COVID-19 has affected life globally in a short span of time. Nations have taken steps ranging from encouraging usage of masks to lockdowns to curb the spread of the virus. It is critical to understand the COVID-19 virus, how it spreads and how it affects our body, in order to ensure swift recovery and minimal damage. Researchers and virologists across the world are making tremendous progress in understanding the COVID-19 virus to develop a cure and vaccine. Doctors and Healthcare professionals are tirelessly evaluating various combinations of antiviral drugs and other supporting medications to manage the cases better. There is a great scope of improvement in another equally important area - screening and early detection of deterioration to efficiently use our limited healthcare resources.
One of the reasons COVID-19 has been able to spread across the globe is a relatively long incubation period where infected people can spread it while experiencing no or neglected mild symptoms. To understand this, we need to look at the lifecycle of the virus as it infects a person. The virus once it has entered the body looks for suitable receptors to attach. These receptors are located mostly in the respiratory tract, concentrated on a specific type of alveoli (small air sacs) in the lungs, throat, nose and tongue. These receptors are also present in the stomach, spleen, small intestine, etc. If the virus only reaches the throat, nose and tongue before our immune system generates antibodies to fight it, it only causes cold-like symptoms and phases off. However, if it manages to reach the lungs that is where the infection becomes severe. As the virus starts attaching to the alveoli, our immune system mounts its first defence by releasing a ton of cytokines that start causing destruction in the alveoli damaging the walls and causing the fluid to fill in with inflammation. Reduced lung capacity is felt as the shortness of breath at this point. To compensate, the autonomous nervous system increases the respiratory rate maintaining the oxygenation of blood. Further the inflammation causes tiny clots in the capillary blocking the blood flow to the lungs and finally pulmonary hypertension causing the pulmonary artery to constrict and make it harder for the right ventricle of the heart to pump blood to the lungs. As a result oxygen levels in the blood reduce.
In this process the two vital parameters that are critical to measure the progression of the infection are respiratory rate and oxygen saturation. The Ministry of Health and Family Welfare has released guidelines stating Respiratory Rate >24 RPM and 94%> SPO2 > 90% indicates moderate cases and Respiratory Rate > 30 RPM along with SPO2 < 90% indicates severe ones. This is in line with the WHO guidelines followed globally.
A higher respiratory rate as a result of shortness of breath is the first indication of virus reaching the lungs. As the infection progresses the oxygen saturation drops, however this drop can be steep and happen in a matter of hours.
Vigilant monitoring of these vitals even for asymptomatic people, especially resting respiratory rate (controlled purely by the autonomous nervous system) is the most efficient way to identify deterioration early and get access to medical intervention. This is even more critical for vulnerable population - elerdely people and people with preexisting health conditions like diabetes, CKD, etc.
Our autonomous nervous system and lungs start a distress call by increasing the respiratory rate, we just need to keep listening!