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.

Current Needs Assessment for Using Lung Clearance Index for Asthma in Clinical Practice.

PURPOSE OF REVIEW: Asthma pathophysiology has shown that remodeling of the bronchial airways mainly affects the small rather than large airways. The severity of asthma is conventionally measured by forced expiratory volume 1 (FEV1) but this maneuver is insensitive to changes in distal airways with smaller diameter. The aim of this review is to evaluate the current evidence supporting LCI as a clinical tool for assessing small airways disease in asthma patients, as well as whether it is useful as a treatment response parameter in severe therapy-resistant asthma (STRA) patients. RECENT FINDINGS: There is an increasing need for novel tests that can assess distal airway disease in asthma. Lung Clearance Index (LCI) may be a useful test for assessing more severe airway obstruction and the persistence of small airway disease. LCI measurement has been shown to be more sensitive than spirometry in cystic fibrosis (CF), but its clinical utility in asthma has not been thoroughly investigated. LCI abnormalities may be a sensitive marker for the persistence of small distal airway disease and may be associated with a more severe asthma endotype unresponsive to inhaled glucocorticoids. There is a need to identify other lung function tests for asthma that can identify early airway remodeling while simultaneously measuring the rate of lung function impairment. When compared to other conventional methods, multiple-breath washout (MBW) measures the lung clearance index (LCI), a more sensitive predictor of early airway disease that is feasible to perform in children. The goal of this review is to evaluate the current evidence of LCI as a clinical tool in asthma patients.

Índice de aclaramiento pulmonar en pediatría / Lung clearance index

The rate of lung clearance is a measure of the ventilation inhomogeneity determined during multiple breath washout (MBW). Higher values of lung clearance index (LCI) indicate greater ventilation inhomogeneity. The test is performed during tidal breathing, needs little cooperation and coordination, and can be done in all age groups. Different tracer gases can be used; the most common are gas nitrogen as resident gas and sulfohexafluoride (SF6) as an exogenous gas.LCI has been used in various pediatric diseases, such as asthma, bronchopulmonary dysplasia and especially in patients with cystic fibrosis (CF), where high LCI values had been a more sensitive tool that spirometry to detect the early disease and bronchiectasis. It has also been used to monitor the progression of early lung disease, since the value of LCI in preschoolers predicted FEV1 in children of school age. Finally, in patients older than 6 years LCI has proven to be a useful tool to assess response to interventions in patients with normal lung function test. In conclusion the use of LCI is very promising in CF patients with early stages of the disease, and in the clinical monitoring of patients with CF. Its role in other respiratory diseases such as asthma, is still to be determined.

El índice de aclaramiento de pulmón (LCI) es una medida de la falta de homogeneidad de ventilación determinado durante el lavado pulmonar de múltiples respiraciones (MBW). Los valores más altos de LCI indican mayor inhomogeneidad de ventilación. La prueba se realiza durante respiración corriente y necesita poca cooperación y coordinación, por lo que se puede realizar en todos los grupos de edad. Pueden utilizarse diferentes gases trazadores; los más comunes son el nitrógeno como gas residente y sulfohexafluoride (SF6) como gas exógeno.LCI ha sido utilizado en diferentes enfermedades en pediatría, tales como asma, displasia broncopulmonar y especialmente fibrosis quística (FQ). En esta última los valores elevados de LCI son una herramienta más sensible quela espirometría para la detección de la enfermedad pulmonar precoz y bronquiectasias. También ha sido utilizado para monitorizar la progresión de la enfermedad pulmonar, ya que el valor de LCI en los niños en edad preescolar predice el VEF1 en edad escolar. Finalmente en pacientes mayores de 6 años LCI ha demostrado ser una herramienta útil para evaluarla respuesta a intervenciones en pacientes con función pulmonar normal. En conclusión el uso de LCI es muy prometedor en pacientes con FQ en etapa precoz de la enfermedad, su rolen el monitoreo clínico de los pacientes con FQ. En otras enfermedades de las vías respiratorias, como el asma, esto aún está por definirse.

Volumetric capnography in infants with bronchopulmonary dysplasia.

OBJECTIVES: To assess the feasibility of using volumetric capnography in spontaneously breathing small infants and its ability to discriminate between infants with and without bronchopulmonary dysplasia (BPD). STUDY DESIGN: Lung function variables for 231 infants (102 term, 52 healthy preterm, 77 BPD), matched for post-conceptional age of 44 weeks, were collected. BPD was defined as supplemental oxygen requirement at 36 weeks post-menstrual age. Tidal breath-by-breath volume capnograms were obtained by mainstream capnography. The capnographic slope of phase II (SII) and slope of phase III (SIII) were calculated and compared between study groups. The effect of BPD, tidal volume (VT), respiratory rate (RR), and prematurity on the magnitude of the slopes was assessed. RESULTS: SII was steeper in infants with BPD (100 ± 28/L) compared with healthy preterm (88 ± 22/L; P = .007) and term infants (79 ± 18/L; P < .001), but this finding was attributed to differences in VT, RR, and gestational age. SIII was steeper in the BPD group (26.8 ± 14.1/L) compared with healthy preterm (16.2 ± 6.2/L; P < .001) and term controls (14.8 ± 5.4/L; P < .001). BPD was a significant predictor of SIII independently of VT, RR, and gestational age. The ability of SIII to discriminate between BPD and controls was significantly higher compared with lung clearance index (area under the curve 0.83 vs 0.56; P < .001). CONCLUSIONS: Volumetric capnography may provide valuable information regarding functional lung alterations related to BPD and might be considered as an alternative to more involved lung function techniques for monitoring chronic lung disease during early infancy.