Molecular characterization of 39 de novo sSMC: contribution to prognosis and genetic counselling, a prospective study.

Small supernumerary marker chromosomes (sSMCs) are structurally abnormal chromosomes that cannot be characterized by karyotype. In many prenatal cases of de novo sSMC, the outcome of pregnancy is difficult to predict because the euchromatin content is unclear. This study aimed to determine the presence or absence of euchromatin material of 39 de novo prenatally ascertained sSMC by array-comparative genomic hybridization (array-CGH) or single nucleotide polymorphism (SNP) array. Cases were prospectively ascertained from the study of 65,000 prenatal samples [0.060%; 95% confidence interval (CI), 0.042-0.082]. Array-CGH showed that 22 markers were derived from non-acrocentric markers (56.4%) and 7 from acrocentic markers (18%). The 10 additional cases remained unidentified (25.6%), but 7 of 10 could be further identified using fluorescence in situ hybridization; 69% of de novo sSMC contained euchromatin material, 95.4% of which for non-acrocentric markers. Some sSMC containing euchromatin had a normal phenotype (31% for non-acrocentric and 75% for acrocentric markers). Statistical differences between normal and abnormal phenotypes were shown for the size of the euchromatin material (more or less than 1 Mb, p = 0.0006) and number of genes (more or less than 10, p = 0.0009). This study is the largest to date and shows the utility of array-CGH or SNP array in the detection and characterization of de novo sSMC in a prenatal context.

External or internal lateral osteotomy: why I choose the external percutaneous approach.

The authors present their surgical experience with the management of patients with dorsum deformities using a precise technique: the external percutaneous approach. The indications for this technique have still not been set out very clearly in the rhinological textbooks or manuals, and so novices (and not only novices) have difficulty in understanding and applying it. We therefore try to systematise and clarify these indications in brief, together with the technical details, providing a comparison with another technique that is in very widespread use at present: the internal lateral osteotomy. Although the external percutaneous approach is not used very often--in our experience in 30% of cases only--we find the results very satisfactory and we recommend it when it is required by the anatomic conditions.

Cowries derived aragonite as raw biomaterials for bone regenerative medicine.

Carbonate apatites are sought as a bone substitute due to their biocompatibility and excellent resorbability. The present study deals with Cowrie's shell derived powder (CSDP) as natural biomaterial for bone regenerative medicine. Structural and physicochemical analysis showed that Cowrie's shells, presenting brick and mortar microstructures, were mainly composed of aragonite crystals, which were converted into poorly crystalline B-type carbonate apatite once soaked, at 37 °C, in simulated body fluid for 7 days, reflecting bioactive features. Cytotoxic assays showed that CSDP boosted human stem cell proliferation over the study time compared to nacre derived powder (NDP), used as positive control. Human stem cells adopted a flattened morphology and established physical contact with CSDP, signature of a good biocompatibility. Thus, these results suggested that CSDP presents a great interest for bone regenerative medicine, and could be a useful and versatile carrier/scaffold for bone tissue engineering or a raw material for 3D printed orthopedic devices.

Head and neck squamous cell carcinoma transcriptome analysis by comprehensive validated differential display.

Head and neck squamous cell carcinoma (HNSCC) is common worldwide and is associated with a poor rate of survival. Identification of new markers and therapeutic targets, and understanding the complex transformation process, will require a comprehensive description of genome expression, that can only be achieved by combining different methodologies. We report here the HNSCC transcriptome that was determined by exhaustive differential display (DD) analysis coupled with validation by different methods on the same patient samples. The resulting 820 nonredundant sequences were analysed by high throughput bioinformatics analysis. Human proteins were identified for 73% (596) of the DD sequences. A large proportion (>50%) of the remaining unassigned sequences match ESTs (expressed sequence tags) from human tumours. For the functionally annotated proteins, there is significant enrichment for relevant biological processes, including cell motility, protein biosynthesis, stress and immune responses, cell death, cell cycle, cell proliferation and/or maintenance and transport. Three of the novel proteins (TMEM16A, PHLDB2 and ARHGAP21) were analysed further to show that they have the potential to be developed as therapeutic targets.

Phenformin-induced lactic acidosis in diabetic patients.

Eighteen diabetic patients with lactic acidosis (L.A.) were analyzed for possible causal factors, metabolic changes, and efficacy of treatment. An antecedent phenformin therapy was performed in fifteen cases and was associated with renal insufficiency in ten cases and liver disease in eight cases. Tissular anoxia of primary hemodynamic or respiratory origin was absent in all cases. The severe metabolic acidosis (pH m.93 +/- 0,03; HCO3-= 6 +/- 1 MM; PaCO2 = 18 +/- 2 MM. Hg) and hyperlactatemia (14.2 +/- 0.3 mM) were associated with high lactate/pyruvate ration (70 +/- 22). High alanine levels (up to 4.6 mM) were measured in some of these patients. High beta-hydroxybutrate levels were sometimes measured (up to 7.6 mM), and substantial amounts of acetoacetate were also detected in twelve cases. Glucagon level was always increased (1,050 +/- 240 pg./ml.), and insulin/glucagon ratio was low. Cortisol (49 +/- 10 mug./100 ml.) and HGH (10.8 +/- 0.6 ng./ml.) were also elevated. Increased plasma levels of phenformin were measured in five L.A. diabetic subjects (50 +/- 5 mug./ml.) by comparison with other phenformin-treated diabetic subjects. The specificity of the assay was investigated, and phenformin metabolites were characterized by thin-layer chromatography. Por the treatment of L.A., adjunction of dialysis and furosemide improved the efficacy of early and massive sodium bicarbonate infusion. It is suggested that accumulation of phenformin via renal insufficiency plays a determinant role in causing L.A. through an impairment of lactate metabolism in the liver. An accelerated epuration of the drug may be helpful in therapy of L.A. Phenformin treatment should be avoided in case of renal and/or liver insufficiency.

[The project of a law concerning patients' rights at the end of life]. / Le projet de loi relative aux droits des malades et à la fin de vie.

A bill about Patients' rights and the end of life was adopted unanimously by the National Assembly on November 30, 2004. Article 1 provides that the physician is not obligated to continue treatment "when the latter appears futile, disproportional and has no effect other than artificially maintaining the patient's life". Article 2 recognizes that painkillers administered at high doses to terminally ill patients may as a side effect "shorten the patient's life". Conscious patients and the families of unconscious patients must be so informed, and the discussion must be mentioned in the patient's file. Physicians must respect their patients' refusal of treatment, even in life-threatening situations. On the other hand, patients who are not terminally ill must await the expiration of a mandatory waiting period before the physicians must comply with their wishes to refuse care. Article 3 specifies that any treatment can be withheld or withdrawn, including artificial nutrition. The law specifies that it is applicable in 4 different sets of situations: for patients who are or are not terminally and for those who are or are not conscious. Article 9 makes clear that futile treatment of unconscious patients can be withheld or withdrawn. Article 7 specifies that adults may draw up advance directives to indicate their wishes for their end of life and their desires regarding the withholding or withdrawal of treatment. Withholding or withdrawing active treatment is authorized under 3 conditions: the consent from the patient, or if he or she is unconscious, the approval of the health-care proxy, or a family member or close friend if the patient is unconscious; the inclusion of the decision in the patient's medical file, and a group decision-making process.

Inhaled nitric oxide for acute chest syndrome in adult sickle cell patients: a randomized controlled study.

PURPOSE: Previous clinical trials suggested that inhaled nitric oxide (iNO) could have beneficial effects in sickle cell disease (SCD) patients with acute chest syndrome (ACS). METHODS: To determine whether iNO reduces treatment failure rate in adult patients with ACS, we conducted a prospective, double-blind, randomized, placebo-controlled clinical trial. iNO (80 ppm, N = 50) gas or inhaled nitrogen placebo (N = 50) was delivered for 3 days. The primary end point was the number of patients with treatment failure at day 3, defined as any one of the following: (1) death from any cause, (2) need for endotracheal intubation, (3) decrease of PaO2/FiO2 ≥ 15 mmHg between days 1 and 3, (4) augmented therapy defined as new transfusion or phlebotomy. RESULTS: The two groups did not differ in age, gender, genotype, or baseline characteristics and biological parameters. iNO was well tolerated, although a transient decrease in nitric oxide concentration was mandated in one patient. There was no significant difference in the primary end point between the iNO and placebo groups [23 (46 %) and 29 (58 %); odds ratio (OR), 0.8; 95 % CI, 0.54-1.16; p = 0.23]. A post hoc analysis of the 45 patients with hypoxemia showed that those in the iNO group were less likely to experience treatment failure at day 3 [7 (33.3 %) vs 18 (72 %); OR = 0.19; 95 % CI, 0.06-0.68; p = 0.009]. CONCLUSIONS: iNO did not reduce the rate of treatment failure in adult SCD patients with mild to moderate ACS. Future trials should target more severely ill ACS patients with hypoxemia. CLINICAL TRIAL REGISTRATION: NCT00748423.

Slow kinetics of InsP3-induced Ca2+ release: differences between uni- and bi-directional 45Ca2+ fluxes.

The effects of a long-lasting stimulation with inositol 1,4,5-trisphosphate (InsP3) have been studied in monolayers of permeabilized A7r5 cells. When measured under unidirectional 45Ca2+ efflux conditions, i.e. in the presence of 2 microM thapsigargin, an initial fast release was observed which then progressively slowed down into a slow phase which persisted for up to 20 min. When measured under bidirectional 45Ca2+ flux conditions with functional Ca2+ pumps, a transient phase of re-uptake occurred between the initial fast and the subsequent slow release phase. These kinetics are compatible with intrinsic inactivation of the InsP3 receptor. However, this inactivation did not prevent the slow release component. The slow component was not due to the accumulation of an InsP3 metabolite nor to a GTP-dependent translocation of Ca2+ between stores. The slow release phase was more pronounced when the Ca2+ pumps were active than when they were inhibited. This observation is compatible with other findings indicating that the InsP3 receptor is controlled by luminal Ca2+. The decreasing effectiveness of a 20 min lasting InsP3 challenge in mobilizing Ca2+ from less filled stores is most likely due to a progressive depletion of the store and cannot be considered as an experimental artifact caused by a preferential emptying of InsP3-sensitive Ca2+ stores. We conclude that the InsP3 receptor can intrinsically inactivate but that this inactivation is unable to prevent the slow release, which is especially pronounced when Ca2+ pumps are active.

Spontaneous hemomediastinum complicating steroid-induced mediastinal lipomatosis.

Spontaneous hemomediastinum is a rare event, occurring in association with bleeding disorders, intratumoral bleeding, or following an abrupt increase in intrathoracic pressure. We report the case of a patient with systemic lupus erythematosus, nephrotic syndrome, and renal failure, in whom mediastinal lipomatosis (ML) developed following increased corticosteroid therapy. Anticoagulant therapy likely precipitated a massive spontaneous hemomediastinum secondary to diffuse hemorrhage of mediastinal fat, which required emergency decompressive surgery. Steroid-induced ML is common and usually well tolerated, but clinicians should be aware of its potential risk of bleeding when associated with anticoagulant therapy. This case further emphasizes the bleeding complications of treatment with low-molecular-weight heparin in patients with renal failure.

Diagnostic accuracy and therapeutic impact of transthoracic and transesophageal echocardiography in mechanically ventilated patients in the ICU.

STUDY OBJECTIVES: To assess the respective diagnostic accuracy of transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) and their therapeutic implications in mechanically ventilated patients, in the intensive care unit (ICU). DESIGN: A prospective study. SETTINGS: Intensive care units of two tertiary referral teaching hospitals. PATIENTS: One hundred eleven ICU patients (81 men and 30 women; mean age 57 +/- 16 years). Fifty-seven percent were hospitalized for medical illnesses, 16.5 percent after thoracic surgery, 10.5 percent after other surgery, and 16.0 percent for multiple trauma. Their Simplified Acute Physiologic Score was 16 +/- 5. INTERVENTIONS: The echocardiograms were performed in order to solve well-defined clinical problems. TTE was the first step of the procedure and TEE was performed only when (1) TTE did not solve the clinical problems, and (2) TTE yielded unsuspected findings requiring TEE. During each echocardiographic study, the following were noted: ventilatory mode, clinical problems, imaging quality, results, consequence on acute care, duration of the procedure, and potential complications of TEE. Diagnostic accuracy was defined as the proportion of solved problems, and therapeutic impact was defined as changes on acute care that resulted directly from the procedure. MEASUREMENTS AND RESULTS: One hundred twenty-eight consecutive TTE and 96 TEE were performed. TTE solved 60 of 158 clinical problems (38 percent), whether positive end-expiratory pressure (> 4 cm H2O) was present or not (28 of 74 vs 32 of 84: p > 0.50). TTE allowed evaluation of left ventricular function in 77 percent of cases and pericardial effusion in every case, but it did not solve most of the other clinical problems. Indeed, the diagnostic accuracy of TEE was markedly superior (95/98 vs 60/158: p < 0.001), but TEE required a physician's presence longer (43 +/- 17 min vs 27 +/- 12 min: p < 0.001). When TTE and TEE were scheduled (n = 96), TEE yielded an additional diagnosis or excluded with more certitude a suspected diagnosis, except in two cases. TEE had a therapeutic impact more frequently than TTE (35/96 vs 20/128: p < 0.001). Cardiovascular surgery was prompted by echocardiographic findings in ten patients. TEE was well tolerated in all patients; there were no complications. CONCLUSIONS: TEE is a valuable well-tolerated imaging technique in mechanically ventilated patients. For the assessment of left ventricular systolic function and pericardial effusion; however, TTE continues to be an excellent diagnostic tool, even when positive end-expiratory pressure is present. Both TTE and TEE have a therapeutic impact in approximately 25 percent of cases.

Clinically relevant diaphragmatic dysfunction after cardiac operations.

Phrenic nerve injury and diaphragmatic dysfunction can be induced by cardiac operation. The clinical consequences are not well-established. We evaluated 13 consecutive patients over a 2-year period with unexplained and prolonged difficulties in weaning from mechanical ventilation. The mean time of measurement from the operation day was 31 +/- 19 days (range 8 to 78). With the same technique we also evaluated 12 control patients: four patients at day 1 after cardiac operation while they were still intubated; four normally convalescing patients at day 7 or 8 after cardiac operation; and four patients who required prolonged mechanical ventilation because of another identified cause after cardiac operation. Diaphragmatic function was evaluated at the bedside from esophageal and gastric pressure measurements. A low or negative ratio of gastric pressure swing to transdiaphragmatic pressure swing, indicative of diaphragm dysfunction, was found in all 13 patients (mean -0.39 +/- 0.64). The difference between the 13 patients and all control groups was found to be highly significant. Transdiaphragmatic pressure measured during a maximal voluntary inspiratory effort and transdiaphragmatic pressure measured during a short, sharp sniff were markedly diminished (28 +/- 18 cm H2O and 13 +/- 15 cm H2O, respectively) in the 13 patients, significantly different from values in the four control patients studied at day 7 or 8. Transdiaphragmatic pressure measured after magnetic stimulation in four patients was also markedly reduced (7 +/- 5 cm H2O) as compared with normal theoretic values. Aminophylline infusion had no effect on any of these parameters. In one of two patients evaluated a second time, about 5 weeks later, a marked improvement was observed. Estimating the prevalence of clinically relevant diaphragmatic dysfunction, we found it to be 0.5% when no topical cooling was used and 2.1% when iced slush with no insulation pad was added for myocardial protection (p < 0.005). The most striking finding was that the clinical course of the 13 patients was marked by severe intercurrent events, including cardiorespiratory arrest after early tracheal extubation in 5 patients, nosocomial pneumonia in 11, prolonged mechanical ventilation in all (58 +/- 41 days), and a fatal outcome in 3. We conclude that prolonged postoperative diaphragmatic dysfunction may cause severe life-threatening complications after cardiac operation and can be limited to some extent by avoiding the use of iced slush topical cooling of the heart.

Hypoxemia in acute pulmonary embolism.

Most patients with severe, acute pulmonary embolism (PE) have arterial hypoxemia. To further define the respective roles of ventilation to perfusion (VA/Q) mismatch and intrapulmonary shunt in the mechanism of hypoxemia, we used both right heart catheterization and the six inert gas elimination technique in seven patients with severe, acute PE (mean vascular obstruction, 55 percent) and hypoxemia (mean PaO2, 67 +/- 11 mm Hg). None had previous cardiopulmonary disease, and all were studied within the first ten days of initial symptoms. Increased calculated venous admixture (mean QVA/QT 16.6 +/- 5.1 percent) was present in all patients. The relative contributions of VA/Q mismatching and shunt to this venous admixture varied, however, according to pulmonary radiographic abnormalities and the time elapsed from initial symptoms to the gas exchange study. Although all patients had some degree of VA/Q mismatch, the two patients studied early (ie, less than 48 hours following acute PE) had normal chest x-ray film findings and no significant shunt; VA/Q mismatching accounted for most of the hypoxemia. In the others a shunt (3 to 17 percent of cardiac output) was recorded along with radiographic evidence of atelectasis or infiltrates and accounted for most of the venous admixture in one. In all patients, a low mixed venous oxygen tension (27 +/- 5 mm Hg) additionally contributed to the hypoxemia. Our findings suggest that the initial hypoxemia of acute PE is caused by an altered distribution of ventilation to perfusion. Intrapulmonary shunting contributes significantly to hypoxemia only when atelectasis or another cause of lung volume loss develops.

Total respiratory pressure-volume curves in the adult respiratory distress syndrome.

To assess the value of measuring compliance in the adult respiratory distress syndrome, sequential pressure-volume curves were obtained in 19 patients with this syndrome. Analysis of the pressure-volume curves allowed separation of the patients into the following four groups: (1) group 1 (n = 6), normal compliance measured during deflation, little hysteresis, and no inflection in the ascending limb of the pressure-volume tracing; (2) group 2 (n = 8), normal compliance during deflation, increased hysteresis, and presence of an inflection; (3) group 3 (n = 10), decreased compliance during deflation, marked hysteresis, and presence of an inflection; and (4) group 4 (n = 10), reduced compliance during deflation, no increased hysteresis, and no inflection. These patterns were correlated with the stage of the adult respiratory distress syndrome and to the pattern of the chest x-ray film. Group 2 corresponds to the initial stage of the syndrome and to pure alveolar opacities on the chest x-ray film. Group 3 is seen later in the course of the syndrome and corresponds to mixed alveolar and interstitial opacities. Group 4 corresponds to patients with end-stage adult respiratory distress syndrome (two weeks) and a predominant interstitial pattern on the chest x-ray film. Group 1 corresponds to a nearly normal chest x-ray film and to recovery.

PEEP-induced airspace overdistension complicating paraquat lung.

This report describes a case of paraquat poisoning, treated with continuous positive airway pressure. After an initial phase of acute respiratory failure with diffuse pulmonary edema, we observed radiologically a complete clearing of both lungs, associated with an aspect of overdistension. Surprisingly, FRC was above normal, as was total quasi static compliance. The patient died on the 15th day, with intractable hypoxemia. Pathologic analysis revealed large zones of parenchyma with overdistended airspaces, explaining the emphysematous-like aspect of the lungs. We propose that the attempts to increase lung volume with CPAP, at an early phase of diffuse epithelial disorganization, may have, partially at least, dilated the remaining distal airspaces.

Bronchoalveolar lavage in immunocompromised patients. Clinical and functional consequences.

Fiberoptic bronchoscopy and bronchoalveolar lavage are major tools in the diagnosis of acute pneumonia in immunocompromised patients. We conducted a prospective study to assess the morbidity associated with this procedure in 14 patients with AIDS and 16 patients with drug-induced immunosuppression. No patient had a PaO2 lower than 70 mm Hg with additional oxygen. Clinical data, chest roentgenogram, pulmonary function test, forced vital capacity, forced expiratory volume in one second, and arterial blood gases were recorded before and after bronchoscopy. Arterial oxygen saturation was monitored during the procedure, and initial, lowest, and final saturation values were noted. The patients were separated into three groups on the basis of chest roentgenographic findings. No procedure-induced pneumonia or need for tracheal intubation occurred. Minor clinical symptoms induced by the lavage in seven patients resolved spontaneously. By contrast, mean SaO2 decreased markedly during the procedure from 94 +/- 3 to 87 +/- 5 percent (p less than 0.0001) and returned to only 89 +/- 5 percent at the end of the procedure. Lowest SaO2 during the procedure and final SaO2 correlated poorly with initial SaO2 but correlated well with initial FVC and FEV1 (p less than 0.01). The PFT values were lower following bronchoscopy. O2 desaturation was more pronounced in patients with severe roentgenographic abnormalities. No significant differences were found between the three groups of patients, or between the AIDS and DII patients in terms of changes in PFT values. We conclude that in immunocompromised patients, bronchoscopy with BAL induces severe arterial oxygen desaturation which is correlated with initial PFT and chest roentgenographic findings, and most of these abnormalities are transient and do not lead to major complications.

Influence of caloric intake on the respiratory mode during mandatory minute volume ventilation.

Mandatory minute volume ventilation has been proposed as a method for weaning patients from ventilators. The purpose of this study was to delineate the influence of caloric intake on spontaneous ventilation in patients receiving mandatory minute volume ventilation. While the value of such ventilation remained unchanged, eight patients were studied at the following three different levels of daily caloric intake: (1) level A, mean of 223 kcal/sq m; (2) level B, mean of 1,380 kcal/sq m; and (3) level C, mean of 2,100 kcal/sq m. We performed gas exchange measurements and a 24-hour recording of ventilation with a monitoring system providing distinction between spontaneous and mechanical cycles. We found that the ventilatory mode was markedly dependent upon the nutritional intake; the percentage of spontaneous ventilation over 24 hours increased from 11 +/- 7 percent (+/- SE) during diet A to 50 +/- 9 percent during diet B and 79 +/- 8 percent during diet C. This increment paralleled the increase in production of carbon dioxide with caloric intake. We suggest therefore that the patient's ability to breathe spontaneously when receiving mandatory minute volume ventilation should be interpreted according to caloric intake.

Pulmonary gas exchange during venoarterial bypass with a membrane lung for acute respiratory failure.

In patients with fulminating pulmonary edema not responsive to conventional therapy, venoarterial membrane lung bypass can provide assistance if decreased systemic blood pressure prevents use of high-level positive end-expiratory pressure ventilation. In 10 patients with acute respiratory failure, partial venoarterial bypass provided a rapid and marked improvement of systemic oxygenation. Measurement of pulmonary blood flow (PBF) and intrapulmonary shunting (QS/QP) during bypass via prolonged left heart catheterization showed that left ventricular PaO2 was increased through a rapid and profound reduction of QS/QP. During the first days of bypass, derecruitment of pulmonary vessels is probably the mechanism of improved pulmonary oxygenation. When low pulmonary arterial pressures (PAP) are sustained, resorption of pulmonary edema is favored. Despite the beneficial effects of bypass, death occurred in every case due to diffuse interstitial fibrosis and/or parenchymal damage. The absence of healing, due to prolonged circulatory exclusion, may be detrimental despite immediate improvement. Because of this possibility, venovenous or mixed perfusion should be more extensively explored.

Right ventricular function in COPD patients during weaning from mechanical ventilation.

We studied the right ventricular function during a successful weaning period in 7 COPD patients without LV disease who had been mechanically ventilated for several days after an acute exacerbation of their disease. A Swan-Ganz ejection fraction thermodilution catheter performed measurements of right ventricular ejection fraction (RVEF) and right ventricular end-diastolic volume index (RVEDVI) before and fifteen minutes after disconnection from the ventilator at the maintenance FiO2. Although pulmonary artery pressure (PAP) rose from 25 +/- 4 to 28.5 +/- 4.5 mmHg after disconnection from the ventilator, RVEF (0.36 +/- 0.56 to 0.35 +/- 0.12) and RVEDVI (117 +/- 51 to 126 +/- 52 ml/m2) remained similar in both conditions. We concluded that right ventricular systolic function assessed with modified pulmonary artery catheter was maintained during the weaning phase in such weanable patients. This method could easily detect any fall of RVEF or diastolic RV enlargement able to impair the weaning in some patients.

Clinical evaluation of a continuous intra-arterial blood gas system in critically ill patients.

OBJECTIVE: To evaluate the clinical performance of a new, continuous intra-arterial blood gas monitoring system (CIABG) in abnormal ranges of blood gases, and during episodes of low blood pressure, in critically ill patients. DESIGN: Prospective study. SETTINGS: Medical ICU, University Hospital. METHODS: The CIABG system, based on fluorescent dyes, consists of a fiber-optic sensor introduced through an arterial catheter. Twenty-one sensors were evaluated in 15 acutely ill patients. A high failure rate (6/21) was found, due to the brittleness of the fibers. The bias, between CIABG and standard method, and precision were determined for each fiber and for the overall values. Analysis focused on the data collected in patients with arterial oxygen tension (PaO2) values below 75 mmHg, pH lower than 7.35 and arterial carbon dioxide partial pressure (PaCO2) values exceeding 50 mmHg and during episodes of low blood pressure. The accuracy of the CIABG to follow sequential changes in blood gases was studied among the abnormal values. RESULTS: Measurements with CIABG among the abnormal values showed biases of +2mmHg, +0.1mmHg and +0.005 for PaO2, PaCO2 and pH, respectively, and precisions of 9.0mmHg, 3.5mmHg and 0.027, respectively. Bias and precision were not influenced by hemodynamic instability. A substantial difference in the performance of individual CIABG was observed for PaO2 analysis, with 30% of the fibers having a much poorer performance than the others. The sensors were kept in place for 5 +/- 2 days and the drift rate per day was 0.005 for pH, 0.6mmHg for PaCO2 and -1.2mmHg for PaO2. CONCLUSION: In situations of severe hypoxemia, hypercapnia and acidosis, the agreement between CIABG and arterial blood sampling (ABS) is better for PaCO2 and pH than for PaO2, and is not influenced by episodes of low blood pressure.

Total respiratory compliance as a function of lung volume in patients with mechanical ventilation.

In normal subjects breathing spontaneously, compliance has been shown to be influenced by the lung volume from which deflation started. We wondered whether this would also be true for patients with acute respiratory failure who required mechanical ventilation and we accordingly studied 15 such patients. Chest inflation was performed using a continuous flow device (ATM-PV 102), and total compliance was measured as the slope of the pressure-volume relationship during deflation. As inflated lung volumes were increased by 10 to 15, 20 and 25 ml/kg body weight above FRC, mean compliance increased to 38.2, 45.5, 52.2 and 59.3 ml/cmH2O respectively. Each of these increases in mean compliance was statistically significant (p less than 0.001). Increasing the inflated lung volume to 30 ml/kg produced no further significant increase in mean compliance. This study showed that, in patients with acute respiratory failure requiring mechanical ventilation, compliance measured during deflation is a function of the inflated lung volume. We recommend that the compliance should be measured from a constant and high lung volume, equal to 25 ml/kg body weight above FRC.