Do we need a power converter with our adaptor to charge our phones and to use the CPAP machine in Switzerland?
Probably not. Look closely at your CPAP power supply. If it says 100-240 vac, then you just need a plug adapter for Switzerland. It's two thin round pins. Easy to find. German and most of Europe won't work as their pins are a bigger diameter.
Most electronics and CPAPs are multi/dual power. Check labels, of course, but you probably just need a plug adapter.
I used the regular Europe adapters at all my hotels in Switzerland last year without a problem. As long as the adapter's base has pointy ends as shown here, they will fit in the oddly shaped Swiss outlets just fine.
https://store.ricksteves.com/shop/p/european-power-adapter
Virtually all phones and other small electronic chargers these days are multi-voltage, and will operate from 100-240 VAC, 50 / 60 Hz. You can check this by looking at the Nameplate data on the small charging block to verify the specs. It will likely be very small print and hard to read, so use the Magnifier on your phone.
The CPAP power supply will most likely also be multi-voltage and it will also have Nameplate data listed on it, but it's always prudent to check..
Is Switzerland the only country you'll be visiting? I'd suggest packing more than one Plug Adapter as they're small and sometimes get misplaced or forgotten. The link shown in a previous reply is the right one for Switzerland, as it has the "V" shaped ends. Most likely the plugs for both phones and CPAP will only have two prongs. If any have three prongs (grounded), then you'll need a different plug adapter.
Yes always pack more plug adapters than you think you need. I left a great one in a British train plug a few years ago.
. German and most of Europe won't work as their pins are a bigger
diameter.
A C type plug will work in all of continental Europe. That is what most small power appliances sold in Europe have nowadays. So for most usage scenarios one plug adaptor will do for the whole trip.
Pins with a bigger diameter you will only find on grounded plugs, like the German Schuko, and these do not fit in Swiss sockets, true. But using them in Swiss sockets would result in an unsafe situation anyway, as the safety earth would not be connected.