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An investigative team is skeptical on the involvement if autonomic nervous function in cases of idiopathic pulmonary fibrosis.
Researchers in Greece recorded an inadequate adaptive response to oxygen supplementation in patients with idiopathic pulmonary fibrosis (IPF). The study was intended to improve autonomic nervous system (ANS) function within participants.
The study, lead by Afroditi K Boutou , MD, noted the severity of IPF, with high global morbidity and mortality rates and complications including reduced exercise capacity, exertional dyspnea and significant desaturation even when resting oxygen saturation is normal.
The investigators noted an involvement of ANS dysfunction in patients suffering from IPF. As was the case with other respiratory diseases such as chronic obstructive pulmonary disease (COPD), long-term oxygen therapy proved beneficial in managing heart rate variability (HRV) and improving exercise capacity.
While previous studies had investigated the potential effects of oxygen supplementation on exercise capacity in IPF patients, they were not in abundance.
As such, the current study investigated the potential acute effects of oxygen supplementation on heart rate variability (HRV) indices, which serve as markers of ANS regulation, in IPF patients with isolated exertional hypoxemia, for the first time in literature.
The study came from a secondary analysis of a single-blind, randomized, placebo-controlled, cross-over trial from the IPF outpatient clinic of the Department of Respiratory Medicine in Papanikolaou Hospital in Thessaloniki.
In the weeks leading up to the study, participants were tasked with completing a thorough clinical examination, spirometry, carbon dioxide diffusion capacity (DLCO), and 6-minute walking test (6MWT).
A series of laboratory visits, state exercise protocols, and maximal/symptom-limited exercise tests (CPET) followed.
Participants also experienced breathing medical air (FiO2 = 0.21) or oxygen-enriched air (FiO2 = 0.40) via a Venturi mask and were blinded to the inhaled gas concentration and to the pulse-oximetry recordings.
In their study, Boutou and colleagues indicated the presence of ANS dysregulation in participants as well as unchanged HRV indices from rest to exercise.
However, the investigators could not directly link HRV to inadequate oxygen supplementation.
Oxygen supplementation significantly reduced exertional desaturation and prolonged exercise duration by 50% in participants, leading investigators to believe that ANS did not play the primary role in the improvement of IPF’s exercise tolerance.
Despite the results of the study, the team did note this is the first study to analyze HRV in IPF in multiple states and believed further research could be built upon the study.
“Future case-control and cohort studies are warranted to shed light in this field,” the team wrote. “The increase in approximate entropy during exercise, suggests a higher degree of irregularity during exercise in the IPF patients, as increases in entropy non-linear HRV indices have been link to increased cardiovascular events.”
IPF remains a rare-yet-lethal disease, and while there were various successes within the study, it did not highlight any notable improvements in participants due to oxygen supplementation.
The investigators called for further study.
“Several important questions (i.e. ANS function in IPF patients with resting hypoxemia and associations with hard outcomes) are needed to be answered by further longitudinal studies and randomized control trials,” they wrote.
The study, “Effects of oxygen supplementation in autonomic nervous system function during exercise in patients with idiopathic pulmonary fibrosis and exertional desaturation,” was published online in The Clinical Respiratory Journal.