Monitoring patients with acute respiratory failure during non-invasive respiratory support to minimize harm and identify treatment failure

Abstract

Non-invasive respiratory support (NRS), including high flow nasal oxygen therapy, continuous positive airway pressure and non-invasive ventilation, is a cornerstone in the management of critically ill patients who develop acute respiratory failure (ARF). Overall, NRS reduces the work of breathing and relieves dyspnea in many patients with ARF, sometimes avoiding the need for intubation and invasive mechanical ventilation with variable efficacy across diverse clinical scenarios. Nonetheless, prolonged exposure to NRS in the presence of sustained high respiratory drive and effort can result in respiratory muscle fatigue, cardiovascular collapse, and impaired oxygen delivery to vital organs, leading to poor outcomes in patients who ultimately fail NRS and require intubation. Assessment of patients' baseline characteristics before starting NRS, close physiological monitoring to evaluate patients' response to respiratory support, adjustment of device settings and interface, and, most importantly, early identification of failure or of paramount importance to avoid the negative consequences of delayed intubation. This review highlights the role of respiratory monitoring across various modalities of NRS in patients with ARF including dyspnea, general respiratory parameters, measures of drive and effort, and lung imaging. It includes technical specificities related to the target population and emphasizes the importance of clinicians' physiological understanding and tailoring clinical decisions to individual patients' needs.

Keywords: Acute respiratory failure; Non-invasive respiratory support; Respiratory monitoring.

Fig. 1

Integration of baseline characteristics and monitoring tools during non-invasive respiratory support. A simple algorithm is proposed based on baseline characteristics (i.e., oxygenation and clinical severity) to decide on the appropriateness of a trial of non-invasive respiratory support. Available tools to monitor response are also summarized. Duration of short trial and trial of intermediate duration depends on patients’ individual response to therapy, authors suggest considering 1–2 h for a short trial and 3–6 h for a trial of intermediate duration. * intended to guide decisions in patients with acute hypoxemic respiratory failure of infectious etiology (e.g., Community acquired pneumonia) or ARDS. PaO₂/FiO₂ ratio of arterial partial pressure of oxygen to fraction of inspired oxygen; IMV invasive mechanical ventilation; CPAP continuous positive airway pressure; NIV non-invasive ventilation; HFNO high flow nasal oxygen; Vt/PBW ratio of tidal volume to predicted body weight; SPO₂/FiO₂ ratio of oxygen saturation to fraction of inspire oxygen; PaCO₂ arterial partial pressure of carbon dioxide; ΔPes esophageal pressure swing; ΔPnose swing in nasal pressure; ΔCVP swing in central venous pressure; EIT electrical impedance tomography; CoV center of ventilation; GI index inhomogeneity index; TFdi thickening fraction of the diaphragm

Fig. 2

Esophageal catheter insertion during non-invasive respiratory support. Respiratory recordings during non-invasive ventilation through facemask. Airway pressure, auxiliary pressure, and transpulmonary pressure (difference between airway pressure and esophageal pressure) are displayed (top, medium, and bottom respectively). Vertical dotted lines indicate separation between the respiratory cycles. Of note, during high flow nasal oxygen, there is no airway pressure monitoring and identification of individual respiratory cycles, inspiration and expiration require observation of the patient. Panel A) shows the initial position of the catheter in the stomach (approximately 60 cm from the nostril). Gastric pressure (Pga) is recognized by the characteristic positive deflection in auxiliary pressure (Paux) during relaxed inspiration due to the caudal displacement of the diaphragm. Panel B) shows positioning of the catheter in the lower third of the esophagus (approximately 40 cm from the nostril). Paux becomes negative during inspiration and cardiac oscillations become more noticeable. Measurement of esophageal pressure swing (ΔPes) and lung stress (ΔPL) are shown with vertical solid lines. Paw airway pressure; Paux auxiliary pressure; Pga gastric pressure; Pes esophageal pressure; PL transpulmonary pressure