Relationship between exercise capacity and impulse oscillometry parameters after COVID-19 infections

Small Airways Dysfunction and Lung Hyperinflation in Long COVID-19 Patients as Potential Mechanisms of Persistent Dyspnoea

BACKGROUND

Reticulation, ground glass opacities and post-infection bronchiectasis are present three months following hospitalisation in patients recovering from SARS-CoV-2 infection and are associated with the severity of acute infection. However, scarce data exist on small airways impairment and lung hyperinflation in patients with long COVID-19.

AIM

To evaluate small airways function and lung hyperinflation in previously hospitalised patients with long COVID-19 and their association with post-COVID-19 breathlessness.

METHODS

In total, 33 patients (mean ± SD, 53 ± 11 years) with long COVID-19 were recruited 149 ± 90 days following hospital discharge. Pulmonary function tests were performed and lung hyperinflation was defined as RV/TLC ≥ 40%. Small airways function was evaluated by measuring the closing volume (CV) and closing capacity (CC) using the single-breath nitrogen washout technique (SBN2W).

RESULTS

CC was 115 ± 28% pred. and open capacity (OC) was 90 ± 19. CC was abnormal in 13 patients (39%), CV in 2 patients (6.1%) and OC in 9 patients (27%). Lung hyperinflation was present in 15 patients, whilst the mean mMRC score was 2.2 ± 1.0. Lung hyperinflation was associated with CC (r = 0.772, p = 0.001), OC (r = 0.895, p = 0.001) and mMRC (r = 0.444, p = 0.010).

CONCLUSIONS

Long COVID-19 patients present with small airways dysfunction and lung hyperinflation, which is associated with persistent dyspnoea, following hospitalisation.

Impulse oscillometry assessment of respiratory function in pediatric patients with a history of COVID-19

OBJECTIVE

While coronavirus disease 2019 (COVID-19) is generally considered to exhibit a less severe clinical course in children than in adults, studies have demonstrated that respiratory symptoms can endure for more than 3 months following infection in at least one-third of pediatric cases. The present study evaluates the respiratory functions of children aged 3-15 years within 3-6 months of their recovery from COVID-19 using impulse oscillometry (IOS) and compares them with the values of healthy children.

METHODS

Included in this prospective cross-sectional study were 63 patients (patient group) aged 3-15 years who contracted COVID-19 between December 2021 and May 2022, as well as 57 healthy children as a control group, matched for age and sex. The demographic, clinical, and laboratory data of the patients were recorded, and respiratory function was assessed based on airway resistance (zR5, zR20, R5-20) and reactance (zX5, zX20, reactance area [AX], resonant frequency [Fres]) using an IOS device.

RESULTS

There were no significant differences in the age, weight, height, and body weight z score values of the two groups (p > .05). While the zR5 and R5-20 levels of the patient group were higher (p = .008 and p < .001, respectively) than those of the controls, the zR20, AX, and Fres values did not differ significantly between the groups (p > .05). The parameters indicating the reactance, including zX5 and zX20, were significantly lower in the patient group than in the control group (p = .028 and p < .001, respectively).

CONCLUSION

Total and peripheral airway resistances were found to be elevated in children who had recovered from COVID-19 in the preceding 3-6 months.

Window of opportunity for respiratory oscillometry: A review of recent research

Oscillometry has been around for almost 70 years, but there are still many unknowns. The test is performed during tidal breathing and is therefore free from patient-dependent factors that could influence the results. The Forced Oscillation Technique (FOT), which requires minimal patient cooperation, is gaining ground, particularly with elderly patients and children. In pulmonology, it is a valuable tool for assessing obstructive conditions (with a distinction between central and peripheral obstruction) and restrictive disorders (intrapulmonary and extrapulmonary). Its sensitivity allows the assessment of bronchodilator and bronchoconstrictor responses. Different lung diseases show different patterns of changes in FOT, especially studied in asthma and chronic obstructive pulmonary disease. Because of these differences, many studies have analysed the usefulness of this technique in different areas of medicine. In this paper, the authors would like to present the basics of oscillometry with the areas of its most recent clinical applications.

Small airway disease in post-acute COVID-19 syndrome, a non-conventional approach in three years follow-up of a patient with long COVID: a case report

BACKGROUND

Small airways disease (SAD), a novel finding described in post-acute COVID-19 patients, should be suspected when respiratory symptoms continue, air trapping persists on expiratory CT scans, and imaging findings fail to improve despite objectively better conventional pulmonary function test (PFT) parameters. The forced oscillation technique (FOT) and Multiple breathing washout (MBW) are both very sensitive methods for detecting anomalies in the peripheral airways.

CASE PRESENTATION

We discuss the case of a 60-year-old Hispanic patient who had severe COVID-19 pneumonia and developed dyspnea, fatigue, and limited daily activity a year later. The PFTs revealed restrictive lung disease, as seen by significant diffusing capacity of the lungs for carbon monoxide (DLCO) decrease, severe desaturation, and poor 6-min walk test (6MWT) performance. The patient was treated with lowering corticosteroids as well as pulmonary rehabilitation (PR). During the 24-month follow-up, the dyspnea and fatigue persisted. On PFTs, 6MWT performance and restricted pattern improved slightly, but MBW discovered significant ventilatory inhomogeneity. FOT revealed substantial peripheral airway obstructive abnormalities. On CT scans, air trapping and ground-glass opacities (GGO) improved somewhat. The patient used a bronchodilator twice a day and low-dose inhaled corticosteroids (160 µg of budesonide and 4.5 µg of formoterol fumarate dihydrate) for nine months. PR sessions were resuming. The restricting parameters were stabilized and the DLCO had normalized after 36 months, with a 6MWT performance of 87% but significant desaturation. The CT scan revealed traction bronchiectasis, low GGO, and persistent air trapping. Without normalization, FOT and MBW scores improved, indicating small airway disease.

CONCLUSIONS

The necessity of integrating these tests when detecting SAD is emphasized in our paper. This article lays the foundation for future research into the best ways to manage and monitor SAD in post-acute COVID-19 patients.