Pre-discharge Bedside Exercise Gas Exchange Measurements Predict 30 Day Heart Failure Patient Readmissions

Abstract

Thirty day hospital readmissions for heart failure (HF) are associated with high morbidity, mortality and costs. Based on evidence relating a growing array of submaximum exercise gas exchange (Gx) measurements to outcomes in HF we hypothesized that submaximum Gx testing at the time of discharge would be an effective tool to identify which patients have high risk of readmission. Patients hospitalized for acute decompensated HF (N=50, mean age 65±14; 78% male) from 3 participating centers who met inclusion criteria (age> 18, NYHA II-IV chronic HF, and capable of exercise) provided informed consent were enrolled in the study. Subjects performed submax exercise on the day of hospital discharge. Heart and respiratory rate, Gx and O2 saturation were monitored continuously during a 6 min protocol consisting of 2 min of rest, 3 min of step exercise and 1 minute of recovery. A 6- parameter multi-metric Shape Score consisting of resting and exercise delta ETCO2, VE slope and O2 uptake efficiency slope (OUES), pulmonary capacitance (GxCap), and end exercise SaO2 were computed. RER, HR, VO2, and O2 pulse were also assessed during rest and exercise. The overall readmission (RA) rate for those Shape tested was 11 of 50 or 22%. Comparing those HF patients who were RA within 30 days vs. those who were not readmitted (NRA), volitional effort, based on peak RER, was equivalent between groups (0.94±.07 and 0.94±.10, respectively, p=.99). Patients with RA had higher Shape Scores than the NRA group (2.4±1.0 vs. 1.1±1.1, p< .005). Individual gas exchange parameters known to prognosticate in patients with chronic HF also tended to be more impaired in the RA group (Table, i.e. lower achieved VO2, higher VE/VCO2 slope, lower OUES). In this pilot study, exercise Gx using a simple, 6 min. bedside step protocol prior to discharge offers an objective means to predict likelihood for 30 day readmission in patients hospitalized with ADHF. A multi-metric Shape Gx score that integrates sub-maximum exercise Gx parameters outperforms individual Gx variables in predicting hospital readmission. While larger, definitive studies are required, bedside measurement of Gx in HF patients may represent an inexpensive, non-invasive practical clinical tool to track functional status and to effectively indentify HF patients at risk for readmission.Table 1Gas exchange variables at the time of dischargeStudy groupShape Multivariate Composite ScoreVO2 peakVE/VCO2 slopeGxCAP peakOUESΔETCO2End exercise SaO230 day readmitN= 112.4±1.0p=.0029.4±1.5p=.02441.6±16.7NS363±208NS1.12±.34p=0.06-1.0±3.8NS91±5NSNo 30 day readmitN=391.1±1.111.1±2.835.4±10.4432±1631.42±.51-.44±3.093±4 Open table in a new tab