Gas Law’s and the Respiratory System

Most people go about their day not fully realizing the complexities and mechanics that allow them to stay alive. From the process of turning food into energy to the physiology of kicking a ball, there are a myriad of processes our body has to accomplish to perform these tasks. Two of the most essential processes our body is continuously doing are breathing and respiration. These two processes are essential for life and are composed of numerous and complex mechanisms. What’s more, the ability to sustain life in people who cannot function themselves is a monumental process that combines the laws of physics and chemistry. In order to grasp these mechanisms one must step back and understand the bases of the gas laws.

From the 1700 to the early 1800’s there were numerous discoveries in physics that relate to pulmonary physiology. The British chemist, Robert Boyle (1627-1691) first studied the relation of pressure and volume of a gas. He concluded that the volume of a gas is inversely proportional to the absolute pressure exerted at a constant temperature, or V = 1/P. One can manipulate the equation and find that V1P1 = V2P2.¹ Boyle’s law is what allows the alveoli to enlarge and fill with air. As one inspires, the ventilatory muscles contract and increase the thoracic space. This causes a decrease in intrapleural pressure, which, increases the transpulmonary pressure gradient and allows the alveoli to be pulled open.² Moving on, Jacques Charles (1746-1823), a French chemist demonstrated how the volume of a gas changes with temperature. He proposed that the volume of a gas would increase proportionately with an increase of temperature if the pressure remains constant.¹ This can be seen by the equation V1/T1 = V2/T2. Around this same time, another chemist by the name of Joseph Gay-Lussac (1778-1850) extended Charles’s theorem and stated that if the volume of a gas is held constant than as the pressure of the gas increases so too will the temperature, or P1/T1 = P2/T2.¹

With these laws in mind, one can add them together and come up with the combined gas law, or P1V1/T1 = P2V2/T2.¹ From this single law, one can generate assumptions and theory’s based on pressure, volume, and temperature. Moreover, it has led to the existence of equipment and diagnostics that are still used today, such as mechanical ventilation, blood gas measurements, and pulmonary function testing.¹

Works Cited

1. Cairo, J.M. Pilbeam, Susan P. Mosby’s Respiratory Care Equipment, 8th edition. St. Louis, Missouri: Mosby; 2010:779.

2. Beachey W. Respiratory Care Anatomy and Physiology: Foundations for Clinical Practice, 3rd edition. St. Louis, MO: Mosby; 2013:445.