The Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS) continuously remains one of the main problems of modern medicine. This is majorly due to the high frequency of the syndrome development as a complication of respiratory diseases or traumas, the complexity of the pathogenesis mechanisms, large material costs for treatment, and high lethality. ARDS is an extremely serious respiratory failure, accompanied by the development of noncardiogenic pulmonary edema with severe violation of gas exchange and breathing mechanics. Despite the variety of factors leading to ARDS, in its essence lies the damage of pulmonary structures, which causes failures in transporting oxygen to the lungs.

The main principles of ARDS treatment are to protect the air-blood barrier structures, and to correct various types of hypoxia by applying a wide range of pharmacological, respiratory and non-respiratory therapies. In this regard, the treatment of ARDS is inherently different from the treatment of other acute respiratory diseases due to the extensive use of mechanical ventilation. The specific medical and ventilator treatment of ARDS is based on the use of invasive mechanical ventilation (IMV) with low tidal volume.

Modern ventilation technology assumes the mandatory use of positive end-expiratory pressure (PEEP), which makes it possible to reduce shunting in lungs, and increase inspiratory reserve volume, while simultaneously reducing the level of FiO2. Fan et al. (2018) state that “few pharmacologic treatments are available and management remains supportive largely based on physiological approaches to lung-protective mechanical ventilation” (p. 698). To those belong the extracorporeal gas exchange, positional and kinetic therapy, exogenous surfactants, selective pulmonary vasodilators and vasoconstrictors, perfluorocarbons, drugs that affect various links of the nonspecific inflammatory process in the lungs, antioxidants, and antihypoxants.

Findings from different studies presented in Pfeilsticker and Serpa Neto’s paper show that mechanical ventilation remains quite a controversial ARDS treatment methods. For example, according to Pfeilsticker and Serpa Neto (2017), “several trials failed in demonstrating benefits with the use of higher levels of PEEP regarding mortality” (p. 2239). However, the authors also note that the ‘open-lung’ strategy provided some positive results regarding hypoxemia and rescue therapies (Pfeilsticker and Serpa Neto, 2017).

Another study in their review (Pfeilsticker and Serpa Neto, 2017) showed better outcomes for patients with severe ARDS associated with using “a combination of an individual PEEP titration following an alveolar recruitment maneuver” (p. 2239). The authors also emphasize the differences in the ARDS treatment guidelines around the world, as well as the differences in research methods in the reviewed studies.

One of the more controversial treatment methods discussed in the review was the increase of PEEP, which proved to have worse outcomes in surgical patients due to the higher driving pressure. Pfeilsticker and Serpa Neto (2017) state that “the best response to an increase of PEEP would be a decrease in the driving pressure, meaning that the intervention would not cause overdistension” (p. 2239). Papazian et al. (2019) also report that “lowering airway pressures has the theoretical dual benefit of minimizing overdistension of the aerated areas and mitigating negative hemodynamic consequences” (p. 2). Thus, as the authors conclude, additional studies are much required in regards to ARDS treatment using mechanical ventilation, as it proves to have controversial results.

A large number of etiological factors, complex mechanisms of pathogenesis, the absence of standard diagnostic criteria make it difficult to conduct proper therapy. This makes the researchers keep looking for new ways to improve treatment outcomes for ARDS. As of yet, one of the leading places in the complex of ARDS therapy is occupied by respiratory support, as an irreplaceable method of temporary prosthetics of the external respiration function. Additionally, various medical and non-respiratory methods of treatment are used in order to improve gas exchange and biomechanics, protect the lung structures, as well as to reduce the damaging effects of mechanical ventilation. Still, there are many other factors that contribute to the lethality level ARDS poses, and that require further research.

References

Fan, E., Brodie, D., & Slutsky, A. S. (2018). Acute respiratory distress syndrome. JAMA, 319(7), 698. Web.

Papazian, L., Aubron, C., Brochard, L., Chiche, J.-D., Combes, A., Dreyfuss, D., Forel, J.-M., Guérin, C., Jaber, S., Mekontso-Dessap, A., Mercat, A., Richard, J.-C., Roux, D., Vieillard-Baron, A., & Faure, H. (2019). Formal guidelines: Management of acute respiratory distress syndrome. Annals of Intensive Care, 9(1). Web.

Pfeilsticker, F. J., & Serpa Neto, A. (2017). ‘Lung-Protective’ ventilation in acute respiratory distress syndrome: Still a challenge? Journal of Thoracic Disease, 9(8), 2238–2241. Web.