Here is the design of a clinical trial:

Official Title: Sildenafil for Early Pulmonary Vascular Disease in Scleroderma

Included conditions:
- Scleroderma
- Mildly Elevated Pulmonary Pressures

Study Armgroups:
- {'label': 'Sildenafil', 'type': 'EXPERIMENTAL', 'description': 'Sildenafil 20 mg by mouth three(3) times each day', 'interventionNames': ['Drug: Sildenafil']}
- {'label': 'Placebo', 'type': 'PLACEBO_COMPARATOR', 'description': 'Placebo by mouth three(3) times each day', 'interventionNames': ['Other: Placebo']}

Interventions:
- {'type': 'DRUG', 'name': 'Sildenafil', 'description': 'Sildenafil 20 mg three times a day. This is the approved dose for the treatment of pulmonary arterial hypertension. It is being studied in this trial with a population who has mildly elevated pulmonary pressures.', 'armGroupLabels': ['Sildenafil'], 'otherNames': ['Revatio, Viagra']}
- {'type': 'OTHER', 'name': 'Placebo', 'description': 'Oral pill placebo.', 'armGroupLabels': ['Placebo']}

Primary Outcomes:
- {'measure': 'Difference in change in distance walked in 6 minute walk test (6MWT) at 4 months', 'description': 'As assessed by change in 6 minute walk distance (6MWD) in feet (from baseline to 4 months) between the sildenafil group and the placebo group.', 'timeFrame': 'Baseline and 4 months'}

Please estimate the sample size based on the assumption: 
The study assumes a significance level of 0.05 and a power of >80%. A 10% drop-out rate is accounted for, with the possibility of maintaining adequate power even if the drop-out rate increases to 17%.
Sample size
          We have based our effect size estimate of 45Â m upon our preliminary data (not shown) demonstrating a difference in mean 6MWD between SSc patients with normal mPAP and SSc-MEP of â¼â50Â m with a standard deviation of 75Â m. As such, we will have >â80% power to detect this difference at significance level of 0.05 with 27 subjects. To account for a 10% drop-out rate, we are enrolling 30 subjects. Even if our actual drop-out rate nearly doubles our expected rate (17% vs. 10%), we maintain adequate power to detect a difference of 45Â m with 80% power (Fig.Â 3). While this estimate of change in 6MWD exceeds the MID for the 6MWD in PAH, the MID for this test in SSc-MEP is unknown. Further, if differences in 6MWD observed in the study do not reach the predefined detectable alternative, clinical relevance of the effect on 6MWD may be reflected by comparing the proportion of patients who exceeded the MID for 6MWD between arms. Based upon a sample size of 27 subjects completing the trial, we also have adequate power (80% or greater) to detect differences in the proposed secondary outcome measures. For instance, we have 80% power to detect a mean difference in PAC of 0.6 mL/mmHg (SD 1.1) between treatment arms; this difference was the average difference between these SSc-MEP and SSc-normal pressures found in our preliminary studies (data not shown). Further, we will have sufficient power to detect differences of 0.23Â cm (SD 0.5) in TAPSE between groups which is close to the estimated MID for TAPSE in SSc-PAH (0.22Â cm) from prior work from our group [28]. For global RV strain measured by STE, we have more than 85% power to detect a difference of 4.8% (SD 8%); this is the difference detected in our ATPAHSS Study of ambrisentan and tadalafil in treatment naÃ¯ve SSc-PAH patients after therapy [28, 32]. Similarly, we have adequate power to detect a difference of 5% (SD 9%) in RVEF between arms; this difference is the MID for RVEF in PAH [35]. For HRQoL outcomes, we also have adequate power to detect clinically relevant changes in SF-36 of 5 units (SD 7 units) and emPHasis-10 of 6 units (SD 10) [36].
          
Fig. 3Power estimates and detectable alternatives by sample size in the SEPVADIS trial