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

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

Extracorporeal membrane oxygenation for interhospital transfer of severe acute respiratory distress syndrome patients: A 5-year experience

Purpose: Transfer of severely hypoxic patients is a high-risk procedure. Extracorporeal Membrane Oxygenation (ECMO) allows safe transport of these patients to tertiary care institutions. Our ECMO transportation program was instituted in 2004; here we report results after 5 years of activity. Methods: This is a clinical observational study. Criteria for ECMO center activation were: potentially reversibile respiratory failure, PaO2<50 mmHg with FiO2>0.6 for >12 hours, PEEP >5 cmH20, Lung Injury Score (LIS) \ue2\u89\ua53 or respiratory acidosis with pH<7.2, no intracranial bleeding, and no absolute contraindication to anticoagulation. If eligible, a skilled crew applied ECMO at the referral hospital. Transportation was performed with a specially equipped ambulance. Results: Sixteen patients were possible candidates for ECMO transfer. Two patients were excluded while 14 (mean\uc2\ub1SD, age 35.4\uc2\ub118.6, SOFA 8.4\uc2\ub13.7, Oxygenation Index 43.7\uc2\ub113.4) were transported to our institution (distance covered 102\uc2\ub1114 km, global duration of transport 589\uc2\ub1186 minutes). Two patients improved after iNO-trial and were transferred and subsequently managed without ECMO. The remaining 12 patients were transferred on veno-venous ECMO with extracorporeal blood flow 2.7\uc2\ub11 L\uc2\ub7min-1, gas flow 3.8\uc2\ub11.8 L\uc2\ub7min-1, and FiO21. Data were recorded 30 minutes before and 60 minutes after initiation of ECMO. ECMO improved PCO2(75\uc2\ub123 vs. 53\uc2\ub19 mmHg, p<0.01) thus improving pH (7.28\uc2\ub10.13 vs. 7.39\uc2\ub10.05, p<0.01) and allowing a reduction in respiratory rate (35\uc2\ub114 vs. 10\uc2\ub14 breaths/min, p<0.01), minute ventilation (10.1\uc2\ub13.8 vs. 3.7\uc2\ub11.7 L\uc2\ub7min-1, p<0.01), and mean airway pressure (26\uc2\ub16.5 vs. 22\uc2\ub15 cmH2O, p<0.01). No major clinical or technical complications were observed. Conclusions: ECMO effectively enabled high-risk ground transfer of severely hypoxic patients. \uc2\ua9 2011 Wichtig Editore

Fluid leakage across tracheal tube cuff, effect of different cuff material, shape, and positive expiratory pressure: A bench-top study

Purpose: Standard polyvinylchloride (PVC) endotracheal tube (ETT) cuffs do not protect from aspiration across the cuff, a leading cause of ventilator-associated pneumonia (VAP). In a long-lasting in vitro study we compared the effect of different cuff materials (PVC, polyurethane, and guayule latex), shapes (cylindrical, conical), and positive end expiratory pressures (PEEP) in reducing fluid leakage across the cuff. Methods: We compared fluid leakage across a cylindrical double-layer guayule latex prototype cuff, three cylindrical PVC cuffs (Mallinckrodt Hi-Lo, Mallinckrodt HighContour, Portex Ivory), one conical PVC cuff (Mallinckrodt TaperGuard), and two polyurethane cuffs (Mallinckrodt SealGuard, conical; Microcuff, cylindrical). Ten centimeters of dyed water was poured above the cuffs inflated (pressure 30 cmH2O) in a vertical cylinder (diameter 20 mm). A respiratory circuit connected the bottom of the cylinder to a breathing bag inflated at four pressures (PEEP = 0, 5, 10, 15 cmH2O). Pictures were taken every 60 s for 24 h to measure leakage as a reduction in the water column above the cuff. Five new ETTs of each type were tested. Results: The guayule latex cuffs showed no leakage at all the PEEP levels. Both the cylindrical and conical polyurethane cuffs showed limited leakage (2.1 \uc2\ub1 1.8 cm of water) only for PEEP zero. The PVC cuffs showed reduced leakage with increasing PEEP: 8.4 \uc2\ub1 1.5, 7.8 \uc2\ub1 2.2, 2.2 \uc2\ub1 1.0, and 0 cm of water at 0, 5, 10, and 15 cmH2O, respectively. Among all the PVC cuffs, the conical shape ensured higher sealing properties. Conclusions: The guayule latex cuffs always prevented fluid leakage; the polyurethane and PVC cuffs required incremental levels of PEEP to prevent fluid leakage ever-present at zero PEEP. \uc2\ua9 Copyright jointly held by Springer and ESICM 2010

Retroperitoneal laparoendoscopic Single-Site Surgery: Preliminary experience in kidney and ureteral indications

The advantages of retroperitoneoscopic technique are well known. We decided to combine this access with the emerging laparoendoscopic single-site surgery (LESS) technique. We present our preliminary data on 11 renoureteral procedures and describe our retroperitoneoscopic LESS technique. As of March 2009, 10 patients were submitted to retroperitoneal LESS and divided into three groups: Group A, 3 patients underwent ureterolithotomy; Group B, 4 patients underwent renal cyst ablation; Group C, 4 patients underwent renal biopsy. Retroperitoneal access was obtained with an optical trocar. After retroperitoneal space blunt dissection, a multichannel port was placed. Standard and bent 5-mm instruments were used; we also used a 5-mm flexible laparoscope as a single procedure in group A. Ten of 11 procedures were completed without conversion; a single case in group A was converted to open surgery. Retroperitoneoscopic LESS is a safe and feasible procedure for renal biopsy and renal cyst ablation, with shorter convalescence time, less postoperative pain, and better cosmetic outcomes. LESS ureterolithotomy was more challenging for the lack of triangulation, resulting in a prolonged convalescence period. In addition, bent laparoscopic instruments are not suitable for retroperitoneal space; the multichannel port leaks carbon dioxide due to the flank position. Therefore LESS pelvic trainer practice is imperative in this case

Respiratory pattern during neurally adjusted ventilatory assist in acute respiratory failure patients

Purpose: To investigate the effect of a wide range of assistance levels during neurally adjusted ventilatory assist (NAVA) and pressure support ventilation (PSV) on respiratory pattern, breathing variability, and incidence of tidal volumes (VT) above 8 and 10 ml/kg in acute respiratory failure patients. Methods: Eight increasing NAVA levels (0.5, 1, 1.5, 2, 2.5, 3, 4, and 5 cmH2O/\uce\ubcV) and four increasing pressure support (PSV) levels (4, 8, 12, and 16 cmH2O) were applied to obtain 10 min of stable recordings in 15 patients. Results: One out of 15 patients did not sustain the NAVA levels of 3, 4, and 5 cmH2O/\uce\ubcV and was excluded. The 5 cmH2O/\uce\ubcV NAVA level was not tolerated by three patients and it was excluded. Increasing NAVA levels were associated with decreased diaphragm electrical activity (EAdi), and, at variance with PSV, with small changes in VT, no changes in respiratory rate (RR), and increases in VTand EAdi variability. At high NAVA levels, an increase in VTvariability was associated with increased incidence of VTabove 8 and 10 ml/kg and an uncomfortable respiratory pattern in some patients. Conclusions: Increasing NAVA levels were associated with no effect on RR, small increase in VT, and increase in VTand EAdi variability. Effective decrease in EAdi occurred at NAVA levels below 2-2.5 cmH2O/\uce\ubcV, while preserving respiratory variability and low risks of VTabove 8 or 10 ml/kg. \uc2\ua9 2011 jointly held by Springer and ESICM

Blood acidification enhances carbon dioxide removal of membrane lung: An experimental study

Purpose: Extracorporeal CO2removal is an effective procedure to allow a protective ventilatory strategy in ARDS patients, but it is technically challenging due to the high blood flow required. Increasing the CO2transfer through the membrane lung (ML) may lower the demand of extracorporeal blood flow and consequently allow for a wider clinical application of this technique. Since only the dissolved CO2(5% of the total CO2content) is easily removed by the ML, we tested whether acidifying the blood entering the ML to convert bicarbonate ions towards dissolved CO2could enhance the CO2transfer though the ML. Methods: Six pigs were connected to an extracorporeal circuit comprising a ML. The extracorporeal blood flow was 500 ml/min, while the gas flow was 10 l/min. A 15-min continuous infusion of 0.5 N lactic acid was added to the extracorporeal blood flow before the ML at a rate of 1, 2 and 5 mEq/min. Between steps we waited for a reequilibration time of at least 30 min. Results: Acid infusion at 0, 1, 2 and 5 mEq/min increased pCO2(56.19 \uc2\ub1 7.92, 68.24 \uc2\ub1 11.73, 84.28 \uc2\ub1 11.17 and 136.66 \uc2\ub1 18.46 mmHg, respectively) and decreased pH (7.39 \uc2\ub1 0.05, 7.30 \uc2\ub1 0.05, 7.20 \uc2\ub1 0.05 and 6.91 \uc2\ub1 0.05, respectively). ML CO2removal increased 11, 23 and 70% during acid infusion at 1, 2 and 5 mEq/min, respectively. Conclusions: Blood acidification at the inlet of a ML with infusion of 1, 2 and 5 mEq/min of lactic acid can increase the CO2removal capacity of the ML up to 70%. \uc2\ua9 2009 Springer-Verlag

Performance of different continuous positive airway pressure helmets equipped with safety valves during failure of fresh gas supply

Purpose: We assessed the performance of different continuous positive airway pressure (CPAP) helmets equipped with a safety valve during discontinuation of fresh gas flow. Methods: This was a physiological study of five healthy volunteers. We delivered CPAP (fresh gas flow 60 l/min, FiO260%, PEEP 5 cmH2O) with three different helmets in a random sequence: 4Vent (R\uc3\ubcsch), HelmHAR-cp (Harol) and CaStar CP210 (StarMed). For each helmet we randomly applied, for up to 4 min, three disconnections of fresh gas flow: helmet inlet (Dinlet), flowmeter (Dflowmeter) and gas source (Dsource). We continuously recorded from a nostril: end-tidal CO2(PetCO2), inspiratory CO2(PiCO2), fraction of inspired oxygen (FiO2) and respiratory rate (RR). Results: During every disconnection we observed an increase in PiCO2and PetCO2with a drop in FiO2, while RR did not change. FiO2decreased more quickly in the CaStar, equipped with the largest safety valve, during Dsourceand Dflowmeter, while FiO2decreased more quickly during Dinletin CaStar and in 4Vent. PiCO2resulted in a lower increase in CaStar during Dsourceand Dflowmetercompared to 4Vent. PetCO2in CaStar increases more slowly compared to 4Vent during Dsourceand more slowly compared to the other two helmets during Dflowmeter. During Dinletsimilar degrees of CO2rebreathing and PetCO2were recorded among all the helmets. Conclusions: To minimize CO2rebreathing during disconnection of the fresh gas supply while performing helmet CPAP, it is desirable to utilize large helmets with a large anti-suffocation valve. Monitoring and alarm systems should be employed for safe application of helmet CPAP. \uc2\ua9 2011 jointly held by Springer and ESICM

Retroperitoneoscopic single site surgery (LESS): preliminary clinical experience.

Retroperitoneoscopic single site surgery (LESS): preliminary clinical experience