Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2020 Dec 12;13(12):e236811. doi: 10.1136/bcr-2020-236811

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.

This article is made freely available for use in accordance with BMJ’s website terms and conditions for the duration of the covid-19 pandemic or until otherwise determined by BMJ. You may use, download and print the article for any lawful, non-commercial purpose (including text and data mining) provided that all copyright notices and trade marks are retained.

PMC Copyright notice

Video 2.

Download video file^{(279.5KB, mp4)}

DOI: 10.1136/bcr-2020-236811.video02