Clinical lung and heart/lung transplantation
Limiting Factors of Exercise Performance 1 Year After Lung Transplantation

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Background

After lung transplantation (LTx) exercise capacity frequently remains limited, despite significantly improved pulmonary function. The aim of this study was to evaluate maximal exercise capacity and peripheral muscle force before and 1 year after LTx, and to determine whether peripheral muscle force and lactate threshold (LT) limit exercise capacity 1 year after LTx.

Methods

Twenty-five subjects (mean age 43 years, 8 women and 17 men, 4 single-lung transplantations) were included in the study. Measurements included maximal exercise capacity, lactate threshold (symptom-limited bicycle ergometer test) and muscle force test (hand-held dynamometer) were performed before and 1 year after LTx.

Results

Before LTx, all patients showed severe exercise intolerance (mean ± SD): work capacity (Wpeak), 11.6 ± 18 W; peak oxygen uptake (Vo2), 8.6 ± 3.6 ml/min/kg. After LTx, exercise capacity improved significantly: Wpeak, 69 ± 27 W (p < 0.001); peak Vo2, 15.7 ± 4.3 ml/min/kg (p < 0.001). Ventilatory factors did not appear to limit exercise capacity. Quadriceps muscle force pre- vs post-LTx was: 248 ± 73 N vs 281 ± 68 N (p < 0.05). Post-LTx, a significant correlation was found between LT and exercise capacity (r = 0.76, p < 0.001), between muscle force and exercise capacity (r = 0.41, p < 0.05) and between the LT and muscle force (r = 0.53, p < 0.01).

Conclusions

The occurrence of an early and pathologic LT and peripheral muscle weakness contributes to the limitation of exercise capacity and reflects a peripheral deficit post-LTx.

Section snippets

Patients

The patients studied were a cohort of single- and double-lung transplantation (SLT and DLT, respectively) recipients at the University Medical Center Groningen (UMCG, The Netherlands). Twenty-five patients (4 SLTs, 21 DLTs) who survived >1 year after transplantation were studied both before (mean ± SD: 620 ± 477 days) and 1 year after transplantation. All patients had end-stage respiratory disease: emphysema (n = 11); idiopathic pulmonary fibrosis (n = 5); cystic fibrosis (n = 5);

Pulmonary Function Before and 1 Year After LTx

After LTx dynamic lung volumes (FEV1, FVC) improved significantly in all transplant recipients, in contrast to static lung volumes (TLC) (Table 2). Also, Pao2 and Paco2 at rest improved significantly (Table 2).

Exercise Capacity Before and 1 Year After LTx

Before LTx, peak Vo2 and Wpeak were below normal values in all recipients (Table 3). The limitations in exercise, as defined in the Methods section, were caused by impaired ventilation in 21 patients and by impaired oxygen uptake in 4 patients. Before LTx, the lactate threshold could not

Discussion

This study has demonstrated that maximal exercise capacity (Wpeak and Vo2max) improved significantly 1 year after LTx. However, maximal exercise capacity did not reach normal values, despite (near) normal lung function in most recipients. After LTx, maximal exercise capacity was reduced due to peripheral muscle limitation in all recipients, which was reflected by pathologically low lactate thresholds. Peak muscle force of the quadriceps improved modestly after LTx, but remained low compared

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