Low tidal volume, high respiratory rate and auto-PEEP: The importance of the basics

Recent studies have shown that application of the ARDSNet low tidal volume strategy (i.e. allowing an increase in respiratory rate in order to minimize hypercapnia in those with low tidal volume) may generate consistent auto-PEEP (positive end-expiratory pressure), and this is not efficient in improving clearance of carbon dioxide. The present commentary deals with some of the recent controversies related to use of a low tidal volume strategy, as implemented in the ARDSNet trial, which has proved successful in reducing mortality rates in patients with acute respiratory distress syndrome. We emphasize the importance of basic physiological knowledge and sound respiratory monitoring

Clinical management of severely hypoxemic patients

Purpose of Review: To describe a physiopathological-based approach to clinical management of severely hypoxemic patients that integrates the most recent findings on the use of rescue therapies. Recent Findings: Several techniques are available to improve oxygenation in severely hypoxemic patients. Survival benefits have not been proved for most of these techniques. In a recent randomized trial, centralization of acute respiratory distress syndrome patients to a specialized center able to provide extracorporeal membrane oxygenation showed better survival as compared to conventional treatment. Randomized trials failed to prove survival benefits with the use of high levels of positive end-expiratory pressure (PEEP) or prone positioning. However, pooled data from two meta-analyses showed significant higher survival in the most severe patients both with the use of higher PEEP and prone positioning. Summary: Treatment of severely hypoxemic patients should aim to improve oxygenation while limiting ventilator-induced lung injury. A physiopathological approach that accounts for the underlying mechanisms of hypoxemia, and physiological and clinical effects of different treatments is likely the best guide we have to treat severely hypoxemic patients. \uc2\ua9 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins

Nonconventional support of respiration

PURPOSE OF REVIEW: Several alternative treatments have been proposed to decrease mortality of patients with acute respiratory distress syndrome (ARDS). We will discuss most recent trials and meta-analysis studies on nonconventional ventilatory and pharmacological treatments of ARDS patients. RECENT FINDINGS: Nonconventional ventilatory treatments such as prone positioning, high frequency oscillatory ventilation (HFOV), and extracorporeal membrane oxygenation (ECMO) aim to restore gas exchange while further decreasing ventilator induced lung injury. Though randomized trials failed to prove survival benefits with the use of prone positioning or HFOV, recent meta-analyses have shown, for both treatments, a decrease in mortality in the subpopulation of more severe ARDS patients. In a randomized controlled trial, referral of ARDS patients in a center with experience on ECMO was associated with an improved survival rate. Promising results come from new miniaturized extracorporeal techniques optimized for effective CO2 removal from low blood flow. These techniques should allow early application of superprotective ventilator strategies. Pharmacological treatments such as neuromuscular blocking and intravenous \uce\ub22 agonist may be effective in specific times and subsets of patients. SUMMARY: Existing data suggest that some of the available nonconventional treatments may be effective in more severe ARDS patients. New techniques and drugs that should facilitate prevention or healing of lung injury are under investigation. \uc2\ua9 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins

Helmet continuous positive airway pressure: Clinical applications

During noninvasive continuous positive airway pressure (CPAP) the patient's respiratory system is maintained throughout the whole respiratory cycle at a constant pressure higher than the atmospheric pressure, usually termed the positive end-expiratory pressure (PEEP). Noninvasive CPAP is void of any active support for the patient's work of breathing and therefore cannot be considered a form of ventilation. \uc2\ua9 2010 Springer-Verlag Berlin Heidelberg

Post-cardiac arrest extracorporeal life support

Sudden cardiac arrest is a complex, life-threatening event involving a multidisciplinary approach. Despite the use of conventional cardiopulmonary resuscitation, survival rate continues to be low for both in-hospital and out-of-hospital cardiac arrest. In refractory cardiac arrest, defined by the absence of return of spontaneous circulation despite resuscitation manoeuvres, mortality approaches 100%. In the last years, an increasing number of case series, and few propensity-matched cohort studies have reported encouraging results on the use of venoarterial extracorporeal membrane oxygenation for refractory cardiac arrest. Extracorporeal circulation ensures an adequate blood flow, to perform diagnostic and therapeutic interventions even before a return of spontaneous circulation is achieved and to rest the heart by unloading the ventricle while ensuring myocardial perfusion after return of spontaneous circulation. This study reviews the rational, indications, evidence and management of extracorporeal support for cardiac arrest

Computerised tomography scan imaging in acute respiratory distress syndrome

Computerised tomography (CT) is being used with increasing frequency in acute respiratory distress syndrome (ARDS) patients. This brief review will discuss some of the clinical insights that a CT scan can offer. A large number of CT scan studies have provided new insights into the pathophysiology of ARDS and of mechanical ventilation, and are particularly focused on the recruitment-derecruitment phenomenon. To this end, newer fast CT scan technology promises a dynamic, rather than a static view of lung ventilation

Danger of helmet continuous positive airway pressure during failure of fresh gas source supply

Objective: To assess the behavior of different helmets after discontinuation of fresh gas flow by disconnection at the helmet inlet, flow generator, or gas source. Design and setting: Randomized physiological study in a university research laboratory. Patients: Five healthy volunteers. Intervention: CPAP (FIO250%, PEEP 5 cmH2O) delivered in random sequence with three different helmets: 4Vent (R\uc3\ubcsch), PN500 (Harol), CaStar (StarMed) with antisuffocation valve open or locked. For each helmet all three disconnections were randomly employed up to 4 min. Measurements and results: During flow disconnection we measured: respiratory rate and tidal volume by respitrace; inspiratory and expiratory CO2concentration, and FIO2from a nostril; SpO2by pulse oxymetry. Independently of the site of disconnection we observed a fast increase in CO2rebreathing and minute ventilation, associated with a decrease in inspired O2concentration. In the absence of an operational safety valve, larger helmet size and lower resistance of the inlet hose resulted in slower increase in CO2rebreathing. The presence of the safety valve limited the rebreathing of CO2, and the increase in minute ventilation but did not protect from a decrease in FIO2and loss of PEEP. Conclusions: While the use of a safety valve proved effective in limiting CO2rebreathing, it did not protect from the risk of hypoxia related to decrease in FIO2and loss of PEEP. In addition to a safety antisuffocation valve, a dedicated monitoring and alarming systems are needed to employ helmet CPAP safely. \uc2\ua9 2006 Springer-Verlag

Bronchopleural fistulae and pulmonary ossification in posttraumatic acute respiratory distress syndrome: Successful treatment with extracorporeal support

We report a case of severe posttraumatic acute respiratory distress syndrome (ARDS) complicated by bronchopleural fistulae (BPF). The stiff ARDS lung and huge air leaks from BPF resulted in the failure of different protective mechanical ventilation strategies to provide viable gas exchange. Lung rest, achieved by extracorporeal carbon dioxide removal (ECCO2R), allowed weaning from mechanical ventilation, closure of BPF, and resumption of spontaneous breathing. Copyright \uc2\ua9 American Society of Artificial Internal Organs

Measurement of pulmonary edema in patients with acute respiratory distress syndrome

Objective: We measured pulmonary edema by thermal indocyanine green-dye double-dilution technique and quantitative computed tomography (CT) in patients with acute respiratory distress syndrome and compared the two techniques. Design and Setting: Prospective human study in a university hospital. Patients: Fourteen mechanically ventilated patients with acute respiratory distress syndrome (nine primary; nine with intubation <7 days). Interventions: All patients underwent a spiral CT of the thorax. We measured pulmonary thermal volume (PTV) and its components, extravascular lung water and pulmonary blood volume, with an integrated fiberoptic monitoring system (COLD Z-021). Measurements and Results: PTV was tightly correlated with lung weight (LW) measured by CT (PTV = 0.6875 * LWCT+ 292.77; correlation coefficient = 0.91; p < .0001; bias -11 \uc2\ub1 8 %). Neither etiology of acute respiratory distress syndrome (primary vs. secondary) nor days of intubation affected the accuracy of thermal dye dilution in comparison with CT. There was no correlation between the extravascular lung water (12.3 \uc2\ub1 3.4 mL/kg) and CT distribution of lung tissue compartments. Extravascular lung water and pulmonary blood volume showed good reproducibility in 32 pairs of thermal dye dilution measurements. Conclusions: Measurements of lung edema by thermal indocyanine green-dye double-dilution method show good correlation with those by quantitative computed tomography and good reproducibility in patients with acute respiratory distress syndrome. Copyright \uc2\ua9 2005 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins