24-Hour Hypoxia and Pulmonary Hypertension in Patients with Idiopathic Pulmonary Fibrosis

Abstract

Background:The quantification of hypoxia based on resting partial pressure of arterial oxygen (PaO2) may underestimate hypoxia related to activities of daily living or sleep and thus not accurately reflect pulmonary hypertension (PH). The aim of the present study was to investigate the association of resting PaO2 with percent time of SpO2 below 90% (T90) and 88% (T88) in 24 hours. We also evaluated the capacity of hypoxia measures to predict PH in patients with idiopathic pulmonary fibrosis (IPF).Method:This cross-sectional study included 27 patients with IPF presenting PaO2 ≥ 55 mmHg and not receiving home oxygen therapy. All were submitted to blood gas measurement, 24-h oximetry, and transthoracic Doppler echocardiography to estimate systolic pulmonary artery pressure (SPAP). Patients were divided into three groups according to resting PaO2: 55-55.9 mmHg (A); 60-60.9 mmHg (B); ≥ 70 mmHg (C). PH was defined as “likely” if SPAP > 50 mmHg, and as possible for SPAP between 37 and 50 mmHg.Results:T90 and T88 in Groups A, B, and C were as follows: 59.9±29% and 44.1±34%; 49.3±34% and 29.9±31%; 17.1±25% and 8.8±18% respectively, with significant differences between the groups for both T90 (p ≤ 0.01) and T88 (p = 0.02). PaO2 was inversely correlated with T90 (r = -0.398; p = 0.04) and T88 (r = -0.351; p = 0.07). Hypoxia variables did not correlate with SPAP, and were not able to predict PH.Conclusion:Percent time of SpO2 below 90% and 88% in 24 hours revealed periods of severe hypoxia even in patients with borderline-normal resting PaO2. However, none of the present hypoxia variables was capable of predicting PH.

Comparison of 12‐hour and 24‐hour oximetry recordings in preterm infants

“…Use of 24‐h oximetry has been reported in adults with chronic lung disease and also in adults with obstructive sleep apnoea (OSA) . The purpose of these studies has been to look for hypoxic episodes during the day in adults with known OSA or pulmonary compromise.…”

Right ventricular dysfunction in patients with non-severe idiopathic pulmonary fibrosis: a cross-sectional prospective single-center study

“…Of the 11 patients with normal VO 2 , only three (27.3%) had RV dysfunction (p = 0.38). Rodrigues et al [16] observed that patients with partial pressures of arterial oxygen (PaO 2 ) >70 mmHg at rest may experience severe hypoxemia (SpO 2 <90%) for a mean of >4 h per day, which would support the periodic occurrence of PH during the day. In agreement with this explanation, a marked increase in mPAP during exercise, which was frequently associated with a concomitant decline in SpO 2 , was observed in the present study.…”

“…Compared with patients in very advanced IPF stages, patients with mild or moderate IPF may have variable pressure loads because of their broad spectrum of daily life activities. Different daily activity profiles may influence the pressure load due to transient hypoxemia, which is notably variable in IPF patients over a 24-h period [16] or due to differential pressure changes during exercise. In addition, the presence of tissue mediators [17] may contribute to premature PH in IPF patients.…”

Right ventricular dysfunction in patients with non-severe idiopathic pulmonary fibrosis: a cross-sectional prospective single-center study

“…Compared with patients in very advanced IPF stages, patients with mild or moderate IPF may have variable pressure loads because of their broad spectrum of daily life activities. Different daily activity profiles may influence the pressure load due to transient hypoxemia, which is notably variable in IPF patients over a 24-h period [16] or due to differential pressure changes during exercise. In addition, the presence of tissue mediators [17] may contribute to premature PH in IPF patients.…”