Found on Pinterest. Labeled as “Spirometry – Exercise with Waller’s Device, 1920”. Waller’s Device may be the mask and breathing valves since the Douglas bag was already well known by this time. Posted by Françoise Soros.
Found on Pinterest. Labeled as “Spirometry – Exercise with Waller’s Device, 1920”. Waller’s Device may be the mask and breathing valves since the Douglas bag was already well known by this time. Posted by Françoise Soros.