explained-how-why-of-oxygen-therapy

Context: The ongoing second surge in Covid-19 cases has seen a huge rise in the demand for supplemental oxygen. 

  • In India, 1.75% of the patients were in ICU beds, 0.40% were on ventilator, and 4.03% were occupying oxygen beds. 
  • Since the total active cases have now risen to 20,31,977, the number of patients requiring oxygen beds is significant.

Need for oxygen

  • Shortness of breath occurs because of the way Covid-19 affects the patient’s respiratory system. 
  • A small proportion of Covid-19 patients need oxygen support, when shortness of breath progresses to a more acute condition. 
  • Most patients with Covid-19 have a respiratory tract infection, and in the most severe cases their symptoms can include shortness of breath. 
  • In a small proportion of such cases, this can progress to a more severe and systemic disease characterised by Acute Respiratory Distress Syndrome (ARDS).

Mechanism of lungs

  • The lungs enable the body to absorb oxygen from the air and expel carbon dioxide. 
  • When a person inhales, the tiny air sacs in the lungs called alveoli — expand to capture this oxygen, which is then transferred to blood vessels and transported through the rest of the body.
  • Respiratory epithelial cells line the respiratory tract. 
  • Their primary function is to protect the airway tract from pathogens and infections, and also facilitate gas exchange. 

Effect of Covid-19 on lungs:

  • The SARS-CoV-2 coronavirus can infect these epithelial cells.
  • To fight such infection, the body’s immune system releases cells that trigger inflammation. 
  • When this inflammatory immune response continues, it impedes the regular transfer of oxygen in the lungs. 
  • Simultaneously, fluids too build up. 
  • Low levels of oxygen triggered by Covid-19 are inflammatory markers, which include elevated white blood cell counts and neutrophil counts.

Symptoms of Covid-19 in second wave

  • Shortness of breath is the most common clinical feature among symptomatic hospitalised patients at 47.5%, compared to 41.7% during the first wave. 
  • Simultaneously, other symptoms have dropped significantly compared to the first wave.

Conditions under which oxygen is used

  • According to the clinical management protocol, a person is suffering from moderate disease when he or she is diagnosed with 
    • pneumonia with no signs of severe disease; 
    • with the presence of clinical features of dyspnea (shortness of breath) and/or hypoxia (when the body is deprived of adequate oxygen supply at the tissue level); 
    • fever, cough, including SpO2 (oxygen saturation level) less than 94% (range 90-94%) in room air.
    • The “SpO2” reading on a pulse oximeter shows the percentage of oxygen in someone's blood.
    • In silent hypoxia, patients have extremely low blood oxygen levels, yet do not show signs of breathlessness. 
    • They frequently arrive at the emergency room for other reasons, such as muscle aches, fatigue, fever and cough. 
  • Target: In moderate cases, oxygen therapy is the primary form of treatment: the target is to achieve 92-96% SpO2, or 88-92% in patients with chronic obstructive pulmonary disease. 
  • The devices for administering oxygen in moderate disease are nasal prongs, masks, or masks with breathing/non-rebreathing reservoir bags, depending on requirement. 
  • The protocol also recommends awake proning (having patients lie on their stomachs) as a rescue therapy to increase oxygenation.
  • The clinical management protocol recommends oxygen therapy at 5 litres/min. 
  • Severe cases are defined in three categories: 
    • severe pneumonia, 
    • acute respiratory distress syndrome, and 
    • sepsis. 

Emergency measures: When respiratory distress and/or hypoxemia of the patient cannot be alleviated after receiving standard oxygen therapy, the protocol recommends that high-flow nasal cannula oxygen therapy or non-invasive ventilation can be considered.