Hypoxia Altitude Simulation Test Research Articles

Hypoxia Altitude Simulation and Reduction of Cerebral Oxygenation in COPD Patients

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is highly prevalent and often associated with chronic hypoxia. Previous studies have shown alterations of cerebral oxygenation and cardiac repolarization in COPD patients (GOLD stage II-IV). Airplane travel is common in patients with COPD; however, the clinical effects of a diminished oxygen partial pressure in aircraft cabin environments at cruising altitude remain elusive. The aim of this study was to assess changes of cerebral oxygenation as well as parameters of cardiac repolarization during a hypoxia altitude simulation combined with mild physical activity in these patients.METHODS: Patients with COPD and healthy subjects (10 per group) randomly selected from the Charité outpatient clinic conducted a hypoxia altitude simulation test which consisted of three phases. The regional cerebral oxygen saturation (rSO₂) of the frontal cortex was measured at rest using near-infrared spectroscopy (NIRS). Furthermore, oxygen saturation (SpO₂), blood pressure, and heart rate values, as well as a 12-lead-ECG, were recorded. Subsequently, a mild treadmill exercise program (25 W) was divided into 10 min of normoxia (pre-hypoxia), 30 min of mild hypoxia (FIO₂ = 0.15), followed by a second 10-min period of normoxia (post-hypoxia). Meanwhile, mentioned parameters were recorded in 2-min intervals. P, PQ, QRS, QT, QTc, QTd, T-peak-T-end interval (TpTe), and corrected TpTe (TpTec) were measured on three ECG complexes, each at baseline, at the end of the normoxic phase, and at the end of the hypoxic phase.RESULTS: A total of 10 patients with COPD and 10 control subjects were included in this study. SpO₂ was significantly lower in COPD patients throughout the whole test. Frontal cerebral rSO₂ was significantly lower in the left hemisphere during hypoxia altitude simulation in COPD patients (59.5 ± 8.5 vs. 67.5 ± 5.7).CONCLUSIONS: We show reduced left frontal cerebral oxygenation during hypoxia and mild exercise in patients with COPD, suggesting diminished altitude resilience and altitude capabilities. Preflight hypoxia assessment might be recommended to patients with severe COPD.Dehe L, Hohendanner F, Gültekin E, Werth G, Wutzler A, Bender TO. Hypoxia altitude simulation and reduction of cerebral oxygenation in COPD patients. Aerosp Med Hum Perform. 2023; 94(3):102-106.

Hypoxia-altitude simulation test to predict altitude-related adverse health effects in COPD patients.

Amongst numerous travellers to high altitude (HA) are many with the highly prevalent COPD, who are at particular risk for altitude-related adverse health effects (ARAHE). We then investigated the hypoxia-altitude simulation test (HAST) to predict ARAHE in COPD patients travelling to altitude. This prospective diagnostic accuracy study included 75 COPD patients: 40 women, age 58±9 years, forced expiratory volume in 1 s (FEV1) 40-80% pred, oxygen saturation measured by pulse oximetry (S pO2 ) ≥92% and arterial carbon dioxide tension (P aCO2 ) <6 kPa. Patients underwent baseline evaluation and HAST, breathing normobaric hypoxic air (inspiratory oxygen fraction (F IO2 ) of 15%) for 15 min, at low altitude (760 m). Cut-off values for a positive HAST were set according to British Thoracic Society (BTS) guidelines (arterial oxygen tension (P aO2 ) <6.6 kPa and/or S pO2 <85%). The following day, patients travelled to HA (3100 m) for two overnight stays where ARAHE development including acute mountain sickness (AMS), Lake Louise Score ≥4 and/or AMS score ≥0.7, severe hypoxaemia (S pO2 <80% for >30 min or 75% for >15 min) or intercurrent illness was observed. ARAHE occurred in 50 (66%) patients and 23 out of 75 (31%) were positive on HAST according to S pO2 , and 11 out of 64 (17%) according to P aO2 . For S pO2 /P aO2 we report a sensitivity of 46/25%, specificity of 84/95%, positive predictive value of 85/92% and negative predictive value of 44/37%. In COPD patients ascending to HA, ARAHE are common. Despite an acceptable positive predictive value of the HAST to predict ARAHE, its clinical use is limited by its insufficient sensitivity and overall accuracy. Counselling COPD patients before altitude travel remains challenging and best focuses on early recognition and treatment of ARAHE with oxygen and descent.

COPD patients' pre-flight check: A narrative review.

For most of the people with stable and well-controlled chronic obstructive pulmonary disease (COPD), air travel is safe and comfortable, but the flight environment may pose clinical challenges. This narrative review aims to update the requirements for allowance to fly of people with COPD without chronic respiratory failure. A literature review was performed on platforms: Pubmed, Scopus and Ovid, for citations in English from 2000 to 2021. The following key words were used: COPD AND: air-travel, in-flight hypoxemia, fitness to air travel. Official regulatory documents and guidelines were also examined. Current air travel statements recommend supplemental oxygen when in flight arterial oxygen tension (PaO2) is expected to fall below 6.6 or 7.3 kPa. Several lung function variables, prediction equations and algorithms have been proposed to estimate in-flight PaO2, the need for in-flight supplemental oxygen, and to select individuals needing more advanced pre-flight testing, such as the hypoxia-altitude simulation test. Exercise induced desaturation and aerobic capacity correlate significantly with in-flight PaO2. COPD patients with late intensification of disease, new changes in medications, recent acute exacerbation/ hospitalization or anticipated emotional and physical stress during the proposed air-travel should be carefully evaluated by the caring family or specialist physician.

Fit for high altitude: are hypoxic challenge tests useful?

&#x0D; &#x0D; &#x0D; Altitude travel results in acute variations of barometric pres- sure, which induce different degrees of hypoxia, changing the gas contents in body tissues and cavities. Non ventilated air containing cavities may induce barotraumas of the lung (pneumothorax), sinuses and middle ear, with pain, vertigo and hearing loss. Commercial air planes keep their cabin pres- sure at an equivalent altitude of about 2,500 m. This leads to an increased respiratory drive which may also result in symp- toms of emotional hyperventilation. In patients with pre- existing respiratory pathology due to lung, cardiovascular, pleural, thoracic neuromuscular or obesity-related diseases (i.e. obstructive sleep apnea) an additional hypoxic stress may induce respiratory pump and/or heart failure. Clinical pre-altitude assessment must be disease-specific and it includes spirometry, pulsoximetry, ECG, pulmonary and sys- temic hypertension assessment. In patients with abnormal values we need, in addition, measurements of hemoglobin, pH, base excess, PaO2, and PaCO2 to evaluate whether O2- and CO2-transport is sufficient.&#x0D; Instead of the hypoxia altitude simulation test (HAST), which is not without danger for patients with respiratory insuffi- ciency, we prefer primarily a hyperoxic challenge. The supple- mentation of normobaric O2 gives us information on the acute reversibility of the arterial hypoxemia and the reduc- tion of ventilation and pulmonary hypertension, as well as about the efficiency of the additional O2-flow needed during altitude exposure. For difficult judgements the performance of the test in a hypobaric chamber with and without supple- mental O2-breathing remains the gold standard. The increas- ing numbers of drugs to treat acute pulmonary hypertension due to altitude exposure (acetazolamide, dexamethasone, nifedipine, sildenafil) or to other etiologies (anticoagulants, prostanoids, phosphodiesterase-5-inhibitors, endothelin receptor antagonists) including mechanical aids to reduce periodical or insufficient ventilation during altitude exposure (added dead space, continuous or bilevel positive airway pressure, non-invasive ventilation) call for further randomized controlled trials of combined applications.&#x0D; &#x0D; &#x0D;

Pre-flight evaluation of adult patients with cystic fibrosis: a cross-sectional study

BackgroundAir travel may imply a health hazard for patients with cystic fibrosis (CF) due to hypobaric environment in the aircraft cabin. The objective was to identify pre-flight variables, which might predict severe hypoxaemia in adult CF patients during air travel.MethodsThirty adult CF-patients underwent pre-flight evaluation with spirometry, arterial oxygen tension (PaO2), pulse oximetry (SpO2) and cardiopulmonary exercise testing (CPET) at sea level (SL). The results were related to the PaO2 obtained during a hypoxia-altitude simulation test (HAST) in which a cabin altitude of 2438 m (8000 ft) was simulated by breathing 15.1% oxygen.ResultsFour patients fulfilled the criteria for supplemental oxygen during air travel (PaO2 HAST < 6.6 kPa). While walking slowly during HAST, another eleven patients dropped below PaO2 HAST 6.6 kPa. Variables obtained during CPET (PaO2 CPET, SpO2 CPET, minute ventilation/carbon dioxide output, maximal oxygen uptake) showed the strongest correlation to PaO2 HAST.ConclusionsExercise testing might be of value for predicting in-flight hypoxaemia and thus the need for supplemental oxygen during air travel in CF patients.Trial registration The study is retrospectively listed in the ClinicalTrials.gov Protocol Registration System: NCT01569880 (date; 30/3/2012)

Air Travel and Chronic Obstructive Pulmonary Disease: A New Algorithm for Pre-flight Evaluation: Edvardsen A, Akero A, Christensen CC, et al. Thorax 2012;67:964–9.

With chronic obstructive pulmonary disease (COPD) increasing in prevalence and air travel becoming progressively accessible, more and more elderly air passengers are at risk for developing severe hypoxemia and respiratory distress after cabin depressurization. To date, the gold-standard instrument used to predict the need for in-flight supplemental oxygen is the hypoxia-altitude simulation test (HAST). Unfortunately, HAST is time-intensive, invasive (it requires multiple arterial blood samples to determine PaO2), and not widely available.

Commercial Air Travel and In-Flight Pulmonary Hypertension

It has recently been shown that commercial air travel triggers hypoxic pulmonary vasoconstriction and modestly increases pulmonary artery pressure in healthy passengers. There is large interindividual variation in hypoxic pulmonary vasoreactivity, and some passengers may be at risk of developing flight-induced pulmonary hypertension, with potentially dangerous consequences. This study sought to determine whether it is possible for a susceptible passenger to develop pulmonary hypertension in response to a routine commercial flight. Using in-flight echocardiography, a passenger was studied during a 6-h commercial flight from London to Dubai. The passenger was generally well and frequently traveled by air, but had been diagnosed with Chuvash polycythemia, a genetic condition that is associated with increased hypoxic pulmonary vasoreactivity. Hematocrit had been normalized with regular venesection. During the flight, arterial oxygen saturation fell to a minimum of 96% and systolic pulmonary artery pressure (sPAP) rapidly increased into the pulmonary hypertensive range. The in-flight increase in sPAP was 50%, reaching a peak of 45 mmHg. This study has established that an asymptomatic but susceptible passenger can rapidly develop in-flight pulmonary hypertension even during a medium-haul flight. Prospective passengers at risk from such responses, including those who have cardiopulmonary disease or increased hypoxic pulmonary vasoreactivity, could benefit from preflight evaluation with a hypoxia altitude simulation test combined with simultaneous echocardiography (HAST-echo). The use of in-flight supplementary oxygen should be considered for susceptible individuals, including all patients diagnosed with Chuvash polycythemia.

Air travel and chronic obstructive pulmonary disease: a new algorithm for pre-flight evaluation

BackgroundThe reduced pressure in the aircraft cabin may cause significant hypoxaemia and respiratory distress in patients with chronic obstructive pulmonary disease (COPD). Simple and reliable methods for predicting the need...

Pulmonary Artery Pressure Increases During Commercial Air Travel in Healthy Passengers

It is not known whether the mild hypoxia experienced by passengers during commercial air travel triggers hypoxic pulmonary vasoconstriction and increases pulmonary artery pressure in flight. Insidious pulmonary hypertensive responses could endanger susceptible passengers who have cardiopulmonary disease or increased hypoxic pulmonary vascular sensitivity. Understanding these effects may improve pre-flight assessment of fitness-to-fly and reduce in-flight morbidity and mortality. Eight healthy volunteers were studied during a scheduled commercial airline flight from London, UK, to Denver, CO. The aircraft was a Boeing 777 and the duration of the flight was 9 h. Systolic pulmonary artery pressure (sPAP) was assessed by portable Doppler echocardiography during the flight and over the following week in Denver, where the altitude (5280 ft/1610 m) simulates a commercial airliner environment. Cruising cabin altitude ranged between 5840 and 7170 ft (1780 to 2185 m), and mean arterial oxygen saturation was 95 +/- 0.6% during the flight. Mean sPAP increased significantly in flight by 6 +/- 1 mmHg to 33 +/- 1 mmHg, an increase of approximately 20%. After landing in Denver, sPAP was still 3 +/- 1 mmHg higher than baseline and remained elevated at 30 +/- 1 mmHg for a further 12 h. Pulmonary artery pressure increases during commercial air travel in healthy passengers, raising the possibility that hypoxic pulmonary hypertension could develop in susceptible individuals. A hypoxia altitude simulation test with simultaneous echocardiography ('HAST-echo') may be beneficial in assessing fitness to fly in vulnerable patients.

COPD and Air Travel: Oxygen Equipment and Preflight Titration of Supplemental Oxygen

Patients with COPD may need supplemental oxygen during air travel to avoid development of severe hypoxemia. The current study evaluated whether the hypoxia-altitude simulation test (HAST), in which patients breathe 15.1% oxygen simulating aircraft conditions, can be used to establish the optimal dose of supplemental oxygen. Also, the various types of oxygen-delivery equipment allowed for air travel were compared.In a randomized crossover trial, 16 patients with COPD were exposed to alveolar hypoxia: in a hypobaric chamber (HC) at 2,438 m (8,000 ft) and with a HAST. During both tests, supplemental oxygen was given by nasal cannula (NC) with (1) continuous flow, (2) an oxygen-conserving device, and (3) a portable oxygen concentrator (POC).PaO(2) kPa (mm Hg) while in the HC and during the HAST with supplemental oxygen at 2 L/min (pulse setting 2) on devices 1 to 3 was (1) 8.6 ± 1.0 (65 ± 8) vs 12.5 ± 2.4 (94 ± 18) (P < .001), (2) 8.6 ± 1.6 (64 ± 12) vs 9.7 ± 1.5 (73 ± 11) (P < .001), and (3) 7.7 ± 0.9 (58 ± 7) vs 8.2 ± 1.1 (62 ± 8) (P= .003), respectively.The HAST may be used to identify patients needing supplemental oxygen during air travel. However, oxygen titration using an NC during a HAST causes accumulation of oxygen within the facemask and underestimates the oxygen dose required. When comparing the various types of oxygen-delivery equipment in an HC at 2,438 m (8,000 ft), compressed gaseous oxygen with continuous flow or with an oxygen-conserving device resulted in the same PaO(2), whereas a POC showed significantly lower PaO(2) values.ClinicalTrials.gov; No.: Identifier: NCT01019538; URL: clinicaltrials.gov.

Fit for high altitude: are hypoxic challenge tests useful?

Altitude travel results in acute variations of barometric pressure, which induce different degrees of hypoxia, changing the gas contents in body tissues and cavities. Non ventilated air containing cavities may induce barotraumas of the lung (pneumothorax), sinuses and middle ear, with pain, vertigo and hearing loss. Commercial air planes keep their cabin pressure at an equivalent altitude of about 2,500 m. This leads to an increased respiratory drive which may also result in symptoms of emotional hyperventilation. In patients with preexisting respiratory pathology due to lung, cardiovascular, pleural, thoracic neuromuscular or obesity-related diseases (i.e. obstructive sleep apnea) an additional hypoxic stress may induce respiratory pump and/or heart failure. Clinical pre-altitude assessment must be disease-specific and it includes spirometry, pulsoximetry, ECG, pulmonary and systemic hypertension assessment. In patients with abnormal values we need, in addition, measurements of hemoglobin, pH, base excess, PaO2, and PaCO2 to evaluate whether O2- and CO2-transport is sufficient.Instead of the hypoxia altitude simulation test (HAST), which is not without danger for patients with respiratory insufficiency, we prefer primarily a hyperoxic challenge. The supplementation of normobaric O2 gives us information on the acute reversibility of the arterial hypoxemia and the reduction of ventilation and pulmonary hypertension, as well as about the efficiency of the additional O2-flow needed during altitude exposure. For difficult judgements the performance of the test in a hypobaric chamber with and without supplemental O2-breathing remains the gold standard. The increasing numbers of drugs to treat acute pulmonary hypertension due to altitude exposure (acetazolamide, dexamethasone, nifedipine, sildenafil) or to other etiologies (anticoagulants, prostanoids, phosphodiesterase-5-inhibitors, endothelin receptor antagonists) including mechanical aids to reduce periodical or insufficient ventilation during altitude exposure (added dead space, continuous or bilevel positive airway pressure, non-invasive ventilation) call for further randomized controlled trials of combined applications.

Pulse Oximetry in the Preflight Evaluation of Patients with Chronic Obstructive Pulmonary Disease

In a British Thoracic Society (BTS) statement on preflight evaluation of patients with respiratory disease, sea level pulse oximetry (Spo2sl) is recommended as an initial assessment. The present study aimed to evaluate if the BTS algorithm can be used to identify chronic obstructive pulmonary disease (COPD) patients in need of supplemental oxygen during air travel, i.e. patients with an in-flight PaO2 < 6.6 kPa (50 mmHg). There were 100 COPD patients allocated to groups according to the BTS algorithm: Spo2sl > 95%, Spo2sl 92-95% without additional risk factors; Spo2sl 92-95% with additional risk factors; Spo2sl < 92%; and patients using domiciliary oxygen. Pulse oximetry, arterial blood gases, and an hypoxia-altitude simulation test (HAST) to simulate a cabin altitude of 2438 m (8000 ft), were performed. The percentage of patients in the various groups dropping below 6.6 kPa during HAST were: Spo2sl > 95%: 30%; Spo2sl 92-95% without additional risk factors: 67%; Spo2sl 92-95% with additional risk factors: 70%; Spo2sl < 92%: 83%; and patients using domiciliary oxygen: 81%. In patients dropping below P(a)o(2) 6.6 kPa, supplemental oxygen of median 1 L x min(-1) was needed to exceed this limit. If in-flight P(a)o(2) > or = 6.6 kPa is regarded as a strict requirement, the use of pulse oximetry as an initial assessment in the preflight evaluation of COPD patients, as suggested by the BTS, might not discriminate adequately between patients who fulfill the indications for supplemental oxygen during air travel, and patients who can travel without such treatment.

Hypoxia Altitude Simulation Test

A large number of patients with underlying pulmonary disease travel by air each year and are therefore at risk for significant cardiopulmonary effects of induced hypoxia at higher altitudes. The hypoxia altitude simulation test provides a simple way to identify those patients at risk by simulating conditions encountered at high altitude. By asking the patient to breathe a mixture of gases with an oxygen saturation of 15.1%, the test simulates a cabin pressure of 8,000 feet and allows the physician to screen for hypoxia, significant symptoms, and arrhythmias. Repeating the test with supplemental oxygen ensure adequate treatment of those patients who have a decrease in the alveolar pressure of oxygen, significant symptoms, and/or arrhythmias.

Hypoxia During Air Travel in Adults With Pulmonary Disease

At the present time, commercial aircraft cabins are required to be pressurized to the equivalent of 8,000 feet or less. Although in-flight medical emergencies are infrequent, some adults with pulmonary disease may experience significant physiological stress, exacerbation of their underlying illness, and severe hypoxemia during air travel. A careful preflight medical evaluation is essential to determine which patients with pulmonary disease can fly safely, which patients require supplemental oxygen, and which patients should not fly at all. All adults with pulmonary disease who have a preflight arterial oxygen tension of less than 70 mm Hg or a preflight pulse oximetry saturation of less than 92% should receive supplemental oxygen during air travel. The hypoxia altitude simulation test and the 6-minute walk test are useful when additional evaluation for supplemental in-flight oxygen is needed. Patients with an unstable condition, an acute exacerbation of their pulmonary disease, severe pulmonary hypertension (Class III and Class IV), or an active pneumothorax should not fly.

Is normobaric simulation of hypobaric hypoxia accurate in chronic airflow limitation?

Hypobaric hypoxemia is experienced by passengers during commercial aircraft flight. In order to assess the extent of hypoxemia and to test whether hypobaric hypoxia can be accurately estimated at sea level, the results of the normobaric hypoxia altitude simulation test (N-HAST) were compared with those of the hypobaric hypoxia altitude simulation test (H-HAST) in six normal control subjects and nine patients with chronic airflow limitation (CAL) at simulated cabin altitudes of 6,000 ft (1,829 m) and both at rest and during exercise at 8,000 ft (2,438 m). Serial arterial blood samples were drawn during the breathing of 15.1 and 16.3% inspired oxygen at sea level (N-HAST) at rest and during light exercise, and during the breathing of room air at simulated cabin altitudes (H-HAST) of 609 mm Hg (6,000 ft) and 565 mm Hg (8,000 ft) at rest and during light exercise. As measured with the H-HAST technique, the mean (+/- SD) PaO2 of the normal group fell from 96.2 +/- 6.2 mm Hg (sea level) to 70.1 +/- 6.0 mm Hg (6,000 ft), and to 61.7 +/- 1.6 mm Hg (8,000 ft at rest) and 54.8 +/- 7.1 mm Hg (8,000 ft during exercise) (p < 0.005 by analysis of variance [ANOVA]). In the CAL group, the mean (+/- SD) PaO2 fell from 75.8 +/- 8.2 mm Hg (sea level) to 57.0 +/- 6.3 mm Hg (6,000 ft), and 49.5 +/- 6.1 mm Hg (8,000 ft at rest), and 38.6 +/- 7.5 mm Hg (8,000 ft during exercise) (p < 0.005 by ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)