A novel risk score for severe ARDS patients undergoing ECMO after retrieval from peripheral hospitals.

BACKGROUND: Extracorporeal Membrane Oxygenation in severe ARDS unresponsive to conventional protective ventilation is associated with elevated costs, resource and complications, and appropriate risk stratification of candidate patients could be useful to recognize those more likely to benefit from ECMO. We aimed to derive a new outcome prediction score for patients retrieved by our ECMO team from peripheral centers, including systematic echocardiographic evaluation before ECMO start. METHODS: Sixty-nine consecutive patients with refractory ARDS requiring ECMO transferred from peripheral centers to our ICU (a tertiary ECMO referral center), from 1 October 2009 to 31 December 2015, were assessed. RESULTS: All patients were transported on ECMO (distance, median 77, range 4-456 km) The mortality rate was 41% (28/69). Our new risk score included age ≥ 42 years, BMI < 31 kg/m2 , RV dilatation, and pH < 7.35. The proposed cut off (Youden's index method) of nine had a sensitivity of 96% and a specificity of 30% (AUC-ROC: 0.85, 95% CI: 0.76-0.94, P < 0.001). When assessing the discriminatory ability of our risk score in the population of local patients, survivors had a mean value of 15.4 ± 8.6, whereas non-survivors showed a mean value of 20.1 ± 7.4 (P < 0.001). CONCLUSIONS: Our new risk score shows good discriminatory ability both in patients retrieved from peripheral centers and in those implanted at our center. This score includes variables easily available at bedside, and, for the first time, a pathophysiologic element, RV dilatation.

Successful Transplantation of Lungs From an Uncontrolled Donor After Circulatory Death Preserved In Situ by Alveolar Recruitment Maneuvers and Assessed by Ex Vivo Lung Perfusion.

We developed a protocol to procure lungs from uncontrolled donors after circulatory determination of death (NCT02061462). Subjects with cardiovascular collapse, treated on scene by a resuscitation team and transferred to the emergency room, are considered potential donors once declared dead. Exclusion criteria include unwitnessed collapse, no-flow period of >15 min and low flow >60 min. After death, lung preservation with recruitment maneuvers, continuous positive airway pressure, and protective mechanical ventilation is applied to the donor. After procurement, ex vivo lung perfusion (EVLP) is performed. From November 2014, 10 subjects were considered potential donors; one of these underwent the full process of procurement, EVLP, and transplantation. The donor was a 46-year-old male who died because of thoracic aortic dissection. Lungs were procured 4 h and 48 min after death, and deemed suitable for transplantation after EVLP. Lungs were then offered to a rapidly deteriorating recipient with cystic fibrosis (lung allocation score [LAS] 46) who consented to the transplant in this experimental setting. Six months after transplantation, the recipient is in good condition (forced expiratory volume in 1 s 85%) with no signs of rejection. This protocol allowed procurement of lungs from an uncontrolled donor after circulatory determination of death following an extended period of warm ischemia.

Evidence of Air Trapping During Ex Vivo Lung Perfusion: A Swine Experimental Lung Imaging and Mechanics Study.

Ex vivo lung perfusion (EVLP) allows the ventilation and perfusion of lungs to evaluate their viability for transplantation. The aim of this study is to compare the mechanical, morphologic and functional properties of lungs during EVLP with values obtained in vivo to guide a safe mechanical ventilation strategy. Lungs from 5 healthy pigs were studied in vivo and during 4 hours of EVLP. Lung compliance, airway resistance, gas exchange, and hemodynamic parameters were collected at positive end-expiratory pressure (PEEP) of 5 cm H2O. Computed tomography was performed at PEEP 0, PEEP 5, and total lung capacity (TLC). Lung pressure-volume (PV) curves were performed from PEEP 0 to TLC. Lung compliance decreased during EVLP (53 ± 5 mL/cm H2O vs 29 ± 7 mL/cm H2O, P < .05), and the PV curve showed a lower inflection point. Gas content (528 ± 118 mL vs 892 ± 402 mL at PEEP 0) and airway resistance (25 ± 5 vs 44 ± 9 cmH2O/L∗s-1, P < .05) were higher during EVLP. Alveolar dead space (5% ± 2% vs 17% ± 6%, P < .05) and intrapulmonary shunt (9% ± 2% vs 28% ± 13%, P < .05) increased ex vivo compared to in vivo, while the partial pressure of oxygen to inspired oxygen fraction ratio (PO2/FiO2) did not differ (468 ± 52 mm Hg vs 536 ± 14 mm Hg). In conclusion, during EVLP lungs show signs of air trapping and bronchoconstriction, resulting in low compliance and increased alveolar dead space. Intrapulmonary shunt is high despite oxygenation levels acceptable for transplantation.

High flow nasal cannula compared with conventional oxygen therapy for acute hypoxemic respiratory failure: a systematic review and meta-analysis.

BACKGROUND: This systematic review and meta-analysis summarizes the safety and efficacy of high flow nasal cannula (HFNC) in patients with acute hypoxemic respiratory failure. METHODS: We performed a comprehensive search of MEDLINE, EMBASE, and Web of Science. We identified randomized controlled trials that compared HFNC to conventional oxygen therapy. We pooled data and report summary estimates of effect using relative risk for dichotomous outcomes and mean difference or standardized mean difference for continuous outcomes, with 95% confidence intervals. We assessed risk of bias of included studies using the Cochrane tool and certainty in pooled effect estimates using GRADE methods. RESULTS: We included 9 RCTs (n = 2093 patients). We found no difference in mortality in patients treated with HFNC (relative risk [RR] 0.94, 95% confidence interval [CI] 0.67-1.31, moderate certainty) compared to conventional oxygen therapy. We found a decreased risk of requiring intubation (RR 0.85, 95% CI 0.74-0.99) or escalation of oxygen therapy (defined as crossover to HFNC in the control group, or initiation of non-invasive ventilation or invasive mechanical ventilation in either group) favouring HFNC-treated patients (RR 0.71, 95% CI 0.51-0.98), although certainty in both outcomes was low due to imprecision and issues related to risk of bias. HFNC had no effect on intensive care unit length of stay (mean difference [MD] 1.38 days more, 95% CI 0.90 days fewer to 3.66 days more, low certainty), hospital length of stay (MD 0.85 days fewer, 95% CI 2.07 days fewer to 0.37 days more, moderate certainty), patient reported comfort (SMD 0.12 lower, 95% CI 0.61 lower to 0.37 higher, very low certainty) or patient reported dyspnea (standardized mean difference [SMD] 0.16 lower, 95% CI 1.10 lower to 1.42 higher, low certainty). Complications of treatment were variably reported amongst included studies, but little harm was associated with HFNC use. CONCLUSION: In patients with acute hypoxemic respiratory failure, HFNC may decrease the need for tracheal intubation without impacting mortality.

Measurement of end-expiratory lung volume by oxygen washin-washout in controlled and assisted mechanically ventilated patients.

OBJECTIVE: Assessing limits of agreement with helium dilution and repeatability of a new system (lung funcution, LUFU) that measures end-expiratory lung volume (EELV) in mechanically ventilated patients using the O(2) washin (EELV(Win)) and washout (EELV(Wout)) technique. LUFU consists of an Evita 4 ventilator, a side-stream oxygen analyzer, and a dedicated PC software. DESIGN AND SETTING: Prospective human study in a general ICU of a University hospital. PATIENTS: Thirty-six mechanically ventilated patients. INTERVENTIONS: We obtained 36 couples of both EELV(Win) and EELV(Wout) measurements in each patient (5 with healthy lungs, 9 with ALI, 22 with ARDS). Measurements were obtained with patients ventilated either by assisted (ASB, 16 measurements) or controlled (CMV, 20 measurements) ventilation. In 19 of 20 cases in CMV, we obtained helium dilution measurements (EELV(He)). MEASUREMENTS AND RESULTS: Bias for agreement with EELV(He) was -16 +/- 156 and 8 +/- 161 ml, respectively, for EELV(Win) and EELV(Wout). Bias for agreement between EELV(Win) and EELV(Wout) was 28 +/- 78 and 23 +/- 168 ml, respectively, for CMV and ASB. During CMV bias for repeatability were 8 +/- 92 and 23 +/- 165 ml, respectively, for EELV(Win) and EELV(Wout). During ASB bias for repeatability were 32 +/- 160 and -15 +/- 147 ml, respectively, for EELV(Win) and EELV(Wout). CONCLUSIONS: The LUFU method showed good agreement with helium, and good repeatability during partial and controlled mechanical ventilation. The technique is simple and safe.

Ventilation during extracorporeal support : Why and how.

The main target of extracorporeal support is to achieve viable gas exchange, while minimizing the risk of ventilator-induced lung injury, achieved through a decreased mechanical ventilation load on the natural lung. However, during veno-venous extracorporeal membrane oxygenation (ECMO), mechanical ventilation is still necessary in order to prevent lung collapse and/or if extracorporeal blood flow is not sufficient to guarantee adequate gas exchange. In this review, we will summarize the physiology of extracorporeal support and the rationale for continuing mechanical ventilation in this context. Furthermore, we will review the current clinical practice among ECMO centers and their suggestions regarding mechanical ventilator settings. While optimal ventilatory settings are still a matter of debate, the use of a strategy combining low tidal volume and limited inspiratory pressures is accepted worldwide. On the contrary, the choice of applied positive end-expiratory pressure (PEEP) varies between the total rest strategy and open lung strategy. Finally, the use of assisted or spontaneous ventilation will be discussed.

Acute changes in frontoparietal activity after repetitive transcranial magnetic stimulation over the dorsolateral prefrontal cortex in a cued reaction time task.

Lesion and functional imaging studies in humans have suggested that the dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC), and intraparietal sulcus (IPS) are involved in orienting attention. A functional magnetic resonance imaging study supplemented by a behavioral experiment examined the effects of 5 Hz repetitive transcranial magnetic stimulation (rTMS) conditioning to the right and left DLPFC on reaction times and synaptic activity as indexed by changes in the blood oxygenation level-dependent (BOLD) signal during a cued choice reaction time task. Orienting precues were either correct (valid) or incorrect (invalid) with respect to the subsequent move cue. The effects of real and sham rTMS were compared for each site of stimulation. Invalid trials showed a significant increase in response times and increases in the BOLD signal in right frontal and parietal regions when compared with valid trials. Conditioning left DLPFC with rTMS led to decreased BOLD signal during performance of this reorienting task in areas including left VLPFC and left IPS. Comparing invalid to valid trials after right DLPFC conditioning revealed decreased BOLD signal in right VLPFC. Data from the behavioral study showed that right DLPFC rTMS selectively increases response times in invalid trials. This effect was only present in the first 10 min after rTMS conditioning. No effect was found in either validly or invalidly cued trials with left DLPFC conditioning. These results suggest that 5 Hz rTMS over right DLPFC exerts remote effects on the activity of areas that functionally interact with the DLPFC during attentional processes, particularly when the reorienting of attention is more demanding as in invalid trials.

Citrate anticoagulation during CVVH in high risk bleeding patients.

BACKGROUND: Regional citrate anticoagulation (RCA) is an effective form of anticoagulation for continuous renal replacement therapy (CRRT) in patients with contraindications to heparin. Its use has been very limited, possibly because of the need for special infusion solutions and difficult monitoring of the metabolic effects. OBJECTIVE: To investigate the safety and the feasibility of an RCA method for continuous veno-venous hemofiltration (CVVH) using commercially available replacement fluid. METHODS: We evaluated 11 patients at high risk of bleeding, requiring CVVH. RCA was performed using commercially available replacement fluid solutions to maintain adequate acid-base balance. We adjusted the rate of citrate infusion to achieve a post-filter ionized calcium concentration [iCa] <0.4 mmol/L when blood flow was <250 ml/min, or <0.6 mmol/L when blood flow was >250 ml/min. When needed, we infused calcium gluconate to maintain systemic plasma [iCa] within the normal range. RESULTS: Twenty-nine filters ran for a total of 965.5 h. Average filter life was 33.6+/-20.5 h. Asymptomatic hypocalcemia was detected in 6.9% of all samples. No [iCa] values <0.9 mmol/L were observed. Hypercalcemia (1.39+/-0.05 mmol/L) occurred in 2.5% of all samples. We observed hypernatremia (threshold 153 mmol/L) and alkalosis (threshold 7.51) in only 9.3% and 9.4% respectively of all samples, mostly concomitantly. No patient showed any signs of citrate toxicity. CONCLUSIONS: We developed a protocol for RCA during CVVH using commercially available replacement fluid that proved safe, flexible and applicable in an Intensive Care Unit (ICU) setting.

Early stroke care in Italy--a steep way ahead: an observational study.

OBJECTIVES: To measure the performance of selected Italian emergency medical system (EMS) dispatch centres managing calls for patients suffering from stroke. Data on outcome and on early treatment in the ED were collected. METHODS: Prospective data collection for a trimester from interventions for a suspected stroke in 13 EMS dispatch centres over five Italian regions. RESULTS: Altogether, 1041 calls for a suspected stroke were analysed. Mean intervals of the sequential phases were 2.3+/-2 minutes between call and ambulance dispatch, 8.4+/-5.5 minutes to reach the patient, 14.5+/-8.5 minutes on the scene, and 40.2+/-16.2 minutes between call and arrival at the ED. Interventions were performed in 56% of cases by a basic life support (BLS) crew, advanced life support (ALS) crews intervened in 28% of cases, and a combination of ALS and BLS in the remaining 16%. Mean diagnostic interval was 99+/-85 minutes between emergency system call and the first CT scan. This was performed 71+/-27 minutes after ED admission. Only 1.6% were admitted to a stroke unit. One month outcome according to GCS was good recovery in 32%, moderate disability in 28%, severe disability in 14%, and death in 25% of the patients. CONCLUSIONS: Mean times show a rapid response of the selected EMS dispatch centres to calls for a suspected stroke. Nevertheless, mean times of the ED phase are still unacceptable according to international guidelines such as Brain Attack Coalition and American Stroke Association guidelines. Efforts should be spent to reduce the time between the arrival and the CT scan and more patients should be admitted to a stroke unit.

Multimodal neurological approach can lead the treatment in postcardiac arrest persistent refractory status epilepticus.

Refractory status epilepticus (RSE) is a common challenge in the setting of post resuscitation care. We describe how multimodal neurological approach can lead treatment and improve the prognosis. We report on three survivors of cardiac arrest (CA) who had good neurological outcomes after mild hypothermia (TH), despite exhibiting persisting RSE requiring treatment with several antiepileptic (AED) and anesthetic drugs, including barbiturate-induced coma. No evidence-based data exist to guide management of RSE in the setting of anoxic brain injury. Our cases emphasize the need for continuous active treatment led by a multimodal approach in order to improve neurological outcome.

Efficacy, safety and acceptability of the new pen needle 33G × 4 mm. AGO 01 study.

OBJECTIVES: Adherence to insulin therapy can be threatened by pain and needle fear. This cross-over randomized non-inferiority trial evaluated a new Pic Insupen 33G × 4 mm needle vs. a 32G × 4 mm needle in terms of metabolic control, safety and acceptability in patients with diabetes treated with insulin. RESEARCH DESIGN AND METHODS: We used a centralized, permuted block randomization, stratified by center and maximum insulin dose per single injection. Subjects used the two needles in two 3 week treatment periods. The primary endpoint was the absolute percentage variation of the blood fructosamine between the two treatments (% |ΔFru|). Additional endpoints were: glycemic variability, total insulin doses, body weight, severe hypoglycemic episodes, leakage at injection sites and pain measured by visual analogue scale. Equivalent glycemic control was defined a priori as % |ΔFru| (including 95% CI) within 20%. RESULTS: Of 87 subjects randomized, 77 completed the study (median age 53.1 [IR 42.3-61.2], median BMI 24.3 Kg/m(2) [IR 21.3-28.5], median duration of insulin therapy [in months] 141.4 (IR 56.3-256.9), median baseline HbA1c 7.9% [IR 7.2-8.8]). The % |ΔFru| was 7.93% (95% CI 6.23-9.63), meeting the non-inferiority criterion. The fasting blood glucose standard deviation was 46.2 (mean 154.6) with the 33G needle and 42.8 (mean 157.3) with the 32G needle (p=0.42). Insulin daily dose and patients' weight did not show any statistically significant variation. We observed 95 episodes of symptomatic hypoglycemia with the 33G needle and 96 with the 32G needle. One episode of severe hypoglycemia was documented in the latter group. As for insulin leakage we observed 37.55 episodes per 100 patient-days with the 33G needle and 32.21 episodes per 100 patient-days with the 32G needle (p=0.31). Patients reported less pain with the 33G × 4 mm needle (p=0.05). STUDY LIMITATIONS: Study sample was mainly composed of adults with type 1 diabetes and study was not blinded. CONCLUSIONS: The 33G needle is not inferior to the 32G needle in terms of efficacy and safety, with reduced pain and no difference in insulin leakage. CLINICAL TRIAL REGISTRATION: NCT01745549.

Sympathetic modulation of radial artery compliance in congestive heart failure.

Animal studies have suggested that arterial compliance can be modulated by adrenergic influences. Whether this adrenergic modulation also occurs in humans is still a matter of debate. In the present article we address this issue by examining the relationships between sympathetic tone and arterial compliance in a variety of physiological and pathophysiological conditions. We have found that cigarette smoking, ie, an action that produces a marked sympathetic activation, causes a significant reduction in radial artery compliance, as measured by an echotracking device capable of providing continuous beat-to-beat evaluation of this hemodynamic variable. When expressed as compliance index, ie, as the ratio between the area under the compliance-pressure curve and pulse pressure, the reduction amounted to 35.7 +/- 4.8% (mean +/- SEM) and was independent of the smoking-related blood pressure increase. Furthermore, pharmacological stimulation of adrenergic receptors located in the arterial wall was also shown to affect arterial compliance because the radial artery compliance index was markedly reduced (- 29.5 +/- 3.9%) during phenylephrine infusion in the brachial artery at doses devoid of any systemic blood pressure effect. Evidence was also obtained that the relationship between sympathetic activation and arterial compliance has pathophysiological relevance, because in 17 patients with congestive heart failure (New York Heart Association classes II through IV) there was a significant inverse correlation (r = .62, P < .01) between muscle sympathetic nerve activity (directly measured by microneurography in the peroneal nerve) and radial artery compliance.(ABSTRACT TRUNCATED AT 250 WORDS)

Limb immobilization for the treatment of focal occupational dystonia.

BACKGROUND: Occupational focal upper-limb dystonia is characterized by involuntary muscle contractions that selectively interfere with the execution of specific motor tasks such as writing or playing a musical instrument. Occupational dystonias have a severe social impact, especially in certain professions. The available medical treatments offer little benefit. METHODS: In eight patients with idiopathic occupational focal dystonia of the upper limb, the dystonic forearm and hand were immobilized with a plastic splint for mean (+/-SD) 4.5 +/- 0.75 weeks. Before splinting (base line) and at various intervals afterwards (4, 12, and 24 weeks), the authors assessed the severity of dystonia and the patients' motor performance objectively (Arm Dystonia Disability Scale and Tubiana and Chamagne Score) and subjectively (Self-Rating Score). RESULTS: Assessment 4 weeks after splint removal, when patients had regained normal voluntary movements, showed that the severity of dystonia and the patients' performance of the impaired motor task had improved; the benefit persisted unchanged at later follow-up visits (Arm Dystonia Disability Scale: base line 20.6 +/- 30.2%; after 4 weeks 83.9 +/- 23.8%, p = 0.007; after 12 weeks 83.9 +/- 23.8%, p = 0.007; after 24 weeks 79.7 +/- 29.5%, p = 0.015. Tubiana and Chamagne Score: base line 28.6 +/- 22.7%; after 4 weeks 80.0 +/- 23.1%, p = 0.015; after 12 weeks 80.0 +/- 23.1%, p = 0.015; after 24 weeks 74.3 +/- 32.1%, p = 0.031. Self-Rating Score: base line 20.6 +/- 19.3%; after 4 weeks 63.7 +/- 25.2%, p = 0.015; after 12 weeks 66.9 +/- 28.1%, p = 0.015; after 24 weeks 70.6 +/- 31.8%, p = 0.015). At the 24-week visit the improvement disappeared in one patient, was moderate in three, and marked in four. CONCLUSIONS: Limb immobilization can be a simple, effective, safe, and inexpensive treatment for focal occupational upper-limb dystonia.

Clinical pharmacological and therapeutic considerations in general intensive care. A review.

The application of clinical pharmacological concepts and therapeutic standards in intensive care settings presents particularly difficult problems due to the lack of adequately controlled background information and the highly variable and rapidly evolving clinical conditions where drugs must be administered and their impact evaluated. In this review, an attempt has been made to discuss the available knowledge within the framework of a problem-oriented approach, which appears to provide a more clinically useful insight than a drug-centred review. Following a brief discussion of the scanty data and the most interesting models to which reference can be made from a pharmacokinetic point of view (the burn patient being taken as an example), the review concentrates on the main general intervention strategies in intensive care patients. These are based mainly on non-pharmacological measures (correction of fluid and electrolyte balance, total parenteral nutrition, enteral nutrition, oxygenation and ventilatory management) and are discussed with respect to the specific challenge they present in various clinical conditions and organ failure situations. In addition, 4 major selected clinical conditions where general management criteria and careful use of prophylactic and therapeutic drug treatments must interact to cope with the variety of presentations and problems are reviewed. These include: acute cerebral damage; anti-infective prophylaxis and therapy; cardiovascular emergencies; and problems of haemostasis. Each problem is analysed in such a way as to frame the pharmacological intervention in its broader context of the underlying (established or hypothesised) pathophysiology, with special attention being paid to those methodological issues which allow an appreciation of the degree of reliability of the data and the recommendations which appear to be practiced (often haphazardly) in intensive care units. The thorough review of the published literature provided (up to mid-1986) clearly shows that in this field the quality of randomised controlled and epidemiological studies is rather unsatisfactory. It would be highly beneficial to research and to clinical care if larger multicentric protocols and prospective epidemiological comparative investigations could be carried out to investigate more timely and adequately the variables which determine drug action, and the final outcome in the many subgroups of patients which must be considered in a proper stratification of intensive care unit populations.

Amiodarone induced phospholipidosis. Biochemical, morphological and functional changes in the lungs of rats chronically treated with amiodarone.

Amiodarone, an antiarrhythmic drug, causes pulmonary fibrosis in some patients during chronic treatment but the mechanism is unknown. We studied the effects of amiodarone on pulmonary biochemistry, morphology and function at doses of 25 and 50 mg/kg/12 hr given to rats by gavage for four weeks. Plasma and pulmonary phospholipids were significantly augmented, 13% and 88% respectively, in the group given amiodarone 50 mg/kg/12 hr compared to pair-fed controls. Typical phospholipidosis-like light and electron microscopic alterations were seen in the lung, their severity related to the extent of biochemical changes induced by amiodarone. Pulmonary function tests revealed mild but not significant changes in O2 and CO2 alveolar exchange efficiency and lung compliance (P-V curve) of treated animals in comparison to pair fed controls. Plasma average concentrations of amiodarone and its main metabolite, desethylamiodarone, after four weeks were 2.46 +/- 0.18 and 0.73 +/- 0.13 micrograms/ml, respectively, in the 50 mg/kg/12 hr group. In the same group amiodarone and desethylamiodarone concentrations in lung were 163 +/- 26 and 569 +/- 153 times higher than those in plasma. A highly significant correlation was found between amiodarone concentrations in plasma and lung and phospholipid content in the lung. A subgroup of animals received amiodarone 50 mg/kg/12 hr for 8 weeks. The pulmonary phospholipidosis-like lesions were similar to those observed after one month of treatment, no fibrosis was evident on light microscopic examination.

Positive end-expiratory pressure prevents the loss of respiratory compliance during low tidal volume ventilation in acute lung injury patients.

STUDY OBJECTIVE: To study the effect of positive end-expiratory pressure (PEEP) on the decay of respiratory system compliance (Cpl,rs) due to low tidal volume (VT) ventilation in acute lung injury (ALI) patients. SETTING: General ICU in a university hospital. PARTICIPANTS: Eight ALI patients with a lung injury score greater than 2.5. INTERVENTION: Pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV), with an average VT of 8.5 +/- 0.4 mL/kg, were applied at three levels of PEEP (5, 10, and 15 cm H2O). Before each PCV and VCV period, lung volume history was standardized by manual hyperinflation maneuvers. MEASUREMENTS: We measured Cpl,rs at time 0 (start), 10, 20, and 30 (end) min from the beginning of each PCV and VCV period. Gas exchange and hemodynamic data were collected at end. RESULTS: At PEEP 5 and 10 cm H2O, we observed a progressive Cpl,rs decay with both PCV and VCV modes. At PEEP 5 cm H2O, we detected a higher Cpl,rs decrease during PCV, due to a higher Cpl,rs at start, compared with VCV. At PEEP 15 cm H2O, Cpl,rs did not decrease significantly. Cpl,rs values measured at end as well as oxygenation and hemodynamic data did not differ between PCV and VCV. At PEEP 15 cm H2O, PCV provided lower PaCO2 than VCV. CONCLUSIONS: A PEEP of at least 15 cm H2O was needed to prevent Cpl,rs decay. The progressive Cpl,rs loss we observed at lower PEEP probably reflects alveolar instability.

Effects of short-term oxygenation changes on acute lung injury patients undergoing pressure support ventilation.

We investigated the effects of short-term oxygenation changes upon the neuromuscular respiratory drive (airway occlusion pressure [P0.1]), minute ventilation (VE), and respiratory rate (RR) in 12 acute lung injury patients undergoing pressure support ventilation. We ventilated the patients first at a high level (H1) of oxygenation, then at intermediate (I), at low, and again at the high (H2) level. The H1 and H2 periods showed no differences. In the H1, I, and L periods, PaO2 was 158 +/- 68, 75 +/- 12, and 55 +/- 6 mm Hg, respectively. Decreasing oxygenation caused very significant increases in VE, RR, and P0.1. Differences in RR, VE, and rapid shallow breathing index were significant at step H1 versus I. Changes in P0.1 appeared to be higher when the H1 value was higher than normal. An arterial oxygenation target higher than the generally accepted 60 mm Hg level may decrease both RR and VE.