olemus
elutähtis varustus- või sidekanal

Wiktionary:
3. a means or route for transporting indispensable supplies

näiteid
https://www.regionalresilience.org/critical-lifelines.html

https://www.civildefence.govt.nz/cdem-sector/lifeline-utilities/lifelines-groups/examples-of-major-lifelines-reports/