Introduction

More than 202 million people are living with PAD, and of these, a high percentage includes elderly individuals [1]. PAD affects functional status by evoking classic claudication or atypical exertional leg symptoms by favoring functional impairment and decline in asymptomatic subjects [1, 2].

Structured exercise, with supervised exercise being preferred and more effective [3], is part of a comprehensive program to manage disability and cardiovascular risk [4]; however, in recent years, various home-based structured programs have been proposed [2] based on indoor [5, 6] or outdoor (guided or assisted by wearable technologic devices, etc.) walking [2, 7,8,9] not always with proven effectiveness [9].

Recently, the COVID-19 epidemic emergency has seriously limited the possibility of attending in-hospital supervised exercise, performing outdoor structured home-based programs and taking spontaneous walks [10], particularly in countries where strict movement restrictions have been imposed by the government in an attempt to slow virus transmission [11, 12]. Italy was the first European country where, from March 9th to May 3rd (55 days), a series of restrictions on citizens’ mobility were adopted, including exercise and pet walking being allowed only around the home and a self-declaration form specifying the purpose of their movement and their destination being required [10, 13].

The fear of contagion, particularly present among elderly people, due to the higher percentage of deaths among elderly individuals [14], limited their willingness to leave home to perform physical activity, e.g., to walk for claudication or medical reasons [15, 16].

In addition to such dissuading factors, the reduced availability of non-strictly necessary outpatient services and the limited time of practitioners as well as delayed access to treatment [16, 17] in a country where the National Healthcare Service offers free universal access to health care, may have triggered a subsequent wave of worsening of functional status and cardiovascular risk factors including glycemic or blood pressure control [18].

Ten years ago, to improve the mobility of PAD patients and to overcome most barriers to exercise in PAD patients, a structured in-home exercise program was developed for PAD [5, 6] in an area of the Emilia Romagna Region with a very high aging index [19]. The program, regularly offered to patients with PAD as an outpatient program and successfully tested in stroke survivors and dialysis patients [20,21,22,23], is based on bouts of interval walking at progressively increasing speeds that are performed inside the home in a corridor. Only a few controls in the hospital are requested to update the program.

The present study aimed to evaluate the adherence to and the effects of the program in a cohort of elderly patients enrolled right before the lockdown in Italy and assisted by phone during this period. The hypothesis was that a minimum but structured dose of exercise would guarantee functional stability in people deprived of the opportunity to walk freely, considering that in PAD patients a sedentary lifestyle is responsible of a progressive decline of mobility [24].

Methods

Study design

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 care for patients with claudication at University Hospital of Ferrara, at the time of lockdown (March 9th, 2020) were considered eligible for this study. In this study, all patients started the exercise program no more than 9 months before the lockdown date.

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 [25].

Sample size

The study would require a sample size of 59 participants to achieve a power of 85% and a level of significance of 5% (two sided), for detecting a mean of the differences of 25 m on 6 min walking test from the beginning of the rehabilitation program to the post-lockdown visit, assuming the standard deviation of the differences to be 60 m.

Exercise program

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 includes 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-min walking sessions per day (six days per week) of intermittent walking (1-min work and 1-min 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 3–4 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 and the training session execution are reported elsewhere [5, 26], https://www.youtube.com/watch?v=ki8YX_t-0jA].

Outcome measures

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 > 1.4. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were also collected.

Performance assessment

The 6-min walking test was executed according to the published standard [27]. 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 min. The total distance walked (6-min 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 18 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, 26], 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.

Table 1 The telephone questionnaire and the answers provided by the patients
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Statistical analysis

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. One subgroup included patients who started the program within the three months prior to the lockdown (Rookies), whereas the other subgroup included all the other patients who were enrolled more than three months (Veterans) before the lockdown. The cutoff was arbitrarily chosen considering an ideal duration of the program of 6–9 months [5] and a timeframe possibly associated with physiological adaptations to the program [26, 28]. 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), the day of participation in the program before the lockdown, and the items from the telephone questionnaire.

Statistical analyses were performed with MedCalc Statistical Software version 19.4.0 (MedCalc Software bvba, Ostend, Belgium).

Results

Sixty-six out of the 83 patients (80%) who were enrolled in the Ti-To exercise program completed the post-lockdown visit and the outcome measurement session. Seventeen patients (20%) did not show up at the follow-up evaluation (Fig. 1) for the following reasons: lack of availability (n = 10, 12%), acute limb ischemia (n = 1, 1%), intercurrent disease, such as low back pain (n = 3, 4%) or hip prosthesis (n = 1, 1%), and death (neoplastic disease and COVID-19, n = 2, 2%). At the post-lockdown, 35 patients belonged to the Rookies subgroup whereas 31 patients to the Veterans subgroup. At baseline, the two subgroups did not present any differences (Table 2).

Fig. 1
figure 1

Study flow diagram of participants enrolled in the period June 2019–March 2020

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Table 2 Baseline characteristics of the two subgroups of patients
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Telephone questionnaire results and program update

All patients answered the simple telephone questionnaire in a median time of 5 min. The answers provided by the patients to each question are reported in Table 1. Along with the questionnaire, patients were given the updated program by a team member. No adverse events were reported during execution of the program. Fifty-seven patients (86%) underwent the program progression as scheduled, whereas the remaining nine patients (14%), due to an insufficient number of sessions performed or intercurrent problems, were advised to repeat the sequence scheduled in the previous program. Six patients needed to contact the rehabilitation team again during the period for more information about the exercise training.

Outcomes after lockdown

Patients were subsequently called again starting from May 4, 2020, to reschedule a hospital visit that occurred after 117 (95% CI 111–123) days after the previous visit.

Patients reported execution of a median of 85% (95% CI 77–100) of the prescribed exercise sessions, for a total of > 2100 min (35 h). The training time considering a step length of 50 cm, and program execution 6 days/week corresponded to a median of 74 km walked inside the house during the lockdown period. No adverse events related to execution of the training were reported, and the majority of the walking sessions were executed in the absence of claudication pain.

In the whole population, BW showed a significant decrease, while stable values were observed in BP (Table 3). The ABI of both limbs did not show significant variations in the pre–post period; otherwise, PFWD significantly improved (p < 0.001) but not the 6MWD (p = 0.13).

Table 3 Within- and between-subgroup differences in rehabilitation outcomes
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Considering the two groups, different responses were observed. The Rookies showed a significant improvement in the ABI of the less impaired limb, SBP, 6MWD, PFWD, and BW; the DPB and ABI of the more impaired limb also showed favorable variations approaching statistical significance (p < 0.10).

The Veterans exhibited stable values for almost all outcomes, while positive variations were obtained for PFWD, though not reaching statistical significance. Data are reported in Table 3.

The between-group comparisons showed that significantly greater variations were observed for the 6MWD and PFWD in favor of the Rookies group (Table 3).

Factors related to favorable performance variations during the lockdown period

In the whole population, regression analyses were conducted to determine whether any health-related factor or social parameter examined through the telephone questionnaire could be related to a favorable performance.

Multiple regressions identified that in a weak model (R2 = 0.14; p = 0.031), only the Pre values of the 6MWD and the days from the entry to the pre-lockdown visit were inversely related to variations in the pre–post period. A similar model was observed for PFWD variations (R2 = 0.18; p = 0.022), including PFWD-Pre values and again the time elapsed from the entry to the pre-lockdown visit; both parameters presented negative correlations.

In the logistic regression models, the PFWD and 6MWD variations were dichotomized according to variation equal or greater to the MCID, which is 36 m in the PAD population [29, 30]. Seventeen patients achieved an MCID for PFWD during the lockdown period, and 6 achieved an MCID for 6MWD. No variables were retained in the model for 6MWD; otherwise, a significant model was observed for PFWD (R2 = 0.10; p = 0.039) with the question “did your cohabitant exercise with you” showing a favorable odds ratio of 4.68 (95% CI 1.09–20.20).

Finally, cardiovascular risk factors, other comorbidities, age, PAD severity by ABI, cultural level, sex and marital status were not included in any model.

Discussion

The study confirmed the hypothesis that a structured in-home exercise program was able to ensure adherence and maintain the mobility in a population of PAD patients restricted at home during the COVID-19 emergency.

At first, the study highlighted that in the absence of significant spontaneous physical activity, a structured program carried out at low–moderate intensity (3–4 METS) that was able to guarantee a minimum of 1000 steps per day, supported the walking ability of hypomobile patients. Furthermore, this limited amount of activity performed inside the home in a corridor was associated to an acceptable control of risk factors, including body weight, blood pressure and diabetes.

The precise prescription allowed to counteract the progressive decline of mobility [24] and to maintain functional stability in the whole population, with functional improvement in PAD patients who started rehabilitation immediately before the lockdown and with maintenance of the mobility level among the Veterans. If in the program, early significant aerobic adaptations occur in the most ischemic muscles by walking even in confined spaces [28, 31], progressive further adaptations necessary to complete the functional recovery are favored by patient’s spontaneous activity. In Veterans, in absence of this stimulus during the lockdown, the program favored the persistence of the benefits previously achieved. The hemodynamic parameters also showed a similar pattern (slightly improved or stable), confirming previous observations [6, 26, 32].

Interestingly, patients with more severe claudication pre-lockdown showed more favorable functional improvements, which may not regularly be observed following treadmill-based supervised programs [2].

The response was instead not different by sex, cultural level, marital status, comorbidities, type of house (flat or house with garden and courtyard) and city or countryside living. As a matter of interest, some family members (14%) also started the in-home walking program prescribed for their partners, and this proactive behavior was a factor correlated with functional improvements.

The adherence to the program during the lockdown period was high (85%), even without intermediate visits and with only remote control, as previously tested in a large randomized trial among dialysis patients [23]. The dropout rate, consistent with previously published data [6], was slightly increased due to the fear of the contagion in a small sample of patients.

The characteristics of the program may also explain the global response to the training. Unlike home-based programs where patients are generally advised to walk at a self-selected pace or to maximal ischemic leg pain [8, 32, 33], this program is performed at a lower speed for short bouts in the absence of ischemic pain [5, 6, 26]. These facts facilitate execution in limited spaces and favor adherence. Finally, only a metronome for maintaining the prescribed walking cadence, a stop-watch, a corridor and a chair to sit in during the resting phase are required.

Conclusion

The study aimed to report a particular rehabilitative experience in a group of PAD patients during this historical period. The Ti-To home-based program, designed to overcome the barriers to exercise in an area with an aging index almost double the Europe mean value [19, 34], simply relying on the telephonic monitoring passed the test during the COVID-19 epidemic. Even if social frailty, i.e., reduced connections to society and little social activity, may be correlated with reduced physical function [35, 36], the program was able to ensure stable or improved function in a population with disability that was exposed to strict movement restrictions. However, the reduced sample size is a limitation of this observation.

Considering that resilient care systems should be identified to protect vulnerable patients [37], this program may represent a facilitated way to carry out regular and safe structured exercise activities to frail subjects, even with telephone support only, regardless of the type of home, atmospheric conditions or epidemic limitations.