Here is the design of a clinical trial:

Official Title: A Difference in the Cross-section Area of Subclavian Vein Between Supine and Lateral Tilt Position: Its Clinical Impact on Subclavian Venous Catheterization - Stage II

Included conditions:
- Catheterization
- Posture

Study Armgroups:
- {'label': 'Ipsilateral tilt', 'type': 'EXPERIMENTAL', 'description': 'Measuring the cross-sectional area of right subclavian vein in the 20 degree left tilting posture.', 'interventionNames': ['Procedure: Ipsilateral tilt']}
- {'label': 'Supine', 'type': 'NO_INTERVENTION', 'description': 'Measuring the cross-sectional area of right subclavian vein in supine position.'}
- {'label': 'Contralateral tilt', 'type': 'ACTIVE_COMPARATOR', 'description': 'Measuring the cross-sectional area of right subclavian vein in the 20 degree left tilting posture.', 'interventionNames': ['Procedure: Contralateral tilt']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'Ipsilateral tilt', 'description': 'The operation table will be tilted 20 degrees right laterally.', 'armGroupLabels': ['Ipsilateral tilt']}
- {'type': 'PROCEDURE', 'name': 'Contralateral tilt', 'description': 'The operation table will be tilted 20 degrees left laterally.', 'armGroupLabels': ['Contralateral tilt']}

Primary Outcomes:
- {'measure': 'The cross-sectional area of right subclavian vein', 'description': 'The cross-sectional area of right subclavian vein', 'timeFrame': '1 minutes after position change'}

Please estimate the sample size based on the assumption: 
Stage I: alpha level of 0.017, beta level of 0.2, 10% dropout rate; Stage II: alpha level of 0.05, beta level of 0.2, 10% dropout rate
Sample size
        The right csSCV in the supine position for stage I was reported to be 0.93âÂ±â0.17Â cm2 in a previous study [10]. At an alpha level of 0.017 and a beta level of 0.2, a minimum of 15 patients are required to confirm a 15% increase in the csSCV in the ipsilateral tilt position compared to the supine position in the same patient. Considering a 10% dropout rate, 17 patients are needed for stage I.
        In stage II, the primary venipuncture success rate has been reported to be 74.5% in the supine position during right SCV catheterization [11]. At the alpha level of 0.05 and a beta level of 0.2, at least 100 patients per group are needed to determine a 15% increase in primary venipuncture success rate in the ipsilateral tilt position. Assuming a 10% dropout rate, 110 patients are needed in each group.