Right heart function during simulated altitude in patients with pulmonary arterial hypertension

Symposium review: high altitude travel with pulmonary vascular disease

Pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension are the main precapillary forms of pulmonary hypertension (PH) summarized as pulmonary vascular diseases (PVD). PVDs are characterized by exertional dyspnoea and oxygen desaturation, and reduced quality of life and survival. Medical therapies improve life expectancy and physical performance of PVD patients, of whom many wish to participate in professional work and recreational activities including traveling to high altitude. The exposure to the hypobaric hypoxic environment of mountain regions incurs the risk of high altitude adverse events (AEHA) due to severe hypoxaemia exacerbating symptoms and further increase in pulmonary artery pressure, which may lead to right heart decompensation. Recent prospective and randomized trials show that altitude-induced hypoxaemia, pulmonary haemodynamic changes and impairment of exercise performance in PVD patients are in the range found in healthy people. The vast majority of optimally treated stable PVD patients who do not require long-term oxygen therapy at low altitude can tolerate short-term exposure to moderate altitudes up to 2500 m. PVD patients that reveal persistent severe resting hypoxaemia (S p O 2 ${{S}_{{\mathrm{p}}{{{\mathrm{O}}}_{\mathrm{2}}}}}$  <80% for >30 min) at 2500 m respond well to supplemental oxygen therapy. Although there are no accurate predictors for AEHA, PVD patients with unfavourable risk profiles at low altitude, such as higher WHO functional class, lower exercise capacity with more pronounced exercise-induced desaturation and more severely impaired haemodynamics, are at increased risk of AEHA. Therefore, doctors with experience in PVD and high-altitude medicine should counsel PVD patients before any high-altitude sojourn. This review aims to summarize recent literature and clinical recommendations about PVD patients travelling to high altitude.

Identifying the Causes of Unexplained Dyspnea at High Altitude Using Normobaric Hypoxia with Echocardiography

Exposure to high altitude results in hypobaric hypoxia, leading to physiological changes in the cardiovascular system that may result in limiting symptoms, including dyspnea, fatigue, and exercise intolerance. However, it is still unclear why some patients are more susceptible to high-altitude symptoms than others. Hypoxic simulation testing (HST) simulates changes in physiology that occur at a specific altitude by asking the patients to breathe a mixture of gases with decreased oxygen content. This study aimed to determine whether the use of transthoracic echocardiography (TTE) during HST can detect the rise in right-sided pressures and the impact of hypoxia on right ventricle (RV) hemodynamics and right to left shunts, thus revealing the underlying causes of high-altitude signs and symptoms. A retrospective study was performed including consecutive patients with unexplained dyspnea at high altitude. HSTs were performed by administrating reduced FiO2 to simulate altitude levels specific to patients' history. Echocardiography images were obtained at baseline and during hypoxia. The study included 27 patients, with a mean age of 65 years, 14 patients (51.9%) were female. RV systolic pressure increased at peak hypoxia, while RV systolic function declined as shown by a significant decrease in the tricuspid annular plane systolic excursion (TAPSE), the maximum velocity achieved by the lateral tricuspid annulus during systole (S' wave), and the RV free wall longitudinal strain. Additionally, right-to-left shunt was present in 19 (70.4%) patients as identified by bubble contrast injections. Among these, the severity of the shunt increased at peak hypoxia in eight cases (42.1%), and the shunt was only evident during hypoxia in seven patients (36.8%). In conclusion, the use of TTE during HST provides valuable information by revealing the presence of symptomatic, sustained shunts and confirming the decline in RV hemodynamics, thus potentially explaining dyspnea at high altitude. Further studies are needed to establish the optimal clinical role of this physiologic method.

Pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a rare and progressive disease characterised by remodelling of the pulmonary arteries and progressive narrowing of the pulmonary vasculature. This leads to a progressive increase in pulmonary vascular resistance and pulmonary arterial pressure and, if left untreated, to right ventricular failure and death. A correct diagnosis requires a complete work-up including right heart catheterisation performed in a specialised centre. Although our knowledge of the epidemiology, pathology and pathophysiology of the disease, as well as the development of innovative therapies, has progressed in recent decades, PAH remains a serious clinical condition. Current treatments for the disease target the three specific pathways of endothelial dysfunction that characterise PAH: the endothelin, nitric oxide and prostacyclin pathways. The current treatment algorithm is based on the assessment of severity using a multiparametric risk stratification approach at the time of diagnosis (baseline) and at regular follow-up visits. It recommends the initiation of combination therapy in PAH patients without cardiopulmonary comorbidities. The choice of therapy (dual or triple) depends on the initial severity of the condition. The main treatment goal is to achieve low-risk status. Further escalation of treatment is required if low-risk status is not achieved at subsequent follow-up assessments. In the most severe patients, who are already on maximal medical therapy, lung transplantation may be indicated. Recent advances in understanding the pathophysiology of the disease have led to the development of promising emerging therapies targeting dysfunctional pathways beyond endothelial dysfunction, including the TGF-β and PDGF pathways.

Clinician's Corner: Counseling Patients with Pulmonary Vascular Disease Traveling to High Altitude

Ulrich, Silvia, Mona Lichtblau, Simon R. Schneider, Stéphanie Saxer, and Konrad E. Bloch, Clinician's corner: counseling patients with pulmonary vascular disease traveling to high altitude. High Alt Med Biol. 23:201-208, 2022.-Pulmonary vascular diseases (PVDs) with precapillary pulmonary hypertension (PH), such as pulmonary arterial or chronic thromboembolic PH, impair exercise performance and survival in patients. Vasodilators and other treatments improve quality of life and prognosis to an extent in patients who have PVDs as chronic disorders. Obviously, patients with PVD wish to participate in usual daily activities, including travel to popular settlements and mountainous regions located at high altitude. However, the pulmonary hemodynamic impairment due to PVD leads to blood and tissue hypoxia, particularly during exercise and sleep. It is thus of concern that alveolar hypoxia at higher altitude may exacerbate patients' symptoms and lead to decompensation. Current PH guidelines discourage high-altitude exposure for fear of altitude-related adverse health effects. However, several recent well-designed prospective and randomized trials show that despite altitude-induced hypoxemia, pulmonary hemodynamic changes and impairment of exercise performance in patients with PVD are similar to the responses in healthy people or in patients with mild chronic obstructive pulmonary disease. The vast majority of patients with PVD can tolerate short-term exposure to moderate altitudes up to 2,500 m. For the roughly 10% of patients with stable disease who develop severe hypoxemia when ascending to 2,500 m, they respond well to low-level supplemental oxygen support. The best low-altitude predictors for adverse health effects at high altitude are the known clinical risk factors for PVD such as symptoms, functional class, exercise capacity, and exertional oxygen desaturation, whereas hypoxia altitude simulation testing is of little additive value. In any case, patients should be instructed that altitude-related adverse health effects may be difficult to predict and that in case of worsening symptoms, immediate accompanied descent to lower altitude and oxygen therapy are required. Patients with severe hypoxemia near sea level may safely visit high-altitude regions up to 1,500-2,000 m while continuing oxygen therapy and avoiding strenuous exercise. All PH patients should be counseled before any high-altitude sojourn by doctors with experience in PVD and high-altitude medicine and have an action plan for the occurrence of severe hypoxemia and other altitude-related conditions such as acute mountain sickness.

Underlying lung disease and exposure to terrestrial moderate and high altitude: personalised risk assessment

Once reserved for the fittest, worldwide altitude travel has become increasingly accessible for ageing and less fit people. As a result, more and more individuals with varying degrees of respiratory conditions wish to travel to altitude destinations. Exposure to a hypobaric hypoxic environment at altitude challenges the human body and leads to a series of physiological adaptive mechanisms. These changes, as well as general altitude related risks have been well described in healthy individuals. However, limited data are available on the risks faced by patients with pre-existing lung disease. A comprehensive literature search was conducted. First, we aimed in this review to evaluate health risks of moderate and high terrestrial altitude travel by patients with pre-existing lung disease, including chronic obstructive pulmonary disease, sleep apnoea syndrome, asthma, bullous or cystic lung disease, pulmonary hypertension and interstitial lung disease. Second, we seek to summarise for each underlying lung disease, a personalized pre-travel assessment as well as measures to prevent, monitor and mitigate worsening of underlying respiratory disease during travel.

The Impact of Breathing Hypoxic Gas and Oxygen on Pulmonary Hemodynamics in Patients With Pulmonary Hypertension

Background

Pure oxygen breathing (hyperoxia) may improve hemodynamics in patients with pulmonary hypertension (PH) and allows to calculate right-to-left shunt fraction (Qs/Qt), whereas breathing normobaric hypoxia may accelerate hypoxic pulmonary vasoconstriction (HPV). This study investigates how hyperoxia and hypoxia affect mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) in patients with PH and whether Qs/Qt influences the changes of mPAP and PVR.

Study Design and Methods

Adults with pulmonary arterial or chronic thromboembolic PH (PAH/CTEPH) underwent repetitive hemodynamic and blood gas measurements during right heart catheterization (RHC) under normoxia [fractions of inspiratory oxygen (FiO2) 0.21], hypoxia (FiO2 0.15), and hyperoxia (FiO2 1.0) for at least 10 min.

Results

We included 149 patients (79/70 PAH/CTEPH, 59% women, mean ± SD 60 ± 17 years). Multivariable regressions (mean change, CI) showed that hypoxia did not affect mPAP and cardiac index, but increased PVR [0.4 (0.1–0.7) WU, p = 0.021] due to decreased pulmonary artery wedge pressure [−0.54 (−0.92 to −0.162), p = 0.005]. Hyperoxia significantly decreased mPAP [−4.4 (−5.5 to −3.3) mmHg, p &lt; 0.001] and PVR [−0.4 (−0.7 to −0.1) WU, p = 0.006] compared with normoxia. The Qs/Qt (14 ± 6%) was &gt;10 in 75% of subjects but changes of mPAP and PVR under hyperoxia and hypoxia were independent of Qs/Qt.

Conclusion

Acute exposure to hypoxia did not relevantly alter pulmonary hemodynamics indicating a blunted HPV-response in PH. In contrast, hyperoxia remarkably reduced mPAP and PVR, indicating a preserved vasodilator response to oxygen and possibly supporting the oxygen therapy in patients with PH. A high proportion of patients with PH showed increased Qs/Qt, which, however, was not associated with changes in pulmonary hemodynamics in response to changes in FiO2.

Right Ventricular Response to Acute Hypoxia Exposure: A Systematic Review

Background: Acute hypoxia exposure is associated with an elevation of pulmonary artery pressure (PAP), resulting in an increased hemodynamic load on the right ventricle (RV). In addition, hypoxia may exert direct effects on the RV. However, the RV responses to such challenges are not fully characterized. The aim of this systematic review was to describe the effects of acute hypoxia on the RV in healthy lowland adults.

Methods: We systematically reviewed PubMed and Web of Science and article references from 2005 until May 2021 for prospective studies evaluating echocardiographic RV function and morphology in healthy lowland adults at sea level and upon exposure to simulated altitude or high-altitude.

Results: We included 37 studies in this systematic review, 12 of which used simulated altitude and 25 were conducted in high-altitude field conditions. Eligible studies reported at least one of the RV variables, which were all based on transthoracic echocardiography assessing RV systolic and diastolic function and RV morphology. The design of these studies significantly differed in terms of mode of ascent to high-altitude, altitude level, duration of high-altitude stay, and timing of measurements. In the majority of the studies, echocardiographic examinations were performed within the first 10 days of high-altitude induction. Studies also differed widely by selectively reporting only a part of multiple RV parameters. Despite consistent increase in PAP documented in all studies, reports on the changes of RV function and morphology greatly differed between studies.

Conclusion: This systematic review revealed that the study reports on the effects of acute hypoxia on the RV are controversial and inconclusive. This may be the result of significantly different study designs, non-compliance with international guidelines on RV function assessment and limited statistical power due to small sample sizes. Moreover, the potential impact of other factors such as gender, age, ethnicity, physical activity, mode of ascent and environmental factors such as temperature and humidity on RV responses to hypoxia remained unexplored. Thus, this comprehensive overview will promote reproducible research with improved study designs and methods for the future large-scale prospective studies, which eventually may provide important insights into the RV response to acute hypoxia exposure.

Effect of a day-trip to altitude (2500 m) on exercise performance in pulmonary hypertension: randomised crossover trial

Question addressed by the study

To investigate exercise performance and hypoxia-related health effects in patients with pulmonary hypertension (PH) during a high-altitude sojourn.

Patients and methods

In a randomised crossover trial in stable (same therapy for >4 weeks) patients with pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH) with resting arterial oxygen tension (P_aO2) ≥7.3 kPa, we compared symptom-limited constant work-rate exercise test (CWRET) cycling time during a day-trip to 2500 m versus 470 m. Further outcomes were symptoms, oxygenation and echocardiography. For safety, patients with sustained hypoxaemia at altitude (peripheral oxygen saturation <80% for >30 min or <75% for >15 min) received oxygen therapy.

Results

28 PAH/CTEPH patients (n=15/n=13); 13 females; mean±sd age 63±15 years were included. After >3 h at 2500 m versus 470 m, CWRET-time was reduced to 17±11 versus 24±9 min (mean difference −6, 95% CI −10 to −3), corresponding to −27.6% (−41.1 to −14.1; p<0.001), but similar Borg dyspnoea scale. At altitude, P_aO2 was significantly lower (7.3±0.8 versus 10.4±1.5 kPa; mean difference −3.2 kPa, 95% CI −3.6 to −2.8 kPa), whereas heart rate and tricuspid regurgitation pressure gradient (TRPG) were higher (86±18 versus 71±16 beats·min⁻¹, mean difference 15 beats·min⁻¹, 95% CI 7 to 23 beats·min⁻¹) and 56±25 versus 40±15 mmHg (mean difference 17 mmHg, 95% CI 9 to 24 mmHg), respectively, and remained so until end-exercise (all p<0.001). The TRPG/cardiac output slope during exercise was similar at both altitudes. Overall, three (11%) out of 28 patients received oxygen at 2500 m due to hypoxaemia.

Conclusion

This randomised crossover study showed that the majority of PH patients tolerate a day-trip to 2500 m well. At high versus low altitude, the mean exercise time was reduced, albeit with a high interindividual variability, and pulmonary artery pressure at rest and during exercise increased, but pressure–flow slope and dyspnoea were unchanged.

Short-time exposure to high altitude in pulmonary hypertension induces hypoxaemia, reduces constant work-rate cycle time compared to ambient air and is well tolerated overallhttps://bit.ly/3xUAFMs

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.

Effect of Normobaric Hypoxia on Exercise Performance in Pulmonary Hypertension: Randomized Trial

BACKGROUND

Many patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension (PH) wish to travel to altitude or by airplane, but their risk of hypoxia-related adverse health effects is insufficiently explored.

RESEARCH QUESTION

How does hypoxia, compared with normoxia, affect constant work-rate exercise test (CWRET) time in patients with PH, and which physiologic mechanisms are involved?

STUDY DESIGN AND METHODS

Stable patients with PH with resting Pao₂ ≥ 7.3 kPa underwent symptom-limited cycling CWRET (60% of maximal workload) while breathing normobaric hypoxic air (hypoxia; Fio₂, 15%) and ambient air (normoxia; Fio₂, 21%) in a randomized cross-over design. Borg dyspnea score, arterial blood gases, tricuspid regurgitation pressure gradient, and mean pulmonary artery pressure/cardiac output ratio (mean PAP/CO) by echocardiography were assessed before and during end-CWRET.

RESULTS

Twenty-eight patients (13 women) were included: median (quartiles) age, 66 (54; 74) years; mean pulmonary artery pressure, 41 (29; 49) mm Hg; and pulmonary vascular resistance, 5.4 (4; 8) Wood units. Under normoxia and hypoxia, CWRET times were 16.9 (8.0; 30.0) and 6.7 (5.5; 27.3) min, respectively, with a median difference (95% CI) of -0.7 (-3.1 to 0.0) min corresponding to -7 (-32 to 0.0)% (P = .006). At end-exercise in normoxia and hypoxia, respectively, median values and differences in corresponding variables were as follows: Pao₂: 8.0 vs 6.4, -1.7 (-2.7 to -1.1) kPa; arterial oxygen content: 19.2 vs 17.2, -1.7 (-3 to -0.1) mL/dL; Paco₂: 4.7 vs 4.3, -0.3 (-0.5 to -0.1) kPa; lactate: 3.7 vs 3.7, 0.9 (0.1 to 1.6) mM (P < .05 all differences). Values for Borg scale score: 7 vs 6, 0.5 (0 to 1); tricuspid pressure gradient: 89 vs 77, -3 (-9 to 16) mm Hg; and mean PAP/CO: 4.5 vs 3.3, 0.3 (-0.8 to 1.4) Wood units remained unchanged. In multivariable regression, baseline pulmonary vascular resistance was the sole predictor of hypoxia-induced change in CWRET time.

INTERPRETATION

In patients with PH, short-time exposure to hypoxia was well tolerated but reduced CWRET time compared with normoxia in association with hypoxemia, lactacidemia, and hypocapnia. Because pulmonary hemodynamics and dyspnea at end-exercise remained unaltered, the hypoxia-induced exercise limitation may be due to a reduced oxygen delivery causing peripheral tissue hypoxia, augmented lactic acid loading and hyperventilation.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03592927; URL: www.clinicaltrials.gov.

Altitude Travel in Patients With Pulmonary Hypertension: Randomized Pilot-Trial Evaluating Nocturnal Oxygen Therapy

Introduction: Stable patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension (PH) wish to undergo altitude sojourns or air travel but fear disease worsening. This pilot study investigates health effects of altitude sojourns and potential benefits of nocturnal oxygen therapy (NOT) in PH patients. Methods: Nine stable PH patients, age 65 (47; 71) years, 5 women, in NYHA class II, on optimized medication, were investigated at 490 m and during two sojourns of 2 days/nights at 2,048 m, once using NOT, once placebo (ambient air), 3 L/min per nasal cannula, according to a randomized crossover design with 2 weeks washout at <800 m. Assessments included safety, nocturnal pulse oximetry (SpO2), 6-min walk distance (6 MWD), and echocardiography. Results: At 2,048 m, two of nine patients required medical intervention, one for exercise-induced syncope, one for excessive nocturnal hypoxemia (SpO2 < 75% for >30 min). Both recovered immediately with oxygen therapy. Two patients suffered from acute mountain sickness. In 6 patients with complete data, nocturnal mean SpO2 and cyclic SpO2 dips reflecting sleep apnea significantly differed from 490 to 2,048 m with placebo, and 2,048 m with NOT (medians, quartiles): SpO2 93 (91; 95)%, 89 (85; 90)%, 97 (95; 97)%; SpO2 dips 10.4/h (3.1; 26.9), 34.0/h (5.3; 81.3), 0.3/h (0.1; 2.3). 6 MWD at 490, 2,048 m without and with NOT was 620 m (563; 720), 583 m (467; 696), and 561 m (501; 688). Echocardiographic indices of heart function and PH were unchanged at 2,048 m with/without NOT vs. 490 m. Conclusions: 7/9 PH patients stayed safely at 2,048 m but revealed hypoxemia, sleep apnea, and reduced 6 MWD. Hemodynamic changes were trivial. NOT improved oxygenation and sleep apnea. The current pilot trial is important for designing further studies on altitude tolerance of PH patients.

High geographic prevalence of pulmonary artery hypertension: associations with ethnicity, drug use, and altitude

While estimates of pulmonary arterial hypertension incidence and prevalence commonly range from 1-3/million and 15-25/million, respectively, clinical experience at our institution suggested much higher rates. We sought to describe the disease burden of pulmonary arterial hypertension in the geographic area served by our Pulmonary Hypertension Clinic and compare it to the REVEAL registry. Our secondary objectives were to document pulmonary arterial hypertension prevalence in minorities underrepresented in REVEAL (Hispanics and Native Americans) and to address the association of pulmonary arterial hypertension with exposure to drugs and moderately increased residential altitude in this population. Retrospective review of pulmonary arterial hypertension clinic patients alive during 2016 identified 154 patients. Hispanic patients made up 35.7% of the cohort, a much greater percentage than REVEAL, p < .001 but smaller than the percentage of Hispanic patients (48.4%) in geographic area served by the clinic. Pulmonary arterial hypertension due to drug exposure was more common and idiopathic pulmonary arterial hypertension was less common than in REVEAL (p < .001). Overall, pulmonary arterial hypertension incidence was 14 cases per million, greater than the REVEAL registry, odds ratio 6.3 (95% CI: 4.2-9.5), (p < .001). Annual period prevalence of pulmonary arterial hypertension was 93 cases per million, also greater than the REVEAL, odds ratio = 7.5 (95% CI: 6.4-8.8) and remained greater when the clinic cohort was constrained to patients with hemodynamic severity comparable to REVEAL, odds ratio = 3.8 (95% CI: 3.0-4.6), (p < .001). There was a strong association between pulmonary arterial hypertension prevalence and residence at altitude > 4000 ft, odds ratio = 26.6 (95% CI: 8.5-83.5), p < .001; however, this was potentially confounded by pulmonary arterial hypertension treatment referral patterns. These findings document a much higher local pulmonary arterial hypertension incidence and prevalence than previously reported in REVEAL. While population ethnicity differed markedly from REVEAL, the disease burden was not driven by these differences. The possible association of moderately increased residential altitude with pulmonary arterial hypertension warrants further evaluation.

Exertion during a hypoxia altitude simulation test helps identify potential cardiac decompensation

A 64-year-old female with a history of chronic thromboembolic pulmonary arterial hypertension (CTEPH), moderate airway obstruction (forced expiratory volume in 1 second (FEV1) 58% predicted), and resting oxygen saturation below the normal range (SaO2 94%) underwent a hypoxic challenge test (HCT) to determine suitability for long-haul air travel. The HCT showed only a mild decrease in SaO2 (89% at 0.15 fraction of inspired oxygen (FIO2)) at rest. However, a HCT coupled with mild exercise at two metabolic equivalents demonstrated significant hypoxia (SpO2 77%) with worsening right ventricular impairment and an inability to increase cardiac output measured with echocardiography. The case highlights the importance of the evaluating cardiac and pulmonary reserve during hypoxic stress. Resting measures alone may not identify risk, and the addition of an exercise component was essential in this case.

General measures and supportive therapy for pulmonary arterial hypertension: Updated recommendations from the Cologne Consensus Conference 2018

In the summer of 2016, delegates from the German Respiratory Society, the German Society of Cardiology and the German Society of Pediatric Cardiology met in Cologne, Germany, to define consensus-based practice recommendations for the management of patients with pulmonary arterial hypertension (PAH). These recommendations were built on the 2015 European Pulmonary Hypertension guidelines aiming at their practical implementation, considering country-specific issues, and including new evidence, where available. To this end, a number of working groups was initiated, one of which was specifically dedicated to general measures (i.e. physical activity/supervised rehabilitation, pregnancy/contraception, elective surgery, infection prevention, psychological support, travel) and supportive therapy (i.e. anticoagulants, diuretics, oxygen, cardiovascular medications, anaemia/iron deficiency, arrhythmias) for PAH. While the European guidelines provide detailed recommendations for the use of targeted PAH therapies as well as supportive care, detailed treatment decisions in routine clinical care may be challenging, and the relevance of supportive care is often not sufficiently considered. In addition, new evidence became available, thus requiring a thorough reevaluation of specific recommendations. The detailed results and recommendations of the working group on general measures and supportive therapy for PAH, which were last updated in the spring of 2018, are summarized in this article.

Effects of human relaxin-2 (serelaxin) on hypoxic pulmonary vasoconstriction during acute hypoxia in a sheep model

Purpose

Hypoxia induces pulmonary vasoconstriction with a subsequent increase of pulmonary artery pressure (PAP), which can result in pulmonary hypertension. Serelaxin has shown an increase of pulmonary hemodynamic parameters after serelaxin injection. We therefore investigated the response of pulmonary hemodynamic parameters after serelaxin administration in a clinically relevant model.

Methods

Six controls and six sheep that received 30 μg/kg serelaxin underwent right heart catheterization during a 12-minute hypoxia period (inhalation of 5% oxygen and 95% nitrogen) and subsequent reoxygenation. Systolic, diastolic, and mean values of both PAP (respectively, PAPs, PAPd, and PAPm) and pulmonary capillary wedge pressure (respectively, PCWPs, PCWPd, and PCWPm), blood gases, heart rate (HR), and both peripheral and pulmonary arterial oxygen saturation were obtained. Cardiac output (CO), stroke volume (SV), pulmonary vascular resistance (PVR), pulmonary arterial compliance (PAcompl), and systemic vascular resistance (SVR) were calculated.

Results

The key findings of the current study are that serelaxin prevents the rise of PAPs (p≤0.001), PAPm, PCWPm, PCWPs (p≤0.03), and PAPd (p≤0.05) during hypoxia, while it simultaneously increases CO and SV (p≤0.001). Similar courses of decreases of PAPm, PAPd, PAPs, CO, SVR (p≤0.001), and PCWPd (p≤0.03) as compared to hypoxic values were observed during reoxygenation. In direct comparison, the experimental groups differed during hypoxia in regard to HR, PAPm, PVR, and SVR (p≤0.03), and during reoxygenation in regard to HR (p≤0.001), PAPm, PAPs, PAPd, PVR, SVR (p≤0.03), and PCWPd (p≤0.05).

Conclusion

The findings of this study suggest that serelaxin treatment improves pulmonary hemodynamic parameters during acute hypoxia.

Acute hemodynamic changes by breathing hypoxic and hyperoxic gas mixtures in pulmonary arterial and chronic thromboembolic pulmonary hypertension

BACKGROUND

There is insufficient evidence to counsel patients with pulmonary hypertension undergoing altitude or air travel. We thus aimed to study hemodynamic response of patients with pulmonary arterial or chronic thromboembolic pulmonary hypertension (PAH/CTEPH) during changes in inspiratory oxygen partial pressure.

METHODS AND RESULTS

Consecutive patients undergoing right heart catheterization had hemodynamic assessments whilst breathing ambient air (normoxia, FiO₂ 0.21, at altitude 490 m), nitrogen-enriched air (hypoxia, FiO₂ 0.16, simulated altitude 2600 m) and oxygen (hyperoxia, FiO₂ 1.0), each for 10 min. Data from patients with PAH/CTEPH with mean pulmonary artery pressure (mPAP) ≥25 mmHg, pulmonary artery wedge pressure ≤15 mmHg, were compared to data from controls, mPAP <20 mmHg. 28 PAH/CTEPH-patients, 15 women, median age (quartiles) 62y (49;73), mPAP 35 mmHg (31;44), PaO₂ 7.1 kPa (6.8;9.3) and 16 controls, 12 women, 60y (52;69), mPAP 18 mmHg (16;18), PaO₂ 9.5 kPa (8.5;10.6) were included. Hypoxia reduced the PaO₂ in PAH/CTEPH-patients by median of 2.3 kPa, in controls by 3.3 kPa, difference (95%CI) in change 1.0 (0.02 to 1.9), p < 0.05. Corresponding changes in pulmonary vascular resistance, mPAP and cardiac output were nonsignificant in both groups. Hyperoxia decreased mPAP in PAH/CTEPH-patients by 4 mmHg (2 to 6), in controls by 2 mmHg (0 to 3), difference in change 3 mmHg (0 to 5), p < 0.05.

CONCLUSIONS

In patients with PAH/CTEPH, very short-term exposure to moderate hypoxia similar to 2600 m altitude or during commercial air travel did not deteriorate hemodynamics. These results encourage studying the response of PAH/CTEPH during daytrips to the mountain or air travel.

Navigating air travel and cardiovascular concerns: Is the sky the limit?

As the population ages and our ability to care for patients with cardiac disease improves, an increasing number of passengers with cardiovascular conditions will be traveling long distances. Many have had cardiac symptoms, recent interventions, devices, or surgery. Air travel is safe for most individuals with stable cardiovascular disease. However, a thorough understanding of the physiologic changes during air travel is essential given the potential impact on cardiovascular health and the risk of complications in passengers with preexisting cardiac conditions. It is important for clinicians to be aware of the current recommendations and precautions that need to be taken before and during air travel for passengers with cardiovascular concerns.