Development of the Lung Transplant Frailty Scale (LT-FS)

BACKGROUND

Existing measures of frailty developed in community dwelling older adults may misclassify frailty in lung transplant candidates. We aimed to develop a novel frailty scale for lung transplantation with improved performance characteristics.

METHODS

We measured the short physical performance battery (SPPB), fried frailty phenotype (FFP), Body Composition, and serum Biomarkers representative of putative frailty mechanisms. We applied a 4-step established approach (identify frailty domain variable bivariate associations with the outcome of waitlist delisting or death; build models sequentially incorporating variables from each frailty domain cluster; retain variables that improved model performance ability by c-statistic or AIC) to develop 3 candidate "Lung Transplant Frailty Scale (LT-FS)" measures: 1 incorporating readily available clinical data; 1 adding muscle mass, and 1 adding muscle mass and research-grade Biomarkers. We compared construct and predictive validity of LT-FS models to the SPPB and FFP by ANOVA, ANCOVA, and Cox proportional-hazard modeling.

RESULTS

In 342 lung transplant candidates, LT-FS models exhibited superior construct and predictive validity compared to the SPPB and FFP. The addition of muscle mass and Biomarkers improved model performance. Frailty by all measures was associated with waitlist disability, poorer HRQL, and waitlist delisting/death. LT-FS models exhibited stronger associations with waitlist delisting/death than SPPB or FFP (C-statistic range: 0.73-0.78 vs. 0.57 and 0.55 for SPPB and FFP, respectively). Compared to SPPB and FFP, LT-FS models were generally more strongly associated with delisting/death and improved delisting/death net reclassification, with greater improvements with increasing LT-FS model complexity (range: 0.11-0.34). For example, LT-FS-Body Composition hazard ratio for delisting/death: 6.0 (95%CI: 2.5, 14.2), SPPB HR: 2.5 (95%CI: 1.1, 5.8), FFP HR: 4.3 (95%CI: 1.8, 10.1). Pre-transplant LT-FS frailty, but not SPPB or FFP, was associated with mortality after transplant.

CONCLUSIONS

The LT-FS is a disease-specific physical frailty measure with face and construct validity that has superior predictive validity over established measures.

The 4-Element Movement System Model to Guide Physical Therapist Education, Practice, and Movement-Related Research

The movement system has been adopted as the key identity for the physical therapy profession, and recognition of physical therapists' primary expertise in managing movement dysfunction is an important achievement. However, existing movement system models seem inadequate for guiding education, practice, or research. Lack of a clear, broadly applicable model may hamper progress in physical therapists actually adopting this identity. We propose a model composed of 4 primary elements essential to all movement: motion, force, energy, and control. Although these elements overlap and interact, they can each be examined and tested with some degree of specificity. The proposed 4-element model incorporates specific guidance for visual, qualitative assessment of movement during functional tasks that can be used to develop hypotheses about movement dysfunction and serve as a precursor to more quantitative tests and measures. Human movement always occurs within an environmental context and is affected by personal factors, and these concepts are represented within the model. The proposed scheme is consistent with other widely used models within the profession, such as the International Classification of Functioning, Disability and Health and the Patient Management Model. We demonstrate with multiple examples how the model can be applied to a broad spectrum of patients across the lifespan with musculoskeletal, neurologic, and cardiopulmonary disorders.

Discharge frailty following lung transplantation

INTRODUCTION

Frailty at listing for lung transplant has been associated with waitlist and post-transplant mortality. Frailty trajectories following transplant, however, have been less well characterized, including whether recipient frailty improves. The objective of this study was to identify prevalence and risk factors for frailty at discharge and to evaluate changes in frail recipients enrolled in an outpatient physical therapy program.

METHODS

This was a single-center prospective cohort study of lung transplant recipients. Enrollees completed a short physical performance battery (SPPB) to assess frailty at listing and at initial hospital discharge.

RESULTS

Of the 111 enrolled recipients, none were frail at listing and 18 (16.2%) were prefrail. At discharge, however, 60 (54.1%) patients were frail. Discharge frailty was associated with prefrailty at listing, acute kidney injury post-transplant, and longer intensive care unit stay. Among the 35 patients who were frail at discharge and who were enrolled in an outpatient PT program, the median improvement in SPPB was 6 points (IQR = 5-7 points), and 85.7% became not frail over a median of 6 weeks.

CONCLUSION

Discharge frailty is common following lung transplantation. In most frail patients, an intensive outpatient physical therapy program is associated with improvement in frailty, as assessed by the SPPB.

Methods and Impact of Correcting Heart Rate Data Errors during Exercise in Older Adults

Heart rate (HR) by time curves could be useful as a measure of treatment fidelity. The purposes were to describe the frequency of common recording irregularities (e.g. errors) observed during exercise, validate a process to correct those errors, and determine whether there is a clinically meaningful benefit to data correction. 1895 exercise sessions from 69 older adults with hip fracture were inspected for errors in the placement of event markers (duration of exercise) and signal artifacts. Marker errors occurred in 33% of the participants, and corrected in 324 sessions. Signal artifacts occurred in 96% of the participants, and eliminated in 702 sessions. Computer code was 85% accurate in detecting signal artifacts, compared to 97% for investigators. HR was significantly higher after correction, but the average change was only 0.69 + 1.20 beats per minute. A HR monitor showing HR by time curves can be used to evaluate treatment fidelity during exercise.

Prognostic value of resting end-tidal carbon dioxide in patients with heart failure

BACKGROUND

Cardiopulmonary exercise testing (CPET) variables provide valuable prognostic information in the heart failure (HF) population. The purpose of the present study is to assess the ability of resting end-tidal carbon dioxide partial pressure (PETCO2) to predict cardiac-related events in patients with HF.

METHODS

121 subjects diagnosed with compensated HF underwent CPET on an outpatient basis. Mean age and ejection fraction were 49.3 years (+/-14.7) and 28.4% (+/-13.4), respectively. Resting P(ET)CO2 was determined immediately prior to the exercise test in the seated position. Peak oxygen consumption (VO2) and the minute ventilation-carbon dioxide production (VE/VCO2) slope were also acquired during CPET.

RESULTS

There were 41 cardiac-related hospitalizations and 9 cardiac-related deaths in the year following CPET. Mean resting P(ET)CO2, peak VO2 and VE/VCO2 slope were 34.1 mmHg (+/-4.6), 14.5 ml*kg(-1)*min(-1) (+/-5.1) and 35.9 (+/-8.7) respectively. Univariate Cox regression analysis revealed that resting P(ET)CO2 (Chi-square=28.4, p<0.001), peak VO2 (Chi-square=21.6, p<0.001) and VE/VCO2 slope (Chi-square=54.9, p<0.001) were all significant predictors of cardiac related events. Multivariate Cox regression analysis revealed resting P(ET)CO2 added to the prognostic value of VE/VCO2 slope in predicting cardiac related events (residual Chi-square=4.4, p=0.04). Peak VO2 did not add additional value and was removed (residual Chi-square=3.2, p=0.08).

CONCLUSIONS

These results indicate a resting ventilatory expired gas variable possesses prognostic value independently and in combination with an established prognostic marker from the CPET. Resting P(ET)CO2 may therefore be a valuable objective measure to obtain during both non-exercise and exercise evaluations in patients with HF.

Influence of etiology on ventilatory expired gas and prognosis in heart failure

BACKGROUND

Mechanisms leading to heart failure (HF) are numerous. Etiology-based differences are, however, frequently not taken into account when assessing results of an exercise test. The purpose of this investigation is to: (1) compare subject characteristics and ventilatory expired gas measures demonstrating clinical value between subjects with ischemic and non-ischemic HF. (2) Examine the prognostic value of HF etiology.

METHODS

71 subjects (44 male/27 female) diagnosed with compensated HF underwent exercise testing with ventilatory expired gas analysis. Mean age and ejection fraction (EF) were 51.3% (+/-12.8) and 27.0% (+/-12.5%) for the entire group. HF etiology was ischemic in 30 subjects (16 male/14 female) and non-ischemic in 41 (28 male/13 female).

RESULTS

Age (57.5+/-10.7 vs. 46.7+/-12.5, p<0.001), minute ventilation-carbon dioxide production (VE/VCO2) slope (39.5+/-9.1 vs. 32.6+/-7.7, p=0.001), and duration of phase 1 kinetics in seconds (46.0+/-23.0 vs. 30.0+/-15.6, p=0.001) were significantly higher while peak oxygen consumption (VO2) in ml O2 kg(-1) min(-1) (12.5+/-4.7 vs. 16.0+/-5.2, p=0.006) and partial pressure of end-tidal CO2 (P(ET)CO2) in mm Hg at rest (32.1+/-4.8 vs. 36.1+/-8.0, p=0.02) and peak exercise (31.7+/-4.3 vs. 36.2+/-5.9, p=0.001) were significantly lower in the ischemic group. Difference in EF did not reach statistical significance (28.4% +/-12.5%-ischemic vs. 26.1%+/-12.5%-non-ischemic, p=0.44). Ischemic etiology was additionally a significant predictor of cardiac-related events (p=0.04).

CONCLUSIONS

These findings demonstrate noninvasive indicators of cardiac function and prognosis is poorer in subjects with ischemic HF etiology. Consideration of HF etiology may therefore be prudent, particularly when considering prognosis.