xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
<Button Content="нажать" >
<i:Interaction.Triggers>
<i:EventTrigger EventName="KeyDown">
<i:InvokeCommandAction Command="{Binding KeyDownCommand}" CommandParameter="param"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</Button>