Brief Answer: Yes, you thought it rightly. Detailed Answer: Hi, thanks for writing to XXXXXXX As you thought rightly, the swelling in the dependent areas of the upper limb is due to effect of gravity as well as compression of the veins (blood vessels which carry impure blood from the peripheries to the heart). Veins are notorious to get easily compressed as they are very thin walled (unlike arteries which are thick walled) and lie very superficially just beneath the skin. Once the veins gets compressed due to any cause (arm hanging off the bed, in your case), the area of the limb distal to the compression becomes swollen as a result of stagnation of blood. Once the compression is relieved and the limb is elevated above the heart level, the swelling subsides. So, if the swelling had only occurred once (owing to the odd position of your limb over the bed), it can be considered as PHYSIOLOGICAL (otherwise normal) and is not a matter of concern. If the swelling has been appearing regularly on a daily basis, then it needs to be investigated for the possible causes. Hope I have addressed your issue. I welcome any more clarification Regards

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