Leakage in air handling units, the effects on the transmission of airborne infections

The possibility of unfavorable leakages, especially with infectious diseases, in heat recovery systems in air handling units (AHU) is an essential issue. Typical configurations of AHU are analyzed in this aspect, based on their pressure distribution. It is shown that analyzing only for the design conditions is insufficient and that the changing pressure drops of the air filters due to their nonuniform soiling should be taken into account. The novelty of this paper is in proposed method of considering these leaks in the Wells-Riley model, widely used in the literature for airborne transmission of infectious diseases, including the leakage correction factor fhrleak (outdoor fresh air correction factor) based on EATR (exhaust air transfer ratio). Using the proposed method, for typical rooms, on the example of the SARS-CoV-2 virus and its Delta and Omicron variants, it is shown that considering leaks in heat recovery systems in AHU increases the probability of pathogen transmission. The highest increase in the absolute value of the probability of infection is observed in the single office scenario (4.1%) and in the auditorium with a sick speaker scenario (2.7%). The highest increase in reproduction number is observed in the auditorium with a sick speaker scenario (2.69). Such significant changes in reproduction number, including its change from R < 1.0 to R > 1.0 (auditorium with sick speaker for Delta variant of the virus), are crucial from the point of view of considering event scenarios;they slow down or accelerate the pandemic. © 2023 Elsevier Ltd

Incidence of Air Leaks in Critically Ill Patients with Acute Hypoxemic Respiratory Failure Due to COVID-19.

Subcutaneous emphysema, pneumothorax and pneumomediastinum are well-known complications of invasive ventilation in patients with acute hypoxemic respiratory failure. We determined the incidences of air leaks that were visible on available chest images in a cohort of critically ill patients with acute hypoxemic respiratory failure due to coronavirus disease of 2019 (COVID-19) in a single-center cohort in the Netherlands. A total of 712 chest images from 154 patients were re-evaluated by a multidisciplinary team of independent assessors; there was a median of three (2-5) chest radiographs and a median of one (1-2) chest CT scans per patient. The incidences of subcutaneous emphysema, pneumothoraxes and pneumomediastinum present in 13 patients (8.4%) were 4.5%, 4.5%, and 3.9%. The median first day of the presence of an air leak was 18 (2-21) days after arrival in the ICU and 18 (9-22)days after the start of invasive ventilation. We conclude that the incidence of air leaks was high in this cohort of COVID-19 patients, but it was fairly comparable with what was previously reported in patients with acute hypoxemic respiratory failure in the pre-COVID-19 era.

Leakage in air handling units, the effects on the transmission of airborne infections

The possibility of unfavorable leakages, especially with infectious diseases, in heat recovery systems in air handling units (AHU) is an essential issue. Typical configurations of AHU are analyzed in this aspect, based on their pressure distribution. It is shown that analyzing only for the design conditions is insufficient and that the changing pressure drops of the air filters due to their nonuniform soiling should be taken into account. The novelty of this paper is in proposed method of considering these leaks in the Wells-Riley model, widely used in the literature for airborne transmission of infectious diseases, including the leakage correction factor fhrleak (outdoor fresh air correction factor) based on EATR (exhaust air transfer ratio). Using the proposed method, for typical rooms, on the example of the SARS-CoV-2 virus and its Delta and Omicron variants, it is shown that considering leaks in heat recovery systems in AHU increases the probability of pathogen transmission. The highest increase in the absolute value of the probability of infection is observed in the single office scenario (4.1%) and in the auditorium with a sick speaker scenario (2.7%). The highest increase in reproduction number is observed in the auditorium with a sick speaker scenario (2.69). Such significant changes in reproduction number, including its change from R < 1.0 to R > 1.0 (auditorium with sick speaker for Delta variant of the virus), are crucial from the point of view of considering event scenarios;they slow down or accelerate the pandemic.

Pneumomediastinum and air leaks secondary to COVID-19: Expectant vs. invasive management of a rare complication.

Several alterations that, due to their pathophysiology, are collectively classified as "air leaks", have been rare complications of COVID-19 pneumonia. In the context of infection by SARS-CoV-2, the debate arises as to whether these are classified as spontaneous or secondary, since the multiple mechanisms of pulmonary structural damage that COVID-19 entails condition lung fragility in a patient in short time. For the above, we presents the case of a 36-year-old female patient with COVID-19 complicated with pneumomediastinum and subcutaneous emphysema in order to illustrate and discuss these complications.

Diversas alteraciones que, por su fisiopatología, son clasificadas en conjunto como «fugas de aire¼, han sido complicaciones raras de la neumonía por COVID-19. Respecto a la infección por SARS-CoV-2, se plantea el debate de si estas se clasifican como espontáneas o secundarias, ya que los múltiples mecanismos de daño estructural pulmonar que conlleva la COVID-19 condicionan fragilidad pulmonar en corto lapso. Por lo anterior, se expone el caso de una paciente de 36 años con COVID-19 complicada con neumomediastino y enfisema subcutáneo con el objetivo de ilustrar y discutir dichas complicaciones.

The role of filter breathability in reducing the fraction of exhaled air leaking from surgical and community face masks

Face masks are used worldwide to reduce COVID-19 transmission in indoor environments. Differently from face respirators, there are no standards methods for measuring the fraction of air leaking at the face seal of loose-fitting masks such as medical and community masks. This study applies a recently developed method to quantify air leakage at the face seal to 14 medical and community mask models with the aim to understand the role of mask design and filter properties in air leakage. An instrumented head-form equipped with sensors for measuring volumetric airflow and differential pressure was used to simulate the air exhalation from the mouth of a person wearing a face mask. Results showed that the fraction of leaking air at the face seal is not negligible and can range from 10% to 95% according to mask model. The higher the exhaled airflow rate and the lower the amount of leaking fraction. A strong correlation was found between leaking fraction and filter breathability, indicating that a better breathability can lower air leakage. Highly breathable filtering materials should be employed in the production of medical and community face masks to maximize user comfort and minimize the fraction of exhaled air leaking unfiltered at the face seal. © 2022 IEEE.

Negative-pressure wound therapy to treat thoracic empyema with COVID-19-related persistent air leaks: A case report.

The novel coronavirus disease (COVID-19) has resulted in a global pandemic. Recently, COVID-19-related pneumothorax has gained attention because of the associated prolonged hospital stay and high mortality. While most cases of pneumothorax respond well to conservative and supportive care, some cases of refractory pneumothorax with persistent air leaks (PALs) do not respond to conventional therapies. There is a lack of evidence-based management strategies to this regard. We describe the case of a 73-year-old man with COVID-19-related acute respiratory distress syndrome (ARDS) who developed delayed tension pneumothorax with PALs caused by alveolopleural fistulas. Despite chest tube drainage, autologous blood pleurodesis, and endoscopic procedures, the PALs could not be closed, and were complicated by thoracic empyema. Subsequent minimally invasive open-window thoracostomy (OWT) with vacuum-assisted closure (VAC) therapy helped successfully control the refractory PALs. Serial chest computed tomography monitoring was useful for the early detection of the pneumothorax and understanding of its temporal relationship with air-filled lung cysts. Our case provides a new perspective to the underlying cause of refractory pneumothorax with PALs, secondary to COVID-19-related ARDS, and underscores the potential of OWT with VAC therapy as a therapeutic alternative in such cases.

Treatment of a pneumatocele in a COVID-19 patient with endobronchial valves.

A man in his 40s was admitted to his local hospital 6 days after the first vague symptoms of COVID-19. His general condition deteriorated, and he was treated in the intensive care unit but did not require mechanical ventilation. During his recovery, he experienced a cough spell, after which his dyspnoea recurred and rapidly increased. CT pulmonary angiogram showed a 10×18 cm cavitary lesion with an air-fluid level and surrounding atelectasis of the right lower lobe. A one-way valve mechanism had developed, leading to the formation of a pneumatocele. The patient was treated by occlusion of all bronchial segments of the right lower lobe with endobronchial valves, and the pneumatocele was evacuated with a pigtail catheter. The valves were removed 4 weeks after insertion, and the right lower lobe re-expanded. Six months after treatment, the patient had recovered completely and almost regained his former lung function.

Successful use of endobronchial valve for persistent air leak in a patient with COVID-19 and bullous emphysema.

Patients with SARS-CoV-2 pneumonia can suffer from pneumothorax and persistent air leak (PAL). The pneumothorax occurs with or without pre-existing lung disease. PAL refers to air leak lasting more than 5-7 days and arises due to bronchopleural or alveolopleural fistula. The management of PAL can be challenging as a standard management guideline is lacking. Here we present the case of a 42-year-old smoker with COVID-19 who presented to the hospital with fever, cough, acute left-sided chest pain and shortness of breath. He suffered from a large left-sided pneumothorax requiring immediate chest tube drainage. Unfortunately, the air leak persisted for 13 days before one-way endobronchial valve (EBV) was used with complete resolution of the air leak. We also review the literature regarding other cases of EBV utilisation for PAL in patients with COVID-19.

Pleural empyema associated with alveolar-pleural fistulas in severe acute respiratory syndrome coronavirus 2.

Surgery in COVID-19 disease complicated by APF represents the last life-saving treatment option. The choice of the therapeutic period to indicate this approach is fundamental. In fact, the clinical stability of patient is necessary in order to allow single-lung ventilation and to minimize postoperative sequelae.

Pneumomediastinum in a patient with COVID-19 due to diffuse alveolar damage.

A 74-year-old man with COVID-19 was admitted and experienced progressive dyspnoea while receiving supplemental oxygen via high-flow nasal cannula (HFNC). A CT of the thorax showed a pneumomediastinum. The HFNC was temporally interrupted, since it was uncertain whether the positive end-expiratory pressure of the HFNC could be the cause of the pneumomediastinum. After restart of the HFNC, there was no increase of symptoms. We suggest that the pneumomediastinum was the result of COVID-19-related alveolar damage, and not due to the use of HFNC. This observation is relevant since HFNC is often used in the treatment of severe COVID-19 pneumonia.