Personalized Respiratory Support in ARDS: A Physiology-to-Bedside Review

Abstract

Acute respiratory distress syndrome (ARDS) is a leading cause of disability and mortality worldwide, and while no specific etiologic interventions have been shown to improve outcomes, noninvasive and invasive respiratory support strategies are life-saving interventions that allow time for lung recovery. However, the inappropriate management of these strategies, which neglects the unique features of respiratory, lung, and chest wall mechanics may result in disease progression, such as patient self-inflicted lung injury during spontaneous breathing or by ventilator-induced lung injury during invasive mechanical ventilation. ARDS characteristics are highly heterogeneous; therefore, a physiology-based approach is strongly advocated to titrate the delivery and management of respiratory support strategies to match patient characteristics and needs to limit ARDS progression. Several tools have been implemented in clinical practice to aid the clinician in identifying the ARDS sub-phenotypes based on physiological peculiarities (inspiratory effort, respiratory mechanics, and recruitability), thus allowing for the appropriate application of personalized supportive care. In this narrative review, we provide an overview of noninvasive and invasive respiratory support strategies, as well as discuss how identifying ARDS sub-phenotypes in daily practice can help clinicians to deliver personalized respiratory support and potentially improve patient outcomes.

Keywords: AHRF; ARDS; CPAP; HFOT; NIV; mechanical ventilation.

Figure 1

Traces of airway pressure, esophageal pressure, and transpulmonary pressure for a patient undergoing treatment with high-flow nasal oxygen (left panel) and helmet continuous positive airway pressure (right panel). In the (bottom panels), the pendelluft effect is depicted: areas with a bright red color indicate a high pendelluft effect, while the white regions represent no pendelluft. The percentage scale relates to the total tidal volume. Despite the patient exerting a similar inspiratory effort, resulting in the same transpulmonary pressure during both the high flow and the helmet phase, the PEEP administered via the helmet effectively decreased the pendelluft effect, as shown in the (bottom panels).

Figure 2

Flow chart of the physiological effects of helmet-CPAP, helmet-NIV, and HFNO. This figure shows the most common settings and the main physiological effects of each noninvasive respiratory support.

Figure 3

This flowchart illustrates a proposed treatment protocol for acute hypoxemic respiratory failure, and is based on the patient’s clinical presentation and phenotypes (from the authors’ perspective). The first step entails assessing the inspiratory effort, ideally through direct measurements (via an esophageal balloon) or alternatively through indirect measurements (e.g., PaCO2 < 35 mmHg in the absence of metabolic acidosis).

Figure 4

Respiratory system mechanics during volume-controlled ventilation. The end-expiratory hold allows for an assessment of the total positive end-expiratory positive pressure (PEEP), which results from the sum of the PEEP set on mechanical ventilators and the intrinsic PEEP (PEEPi). Contemporary esophageal manometry shows the end-expiratory esophageal pressure (PES), thus allowing for the measurement of transpulmonary pressure (P_L) via the equation of motion. The end-inspiratory hold allows for the assessment of the plateau pressure (P_PLAT) and the driving pressure (ΔP).

Figure 5

Respiratory system mechanics during assisted ventilation.