Abstract
Idiopathic pulmonary fibrosis (IPF) is a chronic and restrictive disease characterized by fibrosis and inflammatory changes in lung tissue producing a reduction in diffusion capacity and leading to exertional chronic arterial hypoxemia and dyspnea. Furthermore, clinically, supplemental oxygen (SupplO2) has been prescribed to IPF patients to improve symptoms. However, the evidence about the benefits or disadvantages of oxygen supplementation is not conclusive. In addition, the impact of SupplO2 on the autonomic nervous system (ANS) regulation in respiratory diseases needs to be evaluated. In this study the interactions between cardiovascular and respiratory systems in IPF patients, during ambient air (AA) and SupplO2 breathing, are compared to those from a matched healthy group. Interactions were estimated by time series of successive beat-to-beat intervals (BBI), respiratory amplitude (RESP) at BBI onset, arterial systolic (SYS) and diastolic (DIA) blood pressures. The paper explores the Granger causality (GC) between systems in the frequency domain by the extended partial directed coherence (ePDC), considering instantaneous effects. Also, traditional linear and nonlinear markers as power in low (LF) and high frequency (HF) bands, symbolic dynamic indices as well as arterial baroreflex, were calculated. The results showed that for IPF during AA phase: 1) mean BBI and power of BBI-HF band, as well as mean respiratory frequency were significantly lower (p < 0.05) and higher (p < 0.001), respectively, indicating a strong sympathetic influence, and 2) the RESP SYS interaction was characterized by Mayer waves and diminished RESP BBI, i.e., decreased respiratory sinus arrhythmia. In contrast, during short-term SupplO2 phase: 1) oxygen might produce a negative influence on the systolic blood pressure variability, 2) the arterial baroreflex reduced significantly (p < 0.01) and 3) reduction of RSA reflected by RESP BBI with simultaneous increase of Traube-Hering waves in RESP SYS (p < 0.001), reflected increased sympathetic modulation to the vessels. The results gathered in this study may be helpful in the management of the administration of SupplO2.
Highlights
Idiopathic pulmonary fibrosis (IPF) is a chronic, restrictive, and progressive disease characterized by fibrosis and inflammatory changes in lung tissue
For the DIA → beat-tobeat intervals (BBI) interaction, Figure 3C, the time-frequency representation of interactions (TFRi) displayed a magnitude with a trend to be higher in CON, in the upper part of the high frequency (HF) band, while for the IPF group a more uniform distributed magnitude is observed across the frequency bands
The former behavior may be interpreted in terms of an impaired left ventricular (LV) diastolic filling in IPF in contrast to a preserved LV systolic function, as was shown in a previous study (Papadopoulos et al, 2008)
Summary
Idiopathic pulmonary fibrosis (IPF) is a chronic, restrictive, and progressive disease characterized by fibrosis and inflammatory changes in lung tissue. IPF affects lung vasculature and prevents an adequate gas exchange, leading to exertional chronic arterial hypoxemia and dyspnea. The disease has a bad prognosis since after diagnosis the 50% of the patients die within 3–5 years (King et al, 2019). IPF etiology, diagnosis, treatment, and influences on quality of life, among other, have been investigated, but the focus has always been lungs performance. There is evidence that IPF patients manifest comorbidities such as cardiovascular diseases, lung cancer, or pulmonary hypertension (Caminati et al, 2019). Arterial hypertension has been related to dysfunctional autonomic cardiovascular control (Mancia and Grassi, 2014) and considerable impact on IPF disease progression and patient mortality (Buendía-Roldán et al, 2017)
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