How large is the lung recruitability in early acute respiratory distress syndrome: a prospective case series of patients monitored by computed tomography

Introduction: The benefits of higher positive end expiratory pressure (PEEP) in patients with acute respiratory distress syndrome (ARDS) have been modest, but few studies have fully tested the "open-lung hypothesis". This hypothesis states that most of the collapsed lung tissue observed in ARDS can be reversed at an acceptable clinical cost, potentially resulting in better lung protection, but requiring more intensive maneuvers. The short-/middle-term efficacy of a maximum recruitment strategy (MRS) was recently described in a small physiological study. The present study extends those results, describing a case-series of non-selected patients with early, severe ARDS submitted to MRS and followed until hospital discharge or death. Methods: MRS guided by thoracic computed tomography (CT) included two parts: a recruitment phase to calculate opening pressures (incremental steps under pressure-controlled ventilation up to maximum inspiratory pressures of 60 cmH(2)O, at constant driving-pressures of 15 cmH(2)O); and a PEEP titration phase (decremental PEEP steps from 25 to 10 cmH2O) used to estimate the minimum PEEP to keep lungs open. During all steps, we calculated the size of the non-aerated (-100 to +100 HU) compartment and the recruitability of the lungs (the percent mass of collapsed tissue re-aerated from baseline to maximum PEEP). Results: A total of 51 severe ARDS patients, with a mean age of 50.7 years (84% primary ARDS) was studied. The opening plateau-pressure was 59.6 (+/- 5.9 cmH(2)O), and the mean PEEP titrated after MRS was 24.6 (+/- 2.9 cmH(2)O). Mean PaO2/FiO(2) ratio increased from 125 (+/- 43) to 300 (+/- 103; P < 0.0001) after MRS and was sustained above 300 throughout seven days. Non-aerated parenchyma decreased significantly from 53.6% (interquartile range (IQR): 42.5 to 62.4) to 12.7% (IQR: 4.9 to 24.2) (P < 0.0001) after MRS. The potentially recruitable lung was estimated at 45% (IQR: 25 to 53). We did not observe major barotrauma or significant clinical complications associated with the maneuver. Conclusions: MRS could efficiently reverse hypoxemia and most of the collapsed lung tissue during the course of ARDS, compatible with a high lung recruitability in non-selected patients with early, severe ARDS. This strategy should be tested in a prospective randomized clinical trial.

Association Between Use of Lung-Protective Ventilation With Lower Tidal Volumes and Clinical Outcomes Among Patients Without Acute Respiratory Distress Syndrome A Meta-analysis

Context Lung-protective mechanical ventilation with the use of lower tidal volumes has been found to improve outcomes of patients with acute respiratory distress syndrome (ARDS). It has been suggested that use of lower tidal volumes also benefits patients who do not have ARDS. Objective To determine whether use of lower tidal volumes is associated with improved outcomes of patients receiving ventilation who do not have ARDS. Data Sources MEDLINE, CINAHL, Web of Science, and Cochrane Central Register of Controlled Trials up to August 2012. Study Selection Eligible studies evaluated use of lower vs higher tidal volumes in patients without ARDS at onset of mechanical ventilation and reported lung injury development, overall mortality, pulmonary infection, atelectasis, and biochemical alterations. Data Extraction Three reviewers extracted data on study characteristics, methods, and outcomes. Disagreement was resolved by consensus. Data Synthesis Twenty articles (2822 participants) were included. Meta-analysis using a fixed-effects model showed a decrease in lung injury development (risk ratio [RR], 0.33; 95% CI, 0.23 to 0.47; I-2, 0%; number needed to treat [NNT], 11), and mortality (RR, 0.64; 95% CI, 0.46 to 0.89; I-2, 0%; NNT, 23) in patients receiving ventilation with lower tidal volumes. The results of lung injury development were similar when stratified by the type of study (randomized vs nonrandomized) and were significant only in randomized trials for pulmonary infection and only in nonrandomized trials for mortality. Meta-analysis using a random-effects model showed, in protective ventilation groups, a lower incidence of pulmonary infection (RR, 0.45; 95% CI, 0.22 to 0.92; I-2, 32%; NNT, 26), lower mean (SD) hospital length of stay (6.91 [2.36] vs 8.87 [2.93] days, respectively; standardized mean difference [SMD], 0.51; 95% CI, 0.20 to 0.82; I-2, 75%), higher mean (SD) PaCO2 levels (41.05 [3.79] vs 37.90 [4.19] mm Hg, respectively; SMD, -0.51; 95% CI, -0.70 to -0.32; I-2, 54%), and lower mean (SD) pH values (7.37 [0.03] vs 7.40 [0.04], respectively; SMD, 1.16; 95% CI, 0.31 to 2.02; I-2, 96%) but similar mean (SD) ratios of PaO2 to fraction of inspired oxygen (304.40 [65.7] vs 312.97 [68.13], respectively; SMD, 0.11; 95% CI, -0.06 to 0.27; I-2, 60%). Tidal volume gradients between the 2 groups did not influence significantly the final results. Conclusions Among patients without ARDS, protective ventilation with lower tidal volumes was associated with better clinical outcomes. Some of the limitations of the meta-analysis were the mixed setting of mechanical ventilation (intensive care unit or operating room) and the duration of mechanical ventilation. JAMA. 2012;308(16):1651-1659 www.jama.com

Chest associated to motor physiotherapy improves cardiovascular variables in newborns with respiratory distress syndrome

Background We aimed to evaluate the effects of chest and motor physiotherapy treatment on hemodynamic variables in preterm newborns with respiratory distress syndrome. Methods We evaluated heart rate (HR), respiratory rate (RR), systolic (SAP), mean (MAP) and diastolic arterial pressure (DAP), temperature and oxygen saturation (SO2%) in 44 newborns with respiratory distress syndrome. We compared all variables between before physiotherapy treatment vs. after the last physiotherapy treatment. Newborns were treated during 11 days. Variables were measured 2 minutes before and 5 minutes after each physiotherapy treatment. We applied paired Student t test to compare variables between the two periods. Results HR (148.5 ± 8.5 bpm vs. 137.1 ± 6.8 bpm - p < 0.001), SAP (72.3 ± 11.3 mmHg vs. 63.6 ± 6.7 mmHg - p = 0.001) and MAP (57.5 ± 12 mmHg vs. 47.7 ± 5.8 mmHg - p = 0.001) were significantly reduced after 11 days of physiotherapy treatment compared to before the first session. There were no significant changes regarding RR, temperature, DAP and SO2%. Conclusions Chest and motor physiotherapy improved cardiovascular parameters in respiratory distress syndrome newborns.

Changes in respiratory mechanics and gas exchange during the acute respiratory distress syndrome

BACKGROUND: The time course of impairment of respiratory mechanics and gas exchange in the acute respiratory distress syndrome (ARDS) remains poorly defined. We assessed the changes in respiratory mechanics and gas exchange during ARDS. We hypothesized that due to the changes in respiratory mechanics over time, ventilatory strategies based on rigid volume or pressure limits might fail to prevent overdistension throughout the disease process. METHODS: Seventeen severe ARDS patients {PaO2/FiO2 10.1 (9.2-14.3) kPa; 76 (69-107) mmHg [median (25th-75th percentiles)] and bilateral infiltrates} were studied during the acute, intermediate, and late stages of ARDS (at 1-3, 4-6 and 7 days after diagnosis). Severity of lung injury, gas exchange, and hemodynamics were assessed. Pressure-volume (PV) curves of the respiratory system were obtained, and upper and lower inflection points (UIP, LIP) and recruitment were estimated. RESULTS: (1) UIP decreased from early to established (intermediate and late) ARDS [30 (28-30) cmH2O, 27 (25-30) cmH2O and 25 (23-28) cmH2O (P=0.014)]; (2) oxygenation improved in survivors and in patients with non-pulmonary etiology in late ARDS, whereas all patients developed hypercapnia from early to established ARDS; and (3) dead-space ventilation and pulmonary shunt were larger in patients with pulmonary etiology during late ARDS. CONCLUSION: We found a decrease in UIP from acute to established ARDS. If applied to our data, the inspiratory pressure limit advocated by the ARDSnet (30 cmH2O) would produce ventilation over the UIP, with a consequent increased risk of overdistension in 12%, 43% and 65% of our patients during the acute, intermediate and late phases of ARDS, respectively. Lung protective strategies based on fixed tidal volume or pressure limits may thus not fully avoid the risk of lung overdistension throughout ARDS.

Acute respiratory distress syndrome secondary to antisynthetase syndrome is reversible with tacrolimus

Polymyositis and interstitial lung diseases, predominantly nonspecific interstitial pneumonia (NSIP), are known to be frequent in antisynthetase syndrome, where anti-aminoacyl-tRNA synthetase antibodies are often identified. An unusual case of acute respiratory distress syndrome, secondary to such proven NSIP of cellular type with predominant CD8 lymphocytes, is described herein. The patient described in the present case study initially had a poor recovery with high dose of steroids, but this was followed by a good improvement after the prescription of tacrolimus and a low dose of prednisone. A precise diagnosis in similar circumstances may be life-saving, allowing the successful application of new immunosuppressants.

Successful lung transplantation for posttraumatic adult respiratory distress syndrome after extracorporeal membrane oxygenation support

A severe adult respiratory distress syndrome after bilateral lung contusion was successfully treated by extracorporeal membrane oxygenation and subsequent double-lung transplantation in a 19-year-old man. The patient is fully rehabilitated 1 year after transplantation.

Respiratory distress syndrome in near-term babies after caesarean section

OBJECTIVE: Severe respiratory distress syndrome (RDS) caused by surfactant deficiency is described not only in preterm infants but also in (near-) term babies after caesarean section (CS), especially when carried out before the onset of labour. The aim of the present study was to document the severity of this theoretically avoidable entity in order to improve obstetric and perinatal care. PATIENTS: All neonates admitted to the paediatric intensive care unit of the University Hospital of Bern between 1988 and 2000 with RDS on the basis of hyaline membrane disease (HMD) needing mechanical ventilation (MV) after CS and with a birthweight > or = 2500 g were analysed. HMD was diagnosed when respiratory distress and the typical radiological signs were present. Patients were grouped into elective CS before onset of labour and before rupture of membranes (group 1, n = 34) and patients delivered by emergency CS or CS after onset of labour or rupture of membranes (group 2, n = 22). Analysed indices for severity of illness were duration of stay in intensive care unit and MV, ventilation mode, worst oxygenation index (OI), presence of pulmonary air leak, and systemic hypotension. RESULTS: Mean gestational age (GA) was 37 2/7 weeks in group 1 and 36 2/7 weeks in group 2; no patient had a GA of > or = 39 0/7 weeks. Duration of MV was 4.4 days in group 1 and 3.9 days in group 2. Thirteen patients (38%) of group 1 and 7 (32%) of group 2 had to be managed by rescue high-frequency ventilation. A total of 7 patients had an OI>40. Eight patients (24%) in group 1 and 4 (18%) in group 2 developed a pulmonary air leak. Fourteen neonates (41%) in group 1 had to be supported by catecholamines versus 5 (22%) in group 2. There was one death in group 1. CONCLUSION: Severe RDS on the basis of HMD can also occur in near-term babies after CS; even a fatal outcome can not be excluded. The severity of illness in elective CS without labour may be quite high and is comparable to newborns delivered by CS (after onset of labour and/or rupture of the membranes) who were 1 week younger. No case of HMD was found in our population when CS was carried out after completion of 39 post-menstrual weeks of gestation.

The paradox of adult respiratory distress syndrome in neonates

Six full-term newborn infants are described who suffered from severe adult respiratory distress syndrome (ARDS). The triggering event was intrauterine/perinatal asphyxia in five, and group B streptococcal (GBS) septicemia in three. All had severe respiratory distress/failure and were ventilated mechanically with high concentrations of inspired oxygen and positive end-expiratory pressure. Radiography of the chest showed dense bilateral consolidation with air bronchograms and reduced lung volume. Persistent pulmonary hypertension (PPH) was documented in all cases. The coincidence of ARDS and PPH rendered respiratory management extremely difficult. For this reason high-frequency ventilation was instituted in all patients in order to improve CO2 elimination and induce respiratory alkalosis. Acute complications of respiratory therapy were encountered in five patients (pneumothorax, pulmonary interstitial emphysema, pneumopericardium). Three infants died (irreversible septic shock, progressive severe hypoxemia, and sudden cardiac arrest) after 17, 80, and 175 h of life. Histologic examination of the lungs was possible in all fatal cases and revealed typical changes of acute to subacute stages of ARDS. Three infants survived, the mean time of mechanical respiratory support being 703 h. Two patients were still dependent on oxygen after 1 month of life, and all survivors had increased interstitial markings and increased lung volumes on their chest roentgenograms at this time.

Influence of inspiration to expiration ratio on cyclic recruitment and derecruitment of atelectasis in a saline lavage model of acute respiratory distress syndrome*

OBJECTIVE Cyclic recruitment and derecruitment of atelectasis can occur during mechanical ventilation, especially in injured lungs. Experimentally, cyclic recruitment and derecruitment can be quantified by respiration-dependent changes in PaO2 (ΔPaO2), reflecting the varying intrapulmonary shunt fraction within the respiratory cycle. This study investigated the effect of inspiration to expiration ratio upon ΔPaO2 and Horowitz index. DESIGN Prospective randomized study. SETTING Laboratory investigation. SUBJECTS Piglets, average weight 30 ± 2 kg. INTERVENTIONS At respiratory rate 6 breaths/min, end-inspiratory pressure (Pendinsp) 40 cm H2O, positive end-expiratory pressure 5 cm H2O, and FIO2 1.0, measurements were performed at randomly set inspiration to expiration ratios during baseline healthy and mild surfactant depletion injury. Lung damage was titrated by repetitive surfactant washout to induce maximal cyclic recruitment and derecruitment as measured by multifrequency phase fluorimetry. Regional ventilation distribution was evaluated by electrical impedance tomography. Step changes in airway pressure from 5 to 40 cm H2O and vice versa were performed after lavage to calculate PO2-based recruitment and derecruitment time constants (TAU). MEASUREMENTS AND MAIN RESULTS In baseline healthy, cyclic recruitment and derecruitment could not be provoked, whereas in model acute respiratory distress syndrome, the highest ΔPaO2 were routinely detected at an inspiration to expiration ratio of 1:4 (range, 52-277 torr [6.9-36.9 kPa]). Shorter expiration time reduced cyclic recruitment and derecruitment significantly (158 ± 85 torr [21.1 ± 11.3 kPa] [inspiration to expiration ratio, 1:4]; 25 ± 12 torr [3.3 ± 1.6 kPa] [inspiration to expiration ratio, 4:1]; p < 0.0001), whereas the PaO2/FIO2 ratio increased (267 ± 50 [inspiration to expiration ratio, 1:4]; 424 ± 53 [inspiration to expiration ratio, 4:1]; p < 0.0001). Correspondingly, regional ventilation redistributed toward dependent lung regions (p < 0.0001). Recruitment was much faster (TAU: fast 1.6 s [78%]; slow 9.2 s) than derecruitment (TAU: fast 3.1 s [87%]; slow 17.7 s) (p = 0.0078). CONCLUSIONS Inverse ratio ventilation minimizes cyclic recruitment and derecruitment of atelectasis in an experimental model of surfactant-depleted pigs. Time constants for recruitment and derecruitment, and regional ventilation distribution, reflect these findings and highlight the time dependency of cyclic recruitment and derecruitment.

Epidemiology of Acute Lung Injury and Acute Respiratory Distress Syndrome in children in Vietnam

Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS) are life- threatening disorders that can result from many severe conditions and diseases. Since the American European Consensus Conference established the internationally accepted definition of ALI and ARDS, the epidemiology of pediatric ALI/ARDS has been described in some developed countries. In the developing world, however, there are very few data available regarding the burden, etiologies, management, outcome, and factors associated with outcomes of ALI/ARDS in children. ^ Therefore, we conducted this observational, clinical study to estimate the prevalence and case mortality rate of ALI/ARDS among a cohort of patients admitted to the pediatric intensive care unit (PICU) of the National Hospital of Pediatrics in Hanoi, the largest children's hospital in Vietnam. Etiologies and predisposing factors, and management strategies for pediatric ALI/ARDS were described. In addition, we determined the prevalence of HIV infection among children with ALI/ARDS in Vietnam. We also identified the causes of mortality and predictors of mortality and prolonged mechanical ventilation of children with ALI/ARDS. ^ A total of 1,051 patients consecutively admitted to the pediatric intensive care unit from January 2011 to January 2012 were screened daily for development of ALI/ARDS using the American-European Consensus Conference Guidelines. All identified patients with ALI/ARDS were followed until hospital discharge or death in the hospital. Patients' demographic and clinical data were collected. Multivariable logistic regression models were developed to identify independent predictors of mortality and other adverse outcome of ALI/ARDS. ^ Prevalence of ALI and ARDS was 9.6% (95% confidence interval, 7.8% to 11.4%) and 8.8% (95% confidence interval, 7.0% to 10.5%) of total PICU admissions, respectively. Infectious pneumonia and sepsis were the most common causes of ALI/ARDS accounting for 60.4% and 26.7% of cases, respectively. Prevalence of HIV infection among children with ALI/ARDS was 3.0%. The case fatality rate of ALI/ARDS was 63.4% (95% confidence interval, 53.8% to 72.9%). Multiple organ failure and refractory hypoxemia were the main causes of death. Independent predictors of mortality and prolonged mechanical ventilation were male gender, duration of intensive care stay prior to ALI/ARDS diagnosis, level of oxygenation defect measured by PaO2/FiO2 ratio at ALI/ARDS diagnosis, presence of non-pulmonary organ dysfunction at day one and day three after ALI/ARDS diagnosis, and presence of hospital acquired infection. ^ The results of this study demonstrated that ALI/ARDS was a common and severe condition in children in Vietnam. The level of both pulmonary and non-pulmonary organ damage influenced survival of patients with ALI/ARDS. Strategies for preventing ALI/ARDS and for clinical management of the disease are necessary to reduce the associated risks.^