WikiDoc Resources for COVID-19-associated pneumonia
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Synonyms and keywords:2019 novel coronavirus disease, COVID19, Wuhan virus, L type COVID pneumonia, H type Pneumonia
In December 2019, a novel coronavirus was detected in pneumonia patients in the Chinese city of Wuhan. The novel coronavirus was later named as 2019-nCoV. Since it was identified, pneumonia appears to be the most frequent manifestation of infection. Despite mimicking the symptoms and criteria of Berlin's definition of ARDS, COVID-19 pneumonia is a distinct disease with features including severe hypoxemia often associated with the normal or near-normal respiratory system compliance.
- In December 2019, there were case reports of a cluster of acute respiratory illness in the Wuhan, Hubei Province, China.
- In January 2020, novel coronavirus was identified in the samples of bronchoalveolar lavage fluid from a patient in Wuhan.
- Later this has been confirmed as the cause of novel corona virus-infected pneumonia.
- The first cases were reported by Huang et al in which most of the patients had a history of exposure to the seafood wholesale market.
- There have been no effective therapies or vaccines available for NCIP as of yet.
- In May 2020, it was postulated that there is also a third distinctive type. This phenotype usually mimics the patchy ARDS phenotype.
- There is no established system for the classification of coronavirus infected pneumonia. Based on the detailed observation of case reports and case series, it has been found that COVID-19 patients differ in their presentation in the emergency department based upon the following three factors:
- The severity of infection, host immune response, preserved physiological reserve, and associated comorbidities.
- Response of patient to the hypoxemia in terms of ventilator
- the time between the presentation of patient to the emergency department and the onset of the disease.
- Based on these three factors, NCIP has been divided COVID-19 associated pneumonia into the following two different phenotypes :
|COVID‑19 pneumonia, Type L||COVID‑19 pneumonia, Type H|
|Low elastance||High elastance|
|Low ventilation to perfusion ratio||High Left to right shunt|
|Low lung weight||High lung weight|
|Low lung recruitability.||High lung recruitability|
- The H type pattern has been reported to present in 20-30 % patients in one case series. It usually fits the criteria of severe ARDS or progresses rapidly towards ARDS.
- In May 2020, it was postulated that there is also a third distinctive type. This phenotype usually mimics the patchy ARDS phenotype.
The exact pathogenesis behind COVID-19 associated pneumonia is not yet fully understood.
- COVID-19 usually express trans-membrane glycoproteins which are called "spike proteins" that allow the virus to attach itself to the target organ and enter into the cell 
- Spike proteins bind to surface angiotensin converting enzyme 2 (ACE2) receptors. Specifically, the RBD of the S protein of SARS-CoV-2 recognizes ACE2 receptors.
- ACE2 is predominately expressed on type II pneumocytes. Other proteins such as TMPRSS2 is also required for complete binding and transmissibility.
- TMPRSS2 cleaves the S protein and results into the fusion of the viral and host cell membrane.
- The virus replicates itself in the target cell using RNA dependent RNA polymerase.
- Lungs seems to be more vulnerable to the SARS-CoV-2 because of the large surface area.
- Direct lung injury leading to release of various cytokines such as (IL)–1β, IL-2, IL-6, IL-7, IL-12, IL-18, tumor necrosis factor (TNF)–α, interferon (IFN)–γ, and granulocyte colony-stimulating factor (GCSF) initiates local inflammatory response and is responsible for the pulmonary manifestations of COVID-19.
- This leads to a modest local subpleural interstitial edema (ground glass lesions) at the interfaces between lung structures
- Vasoplegia results which further accounts for severe hypoxemia.
Differentiating COVID-19-associated pneumonia from other Diseases
- For further information on COVID-19-associated pneumonia click here.
- To view the COVID-19 differential diagnosis click here.
Epidemiology and Demographics
|Date Published||Author||Country||Total Number Of Patients||Incidence/Prevalence|
|01 June,2020||San-Juan Rafael. ||Spain||65||61.5 %|
|21 April 2020||Streng A. ||China||2143||39–82%|
|10 April 2020||Fu Leiwen. et al ||China||3600||73.2 %|
- In another study it was reported that the mean age of the population was 45 years, and 307 (79%) of 391 cases were adults aged 30–69 years.
- At the time of the first clinical assessment, most cases were mild (102 [26%] of 391) or moderate (254 [65%] of 391), and only 35 (9%) were severe.
- There is no significant data reporting specific race predilection for the patients developing COVID-19 associated pneumonia.
- The risk factors for COVID-19 associated pneumonia have not been properly established. Multiple studies show following factors to be the key to the progression of disease severity:
- There is insufficient evidence to recommend routine screening for COVID-19 associated pneumonia.
Natural History, Complications, and Prognosis
- Due to the evolution of pneumonia and high stress ventilation given as a part of treatment,type L COVID-19 pneumonia may progress to type H pneumonia over time.
- The key feature that regulates this transition is the depth of the negative inspiratory intrathoracic pressure that is associated with increased tidal volume in spontaneous breathing.
- This is based on experimental observation by Barach and Mascheroni. This has been termed as patient self-inflicted lung injury. Over time the increased edema causes lung weight to increase.
- There is superimposed pressure and dependent atelectasis that develops over the progression of time.
- When the lung edema increases massively, the lung's gas volume decreases and then tidal volumes that are usually generated for a given pressure also decreases.
- This leads to the development of dyspnea and worsening of the patient's self-inflicted lung injury.
- Pneumonia due to SARS-CoV-2 can further lead to following complications:
- Generally the progression of L Type pneumonia to the H type co-relates to poor prognosis as it further rapidly progresses to ARDS.
- A study reported development of ARDS in 20% patients with a median of eight days after the onset of symptoms.
Diagnostic Study of Choice
- There is no established criteria for the diagnosis of COVID-19 associated pneumonia.
- Initial chest x-rays maybe normal.
- CT-scan chest is more sensitive than chest x-ray but there are no set criteria to diagnose COVID-19 associated pneumonia in COVID-19 patients.
History and Symptoms
- Exposure to SARS-CoV-2 can result into patients exhibiting following signs and symptoms:
|Mild Illness||Moderate Pneumonia||Severe Pneumonia|
- Common physical examination findings include the following:
- Fever (most common)
- Respiratory rate >24 breaths/minute (almost all patients)
- Pulse rate >100 beats/min.
- Audible crackles (on chest examination)
- Signs of consolidation can be present in as early signs of pneumonia in COVID-19 patients such as:
- Common laboratory findings among hospitalized patients with COVID-19 include:
- There are no specific ECG findings associated with COVID-19 associated pneumonia.
- Chest radiograph may show bilateral, almost symmetrical areas of peripheral consolidation with perihilar infiltrates. In an endemic area, these appearances are highly suggestive of infection with COVID-19.
- The primary findings of COVID-19 are those of atypical or organizing pneumonia.
- Almost 18 % of the patients can have normal chest x-ray findings early in the disease course but only 3% in severe disease.
- Bilateral and/or multilobar involvement is common.
- CXR typically shows patchy or diffuse asymmetric airspace opacities which is also seen in other coronaviruses cases.
Echocardiography or Ultrasound
- There are no specific echocardiography/ultrasound findings associated with COVID-19 associated pneumonia.
- CT-scan chest findings in a patient with COVID-19 pneumonia may show following abnormalities:
Other Diagnostic Studies
- Bronchoalveolar lavage may not be useful in diagnosing COVID-19 pneumonia, however various case reports suggest a collection of BAL fluid when consecutive nasopharyngeal swabs are negative to confirm or exclude the diagnosis of COVID-19-associated pneumonia.
- The mainstay of treatment for COVID-19 associated pneumonia is supportive care and mechanical respiratory support.
- For suspected bacterial co-infection which may depict as elevated WBC, positive sputum culture, positive urinary antigen and atypical chest imaging, administer empiric coverage for community-acquired or health-care associated pneumonia.
- As there have been 3 distinct phenotypes of COVID-19 pneumonia, so there have been different treatment modalities for each of them.
- The first step is to reverse hypoxemia which can be done through increase in FiO2. This is well tolerated in patients with Type L pneumonia.
- For L Type with dyspnea, following different non-invasive options are available:
- High flow nasal cannula (HFNC)
- Continuous positive airway pressure (CPAP)
- Non-invasive ventilation (NIV)
- Esophageal manometry pressure is measured to prevent swings of central venous pressure.
- P0.1 and Pocclusion should be measured in intubated patient.
- Mechanical Ventilation should be instituted at the appropriate time.
- The best way to prevent being infected by COVID-19 is to avoid being exposed to this virus by adopting the following practices for infection control:
- Often wash hands with soap and water for at least 20 seconds.
- Use an alcohol-based hand sanitizer containing at least 60% alcohol in case soap and water are not available.
- Avoid touching the eyes, nose, and mouth without washing hands.
- Avoid being in close contact with people sick with COVID-19 infection.
- Stay home while being symptomatic to prevent spread to others.
- Cover mouth while coughing or sneezing with a tissue paper, and then throw the tissue in the trash.
- Clean and disinfect the objects and surfaces which are touched frequently.
- There is currently no vaccine available to prevent COVID-19.
- The secondary prevention measures of Coronavirus disease 2019 (COVID-19) constitute protective measures to make sure that an infected individual does not transfer the disease to others by maintaining self-isolation at home or designated quarantine facilities.
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