The effects of flight and altitude

Comparative Analysis of Gene Expression at Sea Level and High Altitude: A Quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) Approach

This research studies the gene expression in response to different oxygen environments and looks at high vs low oxygen environments. Tracking down the activity of some of these genes, namely VHLEL, VEGF and HIF-1α, quantitative real-time polymerase chain reaction (PCR) analysis was done for the study group at sea level in Jeddah and at high altitude in Taif city. It has been found that these genes are much more active in higher altitudes which indicates that there is a biological mechanism that makes those specific sites more oversized for the issue of low oxygen. This knowledge is beneficial as it helps in understanding how people grow to live in high-altitude regions. This is positive, especially in justifying the use of the methods in treatment of altitude sickness and other related diseases. Although these findings bring some hope, it would be equally important to include more participants in future studies in order to consolidate our findings and gain deeper understanding of physiological adaptation in low oxygen. This research work has potential significant contribution to the medical profession under conditions of similar environment.

Short communication: Maintained visual performance in birds under high altitude hypoxia

Birds are highly dependent on their vision for orientation and navigation. The avian eye differs from the mammalian eye as the retina is avascular, leaving the inner, highly metabolically active layers with a very long diffusion distance to the oxygen supply. During flight at high altitudes, birds face a decrease in environmental oxygen partial pressure, which leads to a decrease in arterial oxygen levels. Since oxygen perfusion to the retina is already limited in birds, we hypothesize that visual function is impaired by low oxygen availability. However, the visual performance of birds exposed to hypoxia has not been evaluated before. Here, we assess the optomotor response (OMR) in zebra finches under simulated high-altitude hypoxia (10%) and show that the OMR is largely maintained under hypoxia with only a modest reduction in OMR, demonstrating that birds can largely maintain visual function at high altitudes. The method of our study does not provide insight into the mechanisms involved, but our findings suggest that birds have evolved physiological mechanisms for retinal function at low tissue oxygen levels.

The chronic leukocyte and inflammatory cytokine responses of older adults to resistance training in normobaric hypoxia; a randomized controlled trial

TRIAL DESIGN

Older adults experience chronic dysregulation of leukocytes and inflammatory cytokines, both at rest and in response to resistance training. Systemic hypoxia modulates leukocytes and cytokines, therefore this study characterized the effects of normobaric hypoxia on the leukocyte and cytokine responses of older adults to resistance training.

METHODS

20 adults aged 60-70 years performed eight weeks of moderate-intensity resistance training in either normoxia or normobaric hypoxia (14.4% O2), consisting of two lower body and two upper body exercises. Venous blood was drawn before and after the training intervention and flow cytometry was used to quantify resting neutrophils, lymphocytes, monocytes, eosinophils and basophils, in addition to the subsets of lymphocytes (T, B and natural killer (NK) cells). Inflammatory cytokines were also quantified; interleukin 1 beta (IL-1β), IL-4, IL-6, IL-8, IL-10 and tumor necrosis factor alpha (TNF-α). Acute changes in leukocytes and cytokines were also measured in the 24 h following the last training session.

RESULTS

After the intervention there was a greater concentration of resting white blood cells (p = 0.03; 20.3% higher) T cells (p = 0.008; 25.4% higher), B cells (p = 0.004; 32.6% higher), NK cells (p = 0.012; 43.9% higher) and eosinophils (p = 0.025; 30.8% higher) in hypoxia compared to normoxia, though the cytokines were unchanged. No acute effect of hypoxia was detected in the 24 h following the last training session for any leukocyte population or inflammatory cytokine (p < 0.05).

CONCLUSIONS

Hypoxic training caused higher concentrations of resting lymphocytes and eosinophils, when compared to normoxic training. Hypoxia may have an additional beneficial effect on the immunological status of older adults.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ANZCTR).

TRIAL NUMBER

ACTRN12623001046695. Registered 27/9/2023. Retrospectively registered. All protocols adhere to the COSORT guidelines.

Air Transportation Impact on a Late Preterm Neonate

BACKGROUND: Neonatal air transportation is a crucial means of moving critically ill or sick neonates to specialized neonatal intensive care units or medical centers for consultation, regardless of distance or geographical limits. Proper preparation and consideration of air transport can help alleviate medical emergencies and ensure safe delivery. However, crewmembers and neonates may face stress during transportation. To date, there are few studies on neonatal air transportation in Taiwan.CASE REPORT: We present the case of a late preterm neonate born with neonatal respiratory distress syndrome and polycythemia, who was also diagnosed with patent ductus arteriosus and mild pulmonary arterial hypertension on echocardiography. Due to disease progression, the neonate underwent endotracheal intubation and was subsequently transported to a medical center in Taiwan via a rotary-wing aircraft at 3 d of age. During takeoff and landing, a temporary oxygen desaturation event occurred. The physiological changes in these patients have seldom been discussed. This case emphasizes the important considerations of neonatal transport in Taiwan.DISCUSSION: The air transport process could be influenced by both the patient's medical condition and environmental factors. In preterm infants with cardiopulmonary conditions, thorough assessment is necessary for ensuring safe transportation.Li S-P, Hsu P-C, Huang C-Y, Wu P-W, Fang H-H. Air transportation impact on a late preterm neonate. Aerosp Med Hum Perform. 2024; 95(4):219-222.

Retrospective analysis of referrals for hypoxic challenge testing in children born preterm

INTRODUCTION

Children with a history of bronchopulmonary dysplasia (BPD) may be at risk of hypoxaemia at altitude, such as during air travel. We have performed preflight hypoxic challenge testing (HCT) since 2006, incorporating British Thoracic Society (BTS) guidance since 2011, to determine which children may require oxygen during air travel.

AIMS

We aimed to compare the outcome of HCTs in children with a history of BPD who met the 2011 BTS criteria and those who did not and, in addition to this, to interrogate the data for factors that may predict the outcome of HCT in this population.

METHODS

We performed a retrospective analysis of data from HCTs of children with a history of BPD referred 2006-2020. Cases were excluded if the patient had a respiratory comorbidity, was still on oxygen therapy, if the test was a repeat or if the clinical record was incomplete. Descriptive and univariate analysis of the data was performed, and a binary logistic regression model was fitted.

RESULTS

There were 79 HCTs, of which 24/79 (30%) did not meet BTS 2011 guidelines referral criteria. The analysis showed a greater proportion of desaturation in the group that did not meet criteria: 46% vs 27% (no statistical significance). Baseline oxygen saturations were higher in those who did not require oxygen during HCT and this variable was significant when adjusted for confounders.

CONCLUSIONS

This study found that the current criteria for referral for preflight testing may incorrectly identify those most at risk and highlights the need for further investigation to ensure those most at risk are being assessed prior to air travel.

Imaging of Alternobaric Facial Palsy: An Etiologic Hypothesis

OBJECTIVE

To report a case of alternobaric facial palsy (AFP) with a hyperpneumatized temporal bone and to review the relevant literature in order to propose a new facet of AFP pathogenesis.

METHODS

A patient with a hyperpneumatized temporal bone was found to have recurrent episodes of facial palsy associated with air travel. Systematic review of PubMed, Cochrane Library, and Embase characterized all articles related to transient facial palsy associated with altitude changes or diving with a focus on demographics and imaging findings.

RESULTS

A 25 year-old male was referred for recurrent facial palsy associated with commercial air travel. Imaging demonstrated a hyperpneumatized and well-aerated temporal bone. Total air cell volume was calculated to be 8.59 cc on the affected side. A systematic review of the literature identified 49 cases of AFP. Mean age was 34 years old and 80% were male. Twelve cases had imaging of the temporal bone for evaluation, of which 85% demonstrated at least 1 area of hyperpneumatization. Hyperpneumatization was most frequently encountered in the mastoid, zygomatic root, and inferior petrous apex.

CONCLUSION

Hyperpneumatization of the temporal bone is critical to AFP etiology as it predicts higher middle ear pressure, if atmospheric pressure changes cannot be equilibrated, via reduced efficacy of normal tympanic membrane pressure buffering. This hypothesis helps to better account for the rarity of the condition and male preponderance.

Long-distance transfer of unwell neonates: A case series

AIM

The Northern Territory Neonatal Emergency Transport Service (NETS NT) pilot was created in April 2018 to expedite the transfer of critically unwell neonates to specialised interstate centres. The aim of this paper is to describe long-distance retrievals undertaken during the first 3 years of operation of the service.

METHODS

A case series is described comprising neonates requiring long-distance aeromedical transfer (>2500 km) by NETS NT between April 2018 and June 2021. Data were obtained from hospital and transport service documentation. This was supplemented by four semi-structured interviews with transport staff.

RESULTS

Thirty neonates were transferred via NETS NT during the investigation period, including 19 transfers >2500 km. Of these, 18/19 (94.7%) required respiratory support, 8/19 (42.1%) were intubated and 4/19 (21.1%) required inotropic support. The average length of transport was 7.5 h (5.6-8.9). Twelve patients had in-flight documentation available. Eight required increased oxygen administration 8/12 (66.6%). The median change in FiO2 was an increase of 0.02 (-0.05 to 0.45).

CONCLUSIONS

The NETS NT has been successfully established to transport high-risk neonates to interstate quaternary health services when required. Future recommendations for the service include ongoing implementation of systems and processes to strengthen all aspects of governance and operations using suitably adapted resources from established Australian retrievals services.

Pre-Flight Hypoxemia Challenge Testing in Bronchopulmonary Dysplasia

BACKGROUND AND OBJECTIVES

Former premature infants with bronchopulmonary dysplasia (BPD) are at risk for hypoxemia during air travel, but it is unclear until what age. We aimed to determine pass rates for high altitude simulation testing (HAST) by age in children with BPD and identify risks for failure.

METHODS

Retrospective, observational analysis of HAST in children with BPD at Boston Children's Hospital, using interval censoring to estimate the time-to-event curve of first pass. Curves were stratified by neonatal risk factors. Pass was considered lowest Spo2 ≥ 90%, or ≥94% for subjects with ongoing pulmonary hypertension (PH).

RESULTS

Ninety four HAST studies were analyzed from 63 BPD subjects; 59 studies (63%) were passed. At 3 months corrected gestational age (CGA), 50% of subjects had passed; at 6 months CGA, 67% has passed; at 12 and 18 months CGA, 72% had passed; and at 24 months CGA, 85% had passed. Neonatal factors associated with delayed time-to-pass included postnatal corticosteroid use, respiratory support at NICU discharge, and tracheostomy. BPD infants who did not require respiratory support at 36 weeks were likely to pass (91%) at 6 months CGA. At 24 months, children least likely to pass included those with a history of PH (63%) and those discharged from the NICU with oxygen or respiratory support (71%).

CONCLUSIONS

Children with BPD on respiratory support at 36 weeks should be considered for preflight hypoxemia challenges through at least 24 months CGA, and longer if they had PH or went home from NICU on respiratory support.

Prevalence of High-Altitude Polycythemia and Hyperuricemia and Risk Factors for Hyperuricemia in High-Altitude Immigrants

Song Zhen, Anxin Zhang, Jie Luo, Guanghai Xiong, Haibo Peng, Rang Zhou, Yuanfeng Li, Hongqiang Xu, Zhen Li, Wei Zhao, and Haoxiang Zhang. Prevalence of high-altitude polycythemia and hyperuricemia and risk factors for hyperuricemia in high-altitude immigrants. High Alt Med Biol. 24:132-138, 2023. Background: Few studies have investigated the epidemiology of chronic mountain sickness (CMS) in high-altitude immigrants. This study evaluated the prevalence of polycythemia and hyperuricemia (HUA) and risk factors for HUA in high-altitude immigrants. Methods: A cross-sectional study was conducted with 7,070 immigrants 15-45 years of age living on the Tibetan Plateau between January and December 2021. Information from routine physical examinations was obtained from each participant. Binary logistic regression analysis was performed to determine the correlation of several risk factors for HUA. Results: The prevalence of high-altitude polycythemia (HAPC) and HUA was 25.8% (28.7% in males and 9.4% in females) and 54.2% (59.9% in males and 22.5% in females), respectively. The highest prevalence of HAPC in males and females was observed in participants 26-30 and 21-25 years of age, respectively. The highest prevalence of HUA in both males and females was observed in participants 26-30 years of age. Binary logistic regression analysis showed that age, sex, and hemoglobin (Hb) concentration were risk factors for HUA, among which age was a negative factor and male sex and Hb concentration were positive factors. Conclusions: Immigrants are more susceptible to HAPC and HUA. The high prevalence of CMS of immigrants may be associated with Hb concentration, age, and sex.

Modified hypoxic challenge testing in children needing nocturnal ventilation: An observational study

BACKGROUND

Guidelines for air passengers with respiratory disease focus on primary lung pathology. Little evidence exists to guide professionals advising children needing ventilatory support because of neuromuscular or central hypoventilation conditions; these children might risk hypoxia and hypercapnia if unable to mount an adequate hyperventilation response.

OBJECTIVE

This study assessed the response to low ambient oxygen using a modified hypoxic challenge test. In addition to measuring pulse oximetry and response to supplementary oxygen, we also measured transcutaneous carbon dioxide and response to ventilatory support.

METHODS

Twenty children on nocturnal ventilatory support aged 1.6-18 years were recruited in a pragmatic sample from outpatient clinics; 10 with neuromuscular weakness and 10 with central hypoventilation. Participants underwent a two-stage, modified hypoxic challenge test; a conventional stage, where oxygen alone was titrated according to SpO_2, and a new stage, where participants used their routine ventilatory support with oxygen titrated if needed. Participants were interviewed to understand their experiences of testing and of air travel.

RESULTS

Thirteen participants needed supplemental oxygen during the conventional stage, but only two did when using ventilatory support. Transcutaneous carbon dioxide remained within normal range for all participants, on or off ventilatory support. Whilst some participants found testing challenging, participants generally reported both testing and air travel to be valuable.

CONCLUSIONS

Evaluating response to patients' usual ventilation through "fitness-to-fly" assessment aids decision making when considering whether children who receive nocturnal ventilation can travel by air, since for some using a ventilator reduces or avoids the need for supplemental oxygen.

The effects of normobaric hypoxia on the leukocyte responses to resistance exercise

There is growing interest in the use of systemic hypoxia to improve the training adaptations to resistance exercise. Hypoxia is a well-known stimulator of the immune system, yet the leukocyte responses to this training modality remain uncharacterised. The current study characterised the acute leukocyte responses to resistance exercise in normobaric hypoxia. The single-blinded, randomised trial recruited 13 healthy males aged 18-35 years to perform a bout of resistance exercise in normobaric hypoxia (14.4% O₂; n = 7) or normoxia (20.9% O₂; n = 6). Participants completed 4 × 10 repetitions of lower and upper body exercises at 70% 1-repetition maximum. Oxygen saturation, rating of perceived exertion and heart rate were measured during the session. Venous blood was sampled before and up to 24 hours post-exercise to quantify blood lactate, glucose and leukocytes including neutrophils, lymphocytes, monocytes, eosinophils and basophils. Neutrophils were higher at 120 and 180 minutes post-exercise in hypoxia compared to normoxia (p<0.01), however lymphocytes, monocytes, eosinophils and basophils were unaffected by hypoxia. Oxygen saturation was significantly lower during the four exercises in hypoxia compared to normoxia (p < 0.001). However, there were no differences in blood lactate, heart rate, perceived exertion or blood glucose between groups. Hypoxia amplified neutrophils following resistance exercise, though all other leukocyte subsets were unaffected. Therefore, hypoxia does not appear to detrimentally affect the lymphocyte, monocyte, eosinophil or basophil responses to exercise.

Hormonal and metabolic responses of older adults to resistance training in normobaric hypoxia

PURPOSE

In young adults, the hormonal responses to resistance exercise are amplified by normobaric hypoxia. Hormone concentrations and metabolism are typically dysregulated with age, yet the impact of hypoxia on these responses to resistance exercise are uncharacterised. Therefore, this study aimed to characterise the acute and chronic hormonal and metabolic responses of older adults to resistance training in normobaric hypoxia.

METHODS

Adults aged 60-75 years completed 8 weeks of resistance training in either normoxia (20.9% O₂; n = 10) or normobaric hypoxia (14.4% O₂, n = 10) twice weekly at 70% of their predicted 1-repetition maximum. Growth hormone, glucose, lactate, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), cortisol, total testosterone, adrenaline, noradrenaline and dopamine were quantified at pre- and post-training, and in the 60 min following the first training session (untrained state) and the last training session (trained state).

RESULTS

Eight weeks of training in hypoxia did not affect the resting levels of the hormones or physiological factors measured. However, hypoxia significantly blunted the acute growth hormone response in the 15 min following the last training session at week eight (43.87% lower in the hypoxic group; p = 0.017). This novel and unexpected finding requires further investigation. All other hormones were unaffected acutely by hypoxia in the 60 min following the first and the last training session.

CONCLUSION

Chronic resistance training in normobaric hypoxia supresses the growth hormone response to exercise in older adults. All other hormones and metabolic markers were unaffected both acutely and chronically by hypoxia.

Altitude exposure in pediatric pulmonary hypertension-are we ready for (flight) recommendations?

Patients with congenital heart disease are surviving further into adulthood and want to participate in multiple activities. This includes exposure to high altitude by air travel or recreational activities, such as hiking and skiing. However, at an altitude of about 2,500 m, the barometric environmental pressure is reduced and the partial pressure of inspired oxygen drops from 21% to 15% (hypobaric hypoxia). In physiologic response to high-altitude-related hypoxia, pulmonary vasoconstriction is induced within minutes of exposure followed by compensatory hyperventilation and increased cardiac output. Even in healthy children and adults, desaturation can be profound and lead to a significant rise in pulmonary pressure and resistance. Individuals with already increased pulmonary pressure may be placed at risk during high-altitude exposure, as compensatory mechanisms may be limited. Little is known about the physiological response and risk of developing clinically relevant events on altitude exposure in pediatric pulmonary hypertension (PAH). Current guidelines are, in the absence of clinical studies, mainly based on expert opinion. Today, healthcare professionals are increasingly faced with the question, how best to assess and advise on the safety of individuals with PAH planning air travel or an excursion to mountain areas. To fill the gap, this article summarises the current clinical knowledge on moderate to high altitude exposure in patients with different forms of pediatric PAH.

Hyperbaric oxygen therapy for paediatric patients: an unintended consequence of the COVID-19 pandemic

OBJECTIVE

Hyperbaric oxygen therapy (HBOT) is a useful adjunctive treatment for selected complicated wounds, including severe diabetic lower extremity ulcerations and compromised skin grafts or flaps. The Sars-CoV-2 (COVID-19) pandemic has disrupted healthcare delivery, with its effects extending to delivery of HBOT. During the pandemic, paediatric patients in our geographic region who were referred for HBOT faced challenges as centres temporarily closed or were unprepared to treat younger patients. Our monoplace HBOT centre modified existing practices to allow for treatment of these patients. This study aims to outline the steps necessary to adapting a pre-existing HBOT centre for the safe treatment of paediatric patients.

METHOD

A retrospective review was performed to identify patients 18 years of age or younger referred for HBOT during 2020. Patient characteristics, referral indications and HBOT complications were collected. Changes implemented to the HBOT centre to accommodate the treatment of paediatric patients were documented.

RESULTS

A total of seven paediatric patients were evaluated for HBOT and six were treated. The mean patient age was four years (range: 1-11 years). Referral diagnoses included sudden sensorineural hearing loss, skin flap or graft compromise, and radiation-induced soft tissue necrosis. All patients tolerated HBOT treatment in monoplace chambers without significant complications noted. Enhancements made to our clinical practice to facilitate the safe and effective treatment of paediatric patients included ensuring the availability of acceptable garments for paediatric patients, maintaining uninterrupted patient grounding (in relation to fire safety), and enhancing social support for anxiety reduction.

CONCLUSION

The results of our review show that paediatric patients can be safely treated within the monoplace hyperbaric environment.

The Impact of Temporary Stay at High Altitude on the Circulatory System

In recent times many people stay temporarily at high altitudes. It is mainly associated with the growing popularity of regular air travel, as well as temporary trips to mountain regions. Variable environmental conditions, including pressure and temperature changes, have an impact on the human body. This paper analyses the physiological changes that may occur while staying at high altitude in healthy people and in people with cardiovascular diseases, such as arterial hypertension, pulmonary hypertension, heart failure, ischemic heart disease, or arrhythmias. Possible unfavourable changes were underlined. Currently recognized treatment recommendations or possible treatment modifications for patients planning to stay at high altitudes were also discussed.

Altitude and risk of sudden unexpected infant death in the United States

The effect of altitude on the risk of sudden infant death syndrome (SIDS) has been reported previously, but with conflicting findings. We aimed to examine whether the risk of sudden unexpected infant death (SUID) varies with altitude in the United States. Data from the Centers for Disease Control and Prevention (CDC)'s Cohort Linked Birth/Infant Death Data Set for births between 2005 and 2010 were examined. County of birth was used to estimate altitude. Logistic regression and Generalized Additive Model (GAM) were used, adjusting for year, mother's race, Hispanic origin, marital status, age, education and smoking, father's age and race, number of prenatal visits, plurality, live birth order, and infant's sex, birthweight and gestation. There were 25,305,778 live births over the 6-year study period. The total number of deaths from SUID in this period were 23,673 (rate = 0.94/1000 live births). In the logistic regression model there was a small, but statistically significant, increased risk of SUID associated with birth at > 8000 feet compared with < 6000 feet (aOR = 1.93; 95% CI 1.00-3.71). The GAM showed a similar increased risk over 8000 feet, but this was not statistically significant. Only 9245 (0.037%) of mothers gave birth at > 8000 feet during the study period and 10 deaths (0.042%) were attributed to SUID. The number of SUID deaths at this altitude in the United States is very small (10 deaths in 6 years).

Supplemental oxygen therapy recommendations in patients with sickle cell disease during air travel: A cross-sectional survey of North American health care providers

INTRODUCTION

Air travel may expose patients with sickle cell disease (SCD) to an increased risk of disease-related complications. Several factors are felt to contribute including prolonged hypoxia, dehydration, temperature changes, and stress. The Canadian Paediatric Society (CPS) position statement, published in 2007, recommends that SCD patients use supplemental oxygen on flights. While the National Heart, Lung and Blood Institute (NHLBI) recommend that SCD patients dress warmly, stay hydrated, and move about the cabin. Other guidelines do not make specific recommendations.

METHODS

A cross-sectional online survey was circulated through the Canadian Hemoglobinopathy Association (CanHaem) and American Society of Pediatric Hematology and Oncology (ASPHO) listservs to North American health care practitioners (HCPs). Participants were asked to share their air travel recommendations for patients with SCD. Similarly, a patient survey regarding experiences with air travel was circulated through the Sickle Cell Disease Association of Canada (SCDAC) and the Sickle Cell Foundation of Alberta (SCFOA) listservs and discussion boards.

RESULTS

Although air travel is perceived to be a risk factor for sickling complications, only 18% of HCPs recommend supplemental oxygen. Most HCPs advise patients to increase hydration, carry analgesics, and wear warm clothes to prevent sickling complications. The patient survey was limited by a low response rate.

CONCLUSION

The majority of HCPs are not routinely recommending prophylactic oxygen to patients with SCD during air travel.

Why is medical oxygen a challenge for people travelling by air?

There are currently 3.5 million people in Europe who require medical oxygen, and as life expectancies increase, this figure is likely to grow. At the same time, air travel is becoming more accessible to a wider range of people, as costs of flights fall, and airlines and airports make improvements to the accessibility of their services. People who need medical oxygen to fly experience a wide range of difficulties when planning to travel by plane, and sometimes during or after the flight. A European Commission Regulation (EC No 1107/2006) sets the standard for airlines when it comes to making air travel accessible, but healthcare professionals and oxygen providers can both help patients to navigate the various requirements for using medical oxygen when travelling. In this review, we discuss the journey of the patient planning to travel by air, from initial consultation and fit-to-fly test, through to planning their air travel and oxygen supply, travelling, and arriving at their destination. We also highlight some common problems at each stage and suggest points for healthcare professionals to discuss with patients.

KEY POINTS

Patients who require medical oxygen for air travel should begin planning their trip as far in advance as possible.It is very advantageous for healthcare professionals to be able to advise patients on travelling with oxygen and what they need to do.Requirements and policies can vary greatly between airlines, causing problems for patients who are trying to book their flights.Patients or their carers need to be confident operating their oxygen equipment, as the stress of travel and lack of medical assistance on an airplane can put them at risk.Careful arrangements need to be made by the patient to make sure that they have the correct oxygen therapy at their destination, and can access support if they need it.

EDUCATIONAL AIMS

To understand the process and potential challenges for a patient who requires oxygen to travel by plane.To be confident in discussing air travel with patients who are affected by lung disease.

Neonatal Respiratory Support on Transport

Respiratory support is frequently required during neonatal transport. This review identifies the various modalities of respiratory support available during neonatal transport and their appropriate clinical uses. The respiratory equipment required during neonatal transport and appropriate safety checks are also reviewed. In addition, we discuss potential respiratory emergencies and how to respond to them to decrease the risk of complications during transport and improve health outcomes.

Static and dynamic forces in the incudostapedial joint gap

Dynamic pressure at the tympanic membrane is transformed and subsequently transferred through the ossicular chain in the form of forces and moments. The forces are primarily transferred to the inner ear. They are transferred partly to the stapedial annular ligament which exhibits non-linear behavior and stiffens for larger static forces. In unventilated middle ears, static pressure is additionally transferred to the ossicles. The purpose of this study was to measure the force inside the ossicular chain as a physiological parameter. We determined the forces which act for dynamic sound transmission and for static load on the ossicular chain. The study is the first one which introduces these forces. The static forces have direct impact on clinically relevant questions for middle ear reconstructions with passive or active prosthesis. The dynamic forces have an impact on the development of middle ear sensors. Quasi-static forces in the incudostapedial joint (ISJ) gap were measured with two different sensor types in 17 temporal bones. The sensing elements, a single crystal piezo and a strain gauge element for validation, were bonded to a thin flexible titanium plate and encapsulated in a titanium housing to allow the acquisition of the applied force signal inside the ossicular chain. Dynamic forces were measured in 11 temporal bones with the piezo sensor. We measured a static force of 23 mN in the ISJ after sensor insertion. The mean force for dynamic physiological acoustic excitation from 250 Hz to 6 kHz was 26 μN/Pa. If the tympanic membrane is loaded with a static pressure, the static force in the ISJ increases up to 1 N for a maximum static pressure load scenario of 30 kPa.

Critical Care Performance in a Simulated Military Aircraft Cabin Environment

BACKGROUND

Critical Care Air Transport Teams care for 5% to 10% of injured patients who are transported on military aircraft to definitive treatment facilities. Little is known about how the aeromedical evacuation environment affects care.

OBJECTIVES

To determine the effects of 2 stressors of flight, altitude-induced hypoxia and aircraft noise, and to examine the contributions of fatigue and clinical experience on cognitive and physiological performance of the Critical Care Air Transport Team.

METHODS

This repeated measures 2 × 2 × 4 factorial study included 60 military nurses. The participants completed a simulated patient care scenario under aircraft cabin noise and altitude conditions. Differences in cognitive and physiological performance were analyzed using repeated measures analysis of variance. A multiple regression model was developed to determine the independent contributions of fatigue and clinical experience.

RESULTS

Critical care scores (P = .02) and errors and omissions (P = .047) were negatively affected by noise. Noise was associated with increased respiratory rate (P = .02). Critical care scores (P < .001) and errors and omissions (P = .002) worsened with altitude-induced hypoxemia. Heart rate and respiratory rate increased with altitude-induced hypoxemia; oxygen saturation decreased (P < .001 for all 3 variables).

CONCLUSION

In a simulated military aircraft environment, the care of critically ill patients was significantly affected by noise and altitude-induced hypoxemia. The participants did not report much fatigue and experience did not play a role, contrary to most findings in the literature.

Fitness to fly in the paediatric population, how to assess and advice

The number of children on commercial aircrafts is rising steeply and poses a need for their treating physicians to be aware of the physiologic effects and risks of air travel. The most important risk factors while flying are a decrease in partial oxygen pressure, expansion of trapped air volume, low cabin humidity, immobility, recirculation of air and limited options for medical emergencies. Because on-board medical emergencies mostly concern exacerbations of chronic disease, the medical history, stability of current disease and previous flight experience should be assessed before flight. If necessary, hypoxia altitude simulation testing can be performed to simulate the effects of in-flight hypoxia. Although the literature on paediatric safety of air travel is sparse, recommendations for many different situations can be given.

CONCLUSION

We present an overview of the most up to date recommendations to ensure the safety of children during flight. What is Known: • Around 65% of on-board medical emergencies are complications of underlying disease. • In children, the three most common emergencies during flight concern respiratory, neurological and infectious disease. What is New: • Although studies are scarce, some advices to ensure safe air travel can be given for most underlying medical conditions in children, based on physiology, studies in adults and expert opinions. • In former preterm infants without chronic lung disease, hypoxia altitude simulation testing to rule out in-flight desaturation is not recommended.

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.

Hypoxic Challenge Test for airflight in children with respiratory disease

During airflight, cabins are pressurised to 8000ft (2438m) leading to an effective FiO₂ of 0.15. This leads to a fall in oxygen saturation in all passengers, and especially those with underlying lung disease. The hypoxic challenge test using a body plethysmograph can predict a need for supplemental oxygen during airflight, and the process is described.

Negative Association of Hospital Efficiency Under Increasing Geographic Elevation on Acute Myocardial Infarction In-Patient Mortality

Although variation in-patient outcomes based on hospitals' geographic location has been studied, altitude of hospitals above sea level may also affect patient outcomes. Possibly, because of negative physical and psychological effects of altitude on hospital employees, hospital efficiency may decline at higher altitudes. Greater focus on hospital efficiency, despite decreasing efficiency at higher altitudes, could increase demands on hospital employees and further deteriorate patient outcomes. Using data envelopment analysis on a sample of 840 hospital-year observations representing 95,504 patients with acute myocardial infarction (AMI) in the United States, and controlling for patient, hospital, and county characteristics and controlling for hospital, state, and year fixed effects, we find support for the negative association between hospital altitude and efficiency; for 1 percentage point increase in efficiency and every 1,000 feet increase in altitude above the sea level, the mortality of patients with AMI increases by 0.66 percentage points. The findings have implications for hospital performance at increasing geographic elevation and introduces to the literature the notion of "health economics of elevation," to suggest that elevation of a hospital may be an important criterion for consideration for policy makers and insurance firms.

Hypoxia Challenge Testing in Neonates for Fitness to Fly

BACKGROUND

Preflight hypoxia challenge testing (HCT) in a body plethysmograph has previously been done only on infants >3 months of corrected gestational age (CGA). This study aims to determine the earliest fit-to-fly age by testing neonates <1 week old.

METHODS

A prospective observational study was carried out on 3 groups of infants: healthy term infants ≤7 days old, preterm infants (≥34 weeks CGA) 2 to 3 days before discharge, and preterm infants with bronchopulmonary dysplasia (BPD). HCT was conducted using a body plethysmograph with a 15% fraction of inspired oxygen. The oxygen saturation (Spo2) test fail point was <85%.

RESULTS

Twenty-four term (mean CGA 40 weeks), 62 preterm (37 weeks), and 23 preterm with BPD (39.5 weeks) infants were tested. One term infant (4.2%) and 12 preterm infants without BPD (19.4%) failed. Sixteen (69.3%) preterm infants with BPD failed (P < .001), with a median drop in Spo2 of 16%. At 39 weeks CGA, neither preterm infants without BPD nor term infants had an Spo2 <85%. However, 7 of 12 term infants with BPD failed the HCT.

CONCLUSIONS

Term and preterm infants without BPD born at >39 weeks CGA do not appear to be likely to desaturate during a preflight HCT and so can be deemed fit to fly according to current British Thoracic Society Guidelines.

Traveling with children: beyond car seat safety

OBJECTIVE

To spread knowledge and instigate the health professional to give advice on childcare during travels and on child transport safety.

SOURCES OF DATA

Literature review through the LILACS and MEDLINE(®) databases, using the terms: travel, safety, protective equipment, child, preventive medicine, retrieving articles published in the last 21 years.

SUMMARY OF THE FINDINGS

The authors analyzed 93 articles, of which 66 met the inclusion criteria after summaries were read. For drafting this article, the following sub-themes were proposed: getting ready to travel with children; knowing some of the transfer risks (air, land and water transportation) and exploring the destination with children (sun exposure, accommodations, altitude, food, traveler's diarrhea, insect bites) and return from the trip with children.

CONCLUSIONS

Over the years, there has been an increase in the number of children who travel around the world. However, this population is still subject to health problems while traveling and may be even more susceptible than the adult age group. These problems arise from a variety of factors, including exposure to infectious organisms, the use of certain types of transportation, and participation in some activities, such as hiking at high altitudes, among others. However, when traveling with children, these risk factors can be overlooked; a trip that is considered safe for an adult might not be a good choice for this age group. The pediatric consultation should be a good opportunity to optimize preventive guidelines at the pre-trip planning.

Prematurity and respiratory outcomes program (PROP): study protocol of a prospective multicenter study of respiratory outcomes of preterm infants in the United States

Background

With improved survival rates, short- and long-term respiratory complications of premature birth are increasing, adding significantly to financial and health burdens in the United States. In response, in May 2010, the National Institutes of Health (NIH) and the National Heart, Lung, and Blood Institute (NHLBI) funded a 5-year $18.5 million research initiative to ultimately improve strategies for managing the respiratory complications of preterm and low birth weight infants. Using a collaborative, multi-disciplinary structure, the resulting Prematurity and Respiratory Outcomes Program (PROP) seeks to understand factors that correlate with future risk for respiratory morbidity.

Methods/Design

The PROP is an observational prospective cohort study performed by a consortium of six clinical centers (incorporating tertiary neonatal intensive care units [NICU] at 13 sites) and a data-coordinating center working in collaboration with the NHLBI. Each clinical center contributes subjects to the study, enrolling infants with gestational ages 23 0/7 to 28 6/7 weeks with an anticipated target of 750 survivors at 36 weeks post-menstrual age. In addition, each center brings specific areas of scientific focus to the Program. The primary study hypothesis is that in survivors of extreme prematurity specific biologic, physiologic and clinical data predicts respiratory morbidity between discharge and 1 year corrected age. Analytic statistical methodology includes model-based and non-model-based analyses, descriptive analyses and generalized linear mixed models.

Discussion

PROP incorporates aspects of NICU care to develop objective biomarkers and outcome measures of respiratory morbidity in the <29 week gestation population beyond just the NICU hospitalization, thereby leading to novel understanding of the nature and natural history of neonatal lung disease and of potential mechanistic and therapeutic targets in at-risk subjects.

Trial registration

Clinical Trials.gov NCT01435187.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-015-0346-3) contains supplementary material, which is available to authorized users.

Impact of home oxygen therapy on hospital stay for infants with acute bronchiolitis

Acute bronchiolitis has been associated with an increasing hospitalization rate over the past decades. The aim of this paper was to estimate the impact of home oxygen therapy (HOT) on hospital stay for infants with acute bronchiolitis. A retrospective cohort study was done including all children aged ≤ 12 months discharged from a pediatric tertiary-care center with a diagnosis of bronchiolitis, between November 2007 and March 2008. Oxygen was administered according to a standardized protocol. We assumed children with the following criteria could have been sent home with O(2), instead of being kept in hospital: age ≥ 2 months, distance between home and hospital <50 km, in-hospital observation ≥ 24 h, O(2) requirement ≤ 1.0 L/min, stable clinical condition, no enteral tube feeding, and intravenous fluids <50 mL/kg/day. Children with significant underlying disease were excluded. A total of 177 children were included. Median age was 2.0 months (range 0-11), and median length of stay was 3.0 days (range 0-18). Forty-eight percent of patients (85/177) received oxygen during their hospital stay. Criteria for discharge with HOT were met in 7.1 % of patients, a mean of 1.8 days (SD 1.8) prior to real discharge. The number of patient-days of hospitalization which would have been saved had HOT been available was 21, representing 3.0 % of total patient-days of hospitalization for bronchiolitis over the study period (21/701).

CONCLUSIONS

In this study setting, few children were eligible for an early discharge with HOT. Home oxygen therapy would not significantly decrease the overall burden of hospitalization for bronchiolitis.

Altitude, oxygen and the definition of bronchopulmonary dysplasia

OBJECTIVE

The definition of bronchopulmonary dysplasia (BPD) among very-low birth weight (VLBW) infants is based upon oxygen requirement at 36 weeks gestation, but oxygen may be required at altitude because of hypoxia. This study determined the effect of altitude on BPD rates.

STUDY DESIGN

For 63 VLBW infants at high altitude, oxygen concentrations were measured by a hood oxygenation test (HOT) and BPD rates were determined with altitude adjustment.

RESULT

BPD rates before and after altitude adjustment were 71.8 and 26.7%, respectively. Of oxygen-dependent infants analyzed by HOT, 33.3% needed room air. HOT oxygen requirement correlated with gestational age of last apnea episode (r=0.42, P<0.001).

CONCLUSION

Although BPD rates may be adjusted for altitude with the HOT, the test does not accurately predict clinical oxygen need. Persistent requirement for supplemental oxygen beyond that needed in the HOT may be partially due to immaturity of respiratory control mechanisms.

[Children and air travel: national survey results]

Airplanes are widely used by families and their children and pediatricians are increasingly asked to answer questions on this subject. The main purpose of this study was to evaluate the knowledge of pediatricians in this field except for medical transportation. Pediatricians belonging to the AFPA, the SFP, the SNPEH, or the SP2A were emailed a questionnaire on the physiological particularities of airborne transportation, contraindications to flight related to diseases (infections, diabetes, sickle-cell anemia, respiratory diseases, etc.) and the possible medication intake on board. Among the 232 responders, 82.3% had an exclusive hospital practice and 65% were specialized in more than one area of medicine. Regarding contraindications to flying, the rate of correct answers varied from 14 to 84% with divided opinions regarding respiratory and hematological pathologies. However, contraindications related to infections were well known. Items related to oxygen therapy raised questions as 35-68% of pediatricians stated that they could not answer. On the whole, this work demonstrated very fragmented knowledge on this topic.

The hypoxic testicle: physiology and pathophysiology

Mammalian spermatogenesis is a complex biological process occurring in the seminiferous tubules in the testis. This process represents a delicate balance between cell proliferation, differentiation, and apoptosis. In most mammals, the testicles are kept in the scrotum 2 to 7°C below body core temperature, and the spermatogenic process proceeds with a blood and oxygen supply that is fairly independent of changes in other vascular beds in the body. Despite this apparently well-controlled local environment, pathologies such as varicocele or testicular torsion and environmental exposure to low oxygen (hypoxia) can result in changes in blood flow, nutrients, and oxygen supply along with an increased local temperature that may induce adverse effects on Leydig cell function and spermatogenesis. These conditions may lead to male subfertility or infertility. Our literature analyses and our own results suggest that conditions such as germ cell apoptosis and DNA damage are common features in hypoxia and varicocele and testicular torsion. Furthermore, oxidative damage seems to be present in these conditions during the initiation stages of germ cell damage and apoptosis. Other mechanisms like membrane-bound metalloproteinases and phospholipase A2 activation could also be part of the pathophysiological consequences of testicular hypoxia.

Air travel and the risks of hypoxia in children

In infants and children with chronic respiratory disease, hypoxia is a potential risk of aircraft travel. Although guidelines have been published to assist clinicians in assessing an individual's fitness to fly, they are not wholly evidence based. In addition, most evidence relates to adults with chronic obstructive pulmonary disease and thus cannot be extrapolated to children and infants. This review summarises the current literature as it applies to infants and children potentially at risk during air travel. Current evidence suggests that the gold standard for assessing fitness to fly, the hypoxia flight simulation test, may not be accurate in predicting in flight hypoxia in infants and children with respiratory disease. Further research is needed to determine the best methods of assessing safety of flight in infants and children.

[Recommendations for management of patients with lung disease planning a flight or high altitude travel]

Every year a large number of children travel by plane and/or to places with high altitudes. Most of these journeys occur without incident. Immigration and recent socioeconomic changes have also increased the number of patients with cardiopulmonary disease who travel. Environmental changes in these places, especially lower oxygen, can lead to a risk of significant adverse events. The paediatrician must be aware of the diseases that are susceptible to complications, as well as the necessary preliminary studies and recommendations for treatment in these circumstances. The Techniques Group of the Spanish Society of Paediatric Chest Diseases undertook to design a document reviewing the literature on the subject, providing some useful recommendations in the management of these patients.

Sudden deterioration due to intra-tumoral hemorrhage of ependymoma of the fourth ventricle in a child during a flight: a case report

Introduction

To the best of our knowledge, the association between air travel and intra-tumoral hemorrhage in pediatric populations has never been described previously.

Case presentation

We report the case of a two-and-a-half-year-old Caucasian, Iranian boy with a hemorrhaging brain tumor. He had a posterior fossa midline mass and severe hydrocephalus. He had been shunted for hydrocephalus four weeks earlier and was subsequently referred to our center for further treatment. The hemorrhage occurred in an infra-tentorial ependymoma, precipitated by an approximately 700-mile air journey at a maximum altitude of 25,000 feet.

Conclusions

A pre-existing intra-cranial mass lesion diminishes the ability of the brain to accommodate the mild environmental disturbances caused by hypercarbia, increased venous pressure and reduced cerebral blood flow during long air journeys. This is supported by a literature review, based on our current knowledge of physiological changes during air travel.

What is the mechanism of SIDS? Clues from epidemiology

The cause of sudden infant death syndrome (SIDS) is unknown. Many mechanisms have been postulated, although thermal stress, rebreathing of expired gases and infection/inflammation seem the most viable hypotheses for the causation of SIDS. Deaths from SIDS have reduced dramatically following the recommendation not to place infants to sleep prone. Epidemiological data have shown that prone sleeping position is more risky in winter, colder latitudes, higher altitudes, if the infant is unwell or has excessive bedding or clothing. This suggests prone sleeping position involves either directly or indirectly a thermal mechanism. SIDS caused by an infective/inflammatory mechanism might be associated with deaths occurring during the night. Rebreathing of expired gases, airway obstruction, long QT syndrome and other genetic conditions may explain a small number of sudden unexpected deaths in infancy.

Domiciliary oxygen for children

Domiciliary oxygen is used increasingly in pediatric practice, and the largest patient group to receive it is ex-premature babies with chronic neonatal lung disease. Because of a scarcity of good evidence to inform clinicians, there is a lack of consensus over many issues, even those as fundamental as the optimum target oxygen saturation. Nevertheless, many children benefit from receiving supplemental oxygen at home, particularly because it helps to keep them out of the hospital.

Long-distance air medical transport of extremely low birth weight infants with pneumoperitoneum

OBJECTIVE

Long-distance air transport (LDAT) of infants with pneumoperitoneum for pediatric surgical evaluation has not been previously reported. We examined whether extremely low birth weight (ELBW) infants with and without pneumoperitoneum would tolerate transport differently.

STUDY DESIGN

A retrospective cohort study was conducted comparing ELBW infants diagnosed with pneumoperitoneum to other ELBW infants transported>2000 miles by a trained team from a US Department of Defense tertiary care neonatal intensive care unit in Okinawa, Japan.

RESULT

Between 2000 and 2006, 49 air transports met study criteria. Seven of the 49 (14%) infants had pneumoperitoneum at time of transport. The average distance flown was 5346 miles per transport. The 49 infants had a median gestational age of 25 weeks and birth weight of 761+/-127 g. ELBW infants without pneumoperitoneum were transported at a median 58 days of life (DOL; range 30 to 91 days) compared to infants with pneumoperitoneum, who were transported at a median 8 DOL (range 6 to 14 days). At the time of LDAT, infants with pneumoperitoneum were significantly smaller, receiving more arterial and central venous access, more pressors for hypotension, and more mechanical ventilation compared to ELBW infants transported without pneumoperitoneum. In-flight patient-related medical issues were similar regardless of underlying diagnosis or age at the time of transport.

CONCLUSION

Successful LDAT of ELBW infants, including critically ill infants with intestinal perforation, is possible. Use of personnel, experienced and trained in aviation transport physiology, overcomes the extreme physiologic operating environment associated with LDATs.

Is this baby fit to fly? Hypoxia in aeroplanes

During air flight, cabin pressurisation results in a reduced fraction of inspired oxygen to 0.15. Healthy children desaturate by around 4% and remain asymptomatic. However children under the age of 1 year are more susceptible to hypoxia, especially if they were born preterm, and even more so if they are survivors of chronic neonatal lung disease. Pre-flight testing with a 'fitness to fly' test is available in some tertiary respiratory centres. The British Thoracic Society 2004 guideline currently recommends supplemental oxygen be given if the child's oxygen saturation falls below 90% during the test, although 85% may be a more appropriate cut off level.