ABSTRACT
Aim/Introduction: Airborne infections are particularly challenging for in-patient care units. In general, hospitals take more precautions to prevent airborne spread of diseases and several guidelines recommend expiratory filters during nebulizer therapies to reduce exhaled bioaerosols. However, a substantial reduction of virusloaded aerosols depend on a high filter performance for particles 100 -500nm in size. This study aimed to test the effectiveness of filter pads in the reduction of exhaled aerosols by applying 99mTclabeled graphite aerosol. Material(s) and Method(s): In 37 patients with suspected pulmonary embolism or CTEPH an inhalation scintigraphy was performed with 99mTc-labeled graphite aerosol (Technegas ©, particle size 30 -60nm ). The exhalate was filtered by a PARI filter/valve set equipped with a PARI filter pad and then collected in a plastic bag reservoir. Count rates of the filter pads and reservoirs were estimated by planar imaging within a SPECT/ CT. In addition, the individual volumes of the exhaled air were determined. The percentage filter efficacy of the filter pads was calculated. Finally, correlational statistics (Spearman's correlation) addressing the following interactions were performed: (1) exhalate volume and count rates of the filter pads, (2) filter pads' count rates and filter retention efficacy, and (3) exhaled breath volume and filter retention efficacy. Result(s): Mean count rates of the filter pads and the reservoirs containing the filtered exhalate were 26023 +/- 8327 cts/s and 169 +/- 153 cts/s, respectively. The efficacy of the PARI filter/ valve set with PARI filter pad was 98.5 +/- 0.9% (range 96.2 -99.7%). The mean exhaled volume was 9.5 +/- 4.6 l (range 2.4 -21.0 l). The exhalate volumes positively correlate with the filter pad count rates (p=0.006) which, in turn, negatively correlate with the filter pad efficacy (p=0.04). However, an inter-relation of exhaled breath volume and filter pad efficacy failed to reach significance (p=0.07). Conclusion(s): The filter pad of the PARI filter/valve set demonstrated a high retention rate of aerosol particles < 100nm in size. Therefore, in patients suffering from respiratory infections these filter pads used in expiratory filters are suitable to substantially reduce airborne virus load, e.g. COVID-19 SARS CoV2, in their exhalates. Additionally, we found evidence that the filter retention efficacy decreased with increased filter particle load indicating a need for regular filter changes.
ABSTRACT
Introduction: To date, 23 lung transplant recipients have been described with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections worldwide. Eight had severe coronavirus disease 2019 (COVID-19), but none were placed on extracorporeal membrane oxygenation (ECMO) support. We aimed to describe our experience. Methods: Lung transplant recipients who were admitted to our hospital with SARS-CoV-2 infections from the beginning of the pandemia until May 25th, 2020 were included. Clinical charts were retrospectively retrieved and data analysed. Results: Four patients (3 males, 75%) with a median age of 58.5 years (47-66) were admitted for SARS-CoV-2 infections in our center. Three patients had double-lung transplantation for chronic thromboembolic pulmonary hypertension, idiopathic pulmonary fibrosis and cystic fibrosis. One patient had singlelung transplantation for non-specific interstitial pneumonia. SARS-CoV-2 infections were diagnosed by nasopharyngeal swabs in all patients within one month post-transplant (n=2), or after 13 months (n=1) and 15 years (n=1). Dyspnea was present in all patients. Worsening of symptoms occurred in three patients after a median of 8 days (1 to 8) after diagnosis. Imaging showed a highly variable degree of infiltrations. Mechanical ventilation was required in three patients. They all underwent prone positioning. Veno-venous ECMO was required in two patients. In all patients, immunosuppression consisted of prednisone and tacrolimus, while mycophenolate mofetil was stopped. Treatment with hydroxychloroquine was attempted in the first three patients. At last follow-up, one patient was discharged home and one was weaned from mechanical ventilation. Both ECMO supported patients died from multiple organ failure, despite ECMO could be weaned in one patient. Conclusion: A highly variable course of COVID-19 disease was observed in four patients after lung transplantation. More data is needed to better understand prognostic factors and management of this patient cohort.