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 laryngoscope is a medical instrument equipped with a light that is used to look inside the larynx and examine the vocal cords, glottis and the space between the vocal cords. For example, the doctor can determine the cause of voice problems, a sore throat or difficulty in swallowing.
The iron lung is a machine that predated modern respirators, and was frequently used in hospitals to allow patients with respiratory failure to breathe, particularly patients whose respiratory muscles had been paralyzed due to polio. The machine works by creating a depression inside the chamber by means of a bellows, the rib cage expands and produces a depression inside the airways of the patient which then allows air from the atmosphere to flow into the airways and lungs due to the difference in pressure.
In 1942-1943, French naval officer Jacques-Yves Cousteau and engineer Emile Gagnan, an expert in liquefied gas control valves, worked together to solve the problem of air being continuously exhausted from diver Le Pieur’s equipment by delivering it at a constant ambient pressure at different depths through a regulator derived from a gas stove valve.
Hippocrates (460-377 BC) was the first who tried to find a scientific explanation for disease with the theory of the four humors (yellow bile, black bile, phlegm and blood) in the body, which are in balance in healthy beings but out of balance in a sick person if there is an excess of one of the humors. Galen (129-216 AD) expanded on the humoral theory by examining the bodies of people who had suffered a violent death to determine whether they conformed to the theory.