Finite tandem queues are known to be widely applicable but also hard to solve analytically. Particularly by the Covid-19 pandemic these revived as of practical and solvability interest. An Intensive Care system in a hospital can be regarded as a finite tandem queue with a finite Intensive Care (ICU) and a finite Medium Care Unit (MCU) (also known as Step-Down Unit). This may lead to losses or a hold up at the ICU. An ICU patient might pass both stages for recovery and observation. A key-indicator is the ICU congestion probability. The present paper aims to provide: a first-order if not reasonably accurate lower bound by a simple Erlang loss expression and numerical support for a realistic ICU-MCU application.