Ear, nose, and throat effects of high altitude

Do Flights Affect Hearing in Hot Air Balloon Pilots?

PURPOSE

This study aimed to reveal occupational effects on the hearing of hot air balloon (HAB) pilots and examine the relationship between the duration of experience and these effects.

METHOD

This study included 31 male HAB pilots and a control group of 32 male participants. Tympanometry, eustachian tube function (ETF) test, pure-tone audiometry, and transient evoked otoacoustic emission (TEOAE) tests were performed.

RESULTS

Pure-tone audiometry results were significantly worse at 125, 500, and 6000 Hz in the right ear and 125, 500, 4000, and 6000 Hz in the left ear in the HAB group than the control group. Although tympanometry evaluation parameters did not differ between the HAB and control groups, ETF test was significantly worse in the HAB group than the controls bilaterally. TEOAE results were significantly worse at 1000, 2000, and 4000 Hz in the right ear and 4000 Hz in the left ear in the HAB group than the controls. There was a significant positive correlation for 125, 4000, 6000, and 8000 Hz between the duration of experience and right ear hearing thresholds. For the left ear, the duration of experience showed a significant positive correlation at 3000, 4000, 6000, and 8000 Hz. When the relationship between the duration of experience and TEOAE results was evaluated, a significant negative correlation was found at 4000 Hz in the left ear.

CONCLUSION

In HAB pilots, in whom eustachian tube dysfunction is quite common, noise and high altitude affected hearing, especially low and high frequencies, and the duration of experience was found to be associated with hearing thresholds.

Auditory function in humans at high altitude. A scoping review

PURPOSE

High-altitude (HA) affects sensory organ response, but its effects on the inner ear are not fully understood. The present scoping review aimed to collect the available evidence about HA effects on the inner ear with focus on auditory function.

METHODS

The scoping review was conducted following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis extension for scoping reviews. PubMed, Scopus, and Web of Science electronic databases were systematically searched to identify studies conducted in the last 20 years, which quantified in healthy subjects the effects of HA on auditory function.

RESULTS

The systematic search identified 17 studies on a total population of 888 subjects (88.7% male, age: 27.8 ± 4.1 years; median sample size of 15 subjects). Nine studies were conducted in a simulated environment and eight during real expeditions at HA. To quantify auditory function, six studies performed pure tone audiometry, four studies measured otoacoustic emissions (OAE) and eight studies measured auditory evoked responses (AER). Study protocols presented heterogeneity in the spatio-temporal patterns of HA exposure, with highly varying maximal altitudes and exposure durations.

CONCLUSION

Most studies reported a reduction of auditory function with HA in terms of either elevation of auditory thresholds, lengthening of AER latencies, reduction of distortion-product and transient-evoked OAEs. Future studies in larger populations, using standardized protocols and multi-technique auditory function evaluation, are needed to further characterize the spatio-temporal pattern of HA effects along the auditory pathways and clarify the pathophysiological implications and reversibility of the observed changes.

Septal Perforation Repair Using a Temporoparietal Fascia and Polydioxanone Plate Construct: A Multi-Institutional Analysis

Background: Nasal septal perforations (NSPs) are notoriously difficult to fix and closure can paradoxically lead to worsening of symptoms, prompting numerous techniques for repair including temporoparietal fascia (TPF)-polydioxanone (PDS) plate interposition grafting. Objectives: To compare rates of NSP closure with TPF-PDS interposition grafting among a variety of institutions with diverse environmental influences and patient-specific factors. Methods: Retrospective review of patients undergoing TPF-PDS interposition grafting at seven different U.S. institutions over 5 years. Outcomes include closure rate, self-reported symptom improvement, change in Nasal Obstruction Symptomatic Evaluation (NOSE) score, and postoperative complications. Results: Sixty-two patients (39 female) with a mean age of 41.5 years were included. Most common perforation location was anterior (53%), and average size was 1.70 cm². NSP closure with symptomatic improvement was achieved in 95% of participants. Postoperative NOSE scores decreased on average by 42 points. Residual crusting occurred in 29% of patients, independent of external factors. Conclusions: TPF-PDS interposition grafting is highly effective for NSP repair in a wide variety of settings, and NOSE scores correspond well with patient-reported outcomes.

A pilot study comparing hearing thresholds of soldiers at induction and after completion of one year in high altitude area

Background

Despite so much research in high altitude area, our existing knowledge is still lacking on otological effects of long-term stay in high altitude. This pilot study was conducted to compare the hearing thresholds of army soldiers at induction and after completion of one year in high altitude area (HAA).

Methods

Hearing thresholds of 433 soldiers posted in HAA were recorded using pure tone audiometry at the time of induction and second thresholds after one year of stay in high altitude for frequencies of 500Hz, 1KHzs, 2 KHzs and 4 KHzs. The two sets of hearing thresholds for air conduction were compared using paired "t" test for any statistical significance.

Results

The mean Pure Tone Audiometry (PTA) thresholds for 433 left ears worsened from 9.43dB to 9.65dB at 500 HZs ; 14.02dB to 14.32dB at 1 KHZs ; 15.04dB to 16.09dB at 2KHzs and 18.63dB to 22.59dB at 4 KHZs. Similarly for right ear, PTA thresholds worsened from 9.43dB to 9.69dB at 500HZs; 13.95dB to 14.34dB at 1 KHZs; 15.38dB to 17.26dB at 2 KHZs and from 18.59dB to 23.06dB at 4KHZs. These results are found to be statistically significant (p<0.05) for all frequencies.

Conclusion

This pilot study shows deterioration of hearing thresholds in tested frequencies in both ears after a long stay (one year) in high altitude area. We recommend further structured research on otologic effect of long term stay in high altitude.

Hearing Sensitivity of Primates: Recurrent and Episodic Positive Selection in Hair Cells and Stereocilia Protein-Coding Genes

The large spectrum of hearing sensitivity observed in primates results from the impact of environmental and behavioral pressures to optimize sound perception and localization. Although evidence of positive selection in auditory genes has been detected in mammals including in Hominoids, selection has never been investigated in other primates. We analyzed 123 genes highly expressed in the inner ear of 27 primate species and tested to what extent positive selection may have shaped these genes in the order Primates tree. We combined both site and branch-site tests to obtain a comprehensive picture of the positively selected genes (PSGs) involved in hearing sensitivity, and drew a detailed description of the most affected branches in the tree. We chose a conservative approach, and thus focused on confounding factors potentially affecting PSG signals (alignment, GC-biased gene conversion, duplications, heterogeneous sequencing qualities). Using site tests, we showed that around 12% of these genes are PSGs, an α selection value consistent with average human genome estimates (10-15%). Using branch-site tests, we showed that the primate tree is heterogeneously affected by positive selection, with the black snub-nosed monkey, the bushbaby, and the orangutan, being the most impacted branches. A large proportion of these genes is inclined to shape hair cells and stereocilia, which are involved in the mechanotransduction process, known to influence frequency perception. Adaptive selection, and more specifically recurrent adaptive evolution, could have acted in parallel on a set of genes (ADGRV1, USH2A, PCDH15, PTPRQ, and ATP8A2) involved in stereocilia growth and the whole complex of bundle links connecting them, in species across different habitats, including high altitude and nocturnal environments.

Hypoxia and standing balance

PURPOSE

Standing balance control is important for everyday function and often goes unnoticed until impairments appear. Presently, more than 200 million people live at altitudes > 2500 m above sea level, and many others work at or travel to these elevations. Thus, it is important to understand how hypoxia alters balance owing to implications for occupations and travelers. Herein, the influence of normobaric and hypobaric hypoxia on standing balance control is reviewed and summarized. As postural control relies on the integration of sensorimotor signals, the potential hypoxic-sensitive neurophysiological factors that contribute to balance impairments are also reviewed. Specifically, we examine how hypoxia impairs visual, vestibular, and proprioceptive cues, and their integration within subcortical or cortical areas.

METHODS

This systematic review included a literature search conducted via multiple databases with keywords related to postural balance, hypoxia, and altitude. Articles (n = 13) were included if they met distinct criteria.

RESULTS

Compared to normoxia, normobaric hypoxia worsened parameters of standing balance by 2-10% and up to 83 and 240% in hypobaric hypoxia (high-altitude and lab-based, respectively). Although balance was only disrupted during normobaric hypoxia at F_IO₂ <  ~ 0.15, impairments consistently occurred during hypobaric hypoxia at altitudes > 1524 m (~ F_IO₂ < 0.18).

CONCLUSION

Hypoxia, especially hypobaric, impairs standing balance. The mechanisms underpinning postural decrements likely involve alterations to processing and integration of sensorimotor signals within subcortical or cortical structures involving visual, vestibular, and proprioceptive pathways and subsequent motor commands that direct postural adjustments. Future studies are required to determine the sensorimotor factors that may influence balance control in hypoxia.

Evaluation of Middle Ear Function by Tympanometry and the Influence of Lower Barometric Pressure at High Altitude

Jiang, Tao, Liping Zhao, Yanbo Yin, Huiqian Yu, and Qingzhong Li. Evaluation of middle ear function by tympanometry and the influence of lower barometric pressure at high altitude. High Alt Med Biol. 22:70-76, 2021. Objective: To evaluate middle ear function in residents of high-altitude areas in comparison to sea-level participants. Design: Prospective observational study. Setting: All experiments were performed by experienced audiologists with a calibrated tympanometry machine. Participants: Young adults between the age of 17 and 23 were recruited. Seventy-five participants from Shanghai (altitude 4 m) and 133 participants from the Shigatse area (altitude 4,040 m) were recruited. Any participant with any otological disorder was excluded. Main Outcome Measure: Four indexes of the tympanogram were evaluated in the two groups from different altitudes. Results: Our results showed that the peak of static compliance for the participants in Shigatse was smaller, but the absolute compliance of tympanic membrane remained the same. Similarly, the ear canal volume (ECV) from tympanometry was also affected by the elevated altitude in Tibet. In addition, the tympanometric peak pressure was decreased in high-altitude residents, which suggests a slightly declined function of the Eustachian tube at lower barometric pressure. However, no difference was found in the tympanometric width (TW). Conclusion: Our results indicate that tympanograms were affected by decreased atmospheric pressure at high altitude. Therefore, other than pressure-related indexes, TW is better for evaluating the function of the middle ear in high-altitude regions.

Universality vs experience: a cross-cultural pilot study on the consonance effect in music at different altitudes

Background

Previous studies have shown that music preferences are influenced by cultural “rules”, and some others have suggested a universal preference for some features over others.

Methods

We investigated cultural differences on the “consonance effect”, consisting in higher pleasantness judgments for consonant compared to dissonant chords—according to the Western definition of music: Italian and Himalayan participants were asked to express pleasantness judgments for consonant and dissonant chords. An Italian and a Nepalese sample were tested both at 1,450 m and at 4,750 m of altitude, with the further aim to evaluate the effect of hypoxia on this task. A third sample consisted of two subgroups of Sherpas: lowlanders (1,450 m of altitude), often exposed to Western music, and highlanders (3,427 m of altitude), less exposed to Western music. All Sherpas were tested where they lived.

Results

Independently from the altitude, results confirmed the consonance effect in the Italian sample, and the absence of such effect in the Nepalese sample. Lowlander Sherpas revealed the consonance effect, but highlander Sherpas did not show this effect.

Conclusions

Results of this pilot study show that neither hypoxia (altitude), nor demographic features (age, schooling, or playing music), nor ethnicity per se influence the consonance effect. We conclude that music preferences are attributable to music exposure.

A Cross-Sectional Study on the Hearing Threshold Levels Among People in Qinling, Qinghai, and Nanjing, China

PURPOSE

This study aimed to investigate the hearing threshold among different age groups, genders, and geographic areas in China to provide some insight into the appropriate clinical interventions for hearing loss.

METHOD

Using a systematic random sampling technique, 562 participants from Qinling, Qinghai, and Nanjing were included. Participants in the same area were divided into 3 groups according to their age. Pure-tone audiometric thresholds were measured at octave and interoctave frequencies of 0.125-16 kHz for each subject.

RESULTS

There were significant differences in auditory thresholds at nearly all frequencies among young, middle-aged, and elderly people, and hearing thresholds increased with increasing age. People generally had the best hearing ability in Nanjing, better hearing ability in Qinghai, and the worst hearing ability in Qinling. Significant differences in hearing thresholds were found between males and females at several frequencies in Qinling.

CONCLUSION

People living in the rural area of Qinling in China had higher hearing threshold levels, particularly males, and hearing thresholds increased with age.

Middle Ear Function and Pathophysiology in Andean Children Living at High Altitudes

Counter, S. Allen, Leo H. Buchanan, Fernando Ortega, Anthony B. Jacobs, and Göran Laurell. Middle ear function and pathophysiology in Andean children living at high altitudes. High Alt Med Biol. 18:163-170, 2017.-The extent of altitude-related middle ear disorders in children native to high altitudes is unclear. This study examined middle ear pathophysiology in two groups of children living in high-altitude Ecuadorian Andean communities by investigating middle ear pressure (MEP), tympanic membrane compliance (TMC), and ear canal volume (ECV) using tympanometry, and by otological examination. Altitude I Group lived at 2850 m, and Altitude II Group resided at around 4000 m. The two high-altitude groups were compared with a reference group of children residing at sea level. Mean MEP was -3.6 daPa (SD: 39.2), 3.5 daPa (SD: 28.7), and 1.3 daPa (SD: 13.6) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The MEP was not significantly different among the three groups. Mean TMC was 0.63 cm³ (SD: 0.51), 0.60 cm³ (SD: 0.43), and 0.60 cm³ (SD: 0.24) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The TMC was not significantly different among the three groups. Mean ECV was 1.1 (SD: 0.26), 1.2 (SD: 0.26), and 1.0 (SD: 0.23) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The difference in ECV between Altitude I Group and Altitude II Group was significant (p = 0.043), as was the difference between Altitude II Group and the Sea Level Group (p = 0.001). ECV did not differ significantly between Altitude I Group and the Sea Level Group. Otological examination revealed a low incidence of ear canal and middle ear pathology. In conclusion, tympanometric and otological findings did not reveal a high incidence of middle ear pathophysiology in children living at altitudes as high as around 4000 m.

Assessment of the Brainstem-Mediated Stapedius Muscle Reflex in Andean Children Living at High Altitudes

Counter, S. Allen, Leo H. Buchanan, Fernando Ortega, Anthony B. Jacobs, and Göran Laurell. Assessment of the brainstem-mediated stapedius muscle reflex in Andean children living at high altitudes. High Alt Med Biol. 18:37-45, 2017.-This study examined the physiological thresholds, amplitude growth, and contraction duration of the acoustic stapedius reflex (ASR) in Andean children aged 2-17 years living at altitudes of 2850 m (Altitude I Group) and 3973 m (Altitude II Group) as part of a general medical assessment of the health status of the children. The brainstem-mediated ASR reveals the integrity of the neuronal components of the auditory reflex arc, including the cochlea receptors, eight cranial nerves, and brainstem neural projections to the cochlear nuclei, bilateral superior olivary nuclei, facial nerve nuclei, and facial nerve and its stapedius branch. Uncrossed (ipsilateral) and crossed (contralateral) ASR thresholds (ASRT), ASR amplitude growth (ASRG) function, and ASR muscle contraction duration (decay/fatigue) (ASRD) were measured noninvasively with 500, 1000 Hz and broadband (bandwidth = 125-4000 Hz) noise stimulus activators using a middle ear immittance system. Oxygen saturation (SaO₂) level and heart rate were measured in a subsample of the study group. Statistical analyses revealed that the Altitude I and Altitude II groups had ASRT, ASRG function, and ASRD rates comparable to children at sea level and that the two groups were not significantly different for any of the ASR measures. No significant association was found between SaO₂ or heart rate and ASRT, growth, and muscle fatigue rate. In conclusion, the assessment of the ASR in children in the high-altitude groups revealed normal function. Furthermore, the results indicate no adverse oto-physiological effects of altitude on the brainstem-mediated ASR at elevations between 2850 and 4000 m and suggest normal middle ear and auditory brainstem function.

The effect of high altitude on nasal nitric oxide levels

The aim of the present study was to investigate whether nasal nitric oxide (nNO) levels change in relation to high altitude in a natural setting where the weather conditions were favorable. The present study included 41 healthy volunteers without a history of acute rhinosinusitis within 3 weeks and nasal polyposis. The study group consisted of 31 males (76 %) and 10 females (24 %) and the mean age of the study population was 38 ± 10 years. The volunteers encamped for 2 days in a mountain village at an altitude of 1,500 m above sea level (masl) and proceeded to highlands at an altitude of 2,200 masl throughout the day. The measurements of nNO were done randomly, either first at the mountain village or at sea level. Each participant had nNO values both at sea level and at high altitude at the end of the study. The nNO values of sea level and high altitude were compared to investigate the effect of high altitude on nNO levels. The mean of average nNO measurements at the high altitude was 74.2 ± 41 parts-per-billion (ppb) and the mean of the measurements at sea level was 93.4 ± 45 ppb. The change in nNO depending on the altitude level was statistically significant (p < 0.001). The current investigation showed that nNO levels were decreased at high altitude even if the weather conditions were favorable, such as temperature, humidity, and wind.

The effect of high altitude on olfactory functions

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.

Brainstem auditory evoked responses in children living at high altitude in the andes mountains

OBJECTIVES

This neurophysiological study compared brainstem auditory evoked responses (BAER) in children living at high elevations (2800 to 3000 meters) in the Andes Mountains of Ecuador with a reference group of children living at sea level in the U.S.

METHODS

BAER absolute latencies of waves I through V; interpeak latencies I-III, III-V, and I-V; amplitudes of waves I and V; and the V/I amplitude ratio were measured by scalp electrodes at acoustic click stimulus rates of 10 and 50 pulses per second (pps).

RESULTS

Statistical analysis showed that the high-altitude group had significantly longer absolute and interpeak BAER latencies than the sea-level reference group at both the 10 and 50 pps stimulus rates for most wave peaks. The amplitudes of waves I and V were significantly reduced for the high-altitude group at 10 and 50 pps, suggesting blood O2 saturation effects.

CONCLUSIONS

The BAER of children in the high-altitude group suggested physiological anomalies in auditory neural conduction and summation compared with the sea-level group. The results further suggest that small physiological effects of altitude on BAER, especially at elevations near 3000 meters and higher, should be taken into consideration in the evaluation of brainstem auditory function.

Effects of high altitude on sleep and respiratory system and theirs adaptations

High-altitude (HA) environments have adverse effects on the normal functioning body of people accustomed to living at low altitudes because of the change in barometric pressure which causes decrease in the amount of oxygen leading to hypobaric hypoxia. Sustained exposure to hypoxia has adverse effects on body weight, muscle structure and exercise capacity, mental functioning, and sleep quality. The most important step of acclimatization is the hyperventilation which is achieved by hypoxic ventilatory response of the peripheral chemoreceptors. Hyperventilation results in increase in arterial carbon-dioxide concentration. Altitude also affects sleep and cardiac output, which is the other determinant of oxygen delivery. Upon initial exposure to HA, the resting pulse rate increases rapidly, but with acclimatization, heart rate and cardiac output tend to fall. Another important component that leads to decrease in cardiac output is the reduction in the stroke volume with acclimatization. During sleep at HA, the levels of CO2 in the blood can drop very low and this can switch off the drive to breathe. Only after the body senses a further drop in O2 levels breathing is started again. Periodic breathing is thought to result from instability in the control system through the hypoxic drive or the response to CO2.

The physiological impact of high altitude on nasal and lower airway parameters

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.

Assessment of the impact of altitude on nasal airflow via expiratory nasal sound spectral analysis

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.