Primary outcome measure
The primary outcome of this trial will be dyspnoea using the modified Borg Scale. Evaluators will show a printed Borg scale to patients and explain the meaning of each punctuation, then patients will be asked to rate their dyspnoea. Data will be assessed at baseline and after each treatment session (day 1 to day 5). Differences will be assessed comparing groups mean scores at each day (day 1 to day 5). The modified Borg Scale is a valid and reliable assessment tool for dyspnoea in patients with an AECOPD (16).
Secondary outcome measures
Hospitalization length will be measured using the number of days from the time of admission until the patient’s discharge. Scores will be compared using mean differences between groups.
Peak expiratory flow will be assessed using a peak flow meter, using liter per minute units, at baseline and after each treatment session. For each assessment, peak flow will be measured 3 times and only the highest score will be considered. Differences will be assessed between groups using mean scores at each day (day 1 to day 5).
Adverse events will be recorded after each treatment session, the evaluator will ask the patient for any adverse event related to the intervention. Description of each event and its frequency will be described for each group.
Blood gas analysis (PaO2, PaCO2, arterial blood pH, bicarbonate and SaO2) at days 1 to 5 will be recorded if available in the patient’s clinical history since no specific analysis will be made for the trial. Differences will be assessed comparing means at each day (day 1 to day 5).
Relapse and readmissions at 3 months after discharge will be assessed using the participant’s clinical history. Mean number of relapses and readmissions during the 3 months period after discharge will be compared between groups.
Mortality will be assessed using the ratio of patients who died during the 3 months period after discharge in each group.
Quantity of drugs administer during patient’s hospitalization will be extracted from patient’s clinical history. Mean dosages will be compared between groups.
Data will be collected using a standard form designed by the study investigators and database entry will be double checked.
Participant timeline
Participant timeline is described in figure 2.
Randomization and allocation:
Participants will be randomly assigned to the acuTENS or sham acuTENS group with a 1:1 allocation using a computer-generated randomization list. A blocked randomization list will be generated for each centre by the main author, who will not be involve in the recruitment or assessment.
Randomization lists will be kept using electronic key and only will be available to the persons responsible for administering the treatments.
Once participants give consent for participation a consecutive number will be assigned by the head of recruitment, the staff responsible of administrating the treatment will match the patient’s number with the randomization list to define patient’s allocation.
Blinding
Trial participants, outcome assessors and usual care providers will be blinded during the trial, only the physiotherapists who will perform the acuTENS or sham acuTENS procedure will know patient’s allocation. The medical staff will not be present during the application of technology to ensure that they remain blinded to allocation. There will be no circumstances under which unblinding is permissible. Data analysts will be performed by a blinded external statistician.
Sample size
Given that the significant difference in clinical minimally dyspnoea measured by the Borg scale for patients with COPD exacerbation is 2 (15), a common standard deviation of 2.6 and assuming an α error of 0.05, a β error of 0.2 and a 10% of losses, it is calculated that we will need to recruit 60 patients for this study. To reach this target sample size pulmonology service and hospital emergency staff will be informed so they can detect possible candidates.
Statistical methods
There will be a descriptive analysis of the demographic data using means and standard deviations (mean ± SD) for continuous variables and absolute values and percentages for qualitative outcomes.
For the comparative analysis between the two groups, continuous outcomes (such as Borg scale score and number of hospitalization days) will be analysed using mean differences with a 95% confidence interval with a t' Student test or Mann-Whitney U depending on the distribution of these. For dichotomous outcomes (such as mortality at 3 moths) risk ratio will also be used with a confidence interval of 95% and test χ2.
The main analysis will be done by intention to treat, but there will be another per-protocol analysis for patients who have received at least three interventions. Significant difference will be considered as a value of p <0.05.
In case of missing data last value carried forward methods will be used.
In the case of significant baseline differences between the two groups there will be an adjusted analysis for these outcomes.