Effectiveness of Continuous Positive Airway Pressure in Alleviating Hypoxemia and Improving Exertional Capacity at Altitude.

Strickland, Brian, Elan Small, Mary Ryan, and Ryan Paterson. Effectiveness of continuous positive airway pressure in alleviating hypoxemia and improving exertional capacity at altitude. High Alt Med Biol. 00:000-000, 2024. Introduction: Decreased oxygen saturation and exercise tolerance are commonly experienced at high altitude. Continuous positive airway pressure (CPAP) devices have become increasingly portable and battery powered, providing a potentially unique new therapeutic modality for treatment of altitude-related illnesses. This study evaluated the potential use of CPAP devices to improve and maintain oxygen saturation at altitude, both at rest and with exertion, to evaluate the feasibility of using this device at altitude. Methods: Subjects were taken to Mount Blue Sky and monitored while they hiked to the summit (4,350 m), maintaining a consistent level of exertion. Subjects hiked for 0.7 km both with and without CPAP set to 10 cmH2O pressure. Continuous vital signs were collected during the hike and recovery period. Results: All subjects completed the hike wearing CPAP devices at a vigorous level of exertion. Mean oxygen saturation of the CPAP group (M = 83.8%, SD = 3.72) was significantly higher than that of the control group during exertion (M = 78.7%, SD = 2.97); p = 0.005. Recovery after exertion was quicker in the CPAP group than the control group. Three subjects experienced claustrophobia requiring a brief pause, but were able to complete their exercise trial without removing equipment or experiencing adverse events. When pauses from claustrophobia were excluded, there was no difference in completion time between the groups (p = 0.06). Conclusion: CPAP reliably improved oxygen saturation at rest and during vigorous exertion at high altitude. Its ability to correct hypoxemia, even with physical exertion, may prove useful after further study as a portable self-carried device to prevent and treat altitude-related illness, or to improve safety in high-altitude rescues.

Adapting nitric oxide: A review of its foundation, uses in austere medical conditions, and emerging applications.

Nitric oxide was first identified as a novel and effective treatment for persistent pulmonary hypertension of the newborn (PPHN), and has since been found to be efficacious in treating acute respiratory distress syndrome (ARDS) and pulmonary hypertension. Physicians and researchers have also found it shows promise in resource-constrained settings, both within and outside of the hospital, such as in high altitude pulmonary edema (HAPE) and COVID-19. The treatment has been well tolerated in these settings, and is both efficacious and versatile when studied across a variety of clinical environments. Advancements in inhaled nitric oxide continue, and the gas is worthy of investigation as physicians contend with new respiratory and cardiovascular illnesses, as well as unforeseen logistical challenges.

Safety and practicality of high dose inhaled nitric oxide in emergency department COVID-19 patients.

BACKGROUND: Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator and mild bronchodilator that has been shown to improve systemic oxygenation, but has rarely been administered in the Emergency Department (ED). In addition to its favorable pulmonary vascular effects, in-vitro studies report that NO donors can inhibit replication of viruses, including SARS Coronavirus 2 (SARS-CoV-2). This study evaluated the administration of high-dose iNO by mask in spontaneously breathing emergency department (ED) patients with respiratory symptoms attributed to Coronavirus disease 2019 (COVID-19). METHODS: We designed a randomized clinical trial to determine whether 30 min of high dose iNO (250 ppm) could be safely and practically administered by emergency physicians in the ED to spontaneously-breathing patients with respiratory symptoms attributed to COVID-19. Our secondary goal was to learn if iNO could prevent the progression of mild COVID-19 to a more severe state. FINDINGS: We enrolled 47 ED patients with acute respiratory symptoms most likely due to COVID-19: 25 of 47 (53%) were randomized to the iNO treatment group; 22 of 47 (46%) to the control group (supportive care only). All patients tolerated the administration of high-dose iNO in the ED without significant complications or symptoms. Five patients receiving iNO (16%) experienced asymptomatic methemoglobinemia (MetHb) > 5%. Thirty-four of 47 (72%) subjects tested positive for SARS-CoV-2: 19 of 34 were randomized to the iNO treatment group and 15 of 34 subjects to the control group. Seven of 19 (38%) iNO patients returned to the ED, while 4 of 15 (27%) control patients did. One patient in each study arm was hospitalized: 5% in iNO treatment and 7% in controls. One patient was intubated in the iNO group. No patients in either group died. The differences between these groups were not significant. CONCLUSION: A single dose of iNO at 250 ppm was practical and not associated with any significant adverse effects when administered in the ED by emergency physicians. Local disease control led to early study closure and prevented complete testing of COVID-19 safety and treatment outcomes measures.

Sources for Altitude Illness Information for Trekkers in the Himalayas.

INTRODUCTION: Educational materials are important tools in the prevention of altitude illness among individuals traveling to high altitude destinations. Travelers obtain information about altitude illness from many different educational resources. Our objective was to determine which educational resources for altitude illness prevention were used by trekkers on the Everest Base Camp trek and Annapurna Circuit. We also sought to compare which resources were used by individuals from different geographic areas. METHODS: A survey was administered to trekkers attending an altitude illness information lecture at the Himalayan Rescue Association clinic. Trekkers provided their basic demographic information and educational resources they used while preparing for the trek. Comparisons were made between trekkers based on the resources they used, as well as their age and country of origin. RESULTS: Of 1075 surveys administered, 906 were completed. Internet sources were most commonly used by trekkers (49%), followed by friends or family (22%), and healthcare providers (18%). The age of participants using Internet sources was 36±12 y (mean±SD), lower than those who did not use Internet sources (39±14 y, P<0.01). Participants came from 8 geographic areas; Europe (55%), North America (24%), and Oceania (11%) made up the vast majority. Compared to the overall cohort, participants from Oceania demonstrated more Internet reliance at 65% (χ2(1, n=102)=9.7, P<0.01). CONCLUSIONS: In this group of trekkers in the Himalayas, the Internet was the most common source of information on altitude illness prevention and management. Trekkers using Internet sources were slightly younger than non-Internet users.

Hearing Outcomes after Revision Stapedectomy Managed with Total Ossicular Prostheses.

OBJECTIVES: (1) To describe the use of total ossicular prostheses (TOPs) in the setting of stapedectomy requiring an incus bypass procedure. (2) To analyze the short- and long-term audiometric results of TOP utilization in the setting of stapedectomy for an incus bypass procedure. STUDY DESIGN: Case series with chart review. SETTING: Tertiary neurotologic referral center. SUBJECTS AND METHODS: Seventeen cases of TOP reconstruction after stapedectomy were performed due to advanced incus erosion. The cases were assessed for pre- and postoperative bone conduction and air conduction pure-tone averages (PTAs; 0.5, 1, 2, 3 kHz), including high-tone bone conduction (1, 2, 4 kHz), air-bone gap, and speech discrimination scores. Hearing outcomes were measured: short-term (3 weeks) and long-term (average, 22 months). RESULTS: Among 17 ears undergoing revision stapedectomy managed with TOP reconstruction, the average number of previous revision attempts was 1.0 (SD, 1; range, 1-5). The preoperative bone conduction PTA was 30.7 dB preoperatively, while the preoperative air conduction PTA was 64.3 dB. The mean postoperative air-bone gap significantly decreased to 18.9 dB (SD, 12.7; range, 5-46.25; P < .003) with a mean follow-up of 22.2 months (SD, 25.0; range, 0.75-78). No significant decrement in high-tone bone conduction PTA was observed (mean, 0 dB; SD, 12.8; range, -36.7 to 20; P = .427); however, 1 ear revealed a severe decrease in PTA and speech discrimination score postoperatively. No further revisions were noted in follow-up. CONCLUSION: TOP reconstruction in the setting of previous revision stapedectomy with limited incudovestibular reconstructive options may lead to favorable hearing outcomes, but it carries an increased risk of sensorineural hearing loss.

Evaluation of the increased use of partial resection of large vestibular schwanommas: facial nerve outcomes and recurrence/regrowth rates.

OBJECTIVE: To determine whether partial tumor removal in large vestibular schwannoma improves facial nerve outcomes while maintaining a low risk of tumor regrowth/recurrence. STUDY DESIGN: Retrospective chart review and prospective database. SETTING: Tertiary neurotologic referral center. PATIENTS: Four hundred patients with a vestibular schwannoma of 2.5 cm or greater in maximum diameter undergoing translabyrinthine microsurgical resection from 2001 to 2011. There were 325 gross total resections (GTR), 44 near total resections (NTR), and 31 subtotal resections (STR), with an overall mean tumor size of 3.2 cm (standard deviation, 0.7). INTERVENTION(S): Translabyrinthine surgical tumor resection. MAIN OUTCOME MEASURES: House-Brackmann (H-B) facial nerve grade postoperatively and at 1 year, tumor regrowth/recurrence (≥2 mm), additional treatment, and complications. RESULTS: Higher rates of H-B facial nerve Grades I and II were achieved at both the postoperative and 1-year follow-ups in the NTR (78%, 97%) and STR (71%, 96%) groups compared with GTR (53%, 77%) (p ≤ 0.001). Eye treatment, medical or surgical, was required more often in GTR (28.0%) than NTR and STR (8% and 21%, respectively, p ≤ 0.04), with no other differences in complications. The NTR and STR groups had a significantly higher rate of regrowth than GTR resection (21% and 22% versus 3%) (p ≤ 0.001) at average follow-up times of 3.7, 3.7, and 5.1 years, respectively, and need for further treatment occurred at a higher rate, although infrequently, in NTR and STR (2% and 10% versus 0%) (p ≤ 0.001). CONCLUSION: Near total and subtotal removal in large tumors are viable treatment options to maintain facial nerve function. During the follow-up period examined in this study, there was a low risk of need for further treatment. Longer-term follow-up is needed to better assess the need for retreatment in patients treated with NTR and STR.