Survey of interventions for the prevention and treatment of acute respiratory distress syndrome

OBJECTIVE: To determine physicians' opinions and practices related to the management of patients with acute respiratory distress syndrome. DESIGN: Cross-sectional mail survey. SETTING: Province of Ontario, Canada. PARTICIPANTS: Physicians treating patients with acute respiratory distress syndrome at university-affiliated and unaffiliated hospitals. INTERVENTIONS: We searched the literature and consulted experts to generate a list of potential interventions for acute respiratory distress syndrome. Eight intensive care unit physicians selected the most relevant, available, and controversial of these interventions for prevention (n = 5) and treatment (n = 30). Fourteen physicians reviewed the questionnaire before administration to ensure clarity, realism, and clinical sensibility. We asked participants to report their views on a) the efficacy of each intervention; b) published research evaluating efficacy; c) the frequency with which they use each intervention; and d) determinants of utilization. MEASUREMENTS AND MAIN RESULTS: One hundred ten of 194 eligible physicians responded. Respondents varied considerably in their reported use of the 35 interventions. Although physicians cited published research findings as the most powerful determinant of prescribing these interventions, they were unaware of many relevant trials. Physicians also commonly cited "usual local practice" as a determinant of use, although formal practice guidelines were rarely in operation. Other variables directly associated with use of these interventions included increasing frequency of exposure to acute respiratory distress syndrome (p <.0001), increasing size of the intensive care unit in which physicians work (p =.004), and the presence of residents in the intensive care unit (p =.02). CONCLUSIONS: Wide variation in the management of acute respiratory distress syndrome appears related to limited awareness of relevant research, conflicting interpretations of research findings, and adherence to varying local practice patterns. Given physicians' desire to tailor their practice to research findings and to practice in a manner that is consistent with their local intensive care unit colleagues, future research and educational efforts related to evidence-based protocols for the management of patients with acute respiratory distress syndrome might be worthwhile.     

Pediatric acute respiratory distress syndrome

The data available to guide clinical management of acute lung injury and acute respiratory distress syndrome are much more limited for infants and children than for adult patients. This paper reviews the available medical data and the pertinent physiology on the management of pediatric patients with acute lung injury. With the collaboration of multicenter investigation networks, definitive pediatric data may be on the horizon to better guide our clinical practice.     

The acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is an important cause of acute respiratory failure that is often associated with multiple organ failure. Several clinical disorders can precipitate ARDS, including pneumonia, sepsis, aspiration of gastric contents, and major trauma. Physiologically, ARDS is characterized by increased permeability pulmonary edema, severe arterial hypoxemia, and impaired carbon dioxide excretion. Based on both experimental and clinical studies, progress has been made in understanding the mechanisms responsible for the pathogenesis and the resolution of lung injury, including the contribution of environmental and genetic factors. Improved survival has been achieved with the use of lung-protective ventilation. Future progress will depend on developing novel therapeutics that can facilitate and enhance lung repair.     

Imaging in acute respiratory distress syndrome

Purpose

Imaging has become increasingly important across medical specialties for diagnostic, monitoring, and investigative purposes in acute respiratory distress syndrome (ARDS).

Methods

This review addresses the use of imaging techniques for the diagnosis and management of ARDS as well as gaining knowledge about its pathogenesis and pathophysiology. The techniques described in this article are computed tomography, positron emission tomography, and two easily accessible imaging techniques available at the bedside—ultrasound and electrical impedance tomography (EIT).

Results

The use of computed tomography has provided new insights into ARDS pathophysiology, demonstrating that ARDS does not homogeneously affect the lung parenchyma and that lung injury severity is widely distributed in the ARDS population. Positron emission tomography is a functional imaging technique whose value resides in adding incremental insights to morphological imaging. It can quantify regional perfusion, ventilation, aeration, lung vascular permeability, edema, and inflammation. Lung ultrasound and EIT are radiation-free, noninvasive tools available at the bedside. Lung ultrasound can provide useful information on ARDS diagnosis when x-rays or CT scan are not available. EIT is a useful tool to monitor lung ventilation and to assess the regional distribution of perfusion.

Conclusions

The future of imaging in critical care will probably develop in two main directions: easily accessible imaging techniques that can be used at the bedside and sophisticated imaging methods that will be used to aid in difficult diagnostic cases or to advance our understanding of the pathogenesis and pathophysiology of an array of critical illnesses.

     

Imaging of acute respiratory distress syndrome

Chest radiography and computed tomography (CT) have a crucial role to play in the diagnosis and management of acute respiratory distress syndrome (ARDS). The identification of pulmonary opacification is a requirement for the definition of ARDS on the chest radiograph, while CT has a role to play, not only in the diagnosis of ARDS, but also in the identification of complications. This paper reviews the radiological appearances of ARDS that have been documented for some time, and also more recent research that has identified a role for CT in directing ventilation and in prognostication.     

Glucocorticoids in the treatment of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is characterized by local inflammation and an intense systemic inflammatory reaction. Glucocorticoid administration has been suggested due to their anti-inflammatory properties. However, results from the initial studies of glucocorticoids in ARDS, which evaluated high-dose and short-term treatments, were negative. More recent studies have evaluated the effect of lower doses of glucocorticoids administered over longer periods, but the results thus far have been inconclusive.     

Kinetic therapy for acute respiratory distress syndrome

The authors evaluated the clinical and physiological effects of kinetic therapy (KT) in the treatment of acute respiratory distress syndrome (ARDS). Forty-six patients with ARDS underwent successive postural positioning in accordance with two regimens: 1) lateral, prone, contralateral, supine positions; 2) prone, lateral, contralateral, supine positions. The criterion for changing each position was the change in monitoring indices: SpO2, PaO2, and thoracopulmonary compliance (C). KT was performed until a respirator was withdrawn from the patient. In 25 patients, each maneuver of positioning was made during 30-minute propofol sedation. The control group included 24 patients with ARDS who received neither KT nor propofol sedation. KT caused a decrease in Vd/Vt, Qs/Qt and an increase in PaO2/FiO2 and C was more intensive, as compared with the control group. The duration of the patient's prone position was 3.2-0.7 hours and that of the supine position was 3.4-0.8 hours. The right and left lateral positions lasted 1.1-0.2 and 1.3-0.2 hours, respectively. KT regimen 1 was found to be more effective than KT regimen 2. Propofol sedation enhanced the efficiency of KT. The latter reduced death rates in patients with ARDS.     

Translaryngeal tracheostomy in acute respiratory distress syndrome patients

OBJECTIVE: To prevent gas exchange deterioration during translaryngeal tracheostomy (TLT) in patients with acute respiratory distress syndrome (ARDS) ventilation is maintained through a small diameter endotracheal tube (ETT; 4.0 mm i.d.) advanced beyond the tracheostoma. We report on the feasibility of uninterrupted ventilation delivered through a high-resistance ETT in ARDS patients, and relevant ventilatory adjustments and monitoring. DESIGN AND SETTING: Prospective, observational clinical study in an eight-bed intensive care unit of a university hospital. Patients: Eight consecutive ARDS patients scheduled for tracheostomy. INTERVENTIONS: During TLT volume control ventilation was maintained through the 4.0-mm i.d. ETT. Tidal volume, respiratory rate, and inspiratory to expiratory ratio were kept constant. Fractional inspiratory oxygen was 1. Positive end expiratory pressure (PEEP) set on the ventilator (PEEP(vent)) was reduced to maintain total PEEP (PEEP(tot)) at baseline level according to the measured intrinsic PEEP (auto-PEEP). MEASUREMENTS AND MAIN RESULTS: Data were collected before tracheostomy and while on mechanical ventilation with the 4.0-mm i.d. ETT. Neither PaCO(2) nor PaO(2) changed significantly (54.5+/-10.0 vs. 56.4+/-7.0 and 137+/-69 vs. 140+/-59 mmHg, respectively). Auto-PEEP increased from 0.6+/-1.1 to 9.8+/-6.5 cmH(2)O during ventilation with the 4.0-mm i.d. ETT. By decreasing PEEP(vent) we obtained a stable PEEP(tot) (11.4+/-4.3 vs. 11.8+/-4.3 cmH(2)O), and end-inspiratory occlusion pressure (26.7+/-7.4 vs. 28.0+/-6.6 cmH(2)O). Peak inspiratory pressure rose from 33.8+/-8.1 to 77.8+/-12.7 cmH(2)O. CONCLUSIONS: The high-resistance ETT allows ventilatory assistance during the whole TLT procedure. Assessment of stability in plateau pressure and PEEP(tot) by end-inspiratory and end-expiratory occlusions prevent hyperinflation and possibly barotrauma.     

机械通气与急性呼吸窘迫综合征

经过多年来对机械通气认识水平的提高与操作技能的发展,机械通气已经成为临床常用的治疗方法,尤其是在对急性肺损伤/急性呼吸窘迫综舍征(ALI/ARDS)的治疗过程中,已经得到了较为广泛的共识和普遍的应用.ALI与ARDS在重症患者中仍然具有非常高的发病率和相关病死率,也因在最近一些公共医疗卫生重大事件中作为影响预后的主要因素,而被广为关注.     

Extending inspiratory time in acute respiratory distress syndrome

OBJECTIVE: To assess the short-term effects of extending inspiratory time by lengthening end-inspiratory pause (EIP) without inducing a clinically significant increase in intrinsic positive end-expiratory pressure (PEEPi) in patients with acute respiratory distress syndrome (ARDS). DESIGN: Controlled, randomized, crossover study. SETTING: Two medical intensive care units of university hospitals. PATIENTS: Sixteen patients with early (< or =48 hrs) ARDS. INTERVENTION: We applied two durations of EIP (0.2 secs and extended) each for 1 hr while keeping all the following ventilatory parameters constant: FIO2, total PEEP (PEEPtot = applied PEEP + PEEPi), tidal volume, inspiratory flow, and respiratory rate. The duration of extended EIP was titrated to avoid an increase of PEEPi of > or =1 cm H2O. MEASUREMENTS AND MAIN RESULTS: Despite an increase in mean airway pressure (20.6 +/- 2.3 vs. 17.6 +/- 2.1 cm H2O, p < .01), extended EIP did not significantly improve PaO2 (93 +/- 21 vs. 86 +/-16 torr [12.40 +/- 2.80 vs. 11.46 +/- 2.13 kPa] with 0.2 secs EIP, NS). However, although the difference in PaO2 between the two EIP durations was <20 torr (<2.66 kPa) in 14 patients, two patients exhibited a >40 torr (>5.33 kPa) increase in PaO2 with extended EIP. Extended EIP decreased PaCO2 (62 +/- 13 vs. 67 +/- 13 torr [8.26 +/- 1.73 vs. 8.93 +/- 1.73 kPa] with 0.2 secs EIP, p < .01), which resulted in a higher pH (7.22 +/- 0.10 vs. 7.19 +/- 0.09 with 0.2 secs EIP, p < .01) and contributed to a slight increase in arterial hemoglobin saturation (94 +/- 3 vs. 93 +/- 3% with 0.2 EIP, p < .01). No significant difference in hemodynamics was observed. CONCLUSION: In patients with ARDS, extending EIP without inducing a clinically significant increase in PEEPi does not consistently improve arterial oxygenation but enhances CO2 elimination.     

Nonsteroidal anti-inflammatory drug-induced acute respiratory distress syndrome

Drug induced acute respiratory distress syndrome (ARDS) is a common clinical condition. Patients typically present with noncardiogenic pulmonary edema. Large number of ARDS cases reported induced by antineoplastic drugs and other drug intoxications. The pathophysiologic mechanisms of drug induced ARDS remains unknown. One of the postulated mechanisms of drug induced ARDS is anaphylaxis. We present a case of acute respiratory distress syndrome complicated by anaphylactic shock after use of two different nonsteroidal antiinflammatory drugs (NSAID). To the best of our knowledge, ARDS following normal doses of NSAID ingestion has not been reported previously. The case showed that ARDS may occur after ingestion of therapeutic doses of NSAID. NSAID ingestion should be considered in the differential diagnosis of patients with non-cardiogenic pulmonary edema.     

Update on pediatric acute respiratory distress syndrome

Pediatric acute respiratory distress syndrome (ARDS) remains an important challenge for the intensive care clinician. ARDS, which can result from either direct lung injury or from a "downstream" inflammatory process, is manifested by profound hypoxemia and respiratory failure. The care of pediatric ARDS is based on a meticulous, multidisciplinary, intensive care team approach. This review discusses the changing definition of ARDS and available intensive care treatment modalities, including newer lung-protective mechanical ventilation strategies and adjunct therapies. The prognosis of children suffering pediatric ARDS is examined with a look toward areas of potential future intervention in this often deadly disease.