Study protocol: understanding the pathophysiologic mechanisms underlying delirium in older people undergoing hip fracture surgery.

BACKGROUND: Postoperative delirium (POD) is a common complication of older people undergoing hip fracture surgery, which negatively affects clinical- and healthcare-related outcomes. Unfortunately, POD pathophysiology is still largely unknown, despite previous studies showing that neuroinflammation, neuroendocrine dysfunction, increased reactive oxidative stress (ROS), and endothelial dysfunctions may be involved. There is also evidence that many of the pathophysiological mechanisms which are involved in delirium are involved in sarcopenia too. This article describes the protocol of a pilot study to evaluate the feasibility of a larger one that will explore the pathophysiological mechanisms correlating POD with sarcopenia. We will analyse whether various biomarkers reflecting neuroinflammation, ROS, neuroendocrine disorders, and microvasculature lesions will be simultaneously expressed in in the blood, cerebrospinal fluid (CSF), and muscles of patients developing POD. METHODS: Two centres will be involved in this study, each recruiting a convenient sample of ten older patients with hip fracture. All of them will undergo a baseline Comprehensive Geriatric Assessment, which will be used to construct a Rockwood-based Frailty Index (FI). Blood samples will be collected for each patient on the day of surgery and 1 day before. Additionally, CSF and muscle fragments will be taken and given to a biologist for subsequent analyses. The presence of POD will be assessed in each patient every morning until hospital discharge using the 4AT. Delirium subtypes and severity will be assessed using the Delirium Motor Subtype Scale-4 and the Delirium-O-Meter, respectively. We will also evaluate the patient's functional status at discharge, using the Cumulated Ambulation Score. DISCUSSION: This study will be the first to correlate biomarkers of blood, CSF, and muscle in older patients with hip fracture.

Association between maternal serum high mobility group box 1 levels and pregnancy complicated by gestational diabetes mellitus.

BACKGROUND AND AIMS: Gestational diabetes mellitus (GDM), is characterized by chronic, low-grade subclinical inflammation with altered production of cytokines and mediators. Recently, a new protein acting as a "danger signal", high mobility group box 1 (HMGB1), that migrates quickly during electrophoresis, has been identified. The aim of our study was to analyze serum levels of HMGB1 in pregnant women, with or without GDM, in the third trimester of pregnancy to evaluate correlation with insulin resistance and other risk factors for GDM. METHODS AND RESULTS: Seventy five pregnant women positive to the 75 g oral glucose tolerance test (OGTT) were included in the study group and 48 pregnant women who were negative to the screening test, were randomly selected using a computer-generated randomisation table. A significant positive univariate correlation was observed between serum HMGB1 levels, HOMA-IR index, glycaemia values at OGTT and pre-pregnancy BMI. Moreover, logistic regression analysis showed that serum HMGB1 was independent linked to GDM. CONCLUSION: Our study demonstrated that HMGB1, a marker of chronic inflammation, is associated to GDM and insulin resistance level, in the third trimester of pregnancy.

Future research and collaboration: the "SINERGIE" project on HCV (South Italian Network for Rational Guidelines and International Epidemiology).

The SINERGIE (South Italian Network for Rational Guidelines and International Epidemiology) project is intended to set up a collaborative network comprising virologists, clinicians and public health officials dealing with patients affected by HCV disease in the Calabria Region. A prospective observational data-base of HCV infection will be developed and used for studies on HCV natural history, response to treatment, pharmaco-economics, disease complications, and HCV epidemiology (including phylogenetic analysis). With this approach, we aim at improving the identification and care of patients, focusing on upcoming research questions. The final objective is to assist in improving care delivery and inform Public Health Authorities on how to optimize resource allocation in this area.

Contrast-enhanced ultrasonography (CEUS) vs. MRI of the small bowel in the evaluation of Crohn's disease activity.

PURPOSE: The presence of disease activity in Crohn's disease (CD) is one of the main parameters used to establish whether optimal therapy should be drug therapy or surgery. However, a major problem in monitoring CD is the common mismatch between the patient's symptoms and imaging objective signs of disease activity. Bowel ultrasonography (US) has emerged as a low-cost, noninvasive technique in the diagnosis and follow-up of patients with CD. Accordingly, the use of contrast-enhanced US (CEUS) has made possible an evaluation of the vascular enhancement pattern, similar to the use of magnetic resonance imaging (MRI). The aim of our study was to evaluate the role of CEUS in comparison with small-bowel MRI for assessing Crohn's disease activity. MATERIALS AND METHODS: We prospectively enrolled 30 consecutive patients with known CD. Clinical and laboratory data were compared with imaging findings obtained from MRI and CEUS of the small bowel. MRI was performed with a 1.5-T system using phased-array coils and biphasic orally administered contrast agent prior to and after gadolinium chelate administration. We performed US with a 7.5-MHz linear-array probe and a second-generation contrast agent. The parameters analysed in both techniques were the following: lesion length, wall thickness, layered wall appearance, comb sign, fibroadipose proliferation, presence of enlarged lymph nodes and stenosis. We classified parietal enhancement curves into two types in relation to the contrast pattern obtained with the time-intensity curves at MRI and CEUS: (1) quick washin, quick washout, (2) slow washin, plateau with a slow washout. RESULTS: Comparison between Crohn's disease activity index (CDAI) and MRI showed a low correlation, with an rho=0.398; correlation between CDAI-laboratory data and CEUS activity was low, with rho=0.354; correlation between MRI activity and CEUS activity was good, with rho = 0.791; high correlation was found between CEUS and MRI of the small bowel when assessing wall-thickness, lymph nodes and comb sign; good correlation was fund when assessing layered wall appearance, disease extension and fibroadipose proliferation. At MRI, time-intensity curves for 12/30 patients were active, compared with for 14/30 patients at CEUS; therefore there was a poor correlation between curve on CEUS and curve on MRI (r=0.167; p=0.36). CONCLUSIONS: The use of CEUS can be recommended if there is a discrepancy between MRI and clinical/laboratory parameters. MRI of the small bowel remains the most accurate method for evaluating disease activity.

Where are we with the use of N-acetylcysteine as a preventive and adjuvant treatment for COVID-19?

OBJECTIVE: As N-acetylcysteine (NAC) is promising as a re-purposed drug for the adjunctive or supportive treatment of serious COVID-19, this article aimed to describe current evidence. MATERIALS AND METHODS: A search was performed in PubMed/Medline for "NAC", "viral Infection", COVID-19", oxidative stress", "inflammation", retrieving preclinical and clinical studies. RESULTS: NAC is a pleiotropic molecule with a dual antioxidant mechanism; it may neutralize free radicals and acts as a donor of cysteine, restoring the physiological pool of GSH. Serious COVID-19 patients have increased levels of reactive oxygen species (ROS) and free radicals and often present with glutathione depletion, which prompts a cytokine storm. NAC, which acts as a precursor of GSH inside cells, has been currently used in many conditions to restore or protect against GSH depletion and has a wide safety margin. In addition, NAC has anti-inflammatory activity independently of its antioxidant activity. CONCLUSIONS: Clinical and experimental data suggest that NAC may act on the mechanisms leading to the prothrombotic state observed in severe COVID-19.

Cost-effectiveness of introducing cone-beam computed tomography (CBCT) in the management of complex phalangeal fractures: economic simulation.

PURPOSE: The purpose of this study was to evaluate the cost-effectiveness of introducing cone-beam computed tomography (CBCT) in the management of the complex finger fractures with articular involvement. METHODS: We created a decision tree model simulating the diagnostic pathway of complex finger fractures, suggesting the use of CBCT as alternative to multi-slice computed tomography (MSCT), and we compared their clinical outcomes, costs, and cost-effectiveness for a hypothetical cohort of 10,000 patients. Measures of effectiveness are analysed by using quality-adjusted life years, incremental cost-effectiveness ratio, and net monetary benefit. RESULTS: Diagnosis of a complex finger fracture performed with CBCT costed 67.33€ per patient, yielded 9.08 quality-adjusted life years, and gained an incremental cost-effectiveness ratio of 29.94€ and a net monetary benefit of 9.07 € at 30,000€ threshold. Using MSCT for diagnosis costed 106.23 €, yielded 8.18 quality-adjusted life years, and gained an incremental cost-effectiveness ratio of 371.15 € and a net monetary benefit of 8.09 €. CBCT strategy dominated the MSCT strategy. The acceptability curve shows that there is 98% probability of CBCT being the optimal strategy at 30,000€ threshold (1 EUR equal to 1.11 USD; updated on 02/02/2020). CONCLUSION: CBCT in complex finger fractures management is cost saving compared with MSCT and may be considered a valuable imaging tool in preoperative assessment, allowing early detection and appropriate treatment. It shortens the time to completion of diagnostic work-up, reduces the number of additional diagnostic procedures, improves quality of life, and may reduce costs in a societal perspective.

High efficiency particulate air filters and heat & moisture exchanger filters increase positive end-expiratory pressure in helmet continuous positive airway pressure: A bench-top study.

BACKGROUND: Helmet continuous positive airway pressure (CPAP) has been widely used during the COVID-19 pandemic. Specific filters (i.e. High Efficiency Particulate Air filter: HEPA; Heat & Moisture Exchanger Filter: HMEF) were used to prevent Sars-CoV2 environmental dispersion and were connected to the CPAP helmet. However, HEPA and HMEF filters may act as resistors to expiratory gas flow and increase the levels of pressure within the hood. METHODS: In a bench-top study, we investigated the levels of airway pressure generated by different HEPA and HMEF filters connected to the CPAP helmet in the absence of a Positive End Expiratory Pressure (PEEP) valve and with two levels of PEEP (5 and 10 cmH2O). All steps were performed using 3 increasing levels of gas flow (60, 80, 100 L/min). RESULTS: The use of 8 different commercially available filters significantly increased the pressure within the hood of the CPAP helmet with or without the use of PEEP valves. On average, the increase of pressure above the set PEEP ranged from 3 cmH2O to 10 cmH2O across gas flow rates of 60 to 100 L/min. The measure of airway pressure was highly correlated between the laboratory pressure transducer and the Helmet manometer. Bias with 95% Confidence Interval of Bias between the devices was 0.7 (-2.06; 0.66) cmH2O. CONCLUSIONS: The use of HEPA and HMEF filters placed before the PEEP valve at the expiratory port of the CPAP helmet significantly increase the levels of airway pressure compared to the set level of PEEP. The manometer can detect accurately the airway pressure in the presence of HEPA and HMEF filters in the helmet CPAP and its use should considered.

Role of echocardiography and cardiac MRI in depicting morphological and functional imaging findings useful for diagnosing hypertrophic cardiomyopathy.

PURPOSE: Hypertrophic cardiomyopathy (HCM) is a hereditary disease characterised by primary hypertrophy of the left and/or right ventricle. The reference standard for imaging diagnosis is echocardiography. The aim of our study was to prospectively compare the diagnostic accuracy of echocardiography and cardiac magnetic resonance (MR) imaging in patients with HCM. MATERIALS AND METHODS: Twenty-two consecutive patients with a known diagnosis of HCM were prospectively evaluated, with echocardiography and cardiac MR imaging performed within 2 weeks of each other (mean interval 7 days, range 2-14 days). Two experienced radiologists blinded to the previous clinical and imaging findings separately reviewed the images. The following parameters were calculated for both techniques: myocardial mass, wall thickness, end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), systolic anterior motion (SAM) of the mitral valve and degree of myocardial fibrosis (based on the ultrasonic reflectivity at echocardiography and degree of late enhancement at cardiac MR imaging). The statistical correlation was calculated with Student's t test, Spearman coefficient and Fisher's exact test. A value of p<0.05 was considered significant. RESULTS: The diagnosis of HCM was confirmed in all patients with both techniques, with absolute agreement in terms of the site of disease. The mean value of myocardial mass presented a statistically significant difference between the two techniques (114 g, p<0.001). In contrast, a nonsignificant difference between echocardiography and cardiac MR imaging was found for EDV (102 ml vs 111 ml; p=0.31), ESV (30 ml vs 38 ml; p=0.1), EF (74% vs 68%, p=0.5), SAM (p=0.1) and myocardial fibrosis (p=0.15). CONCLUSIONS: Cardiac MR imaging correlates well with echocardiography in defining the morphological and functional parameters useful for the imaging diagnosis of HCM and therefore, in selected cases (poor acoustic window, doubtful echocardiography findings), it may be a valid alternative to echocardiography.

A simplified approach to virtual colonoscopy using different intestinal preparations: preliminary experience with regard to quality, accuracy and patient acceptability.

PURPOSE: The authors assessed the quality, diagnostic accuracy and patient acceptability of computed tomography (CT) colonography performed using a simplified bowel preparation and software for post-processing digital elimination of stool and fluid data from images compared with the examination obtained with conventional preparation. MATERIALS AND METHODS: Two groups of 40 consecutive asymptomatic patients aged between 48 and 72 years underwent CT colonography. In group A, the CT scan was performed with conventional bowel preparation (a full cathartic dose and oral contrast medium to tag any residue in the 3 days preceding the study). In the second group, CT colonography was performed after a reduced bowel preparation, with the oral contrast medium for residue tagging being administered only on the day of the investigation. Examination quality, diagnostic performance and patient acceptability (rated with a self-completed questionnaire) in the two groups of patients were compared by using the McNemar test. RESULTS: No significant difference was obtained with regard to examination quality (180 vs. 165 segments free from stools and fluid, p>0.05) and overall diagnostic accuracy (16/17 colonic polyps detected in group A and 12/13 in group B, p>0.05). The questionnaires revealed a greater acceptability of the reduced bowel preparation compared with the standard procedure (p=0.01). CONCLUSIONS: In asymptomatic patients, the use of software for post-processing digital elimination of residue from images in conjunction with reduced bowel preparation does not reduce examination quality or diagnostic performance when compared with the conventional CT colonography technique and is more acceptable to and better tolerated by the patient.

Evaluation of colonic involvement in endometriosis: double-contrast barium enema vs. magnetic resonance imaging.

BACKGROUND: The purpose of the study was to compare the accuracy of double-contrast barium enema (DCBE) and magnetic resonance imaging (MRI) in the diagnosis of intestinal endometriosis using the histological examination on resected specimen as comparative standard. METHODS: Eighty-three consecutive patients with suspected intestinal endometriosis, resected between 2005 and 2007, were prospectively evaluated. All of the women underwent preoperative DCBE and MRI on the same day. We evaluated number, site (rectum, sigmoid, cecum), and size of the lesions. The imaging findings were correlated with those resulting at pathology. RESULTS: Among the 65 women who underwent surgery, 50/65 (76.9%) were found to have bowel endometriosis, with 9/50 (18%) patients presenting two lesions; DCBE allowed to detect 50/59 (84.7%) lesions. MRI allowed to detect 42/59 (71.1%) lesions. DCBE showed sensibility, specificity, PPV, NPV, and accuracy of respectively 84.7, 93.7, 98.0, 62.5, and 86.6%, MRI of 71.1, 83.3, 93.3, 46.8, and 74.6%. CONCLUSION: DCBE is more accurate than unenhanced MRI in the diagnosis of bowel endometriosis, and should be preferred in the preoperative management of this disease, since it usually enables a proper surgical planning.

Evaluation of a method of computer-aided detection (CAD) of pulmonary nodules with computed tomography.

PURPOSE: The authors sought to compare the sensitivity and reading time obtained using computer-aided detection (CAD) software as second reader (SR) or concurrent reader (CR) in the identification of pulmonary nodules. MATERIALS AND METHODS: Unenhanced CT scans of 100 consecutive cancer patients were retrospectively reviewed by four readers to identify all solid, noncalcified pulmonary nodules ranging from 3 to 30 mm in diameter. The sensitivity and reading time of each reader and of CAD alone were calculated at 3-mm and 5-mm thresholds with respect to the reference standard, consisting of a consensus reading by the four radiologists involved in the study. The McNemar test was used to compare the sensitivities obtained by reading without CAD (readers 1 and 2), with CAD as SR (readers 1 and 2 with a 2-month delay), and with CAD as CR (readers 3 and 4). The paired Student's t test was used to compare reading times. A value of p<0.05 was considered statistically significant. RESULTS: A total of 258 and 224 nodules were identified at 3-mm and 5-mm thresholds, respectively. The sensitivity of CAD alone was 62.79% and 67.41% at the 3-mm and 5-mm threshold values respectively, with 4.15 and 2.96 false-positive findings per examination. CAD as SR produced a significant increase in sensitivity (p<0.001) in nodule detection with respect to reading without CAD both at 3 mm (12.01%) and 5 mm (10.04%); the average increase in sensitivity obtained when comparing CAD as SR to CAD as CR was statistically significant (p<0.025) both at the 3-mm (5.35%) and 5-mm (4.68%) thresholds. CAD as CR produced a nonsignificant increase in sensitivity compared with reading without CAD (p>0.05). Mean reading time using CAD as SR (330 s) was significantly longer than reading without CAD (135 s, p<0.001) and reading with CAD as CR (195 s, p<0.025). CONCLUSIONS: The use of CAD as CR, without any significant increase in reading time, produces no significant increase in sensitivity in pulmonary nodule detection when compared with reading without CAD (p>0.05); CAD as SR, at the cost of longer reading times, increases sensitivity when compared with reading without CAD (p<0.001) or with CAD as CR (p<0.025).

A life-threatening paediatric case of acute autoimmune haemolytic anaemia (AIHA) successfully cured by plasma-exchange and combined immunosuppressive treatment.

A 3-year-old boy present with a severe autoimmune haemolytic anaemia, triggered by IgG-class auto-antibodies, with hemoglobin levels decreased to 2, 1 gr/dL. A combined immunosuppressive regimen was begun together with multiple plasma-exchanges and transfusions which sustained the cardio-vascular balance until the specific therapy became effective.

MR imaging findings of elastofibroma dorsi in correlation with pathological features: our experience.

PURPOSE: This paper describes the role of magnetic resonance (MR) imaging for characterising elastofibroma dorsi in correlation with pathological findings. MATERIALS AND METHODS: Over a period of 9 years, 1,233 MR examinations of the periscapular region assessed for the presence of elastofibroma dorsi with superconductive 1.5-T MR scanners at three different radiology institutes were retrospectively reviewed. RESULTS: Our study population included 15 patients (12 women, three men; mean age 58 years, range 28-82 years) presenting with 17 lesions. Two patients had bilateral elastofibroma dorsi. Thirteen of 15 patients underwent MR examination for clinical suspicion of a lesion located in the periscapular region, whereas in 2/15 cases it was an incidental finding during MR examination performed for other diseases. Diagnosis of elastofibroma dorsi was confirmed by histopathology in 11/17 cases. The remaining lesions were considered benign, as their size and morphology did not change over a mean follow-up period of 1.5 years. CONCLUSIONS: MR imaging with its multiplanar capabilities and high-contrast resolution has a high level of accuracy in characterising elastofibroma dorsi and may avoid the need for biopsy or surgical operation.

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.

Indicators for preventable drug-related morbidity. Practical application in home-based care.

AIM: The aim of this study is of evaluating Morris' PDRM indicator system in the Italian Health Care System, especially in the context of home-based health care assistance, so as to assess the reliability of such a system to detect preventable events of drug-related morbidity (DRM). METHODS: This is a pilot study which has been carried out on a control group of patients. The results, which have been obtained, have then been used to calculate the incidence of the preventable drug-related morbidity (PDRM) in the entire population. The sample of patients was taken from the Health District of Chivasso (Local Health Unit 7 in Piedmont). The subjects had all been inserted in the Integrated Home Healthcare Assistance programme in the period from 1st January to 31st December 2004. RESULTS: The PDRM is equal to 32, with an incidence of 15.6% in the entire population (205). Seven indicators out of 19 were able to identify PDRM. Of these, the indicator which showed the best detection rate scored 72%. CONCLUSIONS: The study revealed that this indicator system has the capability of detecting events of PDRM. In addition to this, the version of the system which has been approved by the expert panel has proved executable in the Italian healthcare system, especially in home-based healthcare.

Outpatient parenteral antibiotic therapy for bone and joint infections: an italian multicenter study.

In the early eighties, the advantages of outpatient parenteral antibiotic therapy (OPAT) (reduced costs, no hospitalization trauma in children, no immobilization syndrome in elderly, reduction in nosocomial infections by multiresistant organisms) were identified in the United States, and suitable therapeutic programs were established. Currently, more than 250,000 patients per year are treated according to an OPAT program. In order to understand the different ways of managing OPAT and its results, a National OPAT Registry was set up in 2003 in Italy. Analysis of data concerning osteomyelitis, septic arthritis, prosthetic joint infection and spondylodiskitis, allowed information to be acquired about 239 cases of bone and joint infections, with particular concern to demographics, therapeutic management, clinical response, and possible side effects. Combination therapy was the first-line choice in 66.9% of cases and frequently intravenous antibiotics were combined with oral ones. Teicoplanin (38%) and ceftriaxone (14.7%), whose pharmacokinetic/pharmacodynamic properties permit once-a-day administration, were the two top antibiotics chosen; fluoroquinolones (ciprofloxacin and levofloxacin) were the most frequently utilized oral drugs. Clinical success, as well as patients' and doctors' satisfaction with the OPAT regimen was high. Side-effects were mild and occurred in 11% of cases. These data confirm that the management of bone and joint infections in an outpatient setting is suitable, effective and safe.

On the mechanical and electronic properties of thiolated gold nanocrystals.

We present a quantitative exploration, combining experiment and simulation, of the mechanical and electronic properties, as well as the modifications induced by an alkylthiolated coating, at the single nanoparticle (NP) level. We determined the response of the NPs to external pressure in a controlled manner using an atomic force microscope tip. We found a strong reduction in their Young's modulus, as compared to bulk gold, and a significant influence of strain on the electronic properties of the alkylthiolated NPs. Electron transport measurements of tiny molecular junctions (NP/alkylthiol/CAFM tip) show that the effective tunnelling barrier through the adsorbed monolayer strongly decreases by increasing the applied load, which translates in a remarkable and unprecedented increase in the tunnel current. These observations are successfully explained using simulations based on the finite element analysis (FEA) and first-principles calculations that permit one to consider the coupling between the mechanical response of the system and the electric dipole variations at the interface.

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.