction of contralateral secretion but no effect on ipsilateral secretion. Topical anesthesia with lidocaine given ipsilateral to UniCDA inhibited ipsilateral (p < 0.02) and contralateral (p < 0.05) secretion immediately after challenge. Topical anesthesia did not inhibit methacholine-induced nasal secretion. Thus, UniCDA stimulates reflex secretion both ipsilateral and contralateral to challenge which is inhibitable by interrupting either the efferent or the afferent arm of the reflex arc. This human in vivo model supports the importance of neural mechanisms in airway responsiveness to an environmental stimulus.
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Hypoxia inhibits activity and expression of ion transport proteins of cultured lung alveolar epithelial cells. Here we tested, whether in vivo hypoxia at high altitude (4,559 m) also inhibits lung ion transport. Transepithelial nasal potentials (NP) were determined as a surrogate measure of lung ion transport activity before and during the stay at altitude. In normoxia, total NP was approximately 20% higher in control subjects than in susceptibles to high-altitude pulmonary edema, but there was no difference between groups in amiloride-inhibitable NPs. At high altitude total NP increased 250% in both groups, whereas amiloride-sensitive NP decreased in control subjects only (-80%), and the chloride ion (Cl-)-sensitive portion of NP almost doubled. Because many mountaineers suffer from nasal dryness at high altitude, a control study was performed in normobaric hypoxia (12% oxygen, 6 hours) at a controlled humidity of 50%. In this study, no change in total NP or its amiloride- and Cl-sensitive portions was observed. The increased Cl- secretion at high altitude but no such change in normobaric hypoxia suggests that nasal dryness may stimulate local active Cl- and fluid secretion in the upper respiratory tract. It is therefore uncertain whether similar changes also occur at the alveolar epithelium.
The aim of this study was to investigate the impact of high altitude on nasal and lower airway parameters in a healthy population. This was a prospective study of 61 individuals who climbed to the summit of Mount Kackar, at 3,937 m. Peak nasal inspiratory flow rates were recorded in all participants at sea level and at the summit. In 32 participants who ascended to the summit, sea-level and summit peak expiratory flow rates and olfactory function were evaluated. A rise in altitude significantly decreased peak nasal inspiratory flow by a mean of 27.43%. Mean peak expiratory flow values measured at the summit were 8.94% lower than basal values. Between-value differences were statistically significant (p < 0.001, p < 0.05). At high altitude, there was a significant decrease in olfactory function, as determined by a significant reduction in smell detection (p < 0.05) and smell identification (p < 0.05). The effect of high altitude on nasal function was found to parallel that of the effect on lower airway function, together accounting for an adverse effect on airway flow rates. The nasal mucosa responded to high altitude with an increase in airway resistance and a consequent impaired sense of smell.
The aim of the study was to evaluate the effects of high altitude (HA) on the expiratory nasal sound spectra. The design consisted of a prospective analysis. The study group consisted of 24 otorhinolaryngologists and a student (2 females, 23 males) climber of the mountain of Kackar in Rize, a city located in northeastern Turkey. The elevation of the highest peak of the Kackar Mountain is 3,937 m (12,920 ft) and that of mountain plateaus at about 3,000 m (9,800 ft). Nasal sound spectral analysis was performed on 25 subjects at 700 and 3,937 m, respectively. We found that sound intensity (dB) at high frequency (Hf) was below 18.6 dB in the subjects at low altitude, while the results were found to be above 25.1 dB in the subjects at HA during expiration. A correlation was observed between the degree of HA and 'Odiosoft-rhino' findings at Hf intervals of the subjects. At the top of the mountain, the sound intensities at low and medium frequency were observed to be significantly lower than at low altitude (p < 0.05). We concluded that Hf values of HA were significantly higher than at low altitude because of nasal congestion and also narrowing of the cross-sectional area of the nasal airway. Nasal conchal and mucosal congestion affects airflow through the nasal cavity at HA, transforming it from a laminar pattern to turbulent flow. We found significant increases in the sound intensity level at Hf in the sound spectra at HA. Awareness of the impact of HA in nasal airflow is important in the diagnosis and treatment of nasal obstruction symptoms.
Article
There have been a number of anecdotal reports of rhinitis and nasal obstruction occurring at altitude. To quantify these reports, we investigated nasal obstruction and mucociliary transport in a group of healthy volunteers trekking to Mount Everest Base Camp, Nepal, altitude 5,300 m. Nasal obstruction was estimated by subjective scoring and mucociliary transport was determined by the saccharin method. Subjective assessment showed that nasal obstruction was increased on arrival at 5,300 m in 23 out of 54 subjects, unchanged in 24, and decreased in seven (McNemar's test: chi 2 = 7.5; p < 0.01). The median saccharin time at sea level was 11 min (95% confidence interval (95% CI) 8-17 min) and increased to 60 min (95% CI 27-60 min) on arrival at 5,300 m. Compared to sea level, the saccharin time was prolonged in 25 out of 33 subjects (McNemar's test: chi 2 = 14.7; p < 0.01), and remained prolonged after 2 weeks at altitude (median 60 min; 95% CI 38-60 min). These results confirm the subjective feelings of nasal obstruction and show that nasal mucociliary transport times are increased at altitude. The mechanisms of these findings are not clear, but nasal obstruction may impede breathing and adversely affect performance at altitude.
Article
'Sniffin' Sticks' is a new test of nasal chemosensory performance based on pen-like odor dispensing devices. It comprises three tests of olfactory function, namely tests for odor threshold (n-butanol, testing by means of a single staircase), odor discrimination (16 pairs of odorants, triple forced choice) and odor identification (16 common odorants, multiple forced choice from four verbal items per test odorant). After extensive preliminary investigations the tests were applied to a group of 104 healthy volunteers (52 female, 52 male, mean age 49.5 years, range 18-84 years) in order to establish test-retest reliability and to compare them with an established measure of olfactory performance (the Connecticut Chemosensory Clinical Research Center Test, CCCRC). Performance decreased with increasing age of the subjects (P < 0.001). Coefficients of correlation between sessions 1 and 2 were 0.61 for thresholds, 0.54 for discrimination and 0.73 for identification. Butanol thresholds as obtained with the CCCRC increased as a function of age; this relation to the subjects' age was not found for the CCCRC odor identification task. The test-retest reliability for CCCRC thresholds was 0.36, for odor identification it was 0.60. It is concluded that 'Sniffin' Sticks' may be suited for the routine clinical assessment of olfactory performance.
Article
"Sniffin' Sticks" is a test of nasal chemosensory performance that is based on penlike odor-dispensing devices. It is comprised of three tests of olfactory function: tests for odor threshold, discrimination and identification. Previous work has already established its test-retest reliability and validity in comparison to established measures of olfactory sensitivity. The results of this test are presented as a composite TDI score--i.e., the sum of results obtained for threshold, discrimination and identification measures. The present multicenter investigation aimed at providing normative values in relation to different age groups. To this end, 966 patients were investigated in 11 centers. An additional study tried to establish values for the identification of anosmic patients, with 70 anosmics investigated in five specialized centers where the presence of anosmia was confirmed by means of olfactory evoked potentials. For healthy subjects, the TDI score at the 10th percentile was 24.5 in subjects younger than 15 years, 30.3 for ages from 16 to 35 years, 28.8 for ages from 36 to 55 years and 27.5 for subjects older than 55 years. While these data can be used to estimate individual olfactory abilities in relation to a subject's age, hyposmia was defined as the 10th percentile score of 16- to 35-year-old subjects. Our latter study revealed that none of 70 anosmics reached a TDI score higher than 15. This score of 15 is regarded as the cut-off value for functional anosmia. These results provide the basis for the routine clinical evaluation of patients with olfactory disorders using "Sniffin' Sticks."
Article
Despite the presence of a number of anecdotal reports in the mountaineering literature, mucociliary dysfunction at high altitude has received little scientific attention. However, the dry, cold, thin air at high altitude has the potential to undermine normal mucociliary function. This seems increasingly likely in mountaineers who also experience dehydration, nasal obstruction, and extremes of aerobic respiration when climbing in such environments. These factors may result in a number of clinical conditions that range from sore throats and coughs commonly seen at altitude to rarer cases of bronchiolar collapse and lung atelectasis. The purpose of this review is to discuss the etiology of mucociliary dysfunction at altitude and outline a number of potential solutions to the problems this phenomenon presents.
Article
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.
ed) Wilderness medicine, 5th edn
  • P H Hackett
  • R C Roach
  • PH Hackett
Hackett PH, Roach RC (2007) High-altitude medicine. In: Auerbach PS (ed) Wilderness medicine, 5th edn. Mosby Elsevier, Philadelphia