Long-term extracorporeal membrane oxygenation with minimal ventilatory support: a new paradigm for severe ARDS?

Pulmonary tuberculosis can lead to acute respiratory distress syndrome (ARDS) which is associated with high mortality. We report the case of a patient with pulmonary tuberculosis and severe ARDS (PaO2/FiO2<100 mmHg) who was initially managed with advanced up-to-date treatments (protective ventilation and extracorporeal membrane oxygenation, ECMO) but failed to improve. After a month of failure and the development of bilateral pneumothoraces, we drastically changed our therapeutic strategy: we maximized ECMO support to maintain oxygenation, we greatly reduced ventilation pressures and we left the pneumothoraces undrained. From then on, the patient improved and he eventually survived. This case suggests that ECMO permits large reductions in lung inflation and ventilation to rest the lungs, while maintaining acceptable oxygenation. The combination of ECMO and markedly attenuated ventilation strategy may be effective in cases of severe ARDS.

Management of acute respiratory complications from influenza A (H1N1) infection: experience of a tertiary-level Intensive Care Unit.

BACKGROUND: The novel influenza A (H1N1) pandemic was associated with an epidemic of critical illness. METHODS: We describe the clinical profiles of critically ill patients with severe complications due to microbiologically confirmed pandemic influenza A (H1N1) infection admitted to a medical ICU in Monza, Italy, over a 6-month period. RESULTS: From August 2009 to January 2010, 19 patients (13 adults and 6 children) required ICU admission. Nine subjects were referred to our hospital from other ICUs. In all patients, with the exception of a case of severe septic shock, the cause of ICU admission was acute respiratory failure. Other nonpulmonary organ failures were common. A trial of non-invasive ventilation was attempted in 13 cases and was successful in four of them. The majority of the patients required invasive mechanical ventilation. In the 7 most severely hypoxemic patients, we applied veno-venous ECLS, with a very high rate of success. The median ICU stay was 9 days (range 1-78 days). Sixteen out of 19 (84%) patients survived. CONCLUSION: In the majority of our patients, critical illness caused by pandemic influenza A (H1N1) was associated with severe hypoxemia, multiple organ failure, requirement for mechanical ventilation and frequent use of rescue therapies and ECLS support.

Percutaneous bridge to heart transplantation by venoarterial ECMO and transaortic left ventricular venting.

We report a case in which life support for cardiogenic shock was achieved by a nonpulsatile venoarterial bypass, and left ventricular decompression was obtained by a catheter placed percutaneously through the aortic valve into the left ventricle. The blood drained from the left ventricle was pumped into the femoral artery. The normalization of left heart filling pressures allowed the resolution of pulmonary edema, and the patient underwent a successful heart transplantation following 7 days of mechanical cardiocirculatory support.

[Vital signs of hemodynamic monitoring]. / I parametri vitali del monitoraggio emodinamico.

The aim of hemodynamic monitoring in intensive care is to recognize derangements in physiologic variables, which herald the progression toward organ failure. Traditionally the term "vital signs" refers to heart rate, arterial pressure, respiratory rate and body temperature monitoring. Continuous monitoring of vital signs, is advocated, since trends are more significant than single measurements, and is still a cornerstone, in the hemodynamic evaluation of a critically ill patient. Nevertheless, the spectrum of hemodynamic derangements that can arise during intensive care unit stay is very large and often additional information, beside the vital signs, are needed to evaluate correctly the individual patient.

Small pore size microporous membrane oxygenator reduces plasma leakage during prolonged extracorporeal circulation: a case report.

Plasma leakage has been regarded as the main technical problem during prolonged extracorporeal circulation (ECC) with microporous membrane oxygenators (MMOs). We report the case of a 15 year old male who underwent long term ECC for ARDS and in whom, by using new MMOs with reduced pore size, we were able to achieve prolonged artificial gas exchange efficiency with minimal plasma leakage. We conclude that reduced pore size MMOs might represent a valuable technical advance in extracorporeal oxygenation therapy.

Lung structure and function in different stages of severe adult respiratory distress syndrome.

OBJECTIVE: To assess the clinical consequences of duration of adult respiratory distress syndrome (ARDS) on lung structure and function. DESIGN: Retrospective analysis. SETTING: A university hospital referral center for extracorporeal support. PATIENTS: A total of 84 patients with severe ARDS (Murray score > 2.5) recruited from 48 intensive care units (1979 to 1992), who suffered ARDS and underwent mechanical ventilation for up to 1 week (37 patients with early ARDS), between 1 and 2 weeks (24 patients with intermediate ARDS), or more than 2 weeks (23 patients with late ARDS) and subsequently underwent extracorporeal support. MAIN OUTCOME MEASURES: Before beginning extracorporeal support, we measured gas exchange, pulmonary mechanics, hemodynamics, oxygen transport and delivery, incidence of barotrauma (presence of one or more thoracic tubes for pneumothorax drainage), and organ dysfunctions. In a subgroup of 16 patients, we studied lung structure by computed tomographic scan, scoring the densities and quantifying the emphysemalike lesions (bullae). RESULTS: Late ARDS showed lower respiratory compliance, higher dead space, higher PaCO2, lower venous admixture, and lower positive end-expiratory pressure requirement compared with early ARDS (P < .01). The incidence of pneumothorax (48.8% of the entire population) was significantly (P < .01) higher in late ARDS (87%) vs intermediate ARDS (46%) and early ARDS (30%). The mortality of patients with pneumothorax (66%) was significantly (P < .01) higher compared with patients without pneumothorax (46%). The number of bullae per lung was significantly higher in late ARDS vs intermediate and early ARDS (mean [SD], 8 [4], 4.3 [5], and 1.9 [3.9], respectively; P < .01), and they were preferentially distributed in the dependent lung regions. The number of bullae per lung was significantly higher in patients with pneumothorax vs those without pneumothorax (mean [SD], 13.6 [9.8] vs 1.4 [2.1]; P = .007). The mean (SD) duration of ARDS in patients with pneumothorax was 15.3 (10.0) days vs 7.0 (6.6) days in those without pneumothorax (P = .0001). No differences within the three groups were found in computed tomographic scan densities, hemodynamics, and number of organ system dysfunctions. CONCLUSIONS: The lung structure and function changes markedly with ARDS duration, and the late stages may be described as restrictive lung disease with superimposed emphysemalike lesions. Presence of pneumothorax affects survival and appears to be related to the lung structural changes occurring with time.

Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal CO2 removal for adult respiratory distress syndrome.

The impact of a new therapy that includes pressure-controlled inverse ratio ventilation followed by extracorporeal CO2 removal on the survival of patients with severe ARDS was evaluated in a randomized controlled clinical trial. Computerized protocols generated around-the-clock instructions for management of arterial oxygenation to assure equivalent intensity of care for patients randomized to the new therapy limb and those randomized to the control, mechanical ventilation limb. We randomized 40 patients with severe ARDS who met the ECMO entry criteria. The main outcome measure was survival at 30 days after randomization. Survival was not significantly different in the 19 mechanical ventilation (42%) and 21 new therapy (extracorporeal) (33%) patients (p = 0.8). All deaths occurred within 30 days of randomization. Overall patient survival was 38% (15 of 40) and was about four times that expected from historical data (p = 0.0002). Extracorporeal treatment group survival was not significantly different from other published survival rates after extracorporeal CO2 removal. Mechanical ventilation patient group survival was significantly higher than the 12% derived from published data (p = 0.0001). Protocols controlled care 86% of the time. Average PaO2 was 59 mm Hg in both treatment groups. Intensity of care required to maintain arterial oxygenation was similar in both groups (2.6 and 2.6 PEEP changes/day; 4.3 and 5.0 FIO2 changes/day). We conclude that there was no significant difference in survival between the mechanical ventilation and the extracorporeal CO2 removal groups. We do not recommend extracorporeal support as a therapy for ARDS. Extracorporeal support for ARDS should be restricted to controlled clinical trials.

Role of extracorporeal circulation in adult respiratory distress syndrome management.

Long-term extracorporeal support for acute lung failure was introduced in 1972. In the 1970s, much effort was concentrated on technical improvements. However, a multicenter study comparing continuous positive-pressure ventilation and continuous positive-pressure ventilation plus extracorporeal circulation failed to show improvement in survival rates. In the 1980s, new physiopathologic concepts were developed, such as extracorporeal CO2 removal coupled with lung rest. The main complication of the technique was bleeding due to systemic heparinization. However, the technology used in that period was the same as in the 1970s. Recently, technological improvement--such as percutaneous cannulation and surface-heparinized artificial lungs--has allowed clinical performances to improve substantially. "Lung rest" philosophy, coupled with safe technology, may provide a rational basis to test this technique in a randomized fashion for widespread use.

The value of portable chest roentgenography in adult respiratory distress syndrome. Comparison with computed tomography.

In 17 patients with adult respiratory distress syndrome, we used data derived from computed tomographic (CT) scan densitometric analysis to validate the value of portable chest roentgenograms in objectively estimating the amount of pulmonary edema. Chest roentgenograms and CT scans were taken in the same ventilatory conditions (apnea at 10 cm H2O of positive end-expiratory pressure [PEEP]); blood gas samples and hemodynamic parameters were collected at the same time. Roentgenographic analysis was undertaken by independent observers using two standardized scoring systems proposed in the literature. CT scan analysis was performed using the CT number frequency distribution and the gas lung volume (measured by helium dilution technique) to estimate quantitatively the lung density, the lung weight, and the percentage of normally aerated and nonaerated tissue. Knowing the mean CT number of the pulmonary parenchyma in a group of normal subjects, we also inferred the ideal lung weight expected in the study population and computed the excess tissue mass as the difference between actual and ideal lung weight. Both the roentgenographic scoring systems showed direct correlation with the pulmonary impairment as detected by CT scan densitometric analysis (CT number, percentage of nonaerated tissue, lung weight, and excess tissue mass; p less than 0.01) and inverse relation with the percentage of normally aerated tissue (p less than 0.01). We also found a relationship between roentgenographic scores and the impairment in gas exchange as detected by shunt fraction (p less than 0.05). We conclude that standardized reading of portable chest roentgenograms by means of scoring tables is a valuable tool in estimating the amount of pulmonary edema in a patient with adult respiratory distress syndrome.

Relationships between lung computed tomographic density, gas exchange, and PEEP in acute respiratory failure.

Twenty-two patients with acute respiratory failure underwent lung computed tomography (CT) and physiological measurements at 5, 10, and 15 cm H2O positive end-expiratory pressure (PEEP) to investigate the relationship between morphology and function. Lung densities were primarily concentrated in the dependent regions. From the frequency distribution of CT numbers (difference in x-ray attenuation between water and lung) and lung gas volume measurements the authors obtained a quantitative estimate of normally inflated, poorly inflated, and non-inflated lung tissue weight. This estimated average lung weight was increased twofold above normal and excess lung weight correlated with the mean pulmonary artery pressure (P less than 0.01). Venous admixture correlated with the non-inflated tissue mass (P less than 0.01). Increasing PEEP caused progressive clearing of radiographic densities and increased the mass of normally inflated tissue (anatomic recruitment), while reducing venous admixture. The cardiac index decreased after increasing PEEP while oxygen delivery was unchanged. The authors conclude that CT scan lung density and oxygen exchange efficiency are correlated; the main effect of augmenting PEEP is to recruit perfused alveolar units that were previously collapsed.

Pressure-volume curve of total respiratory system in acute respiratory failure. Computed tomographic scan study.

To investigate the relationship between lung anatomy and pulmonary mechanics in acute respiratory failure (ARF), 20 patients with ARF underwent computerized tomography (CT) at 3 levels of positive end-expiratory pressure (PEEP) (5, 10, and 15 cm H2O). The static pressure-volume curve of the total respiratory system and the lung volumes (helium dilution method) were also measured. By knowing the lung volumes and analyzing the CT number frequency distribution, a quantitative estimate of normally aerated, poorly aerated, and nonaerated lung tissue was obtained at each level of PEEP. The recruitment was defined as the percent increase of normally aerated tissue from 5 to 15 cm H2O. We found that the different compliances (starting compliance, inflation compliance, and deflation compliance) were correlated only with the amount of normally aerated tissue present in the range of pressures explored by a given compliance (5 cm H2O for starting compliance and 15 cm H2O for inflation and deflation compliances). No relationship was found between the compliances and the poorly aerated and nonaerated tissue. The specific compliance was in the normal range, whereas the amount of recruitment was related to the ratio of inflation compliance to starting compliance. Our data suggest that (1) the pressure-volume curve parameters in ARF investigate only the residual healthy zones of the lung and do not directly estimate the "amount" of disease (poorly or nonaerated tissue), (2) the pressure-volume curve may allow an estimate of the anatomic recruitment, and (3) the residual normally aerated zones of the ARF lung seem to maintain a normal intrinsic elasticity.