In addition to exhaustion, persistent dyspnea is at the center of the symptomatology for those affected. Up to 80% of hospitalized patients report this. This occurs as exertional dyspnea after minor, sometimes minimal physical exertion, or as feelings of anxiety, the feeling of not being able to breathe, or as thoracic pressure sensations.
Although changes in lung function can be detected in 22-56% even after 6 months, the extent of the changes found does not explain the severity of the impairment in many cases.
Therefore, as early as 2020, dysfunctional breathing was assumed to be a possible (partial) cause of the complaints.
In one study, 20.9% were found to have an abnormal score with respect to the most commonly used test to detect dysfunctional breathing (Nijmegen questionnaire). In another study, the proportion of patients with hyperventilation was as high as 50%.
In a separate online study of 147 patients who reported having experienced Covid-19 disease, the average response was 21 out of 62 points, close to the threshold for dysfunctional breathing of 22 points.
Several variables may be altered in dysfunctional breathing: such as respiratory rate, depth of breath, or increased mouth breathing. However, the long-term consequence is a biochemical shift associated with high oxygen saturation, decreased CO2, slightly elevated pH, and slightly decreased bicarbonate. Electrolyte shifts may also occur as a result of alkalosis.
Because decreased CO2 leads to cerebral underperfusion, this mechanism may explain a greater proportion of the complaints (fatigue, cognitive impairment, feeling of not getting enough oxygen). Decreased cerebral blood flow with lowered CO2, particularly during standing, was found in a smaller study of long-covid syndrome.
Based on our own experience with 132 long covid patients, we were able to measure either a decreased pCO2 in blood gas analysis and/or respiratory gas analysis in the majority of affected patients, or there was clear evidence of an accompanying hyperventilation problem in the online history collection.
The abnormalities often do not occur at rest ( sitting/lying) but only when standing, walking, or with mild hyperventilation. This observation has also been reported by other authors. There is overlap with postural tachycardia and CFS (chronic fatigue syndrome).
Other cardiological symptoms (palpitations, dysrhythmias) could be explained by alkalosis leading to a change in electrolytes (decrease in ionized calcium, potassium, magnesium).
Thus, it stands to reason that dysfunctional breathing is (partly) responsible for central aspects of the long covid syndrome.