Sandbox:Javaria

Mechanical ventilation

• The COVID-19 respiratoty complications that may require mechanical ventilation include: COVID-19-associated pneumonia, COVID-19-associated acute respiratory distress syndrome and COVID-19-associated respiratory failure.

Ventilatory support

Supplemental Oxygen

• Surviving Sepsis Campaign has the following recommendations regarding the use of supplemental oxygen in COVID-19 patients:
  • It is strongly recommended (with moderate-quality evidence) to start the supplemental oxygen if the Spo2 is < 90% in adults. A weak recommendation states starting the supplemental oxygen at < 92% saturation.
  • In COVID-19 positive adult patients with acute hypoxemic respiratory failure on supplemental oxygen therapy, Spo2 should be maintained no higher than 96% (strong recommendation by Surviving Sepsis Campaign). This based upon the systematic review and meta-analysis of 25 RCTs that showed a linear association between the death risk and higher Spo2 targets.

High Flow Nasal Cannula (HFNC)

• Also known as high flow nasal oxygen (HFNO) or Heated humidified high-flow (HHHF) therapy is a non-invasive technique.
• Surviving Sepsis Campaign has the following recommendations regarding the use of HFNC in COVID-19 patients:
  • In COVID-19 positive adult patients with acute hypoxemic respiratory failure despite supplemental oxygen therapy, a weak recommendation suggests using HFNC over conventional oxygen therapy. A systematic review and meta-analysis of 9 RCTs showed that High Flow Nasal Cannula (HFNC) reduces the need for intubation.
  • A weak recommendation (low-quality evidence) also prefers using HFNC over Non-invasive positive pressure ventilation (NIPPV). It is possibly due to reduced mortality and decreased intubation risk, as proved by a RCT and a meta-analysis respectively. Patient comfort better oxygenation with HFNC than NIPPV is also one of the considering factors.
  • Patient should be monitored closely and intubated in the event of decompensation.

Mechanical Ventilation

Non-Invasive Positive Pressure Ventilation

• Non-invasive positive pressure ventilation (NIPPV) is a technique utilized for delivering mechanical ventilation without the use of endotracheal intubation or tracheostomy. It can be administered through a face mask, nasal mask, or a helmet (not recommended in COVID-19 care due to potential aerosol transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
• Many patients who develop ARDS receive a trial of non-invasive positive pressure ventilation (NIPPV) before intubation for mechanical ventilation before they clinically deteriorate or become unable to maintain adequate oxygenation.
• Studies from China reported (4% to 13%) of COVID-19 patients to have received non-invasive positive pressure ventilation (NIPPV).

Invasive mechanical ventilation

• The vascular endothelial injury in COVID-19-associated acute respiratory distress syndrome (CARDS) and diverse mortality rates across the world in CARDS patients arbitrates the importance of different mechanical ventilation strategies.
• The Chinese CDC reports the case-fatality rate to be higher than 50% in patients who received invasive mechanical ventilation.
• According to the American Society of Anesthesiology based upon the experience of Chinese anesthesiologists, timely (neither premature nor late) intubation and ventilation most effectual breathing assistance.

Marini et al. suggest

• • Lower PEEP: “type L,” characterized by low lung elastance (high compliance), lower lung weight as estimated by CT scan, and a low response to PEEP
  • Higher PEEP: Initially it was recommended that the guidelines for ARDS must be followed for respiratory support in SARS Cov2 patients. But the data from China helped inform and reform regarding the strategies. In Wuhan, patients with acute hypoxemic respiratory failure due to COVID-19 have a poor tolerance to high PEEP, likely as the result of the direct and severe lung damage by the virus and inflammatory reactions.
• it may be best to avoid high-frequency oscillatory ventilation in patients with COVID-19 due to concerns of aerosol generation.19,37,38
• Lower tidal volume ventilation (6 mL/kg predicted body weight) is associated with reduced mortality and a greater number of ventilator-free days

• Lower tidal volume ventilation should be continued even if the arterial partial pressure of carbon dioxide (PaCO₂) rises (this is called permissive hypercapnia)
• Permissive hypercapnia usually results in a drop in blood pH, however, treatment of acidemia (e.g., intravenous administration of sodium bicarbonate or tromethamine) is not indicated if the pH remains at or above 7.15 to 7.20
• Predicted body weight (PBW) in kilograms (kg) may be calculated from height in inches (in) as follows:

• PBW (men) = 50 + 2.3 (height in inches – 60)
• PBW (women) = 45.5 + 2.3 (height in inches – 60)

• Higher positive end-expiratory pressure (PEEP) combined with lower tidal volume ventilation is associated with decreased mortality in patients with moderate or severe ARDS (PaO₂/FIO₂ ≤ 200)
• Cisatracurium, when started within the first 48 hours of ARDS diagnosis and continued for 48 hours, has been associated with improved 90-day survival, a greater number of ventilator-free days, and a decreased incidence of volutrauma

Intubation

_The widely used practice in Wuhan, after lung recruitment maneuvers, is to set PEEP at 20 cm H2O and titrate down in a decrement of 2 to 3 cm H2O each time until the goals of oxygenation, plateau pressure, and compliance are all achieved. The commonly used PEEP in this patient population is less than 10 cm H2O. -No mode of ventilation has been suggested to be superior to others.

Stratagies to improve oxygenation

Prone position ventilation

• Prone positioning is thought to improve oxygenation by improving ventilation/perfusion (V/Q) mismatching via reduced shunting of blood through under-ventilated lung tissue.
• Research has shown that prone position ventilation in ARDS patients with acute hypoxemic respiratory failure and spontaneous or assisted breathing reduces the mortality by 28 and 90-days.
• The strategy was widely used in COVID-19 patients in Wuhan, China.
• Prone position is an early strategy rather than a desperate rescue therapy. A study by Lin Ding et al. suggests that the early application of prone ventilation with HFNC and NIV, especially in COVID-19 patients with moderate ARDS, can help avoid intubation.
• Prone position for awake patients during spontaneous or assisted breathing during NIV or HFNC with mild-moderate ARDS was associated with an improved oxygenation. To answer the question about the effectiveness, two RCTs are in progress Template:NCT04347941 and Template:NCT04350723. In addition, patients with an Spo2 of 95% or greater after an hour of the Prone position was associated with a lower rate of intubation.
• The American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine Clinical Practice and Surviving Sepsis Campaign guidelines strongly recommend (moderate evidence) Prone positioning for more than 12 hours/day in patients with severe ARDS.

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