A novel intermittent shuttle walking protocol in the context of pulmonary rehabilitation in patients with COPD

In patients with COPD pulmonary rehabilitation (PR) delivered using minimal equipment induces clinically meaningful improvements in functional capacity and quality of life that are non inferior to PR delivered using specialist equipment. Within this PR setting, walking is simple to perform and easy to administer, hence there has been a growing interest in studies investigating the effectiveness of different walking modalities. Walking activity is typically prescribed at 70-85% of predicted VO2 peak derived from the incremental shuttle walk test (ISWT) or at 70-80% of the average walking speed recorded during the 6-min walk test(6MWT). Patients with advanced COPD are, however, unable to walk uninterruptedly at such walking paces to optimise training benefits. Intolerable symptoms of dyspnoea typically limit walking tolerance to 5-7 minutes. In these patients, intermittent compared to continuous cycling has shown to prolong endurance time secondary to lower sensations of dyspnoea. A systematic review and meta-analysis, undertaken as part of this thesis, suggested that intermittent compared to continuous cycle training leads to superior improvements in peak exercise capacity and dyspnoea sensations in patients with respiratory diseases. Accordingly, the main objective of the thesis was to evaluate whether acute implementation of an intermittent (IntSW) compared to a continuous (CSW) shuttle walking protocol could enhance walking tolerance in patients with advanced COPD. A mixed methods study design was implemented to evaluate differences in walking distance, endurance time, circulatory and symptom responses between the two walking modalities and to fully appreciate patients’ experiences of undertaking the two walking protocols. Twenty stable patients with COPD (mean age: 66±8; FEV1 % predicted: 53±22) initially undertook an ISWT. On two separate visits, 14/20 patients (FEV1 % predicted: 45±21) undertook a CSW protocol and subsequently an IntSW protocol. The CSW protocol was always performed before the IntSW protocol because walking distance was expected to be shorter during the CSW protocol; this allowed comparisons of physiological variables and symptoms at iso-distance (i.e.: the distance walked during the IntSW protocol corresponding to the distance at the limit of tolerance of the CSW protocol). Both protocols were sustained at a walking pace equivalent to 85% of predicted VO2 peak derived from the ISWT to ensure comparisons of variables were made at the same walking pace. Focus groups engaged 10/14 patients on a separate visit. At the outset of the study patients walking distance during the ISWT corresponded to 41% of that recorded from 20 healthy age-matched individuals (age: 68±3; FEV1 % predicted: 112±16). In patients with COPD, median (IQR) walking distance during the IntSW protocol [735 (375- 1107) m] was almost four times greater (p=0.001) compared to that during the CSW protocol [190 (117-360) m]. At iso-distance, the IntSW compared to the CSW protocol was associated with a lower (p=0.013) circulatory load (cardiac output: 8.6±2.6 versus 10.3±3.7 L/min) and lower (p=0.002) arterial oxygen desaturation (SpO2: 92±6% versus 90±7%) while patients experienced less intense (p=0.001) breathlessness (2.8±1.3 versus 4.9±1.4) and leg discomfort (2.3±1.7 versus 4.2±2.2; p=0.001). At the limit of tolerance, symptoms of breathlessness and leg discomfort were not different between the two modalities, suggesting that both walking modalities were limited by reaching comparable intensity of symptoms which took longer during the IntSW compared to the CSW protocol. The IntSW protocol was perceived as a simple and tolerable activity that could potentially enhance general wellbeing. Based on patients’ views, the IntSW protocol was preferable to the CSW protocol because it resembled activities of daily living. Application of intermittent walking in the PR setting may provide important training benefits to patients with advanced COPD because it allows greater work outputs with less intense exertional symptoms and lower circulatory loads