Effects of oxygen therapy in a pediatric normoxemic patient with pulmonary arterial hypertension and congenital heart disease

To shed light on the efficacy of oxygen therapy in pulmonary arterial hypertension (PAH) when hypoxemia is not present, we report seven years of observational data for a female patient recorded between February 2012 and February 2019 when she was aged 7.8–14.8 years. The patient was born with an atrial septal defect (closed spontaneously at 2.3 years) and ventricular septal defect (surgically repaired at 8.3 years) and then diagnosed with PAH at 8.9 years. The patient was prescribed bosentan soon after diagnosis and for the next 4.8 years, during which a first phase of oxygen therapy (nocturnal) was trialed for 2.8 years. Mean pulmonary arterial pressure (mPAP) and systolic PAP (sPAP) remained stable and at mild levels when oxygen was administered, but then increased progressively to severe levels over two years without oxygen. This coincided with worsening right ventricular pathology during the later part of this period without oxygen. Re-initiation of more intensive oxygen therapy while the patient was still on bosentan and before pharmocotherapy was changed coincided with a large and rapid fall in sPAP, confirmed by right heart catheterization measurements of mPAP. During this entire observation period, the patient remained normoxemic. These observations challenge the notion that oxygen therapy should be restricted to patients with hypoxemia and strengthen calls for further study of oxygen therapy in PAH. © The Author(s) 2019

Power Spectra in V-band and Halpha of Nine Irregular Galaxies

Fourier transform power spectra of major axis cuts in V and Halpha images were made for a sample of 9 irregular galaxies. These power spectra reveal structure over a wide range of scales. For 6 of the galaxies the power spectrum slopes at intermediate scales (1-400 pc) in the V-band images range from -1.3 to -1.5. The similarity of slopes suggests that the same processes are structuring these systems. These slopes are slightly shallower than what is observed in other galaxies in HI, molecular emission, dust extinction, and optical light. Three of the galaxies have flat power spectra like noise from the sky; these three galaxies are relatively indistinct in the direct images. The power spectrum slope for Halpha steepens with increasing star formation rate, ranging from a shallow value comparable to the noise at low rates to a steep value with a slope of -1.5 at high rates. This change reflects the increasing areal filling factor of Halpha emission with increasing star formation rate, and an apparently universal slope inside the Halpha regions that is comparable to that for Kolmogorov turbulence. The power spectrum of HI in one galaxy has a steeper power law, with a slope of -2.9. The fact that the power laws of star formation are about the same for dwarf galaxies and giant spiral galaxies suggests the microscopic processes are the same, independent of spiral density waves and galaxy size.Comment: To be published in AJ, May 200

HI Power Spectra and the Turbulent ISM of Dwarf Irregular Galaxies

HI spatial power spectra (PS) were determined for a sample of 24 nearby dwarf irregular galaxies selected from the LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes - The HI Nearby Galaxy Survey) sample. The two-dimensional (2D) power spectral indices asymptotically become a constant for each galaxy when a significant part of the line profile is integrated. For narrow channel maps, the PS become shallower as the channel width decreases, and this shallowing trend continues to our single channel maps. This implies that even the highest velocity resolution of 1.8 km/s is not smaller than the thermal dispersion of the coolest, widespread HI component. The one-dimensional PS of azimuthal profiles at different radii suggest that the shallower PS for narrower channel width is mainly contributed by the inner disks, which indicates that the inner disks have proportionally more cooler HI than the outer disks. Galaxies with lower luminosity (M_B > -14.5 mag) and star formation rate (SFR, log(SFR (M\odot/yr)) < -2.1) tend to have steeper PS, which implies that the HI line-of-sight depths can be comparable with the radial length scales in low mass galaxies. A lack of a correlation between the inertial-range spectral indices and SFR surface density implies that either non-stellar power sources are playing a fundamental role in driving the interstellar medium (ISM) turbulent structure, or the nonlinear development of turbulent structures has little to do with the driving sources.Comment: 16 pages, 9 figures, 2 tables. Accepted by Ap

Effects of oxygen therapy in a pediatric normoxemic patient with pulmonary arterial hypertension and congenital heart disease

To shed light on the efficacy of oxygen therapy in pulmonary arterial hypertension (PAH) when hypoxemia is not present, we report seven years of observational data for a female patient recorded between February 2012 and February 2019 when she was aged 7.8–14.8 years. The patient was born with an atrial septal defect (closed spontaneously at 2.3 years) and ventricular septal defect (surgically repaired at 8.3 years) and then diagnosed with PAH at 8.9 years. The patient was prescribed bosentan soon after diagnosis and for the next 4.8 years, during which a first phase of oxygen therapy (nocturnal) was trialed for 2.8 years. Mean pulmonary arterial pressure (mPAP) and systolic PAP (sPAP) remained stable and at mild levels when oxygen was administered, but then increased progressively to severe levels over two years without oxygen. This coincided with worsening right ventricular pathology during the later part of this period without oxygen. Re-initiation of more intensive oxygen therapy while the patient was still on bosentan and before pharmocotherapy was changed coincided with a large and rapid fall in sPAP, confirmed by right heart catheterization measurements of mPAP. During this entire observation period, the patient remained normoxemic. These observations challenge the notion that oxygen therapy should be restricted to patients with hypoxemia and strengthen calls for further study of oxygen therapy in PAH. © The Author(s) 2019

Oxygen and pulmonary arterial hypertension : effects, mechanisms, and therapeutic benefits

Oxygen is a pulmonary vasodilator. Although treatment of pulmonary arterial hypertension (PAH) is focused on pulmonary vasodilation, treatment guidelines do not recommend O2 therapy for patients unless they develop hypoxaemia. These guidelines point to a lack of evidence of benefit of O2 therapy from randomized controlled trials (RCTs) and to evidence of lack of benefit in a single RCT involving patients with Eisenmenger syndrome. These guidelines did not identify major limitations with the Eisenmenger study or consider other evidence of therapeutic benefit. Recent advances in mechanistic understanding of O2 effects on pulmonary vascular tone, along with substantial evidence of acute effects of O2 in PAH patients, challenge the view that benefits of O2 arise only through correction of hypoxaemia. Evidence presented in this review shows that O2 acts as a pulmonary vasodilator in patients who are normoxaemic; that this probably involves an alveolar mechanism in addition to a blood-borne (oxyhaemoglobin) mechanism; and that therapeutic benefit of O2 does not depend on arterial O2 levels. This suggests that O2 has potential therapeutic benefit for all patients with PAH. Clinical guidelines and practice related to O2 therapy need to be reassessed, and further research is needed

Oxygen therapy for pulmonary arterial hypertension : we need to rethink and investigate

Pulmonary arterial hypertension (PAH) is characterized by progressive increases in mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR), resulting in right ventricular failure and death. Primary treatment of PAH (Class 1) is based on the use of four classes of drugs in the form of monotherapy or combination therapy. Despite significant advances in drug‐based treatment of PAH and improvements in survival rates, the prognosis for PAH patients remains poor. PAH drugs target mechanisms involved in vasodilation of pulmonary arterial vessels (Fig. 1A), but their vascular effects are not limited to the pulmonary circulation, probably contributing to side effects and limiting drug efficacy. Thus, there is a need for additional therapeutic approaches