Breathe easy: How Covid-19 affects lungs

Dr. Sachin D

COVID-19 infection primarily affects the lungs. Apart from the respiratory complications during the active phase of the disease, it also causes long term damage to the lung tissues. Some of the long-term effects on the lungs include a productive and non-productive cough, pulmonary fibrosis, shortness of breath, chest pain, reduced capacity of the lungs, throat pain, and fatigue.

LUNG COMPLICATIONS

Several patients with COVID-19 sustained severe lung complications. Many of them experience lung function impairment months after the recovery. A study performed on 143 patients hospitalized due to COVID-19 concluded that only 13% of the patients were free of their symptoms after 60 days of the symptom onset. The most common symptoms in these patients were fatigue, shortness of breath, and chest pain.

Several studies tested the diffusing capacity of the lungs for carbon monoxide (DLCO) after the recovery from COVID-19. It is a predictor of lung function. A study concluded that approximately 70% of the patients have lung CT anomalies and DLCO anomalies in 16% of the patients three months after discharge. These patients are still under-recovery.

Another study reported that the DLCO anomalies increased with increased severity of the disease during the active phase. For example, the DLCO value was significantly lower in 84.2% of patients with severe pneumonia, while it was substantially lower in 30.4% of those with mild illness. From the available data of other severe respiratory infections, such as the Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS), it can be predicted that almost 50% of the COVID-19 patients may have some degree of lung damage.

FACTORS RESPONSIBLE FOR LONG-TERM LUNG COMPLICATIONS

Not all people with COVID-19 suffer from longterm lung complications. However, some factors that may be responsible for this damage are:

• Underlying medical conditions:People with underlying medical conditions, such as Chronic lung/cardiac diseases and diabetes, are at increased risk for developing severe COVID-19 infections. Such people should take good care, and eat healthily. If they are eligible for vaccination, they must be vaccinated, including the COVID-19, flu and pneumonia vaccine.Older people and people with heart disease are also at increased risk. With age, the immunity reduces, and the lung tissues also become less compliant.
• The severity of the disease:Severity also affects the chances of long-term lung complications. People with severe COVID-19 infection are more likely to have complications than people with mild to moderate severity.
• Treatment: The timing and level of treatment and care provided to the patients significantly affect the recovery and long-term effects. Patients with quick and good treatment recover early and have fewer chances of severe lung damage.

MECHANISM OF LUNG DAMAGE

There are several mechanisms through which COVID- 19 affects the lungs. One of the vital processes which the virus disturbs is the gaseous exchange. COVID- 19 infection damages the connection between the lung cells and blood vessels. It results in preventing gaseous exchange. Further, the disease also results in clots that also prevent the exchange of gases. The patients who develop severe lung infection and inflammationpresent with pneumonia. Severe inflammation of the lungs results in acute respiratory distress syndrome. Patients with this condition require assisted ventilation (mechanical ventilation). Some patients may also require extracorporeal membrane oxygenation (ECMO). In addition, this syndrome may cause fibrosis in the lungs which may take months to recover.

IS THERE A REVERSAL OF LUNG FUNCTION?

Fortunately, there is a significant reversal of lung function in most patients. However, it is not a quick process. The attack on the lungs by the COVID-19 virus is through different phases. Initially there is an injury to the cells of the lungs, and in the next stage, there is scarring. The time of reversal of the lung function depends upon the severity of the disease. Generally, it may take around three months to one year for the lung function to recover, similar to the pre-infection period. Therefore, the patients and healthcare providers should be prepared for long-term care and management.

MANAGEMENT

Patients with post Covid19 lung complications are usually managed with a multidisciplinary approach. This involves treatment of underlying infection, medications to prevent lung fibrosis, medications and pulmonary rehabilitation to improve lung capacity and lung function and improve exercise tolerance. Optimization of underlying co morbidities and monitoring lung function in a goal to achieve near normal lung