This is an observational study that was carried out at the Department of Rehabilitation Medicine at the University Hospital of Ferrara. The Ethics Committee CE-AV approved the study (n. 539/2020) and written informed consent was obtained.
Subjects and inclusion criteria
All of the patients who were participating in the vascular rehabilitation program, which is part of the usual care for patients with claudication at University Hospital of Ferrara, at the time of lockdown (March 9th, 2020) were considered eligible for this study.
Males and females aged > 18 years with Leriche-Fontaine Stage II vascular claudication that was stable for at least 3 months are usually enrolled, whereas patients with conditions contraindicating safe training execution at home (e.g., unstable angina, severe heart failure, major amputation or clinical conditions limiting exercise testing) are usually excluded. The presence of PAD was previously diagnosed at the Vascular Surgery Unit of the Hospital of Ferrara by clinical and echo-color-Doppler examination .
In this study, all patients started the exercise program no more than 9 months before the lockdown date.
All the patients enrolled were executing the “Test in - Train out” (Ti-To), structured, pain-free home-based exercise program [5,6]. Ti-To program include a center-based phase and a home-based phase with walking exercises. The first phase is composed of circa-monthly visits at the hospital for clinical assessment, hemodynamic and performance measurements, an update of the home-based walking program prescription, and evaluation of patient adherence. The home-based phase includes the execution of training at home, preferably indoors (e.g., hallway, heated garage). The program is based on two daily 8-minute walking sessions per day (six days per week) of intermittent walking (1-minute work and 1-minute seated rest) at a prescribed speed. The training speed, converted into walking cadence (steps/minute), is maintained at home by a metronome as learned in a training session executed during the first visit. The exercise program increases weekly by 3 to 4 steps/min, from 60 to 92-100 steps/min according to the severity of claudication at baseline. Progressively, the length of each bout is amplified with a work:rest ratio from 1:1 to 2:1 and 3:1, while the whole duration of each session remains constant. Patients are asked to fill out a daily training diary, indicating completion of the exercise and any related symptoms. The exercise program ends when the patients reach a pain-free walking distance that is normal for their sex and age or when a stable satisfactory performance is attained. Additional details on the exercise program are reported elsewhere [5,25].
At entry into the program, information regarding clinical status and functional impairment was collected by consulting patients’ medical documents, by means of physician examination or by specific tests. Body weight (BW) and height were measured for body mass index (BMI) calculation.
Hemodynamic assessment: After five minutes of rest, patients underwent ankle-brachial index (ABI) measurements according to a standard procedure using Doppler ultrasound (Dopplex SD2, Huntleigh Healthcare Ltd. Diagnostics, Cardiff, United Kingdom) and a standard blood pressure (BP) cuff. The leg with the lowest ABI value was considered the worst leg. The vessels were considered “not compressible” for ABI measurements > 1.31. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were also collected.
Performance assessment: The 6-minute walking test was executed according to the published standard . Patients were instructed to walk back and forth along a 21-m corridor alone at their own pace with the aim of covering as much distance as possible in 6 minutes. The total distance walked (6-minute walking distance, 6MWD) and the pain-free walking distance (PFWD) were recorded.
For this specific study, two time points of collection were considered: the last hospital visit before the lockdown (Pre) and the first return to the hospital after the lockdown (Post).
Program update during the lockdown period
Considering that the vascular rehabilitation program was closed from March 9th to May 18th 2020, the rehabilitation team remained available by phone during the entire period of closure. A team member called all the patients enrolled to check their health status and to update the exercise program. The scheduled training program progression [5,25], was confirmed if the patients reported regular program execution in the absence of general or peripheral symptoms. Otherwise, the progression was delayed in the presence of incomplete execution or limiting symptoms, with the patients being advised to repeat part of the previous program in the following weeks.
In addition, a quick telephone questionnaire was administered to the patients to examine factors related to exercise execution, clinical status and the characteristics of their home. The questionnaire was composed of nine Yes/No questions, which are reported in Table 1.
Data are expressed as the mean ± standard deviation for continuous data and as the percentage frequency for categorical data.
The entire enrolled PAD population was divided into two subgroups according to the time since they started the rehabilitation program. The “Rookies” subgroup included patients who started the program within the three months prior to the lockdown, whereas the “Veterans” subgroup included all the other patients who were enrolled more than three months before the lockdown. The cutoff was arbitrarily chosen considering an ideal duration of the program of 6 to 9 months  and a timeframe possibly associated with physiological adaptations to the program [25,27]. Pre versus Post comparisons of all outcomes were performed by paired samples t tests or Wilcoxon rank tests according to the data distribution. The between-subgroup comparisons were performed with chi-squared tests, independent samples t tests or Mann-Whitney tests, as appropriate.
Multiple and logistic regression models were employed to identify any factor potentially related to an increased walking ability by defining the performance variations (PFWD and 6MWD) in the Pre-Post period, properly dichotomized when needed, as dependent variables. Independent variables included patient characteristics (age, sex and marital status, cultural level), cardiovascular risk factors, comorbidities, hemodynamic severity and functional limitation (ABI, Pre-PFWD and 6MWD) and the items from the telephone questionnaire.
Statistical analyses were performed with MedCalc Statistical Software version 19.4.0 (MedCalc Software bvba, Ostend, Belgium).