Spontaneous breathing: a double-edged sword to handle with care

Abstract

In acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS) patients, spontaneous breathing is associated with multiple physiologic benefits: it prevents muscles atrophy, avoids paralysis, decreases sedation needs and is associated with improved hemodynamics. On the other hand, in the presence of uncontrolled inspiratory effort, severe lung injury and asynchronies, spontaneous ventilation might also worsen lung edema, induce diaphragm dysfunction and lead to muscles exhaustion and prolonged weaning. In the present review article, we present physiologic mechanisms driving spontaneous breathing, with emphasis on how to implement basic and advanced respiratory monitoring to assess lung protection during spontaneous assisted ventilation. Then, key benefits and risks associated with spontaneous ventilation are described. Finally, we propose some clinical means to promote protective spontaneous breathing at the bedside. In summary, early switch to spontaneous assisted breathing of acutely hypoxemic patients is more respectful of physiology and might yield several advantages. Nonetheless, risk of additional lung injury is not completely avoided during spontaneous breathing and careful monitoring of target physiologic variables such as tidal volume (Vt) and driving transpulmonary pressure should be applied routinely. In clinical practice, multiple interventions such as extracorporeal CO removal exist to maintain inspiratory effort, Vt and driving transpulmonary pressure within safe limits but more studies are needed to assess their long-term efficacy.

Weaning from Mechanical Ventilation in ARDS: Aspects to Think about for Better Understanding, Evaluation, and Management

“…The monitoring of pulmonary pressures through the usual pressure curves shown by ventilators during weaning is mixed by the presence of spontaneous ventilation. The pressures abolished by the effect of the BNM appear after their withdrawal and can influence the lung lesion as well as during the transition from controlled to spontaneous [ 70 , 72 ]. Amato et al in a large retrospective analysis showed the increase in DP as a worse predictor of outcome in patients with ARDS [ 56 ].…”

Can CPAP machines be repurposed to solve the ventilator shortage?

“…Patients who receive no sedation may breathe spontaneously during ventilation 22,23 . To support such events, the ventilator must be able to recognise the patient's breathing effort, so that they can trigger and/or cycle the inspiration phase themselves.…”

American Thoracic Society 2018 pediatric core curriculum

“…Spontaneous negative-pressure breathing depends on the generation of a pressure gradient between the atmosphere and the alveoli, wherein the respiratory muscles create a "negative pressure" in the thorax to facilitate the flow of air from the higher pressure atmosphere to the lower pressure alveoli. 74 Thus, Pres is the difference between the peak and plateau pressures in the inspiratory hold maneuver, while Pel is the difference between the plateau and PEEP. Resistance and compliance can be derived from pressure pre-set modes, in a slightly more complex manner.…”