Annals of translational medicine
-
Several factors have been recognized as possible triggers of ventilator-induced lung injury (VILI). The first is pressure (thus the 'barotrauma'), then the volume (hence the 'volutrauma'), finally the cyclic opening-closing of the lung units ('atelectrauma'). Less attention has been paid to the respiratory rate and the flow, although both theoretical considerations and experimental evidence attribute them a significant role in the generation of VILI. ⋯ For the same elastance driving pressure is a predictor similar to plateau pressure or tidal volume. Driving pressure is one of the components of the mechanical power, which also includes respiratory rate, flow and PEEP. Finding the threshold for mechanical power would greatly simplify assessment and prevention of VILI.
-
The positive end-expiratory pressure (PEEP), since its introduction in the treatment of acute respiratory failure, up to the 1980s was uniquely aimed to provide a viable oxygenation. Since the first application, a large debate about the criteria for selecting the PEEP levels arose within the scientific community. Lung mechanics, oxygen transport, venous admixture thresholds were all proposed, leading to PEEP recommendations from 5 up to 25 cmH2O. ⋯ In fact, all the other methods estimate as recruitment the gas entry in pulmonary units already open at lower PEEP, but increasing their compliance at higher PEEP. Since higher PEEP is usually more indicated (also for oxygenation) when the recruitability is higher, as occurs with increasing severity, a meaningful PEEP selection requires the assessment of recruitment. The Berlin definition may help in this assessment.
-
Mechanical ventilation (MV) is the cornerstone of acute respiratory distress syndrome (ARDS) management. The use of protective ventilation is a priority in this acute phase of lung inflammation. Neuromuscular blocking agents (NMBAs) induce reversible muscle paralysis. ⋯ The major risk is an increase in ventilator-induced lung injury. However, the adverse effects of NMBAs are widely discussed, particularly the occurrence of intensive care unit (ICU)-acquired weakness. This review analyses the recent findings in the literature concerning sedation and paralysis in managing ARDS.
-
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. ⋯ 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 CO2 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.
-
High-flow nasal cannula (HFNC) oxygen therapy is a recent technique delivering a high flow of heated and humidified gas. HFNC is simpler to use and apply than noninvasive ventilation (NIV) and appears to be a good alternative treatment for hypoxemic acute respiratory failure (ARF). HFNC is better tolerated than NIV, delivers high fraction of inspired oxygen (FiO2), generates a low level of positive pressure and provides washout of dead space in the upper airways, thereby improving mechanical pulmonary properties and unloading inspiratory muscles during ARF. ⋯ Despite improved oxygenation, NIV delivered with face mask may generate high tidal volumes and subsequent ventilator-induced lung injury. An approach applying NIV with a helmet, high levels of positive end-expiratory pressure (PEEP) and low pressure support (PS) levels seems to open new opportunities in patients with hypoxemic ARF. However, a large-scale randomized controlled study is needed to assess and compare this approach with HFNC.