Use of Gases to Treat Cochlear Conditions

Although the cochlear vascular supply (stria vascularis) is designed to block to certain compounds and molecules, it must enable gas exchange to survive. The inner ear capillaries must deliver oxygen and remove carbon dioxide for the cochlea to function. These gases diffuse through tissues across a concentration gradient to reach the desired target. Tight junctions or the endothelial basement membrane do not impede them. Therefore, gases that can diffuse into the inner ear are attractive as therapeutic agents. The two gases most often used in this way are oxygen and hydrogen, although carbon dioxide, ozone, and argon have also been investigated. Typically, oxygen is delivered as hyperbaric oxygen (HBO) (oxygen at pressure higher than atmospheric) to provide increased oxygen levels to the inner ear. This not only relieves hypoxia, but also has anti-inflammatory and other biochemical effects. HBO is used clinically to treat idiopathic sudden sensorineural hearing loss, and both animal and human studies suggest it may also assist recovery after acute acoustic trauma. Laboratory studies suggest hydrogen works as a free radical scavenger and reduces the strong oxidants hydroxyl radicals and peroxynitrite. It also has anti-apoptotic effects. Because of its anti-oxidant and anti-inflammatory effects, it has been studied as a treatment for ototoxicity and shows benefit in an animal model of cisplatinum toxicity. Gas diffusion offers an effective way to provide therapy to the inner ear, particularly since some gases (oxygen, hydrogen, carbon dioxide, ozone, argon) have important therapeutic effects for minimizing cochlear damage.

Hyperbaric oxygen therapy is well tolerated and effective for ulcerative colitis patients hospitalized for moderate-severe flares: a phase 2A pilot multi-center, randomized, double-blind, sham-controlled trial

BACKGROUND

Hyperbaric oxygen therapy (HBOT) markedly increases tissue oxygen delivery. Case series suggest it may have a potential therapeutic benefit in ulcerative colitis (UC). We investigated the therapeutic potential of HBOT as an adjunct to steroids for UC flares requiring hospitalization.

METHODS

The study was terminated early due to poor recruitment with 18 of the planned 70 patients enrolled. UC patients hospitalized for moderate-severe flares (Mayo score ≥6, endoscopic sub-score ≥2) were block randomized to steroids + daily HBOT (n = 10) or steroids + daily sham hyperbaric air (n = 8). Patients were blinded to study assignment, and assessments were performed by a blinded gastroenterologist. Primary outcome was the clinical remission rate at study day 5 (partial Mayo score ≤2 with no sub-score >1). Key secondary outcomes were: clinical response (reduction in partial Mayo score ≥2, rectal bleeding sub-score of 0-1) and progression to second-line therapy (colectomy or biologic therapy) during the hospitalization.

RESULTS

A significantly higher proportion of HBOT-treated patients achieved clinical remission at study day 5 and 10 (50 vs. 0%, p = 0.04). HBOT-treated patients less often required progression to second-line therapy during the hospitalization (10 vs. 63%, p = 0.04). The proportion requiring in-hospital colectomy specifically as second-line therapy for medically refractory UC was lower in the HBOT group compared to sham (0 vs. 38%, p = 0.07). There were no serious adverse events.

CONCLUSION

In this small, proof-of-concept, phase 2A trial, the use of HBOT as an adjunctive therapy to steroids for UC patients hospitalized for moderate-severe flares resulted in higher rates of clinical remission, and a reduction in rates of progression to second-line therapy during the hospitalization. Larger well-powered trials are needed, however, to provided definitive evidence of therapeutic benefit.

Transcutaneous oxygen measurement in humans using a paramagnetic skin adhesive film

PURPOSE

Transcutaneous oxygen tension (TcpO₂ ) provides information about blood perfusion in the tissue immediately below the skin. These data are valuable in assessing wound healing problems, diagnosing peripheral vascular/arterial insufficiency, and predicting disease progression or the response to therapy. Currently, TcpO₂ is primarily measured using electrochemical skin sensors, which consume oxygen and are prone to calibration errors. The goal of the present study was to develop a reliable method for TcpO₂ measurement in human subjects.

METHODS

We have developed a novel TcpO₂ oximetry method based on electron paramagnetic resonance (EPR) principles with an oxygen-sensing skin adhesive film, named the superficial perfusion oxygen tension (SPOT) chip. The SPOT chip is a 3-mm diameter, 60-μm thick circular film composed of a stable paramagnetic oxygen sensor. The chip is covered with an oxygen-barrier material on one side and secured on the skin by a medical adhesive transfer tape to ensure that only the oxygen that diffuses through the skin surface is measured. The method quantifies TcpO₂ through the linewidth of the EPR spectrum.

RESULTS

Repeated measurements using a cohort of 10 healthy human subjects showed that the TcpO₂ measurements were robust, reliable, and reproducible. The TcpO₂ values ranged from 7.8 ± 0.8 to 22.0 ± 1.0 mmHg in the volar forearm skin (N = 29) and 8.1 ± 0.3 to 23.4 ± 1.3 mmHg in the foot (N = 86).

CONCLUSIONS

The results demonstrated that the SPOT chip can measure TcpO₂ reliably and repeatedly under ambient conditions. The SPOT chip method could potentially be used to monitor TcpO₂ in the clinic.

Portable Autorefractors for Detecting Axial Length Changes in Space

INTRODUCTION

We evaluated the reproducibility of two portable, self-administered autorefractors (Netra and SVOne Pro) to assess the time course of visual changes on the ISS.

METHODS

We measured cycloplegic refractive error at 5 visits at least a week apart in 13 subjects (6 women, 7 men, 30 ± 9 yr) using both devices seated and also prone with lower body positive pressure (LBPP) applied. Axial length was measured with an optical biometer. Subjects completed a questionnaire on device preferences.

RESULTS

The SVOne seated intrasession reproducibility coefficient (RPC) was 0.37 diopters (D), while the Netra's was 0.41 D. Intersession seated results were: RPC = 0.67 D for the SVOne and RPC = 0.54 D for the Netra. The average seated to prone LBPP differences were significantly different from zero for both the SVOne and Netra. The SVOne was preferred in four out of five categories on the questionnaire and took half the time to complete a measurement set compared to the Netra.

DISCUSSION

Users preferred the SVOne and it took less time. An SVOne refraction change of 0.67 D from baseline would happen by chance less than 5% of the time. If multiple separate measurements were taken, the detection limit could be reduced (e.g., three repeated measurements could reduce it to 0.38 D). Since astronauts with visual changes show spherical equivalent changes of 0.5 to 1.0 D, in-flight autorefractors could help determine the time course of refractive changes in space from which changes in axial length could be inferred.Masterova KS, Anderson AP, Cowan DR, Fellows AM, Zegans ME, Buckey JC. Portable autorefractors for detecting axial length changes in space. Aerosp Med Hum Perform. 2018; 89(8):724-730.

Microgravity-induced ocular changes are related to body weight

On Earth, tissue weight generates compressive forces that press on body structures and act on the walls of vessels throughout the body. In microgravity, tissues no longer have weight, and tissue compressive forces are lost, suggesting that individuals who weigh more may show greater effects from microgravity exposure. One unique effect of long-duration microgravity exposure is spaceflight-associated neuroocular syndrome (SANS), which can present with globe flattening, choroidal folds, optic disk edema, and a hyperopic visual shift. To determine whether weight or other anthropometric measures are related to ocular changes in space, we analyzed data from 45 individual long-duration astronauts (mean age 47, 36 male, 9 female, mean mission duration 165 days) who had pre- and postflight measures of disk edema, choroidal folds, and manifest ocular refraction. The mean preflight weights of astronauts who developed new choroidal folds [78.6 kg with no new folds vs. 88.6 kg with new folds ( F = 6.2, P = 0.02)] and disk edema [79.1 kg with no edema vs. 95 kg with edema ( F = 9.6, P = 0.003)] were significantly greater than those who did not. Chest and waist circumferences were also significantly greater in those who developed folds or edema. The odds of developing disk edema or new choroidal folds were 55% in the highest- and 9% in the lowest-weight quartile. In this cohort, no women developed disk edema or choroidal folds, although women also weighed significantly less than men [62.9 vs. 85.2 kg ( F = 53.2, P < 0.0001)]. Preflight body weight and anthropometric factors may predict microgravity-induced ocular changes.

Magnetic Resonance Imaging Evidence for Human Immunodeficiency Virus Effects on Central Auditory Processing: A Review

New research suggests that individuals with human immunodeficiency virus (HIV) have central auditory processing deficits. To review the evidence for HIV affecting parts of the central nervous system involved in central auditory processing, we performed a systematic review of the literature. The objective was to determine whether existing studies show evidence for damage to structures associated with central auditory pathways in HIV. We searched PubMed for papers that used structural magnetic resonance imaging (MRI), diffusion tensor imaging, magnetic resonance spectroscopy or functional MRI in individuals infected with HIV. The review showed that HIV affects several areas involved in central auditory processing particularly the thalamus, internal capsule and temporal cortex. These findings support the idea that HIV can affect central auditory pathways and support the potential use of central auditory tests as a way to assess central nervous system effects of HIV.

Relaxation with Immersive Natural Scenes Presented Using Virtual Reality

INTRODUCTION

Virtual reality (VR) can provide exposure to nature for those living in isolated confined environments. We evaluated VR-presented natural settings for reducing stress and improving mood.

METHODS

There were 18 participants (9 men, 9 women), ages 32 ± 12 yr, who viewed three 15-min 360° scenes (an indoor control, rural Ireland, and remote beaches). Subjects were mentally stressed with arithmetic before scenes. Electrodermal activity (EDA) and heart rate variability measured psycho-physiological arousal. The Positive and Negative Affect Schedule and the 15-question Modified Reality Judgment and Presence Questionnaire (MRJPQ) measured mood and scene quality.

RESULTS

Reductions in EDA from baseline were greater at the end of the natural scenes compared to the control scene (-0.59, -0.52, and 0.32 μS, respectively). The natural scenes reduced negative affect from baseline ( 1.2 and 1.1 points), but the control scene did not ( 0.4 points). MRJPQ scores for the control scene were lower than both natural scenes (4.9, 6.7, and 6.5 points, respectively). Within the two natural scenes, the preferred scene reduced negative affect ( 2.4 points) more than the second choice scene ( 1.8 points) and scored higher on the MRJPQ (6.8 vs. 6.4 points).

DISCUSSION

Natural scene VR provided relaxation both objectively and subjectively, and scene preference had a significant effect on mood and perception of scene quality. VR may enable relaxation for people living in isolated confined environments, particularly when matched to personal preferences.Anderson AP, Mayer MD, Fellows AM, Cowan DR, Hegel MT, Buckey JC. Relaxation with immersive natural scenes presented using virtual reality. Aerosp Med Hum Perform. 2017; 88(6):520526.

Ocular changes over 60 min in supine and prone postures

Some astronauts are returning from long-duration spaceflight with structural ocular and visual changes. We investigated both the transient and sustained effects of changes in the direction of the gravity vector acting on the eye using changes in body posture. Intraocular pressure (IOP; measured by Perkins tonometer), ocular geometry (axial length, corneal thickness, and aqueous depth-noncontact biometer), and the choroid (volume and subfoveal thickness optical coherence tomography) were measured in 10 subjects (5 males and 5 females). Measures were taken over the course of 60 min and analyzed with repeated-measures analysis of covariance to assess the effects of posture and time. In the supine position, choroidal volume increased significantly with time (average value at <5 min = 8.8 ± 2.3 mm³, 60 min = 9.0 ± 2.4 mm³, P = 0.03). In the prone position, IOP and axial length increased with time (IOP at <5 min 15 ± 2.7 mmHg, 60 min = 19.8 ± 4.1 mmHg, P < 0.0001; axial length at <5 min = 24.29 ± 0.77 mm, 60 min = 24.31 ± 0.76 mm, P = 0.002). Each increased exponentially, with time constants of 5.3 and 14 min, respectively. Prone corneal thickness also increased with time (<5 min = 528 ± 35 μm, 60 min = 537 ± 35 μm³, P < 0.001). Aqueous depth was shortened in the prone position (baseline = 3.22 ± 0.31 mm, 60 min = 3.18 ± 0.32 mm, P < 0.0001) but did not change with time. The data show that changes in the gravity vector have pronounced transient and sustained effects on the geometry and physiology of the eye.NEW & NOTEWORTHY We show that gravity has pronounced transient and sustained effects on the eye by making detailed ocular measurements over 60 min in the supine and prone postures. These data inform our understanding of how gravitational forces can affect ocular structures, which is essential for hypothesizing how ocular changes could occur with microgravity exposure.

Autonomous, Computer-Based Behavioral Health Countermeasure Evaluation at HI-SEAS Mars Analog

INTRODUCTION

Living in an isolated, confined environment (ICE) can induce conflict, stress, and depression. Computer-based behavioral health countermeasures are appealing for training and treatment in ICEs because they provide confidentiality and do not require communication with the outside environment. We evaluated the Virtual Space Station (VSS), a suite of interactive computer-delivered psychological training and treatment programs, at the Hawaii Space Exploration Analog and Simulation (HI-SEAS) III expedition.

METHODS

Six subjects (3 male, 3 female) spent 8 mo in group-isolation and used the Conflict, Stress, and Depression modules in the VSS. Survey evaluations, data collected within the program, and postdeployment interviews were collected.

RESULTS

This crew dealt with behavioral health issues common to ICEs. The VSS proved to be a valuable resource and was used both as intended, and in unanticipated ways, to help maintain behavioral health. The Conflict and Stress Modules were rated as highly acceptable (1.8 on a 7-point Likert scale). The crew identified a total of 13 stressors and worked on 9 problems through the VSS. Opinions about the modules were highly individualized. Crewmembers identified exercises in the VSS that were applicable and not applicable to their needs. Additional content to improve the program was identified.

DISCUSSION

Autonomous, confidential training and treatment for behavioral health issues will need to be a critical component of long duration spaceflight travel. This work provides an evaluation of such a tool in a relevant ICE. Anderson AP, Fellows AM, Binsted KA, Hegel MT, Buckey JC. Autonomous, computer-based behavioral health countermeasure evaluation at HI-SEAS Mars analog. Aerosp Med Hum Perform. 2016; 87(11):912-920.

Respiratory modulation of human autonomic function on Earth

KEY POINTS

We studied healthy supine astronauts on Earth with electrocardiogram, non-invasive arterial pressure, respiratory carbon dioxide concentrations, breathing depth and sympathetic nerve recordings. The null hypotheses were that heart beat interval fluctuations at usual breathing frequencies are baroreflex mediated, that they persist during apnoea, and that autonomic responses to apnoea result from changes of chemoreceptor, baroreceptor or lung stretch receptor inputs. R-R interval fluctuations at usual breathing frequencies are unlikely to be baroreflex mediated, and disappear during apnoea. The subjects' responses to apnoea could not be attributed to changes of central chemoreceptor activity (hypocapnia prevailed); altered arterial baroreceptor input (vagal baroreflex gain declined and muscle sympathetic nerve burst areas, frequencies and probabilities increased, even as arterial pressure climbed to new levels); or altered pulmonary stretch receptor activity (major breathing frequency and tidal volume changes did not alter vagal tone or sympathetic activity). Apnoea responses of healthy subjects may result from changes of central respiratory motoneurone activity.

ABSTRACT

We studied eight healthy, supine astronauts on Earth, who followed a simple protocol: they breathed at fixed or random frequencies, hyperventilated and then stopped breathing, as a means to modulate and expose to view important, but obscure central neurophysiological mechanisms. Our recordings included the electrocardiogram, finger photoplethysmographic arterial pressure, tidal volume, respiratory carbon dioxide concentrations and peroneal nerve muscle sympathetic activity. Arterial pressure, vagal tone and muscle sympathetic outflow were comparable during spontaneous and controlled-frequency breathing. Compared with spontaneous, 0.1 and 0.05 Hz breathing, however, breathing at usual frequencies (∼0.25 Hz) lowered arterial baroreflex gain, and provoked smaller arterial pressure and R-R interval fluctuations, which were separated by intervals that were likely to be too short and variable to be attributed to baroreflex physiology. R-R interval fluctuations at usual breathing frequencies disappear during apnoea, and thus cannot provide evidence for the existence of a central respiratory oscillation. Apnoea sets in motion a continuous and ever changing reorganization of the relations among stimulatory and inhibitory inputs and autonomic outputs, which, in our study, could not be attributed to altered chemoreceptor, baroreceptor, or pulmonary stretch receptor activity. We suggest that responses of healthy subjects to apnoea are driven importantly, and possibly prepotently, by changes of central respiratory motoneurone activity. The companion article extends these observations and asks the question, Might terrestrial responses to our 20 min breathing protocol find expression as long-term neuroplasticity in serial measurements made over 20 days during and following space travel?

Respiratory modulation of human autonomic function: long-term neuroplasticity in space

KEY POINTS

We studied healthy astronauts before, during and after the Neurolab Space Shuttle mission with controlled breathing and apnoea, to identify autonomic changes that might contribute to postflight orthostatic intolerance. Measurements included the electrocardiogram, finger photoplethysmographic arterial pressure, respiratory carbon dioxide levels, tidal volume and peroneal nerve muscle sympathetic activity. Arterial pressure fell and then rose in space, and drifted back to preflight levels after return to Earth. Vagal metrics changed in opposite directions: vagal baroreflex gain and two indices of vagal fluctuations rose and then fell in space, and descended to preflight levels upon return to Earth. Sympathetic burst frequencies (but not areas) were greater than preflight in space and on landing day, and astronauts' abilities to modulate both burst areas and frequencies during apnoea were sharply diminished. Spaceflight triggers long-term neuroplastic changes reflected by reciptocal sympathetic and vagal motoneurone responsiveness to breathing changes.

ABSTRACT

We studied six healthy astronauts five times, on Earth, in space on the first and 12th or 13th day of the 16 day Neurolab Space Shuttle mission, on landing day, and 5-6 days later. Astronauts followed a fixed protocol comprising controlled and random frequency breathing and apnoea, conceived to perturb their autonomic function and identify changes, if any, provoked by microgravity exposure. We recorded the electrocardiogram, finger photoplethysmographic arterial pressure, tidal carbon dioxide concentrations and volumes, and peroneal nerve muscle sympathetic activity on Earth (in the supine position) and in space. (Sympathetic nerve recordings were made during three sessions: preflight, late mission and landing day.) Arterial pressure changed systematically from preflight levels: pressure fell during early microgravity exposure, rose as microgravity exposure continued, and drifted back to preflight levels after return to Earth. Vagal metrics changed in opposite directions: vagal baroreflex gain and two indices of vagal fluctuations (root mean square of successive normal R-R intervals; and proportion of successive normal R-R intervals greater than 50 ms, divided by the total number of normal R-R intervals) rose significantly during early microgravity exposure, fell as microgravity exposure continued, and descended to preflight levels upon return to Earth. Sympathetic mechanisms also changed. Burst frequencies (but not areas) during fixed frequency breathing were greater than preflight in space and on landing day, but their control during apnoea was sharply altered: astronauts increased their burst frequencies from already high levels, but they could not modulate either burst areas or frequencies appropriately. Space travel provokes long-lasting sympathetic and vagal neuroplastic changes in healthy humans.

Acute effects of changes to the gravitational vector on the eye

Intraocular pressure (IOP) initially increases when an individual enters microgravity compared with baseline values when an individual is in a seated position. This has been attributed to a headward fluid shift that increases venous pressures in the head. The change in IOP exceeds changes measured immediately after moving from seated to supine postures on Earth, when a similar fluid shift is produced. Furthermore, central venous and cerebrospinal fluid pressures are at or below supine position levels when measured initially upon entering microgravity, unlike when moving from seated to supine postures on Earth, when these pressures increase. To investigate the effects of altering gravitational forces on the eye, we made ocular measurements on 24 subjects (13 men, 11 women) in the seated, supine, and prone positions in the laboratory, and upon entering microgravity during parabolic flight. IOP in microgravity (16.3 ± 2.7 mmHg) was significantly elevated above values in the seated (11.5 ± 2.0 mmHg) and supine (13.7 ± 3.0 mmHg) positions, and was significantly less than pressure in the prone position (20.3 ± 2.6 mmHg). In all measurements, P < 0.001. Choroidal area was significantly increased in subjects in a microgravity environment ( P < 0.007) compared with values from subjects in seated (increase of 0.09 ± 0.1 mm2) and supine (increase of 0.06 ± 0.09 mm2) positions. IOP results are consistent with the hypothesis that hydrostatic gradients affect IOP, and may explain how IOP can increase beyond supine values in microgravity when central venous and intracranial pressure do not. Understanding gravitational effects on the eye may help develop hypotheses for how microgravity-induced visual changes develop.

DPOAE level mapping for detecting noise-induced cochlear damage from short-duration music exposures

Distortion product otoacoustic emission (DPOAE) level mapping provides a comprehensive picture of cochlear responses over a range of DP frequencies and f₂/f₁ ratios. We hypothesized that individuals exposed to high-level sound would show changes detectable by DPOAE mapping, but not apparent on a standard DP-gram. Thirteen normal hearing subjects were studied before and after attending music concerts. Pure-tone audiometry (500-8,000 Hz), DP-grams (0.3-10 kHz) at 1.22 ratio, and DPOAE level maps were collected prior to, as soon as possible after, and the day after the concerts. All maps covered the range of 2,000-6,000 Hz in DP frequency and from 1.3 to -1.3 in ratio using equi-level primary tone stimuli. Changes in the pure-tone audiogram were significant (P ≤ 0.01) immediately after the concert at 1,000 Hz, 4,000 Hz, and 6,000 Hz. The DP-gram showed significant differences only at f₂ = 4,066 (P = 0.01) and f₂ = 4,348 (P = 0.04). The postconcert changes were readily apparent both visually and statistically (P ≤ 0.01) on the mean DP level maps, and remained statistically significantly different from baseline the day after noise exposure although no significant changes from baseline were seen on the DP-gram or audiogram the day after exposure. Although both the DP-gram and audiogram showed recovery by the next day, the average DPOAE level maps remained significantly different from baseline. The mapping data showed changes in the cochlea that were not detected from the DP-gram obtained at a single ratio. DPOAE level mapping provides comprehensive information on subtle cochlear responses, which may offer advantages for studying and tracking noise-induced hearing loss (NIHL).

Hyperbaric oxygen for patients with above-knee amputations, persistent ischemia, and nonreconstructable vascular disease

We describe four patients with above-knee amputations whose stump wounds failed to heal. After numerous revascularization attempts, these patients were diagnosed with nonreconstructable pelvic and groin vascular disease and were facing hip disarticulation. With the addition of hyperbaric oxygen treatment to vigilant wound care and negative pressure therapy, these patients healed their amputation stumps and were fit with prostheses. At their most recent follow-up, all patients were ambulating and using their prostheses.

Systematic review: The safety and efficacy of hyperbaric oxygen therapy for inflammatory bowel disease

BACKGROUND

Hyperbaric oxygen therapy (HBOT) provides 100% oxygen under pressure, which increases tissue oxygen levels, relieves hypoxia and alters inflammatory pathways. Although there is experience using HBOT in Crohn's disease and ulcerative colitis, the safety and overall efficacy of HBOT in inflammatory bowel disease (IBD) is unknown.

AIM

To quantify the safety and efficacy of HBOT for Crohn's disease (CD) and ulcerative colitis (UC). The rate of adverse events with HBOT for IBD was compared to the expected rate of adverse events with HBOT.

METHODS

MEDLINE, EMBASE, Cochrane Collaboration and Web of Knowledge were systematically searched using the PRISMA standards for systematic reviews. Seventeen studies involving 613 patients (286 CD, 327 UC) were included.

RESULTS

The overall response rate was 86% (85% CD, 88% UC). The overall response rate for perineal CD was 88% (18/40 complete healing, 17/40 partial healing). Of the 40 UC patients with endoscopic follow-up reported, the overall response rate to HBOT was 100%. During the 8924 treatments, there were a total of nine adverse events, six of which were serious. The rate of adverse events with HBOT in IBD is lower than that seen when utilising HBOT for other indications (P < 0.01). The risk of bias across studies was high.

CONCLUSIONS

Hyperbaric oxygen therapy is a relatively safe and potentially efficacious treatment option for IBD patients. To understand the true benefit of HBOT in IBD, well-controlled, blinded, randomised trials are needed for both Crohn's disease and ulcerative colitis.

Feasibility study of an interactive multimedia electronic problem solving treatment program for depression: a preliminary uncontrolled trial

Computer-based depression interventions lacking live therapist support have difficulty engaging users. This study evaluated the usability, acceptability, credibility, therapeutic alliance and efficacy of a stand-alone multimedia, interactive, computer-based Problem Solving Treatment program (ePST™) for depression. The program simulated live treatment from an expert PST therapist, and delivered 6 ePST™ sessions over 9weeks. Twenty-nine participants with moderate-severe symptoms received the intervention; 23 completed a minimally adequate dose of ePST™ (at least 4 sessions). Program usability, acceptability, credibility, and therapeutic alliance were assessed at treatment midpoint and endpoint. Depressive symptoms and health-related functioning were assessed at baseline, treatment midpoint (4weeks), and study endpoint (10weeks). Depression outcomes and therapeutic alliance ratings were also compared to previously published research on live PST and computer-based depression therapy. Participants rated the program as highly usable, acceptable, and credible, and reported a therapeutic alliance with the program comparable to that observed in live therapy. Depressive symptoms improved significantly over time. These findings also provide preliminary evidence that ePST™ may be effective as a depression treatment. Larger clinical trials with diverse samples are indicated.

Microbubbles are detected prior to larger bubbles following decompression

Using dual-frequency ultrasound (DFU), microbubbles (<10 μm diameter) have been detected in tissue following decompression. It is not known if these microbubbles are the precursors for B-mode ultrasound-detectable venous gas emboli (bmdVGE). The purpose of this study was to determine if microbubbles could be detected intravascularly postdecompression and to investigate the temporal relationship between microbubbles and larger bmdVGE. Anesthetized swine (n = 15) were exposed to 4.0-4.5 ATA for 2 h, followed by decompression to 0.98 ATA. Microbubble presence and VGE grade were measured using DFU and B-mode ultrasound, respectively, before and for 1 h postdecompression, approximately every 4-5 min. Microbubbles appeared in the bloodstream postdecompression, both in the presence and absence of bmdVGE. In swine without bmdVGE, microbubbles remained elevated for the entire 60-min postdecompression period. In swine with bmdVGE, microbubble signals were detected initially but then returned to baseline. Microbubbles were not detected with the sham dive. Mean bmdVGE grade increased over the length of the postdecompression data collection period. Comparison of the two response curves revealed significant differences at 5 and 10 min postdecompression, indicating that microbubbles preceded bmdVGE. These findings indicate that decompression-induced microbubbles can 1) be detected intravascularly at multiple sites, 2) appear in the presence and absence of bmdVGE, and 3) occur before bmdVGE. This supports the hypothesis that microbubbles precede larger VGE bubbles. Microbubble presence may be an early marker of decompression stress. Since DFU is a low-power ultrasonic method, it may be useful for operational diving applications.

Pure-tone audiometric threshold assessment with in-ear monitoring of noise levels

OBJECTIVE

Our objective was to obtain reliable threshold measurements without a sound booth by using a passive noise-attenuating hearing protector combined with in-ear 1/3-octave band noise measurements to verify the ear canal was suitably quiet.

DESIGN

We deployed laptop-based hearing testing systems to Tanzania as part of a study of HIV infection and hearing. An in-ear probe containing a microphone was used under the hearing protector for both the in-ear noise measurements and threshold audiometry. The 1/3-octave band noise spectrum from the microphone was displayed on the operator's screen with acceptable levels in grey and unacceptable levels in red. Operators attempted to make all bars grey, but focused on achieving grey bars at 2000 Hz and above.

STUDY SAMPLE

624 adults and 197 children provided 3381 in-ear octave band measurements. Repeated measurements from 144 individuals who returned for testing on three separate occasions were also analysed.

RESULTS

In-ear noise levels exceeded the maximum permissible ambient noise levels (MPANL) for ears not covered, but not the dB SPL levels corresponding to 0 dB HL between 2000-4000 Hz. In-ear noise measurements were repeatable over time.

CONCLUSIONS

Reliable audiometry can be performed using a passive noise-attenuating hearing protector and in-ear noise measurements.

Unusual neurological syndrome induced by atmospheric pressure change

BACKGROUND

We describe a case of a 46-yr-old female who developed hypertension, tachycardia, dysarthria, and leg weakness provoked by pressure changes associated with flying. Typically during the landing phase of flight, she would feel dizzy and note that she had difficulty with speech and leg weakness. After the flight the leg weakness persisted for several days. The symptoms were mitigated when she took a combined alpha-beta blocker (labetalol) prior to the flight.

CASE STUDY

To determine if these symptoms were related to atmospheric pressure change, she was referred for testing in a hyperbaric chamber. She was exposed to elevated atmospheric pressure (maximum 1.2 ATA) while her heart rate and blood pressure were monitored. Within 1 min she developed tachycardia and hypertension. She also quickly developed slurred speech, left arm and leg weakness, and sensory changes in her left leg. She was returned to sea level pressure and her symptoms gradually improved. A full neurological workup has revealed no explanation for these findings. She has no air collections, cysts, or other anatomic findings that could be sensitive to atmospheric pressure change.

DISCUSSION

The pattern is most consistent with a vascular event stimulated by altitude exposure. This case suggests that atmospheric pressure change can produce neurological symptoms, although the mechanism is unknown.

Hearing loss and heavy metal toxicity in a Nicaraguan mining community: audiological results and case reports

We measured fingernail metal levels, Békésy-type pure-tone thresholds and distortion product otoacoustic emission (DPOAE) levels in 59 subjects residing in the gold mining community of Bonanza, Nicaragua. Auditory testing revealed widespread hearing loss in the cohort. Nail metal concentrations (mercury, lead, aluminum, manganese and arsenic) far exceeded reference levels. No relationship was found between metal levels and auditory test results for the group as a whole. Statistically significant relationships were found between DPOAE response amplitudes and metal concentrations in a subgroup with less than 40 h per week of significant noise exposure; however, conclusions regarding these relationships should be tempered by the large number of analyses performed. Several young individuals with high metal levels reported neurological symptoms and had poor hearing. The data suggest that metal levels in artisanal mining communities present a significant public health problem and may affect hearing.

Electronic problem-solving treatment: description and pilot study of an interactive media treatment for depression

Background

Computer-automated depression interventions rely heavily on users reading text to receive the intervention. However, text-delivered interventions place a burden on persons with depression and convey only verbal content.

Objective

The primary aim of this project was to develop a computer-automated treatment for depression that is delivered via interactive media technology. By using branching video and audio, the program simulates the experience of being in therapy with a master clinician who provides six sessions of problem-solving therapy. A secondary objective was to conduct a pilot study of the program’s usability, acceptability, and credibility, and to obtain an initial estimate of its efficacy.

Methods

The program was produced in a professional multimedia production facility and incorporates video, audio, graphics, animation, and text. Failure analyses of patient data are conducted across sessions and across problems to identify ways to help the user improve his or her problem solving. A pilot study was conducted with persons who had minor depression. An experimental group (n = 7) used the program while a waitlist control group (n = 7) was provided with no treatment for 6 weeks.

Results

All of the experimental group participants completed the trial, whereas 1 from the control was lost to follow-up. Experimental group participants rated the program high on usability, acceptability, and credibility. The study was not powered to detect clinical improvement, although these pilot data are encouraging.

Conclusions

Although the study was not powered to detect treatment effects, participants did find the program highly usable, acceptable, and credible. This suggests that the highly interactive and immersive nature of the program is beneficial. Further clinical trials are warranted.

Trial Registration

ClinicalTrials.gov NCT00906581; http://clinicaltrials.gov/ct2/show/NCT00906581 (Archived by WebCite at http://www.webcitation.org/6A5Ni5HUp)

Microbubble detection following hyperbaric chamber dives using dual-frequency ultrasound

Venous gas emboli (VGE) can be readily detected in the bloodstream using existing ultrasound methods. No method currently exists to detect decompression-induced microbubbles in tissue. We hypothesized that dual-frequency ultrasound (DFU) could detect these microbubbles. With DFU, microbubbles are driven with two frequencies: a lower "pump" (set to the resonant frequency of the desired bubble size) and a higher "image" frequency. A bubble of the resonant size emits the sum and difference of the two transmitted frequencies. For this study we used a pump frequency of 2.25 MHz and an image frequency of 5.0 MHz, which detects bubbles of roughly 1-10 μm in diameter in a water tank. Four anesthetized swine were pressurized at 4.5 ATA for 2 h and decompressed over 5 min, inducing moderate to very severe VGE scores. Four sites on the thigh of each swine were monitored with DFU before and after the dives. A single mock dive was also performed. The number of sites returning signals consistent with microbubbles increased dramatically after the chamber dive (P < 0.01), but did not change with the mock dive. The increase in DFU signal after the chamber dive was sustained and present at multiple sites in multiple swine. This research shows for the first time that decompression-induced tissue microbubbles can be detected using DFU and that DFU could be used to monitor decompression-induced microbubbles at multiple sites on the body. Additionally, DFU could be used to track the time course of microbubble formation and growth during decompression stress.

Dual-frequency ultrasound detection of stationary microbubbles in tissue

Indirect evidence suggests that microbubbles that exist normally in tissue may play a key role in decompression sickness (DCS). Their sizes and locations are unknown. Dual-frequency ultrasound (DFU) exploits bubble resonance to detect bubbles over a wide size range and could potentially detect stationary tissue microbubbles. To test this capability, DFU was used to detect stationary microbubbles of known size (2-3 microm mean diameter) over a range of ultrasound pressures and microbubble concentrations. In gelatin phantoms doped with microbubbles and in ex vivo porcine tissue, signals indicative of bubbles were detected for microbubble concentrations of 5x10(5) per mL and greater. Signals were not returned from solid particle microspheres of similar size to the microbubbles or from saline controls. In the thigh of an anesthetized swine, signals were detected for concentrations of 5x10(7) per mL and greater. Because of its ability to detect bubbles over a wide range of sizes, this technique could potentially detect naturally-existing microbubbles in tissue and lead to (a) an improved understanding of the mechanics of bubble formation during decompression and (b) a new metric for evaluating DCS.

Chlorpheniramine and ephedrine in combination for motion sickness

Background: Chlorpheniramine is effective against motion sickness, but produces sedation. To reduce chlorpheniramine's sedating effect and increase its effectiveness, ephedrine was combined with chlorpheniramine to prevent motion sickness. Methods: Chlorpheniramine (C) and chlorpheniramine plus ephedrine (Chlorphedra) were studied in a randomized, double blind, crossover trial. Eighteen normal subjects were randomized to six different orderings of placebo, C (12 mg) or Chlorphedra (12 mg C + 50 mg ephedrine). They ingested the medication 3.25 hours before off vertical axis rotation in a rotating chair. Cognitive testing with both objective and subjective tests was performed before drug ingestion, at peak drug effect and following rotation. Results: Both C and Chlorphedra significantly increased chair time compared to placebo [6.6 to 10.3 minutes (C), 10.2 minutes (Chlorphedra), p < 0.01]. Subjects reported significantly more sleepiness on the Karolinska sleepiness scale after taking C (3.3 placebo, 4.9 C (p < 0.005)) but not with Chlorphedra (3.3 placebo, 3.1 Chlorphedra). Chlorphedra resulted in significantly higher reported alertness, clearheadedness and attentiveness compared to C. Deficits seen on objective tests with C were corrected with Chlorphedra. Subjects noted more side effects with Chlorphedra. Conclusion: Ephedrine does not increase the effectiveness of chlorpheniramine against motion sickness, but counteracts sedative and performance effects successfully.