17 Dec Discovery of pulmonary plethysmography
A pulmonary plethysmograph is an instrument that can measure total lung capacity, in other words the volume of air entering a person’s lungs after taking a deep breath, and the volume of air left in the lungs after exhaling normally. It resembles a completely sealed, small telephone booth where the patient is seated and breathes through a mouthpiece. The doctor can determine whether there is any obstructive or restrictive pulmonary disease based on the difference in volume when the lungs are full and empty. Obstructive pulmonary disease causes difficulty in exhaling all the air present in the lungs, and includes illnesses such as chronic bronchitis, asthma and cystic fibrosis. Restrictive pulmonary disease causes difficulty in completely expanding the lungs due to stiffness in the lungs themselves or the rib cage, and includes illnesses such as amytrophic lateral sclerosis.
The first example of plethysmography recognized by the scientific community dates back to 1790. Scientist Robert Menzies immersed a person up to the chin in a barrel of water and measured the rise and fall of the level of water and thus determining the amount of air inhaled and exhaled during normal breathing.
Modern plethysmography is based on innovations brought by three American scientists, Arthur B. DuBois, Stella Y. Botelho and Julius H. Comroe, Jr., who in 1956 used their knowledge of mathematics and fluid dynamics to solve technical problems associated with plethysmography at that time.