The Daily Dose • Thursday, June 17, 2021

Optimizing Ventilation in ARDS patients with Marginal Right and Left Ventricular Function

Hana Nadeem

Aranya Bagchi, MD, MBBS, from Massachusetts General Hospital, presented a review course lecture on “Bad Heart-Bad Lungs: How Ventilation in ARDS Impacts Patients with Marginal Right and Left Ventricular Function” on May 16 at the IARS 2021 Annual Meeting. His presentation highlighted the effect of acute respiratory distress syndrome on cardiac dysfunction and how it can accentuate a pre-existing heart condition.

Ventilation offers protective effects to the lung, and ultimately decreases mortality rate in the ICU. To measure the success of ventilation, Dr. Bagchi discussed three different types of pressure: plateau pressure, applied by the mechanical ventilator to the small airway and alveoli measured at end inspiration; driving pressure (ΔP) defined as plateau pressure minus positive end expiratory pressure (PEEP); transpulmonary pressure expressed as airway pressure minus pleural pressure, indicating potential stress on the lung parenchyma. Since plateau pressure is a fixed number and depends on 3 different variables: lung compliance, pleural pressure and PEEP, it isn’t always relevant, Dr. Bagchi explained. A plateau pressure of <30 cm H2O may not be good enough if ΔP is too high, whereas a plateau pressure >30 cm H2O with low ΔP was found to be acceptable. Using driving or Transpulmonary pressure would be more useful to understand the effects of mechanical ventilation on the lungs.

Mentioning the article “Pulmonary Hypertension in severe acute respiratory failure,” published in The New England Journal of Medicine, Dr. Bagchi explained that the outcome of acute respiratory distress syndrome (ARDS) and its associated pulmonary hypertension increases right ventricular (RV) pressure, followed by RV dilatation and septal dyskinesia. To improve RV performance, increasing the systemic pressure would cause an elevation in the left ventricular pressure work, improving right coronary artery blood flow and maintains septal geometry. So, in case of heart failure, it has been suggested to change the order of management and follow the subsequent steps to recuperate the heart function:

  1. Maintain arterial pressure
  2. Consider inotropes reducing cardiac filling pressures
  3. Afterload reduction
  4. Optimize fluid status
  5. Ventilator management

After presenting cases associated with this topic, the main takeaway point emphasized by Dr. Bagchi was to be careful with ventilation. It can allow the patient to experience episodes of hypoxemia, hypercapnia and acidemia with inappropriate PEEP. Due to this fact, optimizing PEEP is important as it will improve forward flow by decreasing central venous pressure, decreasing norepinephrine dose, increasing P:F ratio recruitment and cardiac output. These will help decrease the driving pressure, thus improve RV afterload and heart function.

Dr. Bagchi finished his presentation by stating that ARDS presents with 3 major challenges: inadequate oxygenation, inadequate ventilation and poor lung mechanics. Focusing on only improving oxygen level will not lead to the best optimization. Therefore, it’s better to focus on the lung mechanics and recruit more alveoli in order to improve both oxygenation and ventilation.