Medical devices in the nature of inhalers, sold empty, or inhaler accessory devices, sold empty, used to measure patient inhalation effort and to train patients in personal inhaler use; medical devices in the nature of inhalers, sold empty, or inhaler accessory devices, sold empty, with features for measuring respiratory effort and facilitating the training of patients in use of inhalers; medical devices in the nature of inhalers, sold empty, or inhaler accessory devices, sold empty, with fea...