The MediPines Gas Exchange Monitor utilizes known respiratory principles to provide non-invasive measurements. Below we describe the key scientific aspects upon which the technology is built.
The goal of breathing is to allow for fresh air to enter human lungs and the primary function of the lung is to conduct gas exchange. Fresh oxygen (O2) is brought in during inhalation and carbon dioxide (CO2) from metabolic process is removed during exhalation. Oxygen and carbon dioxide move between air and blood through diffusion deep within the lung at the blood-gas interface barrier as pressure changes due to respiratory movements of the lungs. Typically, a healthy adult person breathes at a rate of approximately 12-18 breaths per minute at rest. Gas diffusion takes place from an area of high to low partial pressure, much as water runs downhill. This process is called pulmonary gas exchange and this process occurs in the air sacs level (alveoli) deep within the lungs. Human lungs contain 300-500 million alveoli that conduct this gas exchange. When patients have a respiratory disease such as COPD (Chronic Obstructive Pulmonary Disease), they experience inefficient gas exchange due to structural damage to their lungs, resulting in abnormal gas measurements (PO2, PCO2 typically measured in mmHg) compared to healthy individual. Furthermore, oxygen and carbon dioxide levels change as they cascade downward (PO2) and upward (PCO2) through the respiratory tract. This situation necessitates different gas measurements at various parts of the respiratory system for clinical applications.
Oxygen Cascades Downward From Mouth to Lungs to Tissue
Pulmonary gas exchange is a vast topic that requires an in-depth understanding of respiratory physiology to appreciate all the intricacies associated with the process. As we age, it becomes crucial to measure the gas exchange process, especially in those with lung disease.
The goal of breathinag is to conduct gas exchange in the lungs. Fresh oxygen is brought in during inhalation and carbon dioxide waste from metabolic processes is expelled during exhalation.
In healthy lungs, this process occurs autonomously, but in diseased lungs the exchange is done inefficiently. This process can only be measured by calculations on precise gas values using advanced oxygen and carbon dioxide sensors. In clinical practice, gas-based indices are compared at different points in the body to source the origin of various causes of gas exchange impairment. The values of oxygen and carbon dioxide in healthy lung tissue (specifically in the alveoli) will be close to that of blood in the arteries.
Gas levels are named according to the phase of the respiratory cycle and the site of measurement. For example, “alveolar” gas values are referred to as “end-tidal” values when referring to the amount of gases left in the lungs at the end of normal exhalation. This distinction in nomenclature provides an important understanding of respiratory medicine. Several breath-based metrics can be obtained simultaneously by the non-invasive MediPines Gas Exchange Monitor/Alveolar Gas Meter (AGM).
The gas exchange process itself begins with oxygen and carbon dioxide moving from the air and into the human body. At sea level, dry atmospheric air (760 mmHg pressure) is composed of 21% oxygen (159 mmHg), 79% nitrogen, and trace amounts of carbon dioxide. As air moves through the upper airways during inspiration, it is saturated and humidified with water vapor, the partial pressure of which at body temperature, pressure, saturated (BTPS) is 47 mmHg. As such, the oxygen partial pressure (PO2) in inspired air is 149 mmHg [21% of (760 – 47) mmHg] and represented as PiO2. In alveolar air, carbon dioxide from gas exchange mixes with the incoming air.1
The human airway is divided into the conducting zone and the respiratory zone. The conducting zone moves air in and out of the lungs. This consists of the upper and lower airways: oral and nasal cavity -> large airways (trachea – bronchi) -> small airways (bronchioles). The respiratory zone is the main region of gas exchange and consists of the following: respiratory bronchioles -> alveolar ducts-> alveoli. Air in this portion is composed of oxygen, nitrogen, water vapor, and carbon dioxide, and precise measurement (mmHg) of Oxygen (PO2) and CO2 (PCO2) levels within the lungs and arterial blood vessels are vital in assessing pulmonary gas exchange efficiency (or inefficiency).
1.West, J.B. “Respiratory Physiology: The Essentials”