Using SpO2 Recovery Index after a 6-Minute Walk Test to Predict Respiratory-Related Events in Hospitalized Patients with Interstitial Pneumonia

Yasunari Sakai,Masayuki Hanaoka,Shuhei Yamamoto,Miho Hoshina,Takashi Ichiyama,Shohei Kawachi

doi:10.1038/s41598-019-51818-1

Yasunari Sakai, Masayuki Hanaoka + Show 4 more

Open Access

https://doi.org/10.1038/s41598-019-51818-1

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Journal: Scientific Reports	Publication Date: Oct 23, 2019
Citations: 6	License type: open-access

Affiliation: Shinshu University Hospital

Abstract

Although the prognostic factors of interstitial pneumonia (IP) patients have been reported, IP has poor prognosis. Hospitalized patients with IP have severely impaired pulmonary diffusion capacity and prominent desaturation. We hypothesized that determining oxygen saturation recovery (SpO2 recovery index) after the 6-minute walk test (6MWT) can provide additional prognostic information regarding rehospitalization for respiratory-related events. We evaluated 73 IP patients at our hospital for demographic characteristics, pulmonary function tests and 6MWT. The Kaplan–Meier method was used to estimate rehospitalisation for respiratory-related events using SpO2 recovery index. Cox regression analysis revealed a relationship between SpO2 recovery index and rehospitalisation. The optimum cutoff value of SpO2 recovery index was 4% (sensitivity, 71.4%; specificity, 79.2%). SpO2 recovery index was most closely related to pulmonary diffusion capacity (r = 0.684, P < 0.001). In a multivariable model, it was the strongest independent predictor of rehospitalisation for respiratory-related events (hazard ratio, 0.3; 95% confidence interval, 0.10–0.90; P = 0.032). In this study, we estimated pulmonary diffusion capacity using SpO2 recovery index values obtained from 6MWT. A SpO2 recovery index of <4% can be useful in predicting rehospitalisation for respiratory-related events.

Highlights

Central pathophysiological features of interstitial pneumonia (IP) include impaired degradation of pulmonary diffusion capacity due to pulmonary interstitium and capillary bed disorders, ventilation perfusion ratio mismatch, and worsening gas exchange with exercise[1]
Determining the breathing pattern, exercise oxygen saturation, post-exercise oxygen saturation recovery and heart rate (HR) changes is crucial because rehospitalisation for acute IP exacerbation and respiratory failure accounts for a majority of the deaths in this disease; the results of such evaluations constitute useful information for risk management
In multivariable analyses using the propensity score, SpO2 recovery index [hazard ratio (HzR) = 0.3; 95% confidence interval (CI) = 0.10–0.90; P = 0.032] and HHR1 (HzR = 0.91; 95% CI = 0.82–0.99; P = 0.045) were significantly associated with respiratory-related events

Summary

Introduction

Central pathophysiological features of interstitial pneumonia (IP) include impaired degradation of pulmonary diffusion capacity due to pulmonary interstitium and capillary bed disorders, ventilation perfusion ratio mismatch, and worsening gas exchange with exercise[1]. Exercise-induced hypoxemia (EIH) of patients with IP is related to the pulmonary diffusion function, which is one of the prognostic factors[6,7,8]. Heart rate recovery (HRR) obtained from 6MWT has drawn attention as a prognostic factor in patients with IP and in those with chronic obstructive pulmonary disease and heart failure[11,12]. Hospitalized patients with IP have severely impaired pulmonary diffusion capacity and prominent desaturation; changes in HR after exercise and desaturation evaluation are important. We examined whether oxygen saturation after 6MWT in hospitalized patients with IP reflected pulmonary diffusion capacity. Oxygen saturation recovery after 6MWT was hypothesized to provide additional prognostic information regarding rehospitalization for respiratory-related events in these patients

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