Causes of Shortness of Breath and Shortness of Breath in Long Covid
Breathing difficulties with Long Covid can have different causes. In addition to physical overexertion, psychological factors such as stress or anxiety can trigger shortness of breath. The causes can also be organic in nature and triggered by the lungs or the cardiovascular system, particularly in severe cases of acute illness.
Overexertion
During physical activity, the oxygen demand in the cells increases. To meet this demand, breathing is naturally accelerated. The respiratory rate increases. If the exertion is too high, the respiratory system can be overtaxed, which can lead to breathlessness.
Acute illnesses, such as a Covid-19 infection, can require a lot of rest and limit the ability to exercise. As a result, the level of exertion decreases. You are ‘out of breath’ more quickly than before the illness. It is therefore important to consciously reset the level of exertion and get to know yourself again. If a long Covid illness is also accompanied by fatigue, pacing can also help to manage energy reserves and not exceed stress limits.
Stress & Anxiety
Persistent breathing difficulties can be worrying for those affected. Shortness of breath in particular can trigger stress and anxiety, which put the body in a state of heightened tension via various mechanisms. As a result, they can trigger and exacerbate breathing difficulties.
stress
Among other things, stress activates the sympathetic nervous system, which triggers the ‘fight or flight’ response. The sympathetic nervous system ensures, for example, that the heart beats faster and stronger, breathing speeds up and the airways widen. This allows the body to absorb and transport more oxygen. In this way, stress prepares the organism to perform physically and mentally via the sympathetic nervous system.However, stress can accelerate breathing via these mechanisms to such an extent that hyperventilation occurs. This is because breathing is accelerated without the body having an increased oxygen requirement, e.g. for additional muscle performance. This hyperventilation can lead to a feeling of breathlessness.
Anxiety
Anxiety can trigger breathlessness because it activates a physiological response in the body known as the ‘fight-or-flight response’. This response is controlled by the sympathetic nervous system and occurs in situations that are perceived as threatening. Anxiety therefore triggers a stress response.
Anxiety also increases the perception of physical symptoms. If breathing difficulties occur, they can be exacerbated by anxiety. Anxiety can lead to shallow, rapid breathing, which makes oxygen exchange inefficient and increases the feeling of breathlessness.
Lung changes and damage
The coronavirus can affect lung function in various ways. For example, it binds to receptors found in cells in the airways and lungs. The alveolar cells, which enable gas exchange, are particularly affected. The virus also multiplies (replicates) in cells of the airways and lungs, which can damage or destroy the infected cells.
If breathing problems such as coughing, shortness of breath or breathlessness persist after the acute phase of the infection has subsided, changes or damage to the lungs may be the cause.
In mild courses of the acute phase, dysfunctions of the small airways appear to cause breathing problems [4,5]. Small airways are airways with a diameter of less than 2 mm. They play an essential role in the transport of oxygen and carbon monoxide. They also have a significant influence on lung mechanics and contribute to the subdivision of the lung volume.
If coronaviruses remain in the cells of the lungs after the disease has subsided, they can cause further damage [6]. Doctors also speak of direct viral toxicity. This damage becomes noticeable in the form of persistent respiratory problems.
A persistent reaction of the immune system in the lung tissue can also cause symptoms. For example, increased levels of cytokines have been detected in Long Covid patients with respiratory problems. Cytokines are messenger substances that play an important role in immune reactions. However, through the immune response to the coronavirus, they can also trigger a hardening of connective tissue between the alveoli. Such hardening is also known as fibrosis, which can cause breathing problems.
Another immunological explanation describes a systemic inflammation of lung tissue structures that is triggered by a persistent immune reaction. So-called cytotoxic T cells & T cells can be decisive [4, 7-10].
This can result in a so-called diffusion disorder. In a diffusion disorder, the diameter of the gas exchange surface in the alveolar cells, i.e. at the transition from the lungs to the vascular system, is thickened. Less oxygen can be transported into the blood and less carbon dioxide can be removed than usual.
In severe courses of acute infection, alveolar damage and thrombosis can also cause persistent breathing problems with long Covid [11].
Cardiovascular causes of shortness of breath
Respiration allows oxygen to enter the blood with the air. Oxygen and nutrients are transported through the body in the blood. In turn, the blood is continuously propelled through the body by the beating of the heart. Along the way, the circulatory system supplies the organs and tissues with the necessary oxygen and nutrients.
Studies have shown that the coronavirus can already affect the heart during the acute phase of the infection [12,13]. For example, in some cases the virus can trigger inflammatory diseases of the heart (myocarditis) and ischaemic/thromboembolic events [14].
As a consequence, respiratory problems in Long Covid can also be a consequence of cardiological symptoms.