Extracorporeal CO2 Research Articles

Combined Use of Alkaline Agents With Low-Flow Extracorporeal Carbon Dioxide Removal in Carbon Dioxide Inhalation Models Preserving Inspiratory Efforts.

Low-flow extracorporeal CO 2 removal (ECCO 2 R), managed using a renal replacement platform, is useful in achieving lung-protective ventilation with low tidal volume. However, its capacity for CO 2 elimination is limited. Whether this system is valuable in reducing strong inspiratory efforts in respiratory failure is unclear. The combined use of alkaline agents with low-flow ECCO 2 R might be useful in hypercapnic subjects preserving inspiratory efforts. This study examined the effects of low-flow ECCO 2 R on respiratory status and investigated the effects of NaHCO 3 , trometamol, and saline on respiratory status during low-flow ECCO 2 R in CO 2 inhalation models. Although low-flow ECCO 2 R did not significantly change the respiratory rate (92.2% ± 24.3% [mean ± standard deviation] of that before ECCO 2 R), it reduced minute ventilation (MV) (78.9% ± 13.5% of that before ECCO 2 R). The addition of NaHCO 3 improved acidemia but did not change MV compared with that of the saline group (0.451 ± 0.026 L/min/kg body weight [BW] vs. 0.556 ± 0.138 L/min/kg BW, respectively). The addition of trometamol improved acidemia and reduced MV compared with that of the saline group (0.381 ± 0.050 L/min/kg BW vs. 0.556 ± 0.138 L/min/kg BW, respectively). The total amounts of CO 2 removed during ECCO 2 R in the NaHCO 3 group were lower than those in the saline and trometamol groups. The low-flow ECCO 2 R reduced MV in subjects preserving spontaneous breathing efforts with CO 2 overload. The addition of NaHCO 3 improved acidemia but did not change MV, whereas the addition of trometamol improved acidemia and reduced MV.

PCO 2 Gradient Between Inlet and Outlet Blood of Extracorporeal Respiratory Support Is a Reliable Marker of CO 2 Elimination.

Our objective was to assess the relationship between the pre-/post-oxygenator gradient of the partial pressure of carbon dioxide (∆ EC PCO 2 ; dissolved form) and CO 2 elimination under extracorporeal respiratory support. All patients who were treated with veno-venous extracorporeal membrane oxygenation and high-flow extracorporeal CO 2 removal in our intensive care unit over 18 months were included. Pre-/post-oxygenator blood gases were collected every 12 h and CO 2 elimination was calculated for each pair of samples (pre-/post-oxygenator total carbon dioxide content in blood [ ct CO 2 ] × pump flow [extracorporeal pump flow {Q EC }]). The relationship between ∆ EC PCO 2 and CO 2 elimination, as well as the origin of CO 2 removed. Eighteen patients were analyzed (24 oxygenators and 293 datasets). Each additional unit of ∆ EC PCO 2 × Q EC was associated with an increase in CO 2 elimination of 5.2 ml (95% confidence interval [CI], 4.7-5.6 ml; p < 0.001). Each reduction of 1 ml STPD/dl of CO 2 across the oxygenator was associated with a reduction of 0.63 ml STPD/dl (95% CI, 0.60-0.66) of CO 2 combined with water, 0.08 ml STPD/dl (95% CI, 0.07-0.09) of dissolved CO 2 , and 0.29 ml STPD/dl (95% CI, 0.27-0.31) of CO 2 in erythrocytes. The pre-/post-oxygenator PCO 2 gradient under extracorporeal respiratory support is thus linearly associated with CO 2 elimination; however, most of the CO 2 removed comes from combined CO 2 in plasma, generating bicarbonate.

Using a Low-Flow Extracorporeal Carbon Dioxide Removal (ECCO 2 R) System in the Management of Refractory Status Asthmaticus: A Case Series.

Rescue treatments for status asthmaticus remain limited. Current literature has mainly focused on using extracorporeal membrane oxygenation (ECMO) as a primary modality of care for these patients. Low-flow extracorporeal CO 2 removal (ECCO 2 R) systems are an attractive option to improve refractory hypercapnic respiratory acidosis because of status asthmaticus. This is a retrospective case series that describes the feasibility and efficacy of the use of a low-flow ECCO 2 R device, the Hemolung Respiratory Assist System, in patients with refractory hypercapnic respiratory failure because of status asthmaticus. Eight patients were treated with the Hemolung Respiratory Assist System in eight separate locations globally. Seven (88%) of the patients survived to discharge in this case series. Both CO 2 and pH resolution were seen in 6 hours. None of the ECCO 2 R runs were stopped because of mechanical- or device-related complications. One patient necessitated transition to ECMO. Low-flow ECCO 2 R systems is an effective option for resolution of refractory hypercapnia in status asthmaticus. Use of these systems are also associated with a survival rate of close to 90% in patients with status asthmaticus.

PULM5: Hyperbaric Blood Oxygenation – Basic Considerations and First Results

Hyperbaric oxygen therapy is beneficial in several applications, but hyperbaric chambers are scarce. We are developing a novel technology for extracorporeal hyperbaric blood oxygenation (HBOX). This extracorporeal procedure uses pressure to increase the oxygen (O2) concentration in blood. The technology can provide support when large amounts of oxygen are needed: In the treatment of CO poisoning the dissolved oxygen displaces the CO from the blood, removing it from the organism. This way, the oxygen deficiency can be ended rapidly, reducing or preventing secondary damage that frequently occurs. In acute respiratory failure (ARF) the HBOX technology can support lung function, by significantly increasing oxygen transport across a specific membrane area, while maintaining adequate CO2-removal. The prototype of the HBOX consists of 2 roller pumps with a hollow-fiber membrane oxygenator (HFMO) placed in between, a control unit for gas and blood flow and a double lumen catheter. By varying the flow rates of the roller pumps, excess pressure is generated in the HFMO without causing significant blood damage. Simultaneously, the oxygen pressure in the HFMO is increased, allowing for hyperbaric oxygenation. To avoid bubble formation, either O2 increase is limited, or excess O2 is removed in second HFMO before reinfusion. The prototype was tested in-vitro using porcine blood that was either CO poisoned or conditioned to mimic ARF. In acute in-vivo experiments for CO poisoning, we used CO-poisoned pigs (ca. 75 kg, COHb = 43 %, n = 3). For in-vivo experiments for ARF, 70 kg sheep were used with ventilator settings simulating respiratory failure, resulting in SaO2 = 69 %, paCO2 = 72 mmHg (n = 2). In-vitro test results show that the HBOX can fully oxygenate hypoxic blood (sO2 ca. 40 %) with a hilite 800 LT at a flow rate of 2 L/min, which is twice the amount of oxygen transferred, compared to conventional mode, Fig. 1. In in-vivo trials, the CO elimination rate from the animals’ blood doubled when using HBOX + oxygen mask compared to oxygen mask alone, see Fig. 2. In the ARF trials, the HBOX approach resulted in SaO2 of 89, 95, and 99 % and paCO2 was 49, 46, and 39 mmHg at blood flows of 0.5, 1.0, and 1.5 L/min, respectively, see Fig. 3. The HBOX is a promising approach to increase oxygen transport across a specific membrane area. The increased oxygen levels can be used for efficient extracorporeal CO removal. For respiratory support, the hyperbaric technology adds a new dimension to ECMO treatment, allowing the use of smaller oxygenators, potentially reducing the need for anticoagulation, as well as inflammatory responses and thus invasiveness. The hyperbaric technology can be used gradually, so that the membrane efficiency can be increased during intervention. This allows us to build an oxygenator with an ideal flow distribution over a wide range of blood flows, which avoids thrombus formation in the device at lower blood flows.Figure 1. Laboratory results oxygenation performanceFigure 2. Elimination rate COHb in in-vivo trialsFigure 3. Arterial blood gases during in-vivo trial for ARF

Enhanced extracorporeal carbon dioxide removal by acidification and metabolic control.

Extracorporeal carbon dioxide removal (ECCO<inf>2</inf>R) promotes protective ventilation in patients with acute respiratory failure, but devices with high CO<inf>2</inf> extraction capacity are required for clinically relevant impact. This study evaluates three novel low-flow techniques based on dialysate acidification, also combined with renal replacement therapy, and metabolic control. Eight swine were connected to a low-flow (350 mL/min) extracorporeal circuit including a dialyzer with a closed-loop dialysate circuit, and two membrane lungs on blood (ML<inf>b</inf>) and dialysate (ML<inf>d</inf>), respectively. The following 2-hour steps were performed: 1) ML<inf>b</inf>-start (ML<inf>b</inf> ventilated); 2) ML<inf>bd</inf>-start (ML<inf>b</inf> and ML<inf>d</inf> ventilated); 3) HLac (lactic acid infusion before ML<inf>d</inf>); 4) HCl-NaLac (hydrochloric acid infusion before ML<inf>d</inf> combined with renal replacement therapy and reinfusion of sodium lactate); 5) HCl-βHB-NaLac (hydrochloric acid infusion before ML<inf>d</inf> combined with renal replacement therapy and reinfusion of sodium lactate and sodium 3-hydroxybutyrate). Caloric and fluid inputs, temperature, blood glucose and arterial carbon dioxide pressure were kept constant. The total MLs CO<inf>2</inf> removal in HLac (130±25 mL/min), HCl-NaLac (130±21 mL/min) and HCl-βHB-NaLac (124±18 mL/min) were higher compared with ML<inf>bd</inf>-start (81±15 mL/min, P<0.05) and ML<inf>b</inf>-start (55±7 mL/min, P<0.05). Minute ventilation in HLac (4.3±0.9 L/min), HCl-NaLac (3.6±0.8 L/min) and HCl-βHB-NaLac (3.6±0.8 L/min) were lower compared to ML<inf>b</inf>-start (6.2±1.1 L/min, P<0.05) and ML<inf>bd</inf>-start (5.8±2.1 L/min, P<0.05). Arterial pH was 7.40±0.03 at ML<inf>b</inf>-start and decreased only during HCl-βHB-NaLac (7.35±0.03, P<0.05). No relevant changes in electrolyte concentrations, hemodynamics and significant adverse events were detected. The three techniques achieved a significant extracorporeal CO<inf>2</inf> removal allowing a relevant reduction in minute ventilation with a sufficient safety profile.

Increased Longevity of a Novel Gas Exchanger System for Low-Flow Veno-Venous Extracorporeal CO2 Removal in Acute Hypercapnic Respiratory Failure

Introduction: Low-flow veno-venous extracorporeal CO2 removal (ECCO2R) is an adjunctive therapy to support lung protective ventilation or maintain spontaneous breathing in hypercapnic respiratory failure. Low-flow ECCO2R is less invasive compared to higher flow systems, while potentially compromising efficiency and membrane lifetime. To counteract this shortcoming, a high-longevity system has recently been developed. Our hypotheses were that the novel membrane system provides runtimes up to 120 h, and CO2 removal remains constant throughout membrane system lifetime. Methods: Seventy patients with pH ≤ 7.25 and/or PaCO2 ≥9 kPa exceeding lung protective ventilation limits, or experiencing respiratory exhaustion during spontaneous breathing, were treated with the high-longevity ProLUNG system or in a control group using the original gas exchanger. Treatment parameters, gas exchanger runtime, and sweep-gas VCO2 were recorded across 9,806 treatment-hours and retrospectively analyzed. Results: 25/33 and 23/37 patients were mechanically ventilated as opposed to awake spontaneously breathing in both groups. The high-longevity system increased gas exchanger runtime from 29 ± 16 to 48 ± 36 h in ventilated and from 22 ± 14 to 31 ± 31 h in awake patients (p < 0.0001), with longer runtime in the former (p < 0.01). VCO2 remained constant at 86 ± 34 mL/min (p = 0.11). Overall, PaCO2 decreased from 9.1 ± 2.0 to 7.9 ± 1.9 kPa within 1 h (p < 0.001). Tidal volume could be maintained at 5.4 ± 1.8 versus 5.7 ± 2.2 mL/kg at 120 h (p = 0.60), and peak airway pressure could be reduced from 31.1 ± 5.1 to 27.5 ± 6.8 mbar (p < 0.01). Conclusion: Using a high-longevity gas exchanger system, membrane lifetime in low-flow ECCO2R could be extended in comparison to previous systems but remained below 120 h, especially in spontaneously breathing patients. Extracorporeal VCO2 remained constant throughout gas exchanger system runtime and was consistent with removal of approximately 50% of expected CO2 production, enabling lung protective ventilation despite hypercapnic respiratory failure.

Spontaneous Breathing Patterns During Maximum Extracorporeal CO2 Removal in Subjects With Early Severe ARDS.

Switching patients affected by early severe ARDS and undergoing extracorporeal membrane oxygenation (ECMO) from controlled ventilation to spontaneous breathing can be either beneficial or harmful, depending on how effectively the breathing pattern is controlled with ECMO. Identifying the factors associated with ineffective control of spontaneous breathing with ECMO may advance our pathophysiologic understanding of this syndrome. We conducted a prospective study in subjects with severe ARDS who were on ECMO support ≤ 7 d. Subjects were switched to minimal sedation and pressure-support ventilation while extracorporeal CO2 removal was increased to approximate the subject's total CO2 production ([Formula: see text]). We calculated the rapid shallow breathing index (RSBI) as breathing frequency divided by tidal volume. We explored the correlation between certain characteristics recorded during pretest controlled ventilation and the development of apnea (ie, expiratory pause lasting > 10 s; n = 3), normal breathing pattern (ie, apnea to RSBI ≤ 105 breaths/min/L; n = 6), and rapid shallow breathing (RSBI > 105 breaths/min/L; n = 6) that occurred during the test study. The ratio of extracorporeal CO2 removal to the subjects' [Formula: see text] was >90% in all 15 subjects, and arterial blood gases remained within normal ranges. Baseline pretest Sequential Organ Failure Assessment score, total [Formula: see text] and ventilatory ratio increased steadily, whereas [Formula: see text]/[Formula: see text] was higher in subjects with apnea compared to intermediate RSBI ≤105 breaths/min/L and elevated RSBI >105 breaths/min/L. In subjects with rapid shallow breathing, baseline lung weight measured with quantitative computed tomography scored higher, as well. In early severe ARDS, the factors associated with rapid shallow breathing despite maximum extracorporeal CO2 extraction include less efficient CO2 and O2 exchange by the natural lung, higher severity of organ failure, and greater magnitude of lung edema.

Extracorporeal CO2 removal and regional citrate anticoagulation in an experimental model of hypercapnic acidosis.

Low flow extracorporeal veno-venous CO2 removal (ECCO2 R) therapy is used to remove CO2 while reducing ventilation intensity. However, the use of this technique is limited because efficiency of CO2 removal and potential beneficial effects on pulmonary hemodynamics are not precisely established. Moreover, this technique requires anticoagulation that may induce severe complications in critically ill patients. Therefore, our study aimed at determining precise efficiency of CO2 extraction and its effects on right ventricular (RV) afterload, and comparing regional anticoagulation with citrate to systemic heparin anticoagulation during ECCO2 R. This study was performed in an experimental model of severe hypercapnic acidosis performed in two groups of three pigs. In the first group (heparin group), pigs were anticoagulated with a standard protocol of unfractionated heparin while citrate was used for ECCO2 R device anticoagulation in the second group (citrate group). After sedation, analgesia and endotracheal intubation, pigs were connected to a volume-cycled ventilator. Severe hypercapnic acidosis was obtained by reducing tidal volume by 60%. ECCO2 R was started in both groups when arterial pH was lower than 7.2. Pump Assisted Lung Protection (PALP, Maquet, Rastatt, Germany) system was used to remove CO2 . CO2 extraction, arterial pH, PaCO2 as well as systemic and pulmonary hemodynamic were continuously followed. Mean arterial pH was normalized to 7.37 ± 1.4 at an extracorporeal blood flow of 400 mL/min, coming from 7.11 ± 1.3. RV end-systolic pressure increased by over 30% during acute hypercapnic acidosis and was normalized in parallel with CO2 removal. CO2 extraction was not significantly increased in citrate group as compared to heparin group. Mean ionized calcium and MAP were significantly lower in the citrate group than in the heparin group during ECCO2 R (1.03 ± 0.20 vs. 1.33 ± 0.19 and 57 ± 14 vs. 68 ± 15 mm Hg, respectively). ECCO2 R was highly efficient to normalize pH and PaCO2 and to reduce RV afterload resulting from hypercapnic acidosis. Regional anticoagulation with citrate solution was as effective as standard heparin anticoagulation but did not improve CO2 removal and lead to more hypocalcemia and hypotension.

Assessment of the optimal operating parameters during extracorporeal CO2 removal with the Abylcap® system.

Lung protective ventilation is recommended in patients with acute respiratory distress syndrome (ARDS) needing mechanical ventilation. This can however be associated with hypercapnia and respiratory acidosis, such that extracorporeal CO2 removal (ECCO2R) can be applied. The aim of this study was to derive optimal operating parameters for the ECCO2R Abylcap® system (Bellco, Italy). We included 4 ARDS patients with a partial arterial oxygen tension over the fraction of inspired oxygen (PaO2/FiO2) lower than 150 mmHg, receiving lung-protective ventilation and treated with the Abylcap® via a double lumen 13.5-Fr dialysis catheter in the femoral vein. Every 24 hours during 5 consecutive days, blood was sampled at the Abylcap® inlet and outlet for different blood flows (QB:200-300-400 mL/min) with 100% O2 gas flow (QG) of 7 L/min, and for different QG (QG: 0.5-1-1.5-3-6-8 L/min) with QB400 mL/min. CO2 and O2 transfer remained constant over 5 days for a fixed QB. We found that, for a fixed QG of 7 L/min, CO2 transfer linearly and significantly increased with QB (i.e. from 58 ± 8 to 98 ± 16 mL/min for QB 200 to 400 mL/min). For a fixed QB of 400 mL/min, CO2 transfer non-linearly increased with QG (i.e. from 39 ± 9 to 98 ± 16 mL/min for QG 0.5 to 8 L/min) reaching a plateau at QG of 6 L/min. Hence, when using the Abylcap® ECCO2R in the treatment of ARDS patients the O2 flow should be at least 6 L/min while QB should be set at its maximum.

Extracorporeal CO2removal as bridge to lung transplantation in life-threatening hypercapnia

In patients awaiting lung transplantation (LTX), adequate gas exchange may not be sufficiently achieved by mechanical ventilation alone if acute respiratory decompensation arises. We report on 20 patients with life-threatening hypercapnia who received extracorporeal CO2 removal (ECCO2-R) by means of the interventional lung assist (ILA®, Novalung) as bridge to LTX. The most common underlying diagnoses were bronchiolitis obliterans syndrome, cystic fibrosis, and idiopathic pulmonary fibrosis, respectively. The type of ILA was pumpless arteriovenous or pump-driven venovenous (ILA activve®, Novalung) in 10 patients each. ILA bridging was initiated in 15 invasively ventilated and five noninvasively ventilated patients, of whom one had to be intubated prior to LTX. Hypercapnia and acidosis were effectively corrected in all patients within the first 12h of ILA therapy: PaCO2 declined from 109 (70-146) to 57 (45-64) mmHg, P<0.0001; pH increased from 7.20 (7.06-7.28) to 7.39 (7.35-7.49), P<0.0001. Four patients were switched to extracorporeal membrane oxygenation due to progressive hypoxia or circulatory failure. Nineteen patients (95%) were successfully transplanted. Hospital and 1-year survival was 75 and 72%, respectively. Bridging to LTX with ECCO2-R delivered by arteriovenous pumpless or venovenous pump-driven ILA is feasible and associated with high transplantation and survival rates.

Extracorporeal support for severe acute respiratory failure.

Extracorporeal membrane oxygenation (ECMO) and extracorporeal CO(2) removal (ECCO(2)R) techniques have increasingly been applied in patients with severe acute lung injury refractory to conventional mechanical ventilatory support. The objectives of this article are to review current concepts of extracorporeal life support techniques (ECMO and ECCO(2)R systems) and provide the rationale for their application in patients with acute respiratory distress syndrome, chronic obstruction pulmonary disease, and as adjunctive therapy for bridging patients to lung transplantation.

Commentary on: centrifugal pump performance during low-flow extracorporeal CO2 removal; safety considerations.

Commentary on: centrifugal pump performance during low-flow extracorporeal CO2 removal; safety considerations.

Arterial Chimney Graft Cannulation for Interventional Lung Assist

An interventional lung assist membrane ventilator (iLA) for arteriovenous extracorporeal CO2 removal was connected to a small-diameter femoral artery by use of a chimney graft in an underweight patient with acute respiratory failure and a previous history of heart-lung transplantation. This concept offers additional therapeutic options in underweight patients requiring extracorporeal CO2 removal with arterial vessels that are too small for percutaneous arterial cannulation with standard-sized percutaneous insertable iLA cannulae.

Role and potentials of low-flow CO2 removal system in mechanical ventilation

An analysis of the technological implementation of extracorporeal CO(2) removal (ECCO(2)R) techniques and of its clinical application. A new classification of ECCO(2)R, based on technological aspects, clinical properties and physiological performance, is proposed. The use of a ventilation with lower tidal volumes has been proved successful in acute respiratory distress syndrome (ARDS) patients but can be extremely problematic, especially when dealing with respiratory acidosis. The implementation of ECCO(2)R devices can represent the missing link between the prevention of ventilator-induced lung injury and pH control. ECCO(2)R has attracted increasing interest because of new less-invasive approaches allowing an easier management of ARDS patients. Recent studies have also shown that ECCO(2)R can also be used in patients with exacerbation of chronic obstructive pulmonary disease (COPD) and as a bridge to lung transplantation. The future ventilatory management of patients with acute respiratory failure may include a minimally invasive extracorporeal carbon dioxide removal circuit associated with the least amount of ventilatory support (noninvasive in COPD and/or invasive in ARDS) to minimize sedation, prevent ventilator-induced acute lung injury and nosocomial infections. Randomized clinical trials in the pipeline will confirm this fascinating hypothesis.

A surge of flu-associated adult respiratory distress syndrome in an Austrian tertiary care hospital during the 2009/2010 Influenza A H1N1v pandemic

SummaryWe report on 17 patients with influenza A H1N1v-associated Adult Respiratory Distress Syndrome who were admitted to the intensive care unit (ICU) between June 11th 2009 and August 10th 2010 (f/m: 8/9; age: median 39 (IQR 29–54) years; SAPS II: 35 (29–48)). Body mass index was 26 (24–35), 24% were overweight and 29% obese. The Charlson Comorbidity Index was 1 (0–2) and all but one patient had comorbid conditions. The median time between onset of the first symptom and admission to the ICU was 5 days (range 0–14). None of the patients had received vaccination against H1N1v. Nine patients received oseltamivir, only two of them within 48 hours of symptom onset. All patients developed severe ARDS (PaO2/FiO2-Ratio 60 (55–92); lung injury score 3.8 (3.3–4.0)), were mechanically ventilated and on vasopressor support. Fourteen patients received corticosteroids, 7 patients underwent hemofiltration, and 10 patients needed extracorporeal membrane-oxygenation (ECMO; 8 patients veno-venous, 2 patients veno-arterial), three patients Interventional Lung Assist (ILA) and two patients pump driven extracorporeal low-flow CO2-elimination (ECCO2–R). Seven of 17 patients (41%) died in the ICU (4 patients due to bleeding, 3 patients due to multi-organ failure), while all other patients survived the hospital (59%). ECMO mortality was 50%. The median ICU length-of-stay was 26 (19–44) vs. 21 (17–25) days (survivors vs. nonsurvivors), days on the ventilator were 18 (14–35) vs. 20 (17–24), and ECMO duration was 10 (8–25) vs. 13 (11–16) days, respectively (all p = n.s.). Compared to a control group of 241 adult intensive care unit patients without H1N1v, length of stay in the ICU, rate of mechanical ventilation, days on the ventilator, and TISS 28 scores were significantly higher in patients with H1N1v. The ICU survival tended to be higher in control patients (79 vs. 59%; p = 0.06). Patients with H1N1v admitted to either of our ICUs were young, overproportionally obese and almost all with existing comorbidities. All patients developed severe ARDS, which could only be treated with extracorporeal gas exchange in an unexpectedly high proportion. Patients with H1N1v had more complicated courses compared to control patients.

Alveolar Accumulation/Concentration of Nitrogen During Apneic Oxygenation With Arteriovenous Carbon Dioxide Removal

In a model of acute lung injury (ALI), previously, we have shown that apneic oxygenation, using an inspiratory O2 fraction (FiO2) of 1.0 combined with extracorporeal arteriovenous CO2 removal (AO-AVCR) maintains adequate arterial O2 and CO2 levels for a prolonged period. However, it is important that FiO2 lower than 1.0 can be used to avoid possible pulmonary oxygen toxicity. In preliminary studies, arterial oxygenation decreased to extreme low levels, when FiO2 <1 was used in apneic oxygenation. We assumed that this was caused either by alveolar accumulation/concentration of N2 or by absorption atelectasis. In four anesthetized and mechanically ventilated pigs, mild lung injury was induced. After a lung recruitment maneuver, we initiated two 20-minute periods of AO-AVCR with FiO2 of 1 and 0.5, respectively. By using FiO2 = 1, PaO2 remained above 300 mm Hg. At the end of the period, the alveolar O2 fraction (FAO2) was 0.89 (0.88-0.89; median and ranges). With FiO2 = 0.5, PaO2 decreased 90% compared with baseline values and FAO2 decreased to 0.07 (0.06-0.07). No atelectasis was visible on computed tomography after either period, and we, therefore, conclude that the alveolar hypoxia was caused by the alveolar N2 accumulation/concentration and subsequently by the O2 depletion.

Extracorporeal Removal CO 2 Using a Venovenous, Low-Flow System (Decapsmart) in a Lung Transplanted Patient: A Case Report

Background Primary graft dysfunction (PGD) is a syndrome that may occur after lung transplantation. In some cases of severe PGD, conventional therapies like ventilatory support, administration of inhaled nitric oxide (iNO), and surfactant and intravenous prostacyclins are inadequate to achieve adequate gas exchange. The only lifesaving option is to use an extracorporeal membrane oxygenator. The Decapsmart is a new venovenous, low-flow extracorporeal device to removal carbon dioxide (CO 2). It does not need a specialized staff. Herein we have presented a case report of a patient who underwent single lung transplantation and experienced respiratory failure. Methods On November 2007, a 52-year-old woman underwent a single right lung transplantation, and developed severe PGD in the postoperative period. After institution of conventional treatments, including ventilatory and hemodynamic support, iNO, and prostaglandine E1, we started treatment with Decapsmart to remove CO 2. Hemodynamic and respiratory parameters were assessed at baseline and after 3, 12, 24, and 48 hours. Results No adverse events occurred. From baseline to 48 hours, pH values increased and partial pressure of CO 2 reduced. At the same time ventilatory support was reduced, thereby mitigating barotrauma and risk of overdistension. Conclusion The use of Decapsmart may be an important aid for patients with severe respiratory acidosis in association with conventional therapy during the perioperative period after lung transplantation.

Hypercapnia in late-phase ALI/ARDS: providing spontaneous breathing using pumpless extracorporeal lung assist

The fibroproliferative phase of late ALI/ARDS as described by Hudson and Hough (Clin Chest Med 27:671-677, 2006) is associated with pronounced reductions in pulmonary compliance and an accompanying hypercapnia complicating low tidal volume mechanical ventilation. We report the effects of extracorporeal CO(2) removal by means of a novel pumpless extracorporeal lung assist (p-ECLA) on tidal volumes, airway pressures, breathing patterns and sedation management in pneumonia patients during late-phase ARDS. Retrospective analysis. Fourteen-bed university hospital ICU. Ten consecutive late-phase ALI/ARDS patients with low pulmonary compliance, and severe hypercapnia. Gas exchange, tidal volumes, airway pressures, breathing patterns and sedation requirements before (baseline) and after (2-4 days) initiation of treatment with p-ECLA were analysed. Patients were ventilated in a pressure-controlled mode with PEEP adjusted to pre-defined oxygenation goals. Median reduction in pCO(2) was 50% following institution of p-ECLA. Extracorporeal CO(2) removal enabled significant reduction in tidal volumes (to below 4 ml/kg predicted body weight) and inspiratory plateau pressures [30 (28.5/32.3) cmH(2)O, median 25, 75% percentiles]. Normalization of pCO(2) levels permitted significant reduction in the dosages of analgesics and sedatives. The proportion of assisted spontaneous breathing increased within 24 h of instituting p-ECLA. Elimination of CO(2) by p-ECLA therapy allowed reduction of ventilator-induced shear stress through ventilation with tidal volumes below 4 ml/kg predicted body weight in pneumonia patients with severely impaired pulmonary compliance during late-phase ARDS. p-ECLA treatment supported control of breathing pattern while sedation requirements were reduced and facilitated the implementation of assisted spontaneous breathing.

Syndrome de Lemierre avec pneumonie nécrosante assistée avec succès par épuration extracorporelle de CO2

We report a case of Lemierre's syndrome complicated with pulmonary septic abscesses, leading to necrotizing pneumonia. In spite of administration of appropriate antibiotics and a protective ventilation strategy, the patient had several bilateral pneumothoraces. In this setting, the mechanical ventilation was unsuccessful leading to two hypoxia-related cardiac arrests. An extracorporeal CO(2) removal was then carried out for 34-days duration. The patient was weaned from mechanical ventilation on day 68. He was then transferred to the chest surgery unit on day 83.

Artificial lung: progress and prototypes

Lung disease is the fourth leading cause of death (one in seven deaths) in the USA. Acute respiratory distress syndrome (ARDS) affects approximately 150,000 patients a year in the USA, and an estimated 16 million Americans are afflicted with chronic lung disease, accounting for 100,000 deaths per year. Medical management is the standard of care for initial therapy, but is limited by the progression of disease. Chronic mechanical ventilation is readily available, but is cumbersome, expensive and often requires tracheotomy with loss of upper airway defense mechanisms and normal speech. Lung transplantation is an option for less than 1100 patients per year since demand has steadily outgrown supply. For the last 15 years, the authors’ group has studied ARDS in order to develop viable alternative treatments. Both extracorporeal gas exchange techniques, including extracorporeal membrane oxygenation, extracorporeal and arteriovenous CO2 removal, and intravenous oxygenation, aim to allow for a less injurious ventilatory strategy during lung recovery while maintaining near-normal arterial blood gases, but precludes ambulation. The paracorporeal artificial lung (PAL), however, redefines the treatment of both acute and chronic respiratory failure with the goal of ambulatory total respiratory support. PAL prototypes tested on both normal sheep and the absolute lethal dose smoke/burn-induced ARDS sheep model have demonstrated initial success in achieving total gas exchange. Still, clinical trials cannot begin until bio- and hemodynamic compatability challenges are reconciled. The PAL initial design goals are for a short-term (weeks) bridge to recovery or transplant, but eventually, for long-term support (months).