Renal Autotransplantation in a Patient with Bilateral Renal Artery Stenosis Secondary to Takayasu Arteritis.

Involvement of the renal artery is common in Takayasu arteritis. We, herein, present on a patient with Takayasu arteritis causing severe renal failure and a successful auto-transplantation. This case shows that early diagnosis and immediate appropriate interventions are life-saving in patients with Takayasu arteritis. Renal auto-transplantation performed in selected cases increases dialysis-free survival.

Familial Mediterranean fever-associated diseases in children.

BACKGROUND: MEditerranean FeVer (MEFV) gene encodes for the pyrin protein and a mutated pyrin is associated with a prolonged or augmented inflammation. Hence, various diseases were reported to be associated with familial Mediterranean fever (FMF) or carriers of MEFV mutations. However, systematic evaluation of all associated diseases in children with FMF has not been done previously. AIM: The aim of this study was to investigate the frequency and type of FMF-associated diseases in children. DESIGN AND METHODS: Files of FMF patients who had been seen in two reference hospitals in Ankara, in the last two years, were retrospectively evaluated. Patients with FMF and concomitant diseases were included to the study. RESULTS: Among 600 FMF patients, 77 were found to have a concomitant disease (12.8%). Thirty patients (5%) had vasculitis; 21 (3.5%) had juvenile idiopathic artritis (JIA); 7 (1.16%) had inflammatory bowel disease (IBD) and 19 had other diseases including 5 patients with isolated sacroiliitis. Overall, 13 (2.17%) patients had sacroiliitis in our cohort. The most frequent mutation was M694V/M694V (44%) and 81% of the patients had at least one M694V mutation. Majority of the patients (74%) developed associated diseases while they were not receiving colchicine therapy. CONCLUSIONS: Certain inflammatory diseases including vasculitis, chronic arthritis and IBD were more frequently detected in patients with FMF during childhood. M694V mutation is a susceptibility factor for associated diseases. In countries where FMF is prevalent, clinicians dealing with FMF and other inflammatory diseases should be aware of these associations.

Plasma exchange therapy for severe gastrointestinal involvement of Henoch Schönlein purpura in children.

OBJECTIVES: The aim of this report is to evaluate the plasma exchange as a choice for the management of life-threating gastrointestinal system (GIS) involvement in Henoch-Schönlein purpura (HSP) when refractory to conventional therapies. METHODS: We retrospectively reviewed the medical records of HSP patients who had plasma exchange therapy due to massive GIS involvement. We reported age, gender, initial HSP presentation, etiological or triggering factors and disease course. Treatment modalities, side effects and their outcomes were noted. RESULTS: We reported 7 cases of childhood HSP with severe gastrointestinal involvement refractory to common immunosuppression with systemic steroid and cytotoxic therapy. All patients gave inadequate response to pulse methyl prednisolone or oral prednisolone therapy with ongoing GIS bleeding and severe abdominal pain. Therefore, pulse cyclophosphamide was added to the treatment. Two patients received additional intravenous immunoglobulin (IVIG) therapy. Gastrointestinal manifestations continued and plasma exchange was performed. All patients improved after plasma exchange treatment. CONCLUSIONS: Treatment of GI involvement in HSP with plasma exchange has been mainly based on case reports. According to our data, we propose that, plasma exchange may be a safe and efficient management choice in paediatric HSP patients with massive GIS involvement that are refractory to other therapies.

Dysnatremia on intensive care unit admission is a stronger risk factor when associated with organ dysfunction.

AIM: Dysnatremia present at the time of intensive care unit (ICU) admission is associated with mortality. In this study, we investigated the epidemiology of dysnatremia present on ICU admission and the impact of organ dysfunction on the association between dysnatremia and mortality. We hypothesized that dysnatremia comorbid with organ dysfunction is associated with higher risk of mortality. METHODS: This retrospective study was conducted on all patients admitted to the International Hospital General ICU in Istanbul over a period of 6 years (2006-2011). Patients were classified, according to the most abnormal serum sodium values measured within 24 hours after ICU admission, into 7 groups as follows: normonatremia (135≤Na≤145 mmol/L), borderline hyponatremia (130≤Na<135 mmol/L), mild hyponatremia (125≤Na<130 mmol/L), severe hyponatremia (Na <125 mmol/L), borderline hypernatremia (145155 mmol/L). RESULTS: The total admitting patient were 1657. A total of 1060 patients' data were analyzed in this study. Sodium levels were normal in 637 (60.1%), hyponatremic in 367 (34.6%) and hypernatremic in 56 (5.3%) patients. Multivariate analysis showed that only SAPS II was associated with increased mortality (OR, 1.05 [95% confidence interval, 1.02-1.09]). The odds ratio (95% CI) of dysnatremia (Na <125 mmol/L and >150 mmol/L) for mortality was 4.37 (2.29-8.36) in patients with organ dysfunction (number of dysfunctional organs ≥1) (P<0.001). CONCLUSION: Below 125 and above 150 mmol/L sodium levels at ICU admission are risk factors for higher mortality rates in patients with comorbid organ dysfunction. The effect of dysnatremia on mortality is observed when organ dysfunction is present.

No additive effects of inhaled iloprost and prone positioning on pulmonary hypertension and oxygenation in acute respiratory distress syndrome.

BACKGROUND: In acute respiratory distress syndrome (ARDS), pulmonary hypertension is associated with a poor prognosis. Prone position is effective to improve oxygenation whereas inhaled iloprost can treat pulmonary hypertension. However, combination of these interventions has not been examined before. The hypothesis was that this combination had additive effects on oxygenation and pulmonary hemodynamics as compared with each intervention alone. METHODS: In a prospective, randomized cross-over study, ten pigs were anesthetized, intubated and ventilated with volume controlled ventilation. Carotid, jugular venous and pulmonary artery catheters were inserted. ARDS was induced with oleic acid (0.20 mL/kg). Measurements were repeated in randomized different sequences of prone or supine positions with or without iloprost inhalation (220 ng/kg/min) (four combinations). Systemic and pulmonary arterial pressures; arterial and mixed venous blood gases; and Qs/Qt and the resistances were recorded. RESULTS: Iloprost decreased pulmonary artery pressures (for MPAP: P=0.034) in both supine (37±10 vs. 31±8 mmHg; P<0.05) and prone positions (38±9 vs. 29±8 mmHg; P<0.05); but did not obtain a significant improvement in oxygenation in both positions. Prone position improved the oxygenation (p<0.0001) compared to supine position in both with (361±140 vs. 183±158 mmHg, P<0.05) or without iloprost application (331±112 vs. 167±117 mmHg, P<0.05); but did not achieve a significant decrease in MPAP. CONCLUSION: Although iloprost reduced pulmonary arterial pressures, and prone positioning improved oxygenation; there are no additive effects of the combination of both interventions on both parameters. To treat both pulmonary hypertension and hypoxemia, application of iloprost in prone position is suggested.

A recruitment maneuver improves apneic oxygenation.

BACKGROUND: Apneic oxygenation (AO) is applied during surgery and in intensive care units. Even with AO, apnea is associated with progressive hypoxemia, limiting the tolerable amount of time in AO. This experimental study evaluates the effects of a recruitment maneuver (RM) on oxygenation, CO2 retention, and survival times during prolonged apnea, supported or not supported with intratracheal apneic oxygenation. METHODS: Following Ethic Committee approval, 15 male Sprague-Dawley rats were anesthetized and ventilated with PCV and FiO2:1 for 15 minutes. After obtaining a basal arterial blood-gas sample, the rats were randomized into 3 groups and disconnected from the ventilator: group (G) 1 (N.=6): AO with a cannula inserted into the carina; G2 (N=6): RM (40 cm H2O CPAP applied for 30 seconds) before AO; and G3 (N.=3): no application after disconnection (G3 was stopped after the first 3 subjects died within 3 minutes). Further arterial blood-gas samples were taken after 1, 3, and 6 minutes (T1, T3, and T6). Survival times after the start of AO were recorded. RESULTS: G2 was associated with significantly higher values of PaO2 at T3 and T6 when compared to G1 (345±56 vs. 233±65 mm Hg at T3 and 258±31 vs. 180±31 mm Hg at T6, respectively, P<0.05). There were significant changes in PaO2, pH, and PaCO2 over time in all subjects, but no differences were observed between G1 and G2 in pH or PaCO2. Survival time in G2 was significantly longer as opposed to G1 (G1: 10.3±2.3 min; G2: 14.3±3.6 min; P<0.05). CONCLUSION: RM prior to AO prolongs tolerance to apnea, probably by increasing the time before intolerable hypoxemia occurs, without a significant difference in PaCO2 levels.

Influence of body mass index on outcome of the mechanically ventilated patients.

BACKGROUND: There are limited data on the impact of body mass index on outcomes in mechanically ventilated patients. METHODS: Secondary analysis of a cohort including 4698 patients mechanically ventilated. Patients were screened daily for management of mechanical ventilation, complications (acute respiratory distress syndrome, sepsis, ventilator associated pneumonia, barotrauma), organ failure (cardiovascular, respiratory, renal, hepatic, haematological) and mortality in the intensive care unit. To estimate the impact of body mass index on acute respiratory distress syndrome and mortality, the authors constructed models using generalised estimating equations (GEE). RESULTS: Patients were evaluated based on their body mass index: 184 patients (3.7%) were underweight, 1995 patients (40%) normal weight, 1781 patients (35.8%) overweight, 792 patients (15.9%) obese and 216 patients (4.3%) severely obese. Severely obese patients were more likely to receive low tidal volume based on actual body weight but high volumes based on predicted body weight. In obese patients, the authors observed a higher incidence of acute respiratory distress syndrome and acute renal failure. After adjustment, the body mass index was significantly associated with the development of acute respiratory distress syndrome: compared with normal weight; OR 1.69 (95% CI 1.07 to 2.69) for obese and OR 2.38 (95% CI 1.15 to 4.89) for severely obese. There were no differences in outcomes (duration of mechanical ventilation, length of stay and mortality in intensive care unit and hospital) based on body mass index categories. CONCLUSIONS: In this cohort, obese patients were more likely to have significant complications but there were no associations with increased mortality.

The effect of taurine on mesenteric blood flow and organ injury in sepsis.

Endotoxin decreases mesenteric blood flow and inflicts organ injury via free radicals. We investigated whether taurine, an endogenous antioxidant and vasodilator, could attenuate the deleterious effects of endotoxin in a mouse model of sepsis. Swiss albino mice were allocated into four groups and treated either with taurine (150 mg/kg, i.p. at 0(th), 8(th), 16(th) h) or its solvent sterile saline (NaCl 0.9%, w/v) while E. coli endotoxin (20 mg/kg, i.p.) or its solvent saline were also given at 8(th) h. At 24(th) h the animals were anaesthetized and the mesenteric blood flow was measured by using perivascular ultrasonic Doppler-flowmeter. The animals were then exsanguinated, the spleen, liver, and kidneys were isolated for histopathological examination. Thiobarbituric acid-reacting substances (TBARS), glutathione, and myeloperoxidase activity were determined in the liver samples. Endotoxin significantly decreased the mesenteric blood flow and glutathione levels in liver while TBARS and myeloperoxidase activity were increased. However, taurine did not block the deleterious effects of endotoxin nor it did attenuate the histopathological injury. Therefore, we concluded that endotoxin-induced organ injury via free radicals is resistant to blockade by taurine.

The value of the levels of acute phase reactants for the prediction of familial Mediterranean fever associated amyloidosis: a case control study.

In order to determine the role of levels of acute phase proteins (APPs) for the development of amyloidosis in familial Mediterranean fever (FMF) patients, the levels of serum amyloid A (SAA), C reactive protein (CRP), fibrinogen and erythrocyte sedimentation rate were measured in paired sera of 36 FMF patients during and in between acute attacks, 39 of their healthy parents (obligate heterozgotes), and 15 patients with FMF associated amyloidosis. To compare the levels of APPs, 39 patients with chronic infections or inflammatory diseases who may develop secondary amyloidosis, 20 patients with acute infections who are known to have elevated acute phase response but will never develop amyloidosis and 19 healthy controls were included. The median levels of all APPs are increased in the patients with FMF during attacks and a significant decrease was observed after the attack was over. The level of SAA was above reference range in all FMF patients during the attack free period and the level of at least one other APP was also above normal in 64% of the patients. Both CRP and SAA levels were found to be higher in obligate heterozygotes compared to controls. The levels of SAA in patients with FMF during the attack-free period, obligate heterozygotes and patients with FMF-amyloidosis were found to be similar. The levels in each group were found to be higher than SAA levels found in healthy controls yet lower than the levels measured in the patients with acute infections and patients with chronic inflammation or chronic infections. In conclusion, our results show that SAA level reflects subclinical inflammation with high sensitivity but its value for the prediction of amyloid formation process seems to be low.

Are carriers for MEFV mutations "healthy"?

OBJECTIVE: We aimed to compare whether carriers for the MEFV mutations display an increase or decrease in certain features. We compared the frequency of a number of inflammatory symptoms and diseases in carriers and a control population. METHODS: A questionnaire was designed to be applied to parents of children with FMF and a control group of parents. Clinical features and some diseases including the frequency of febrile episodes, abdominal pain, arthralgia, prophylaxis with penicillin, acute rheumatic fever, rheumatoid arthritis, vasculitis, spondyloarthropathy, urinary tract infection, asthma, allergy, irritable bowel disease, appendectomy and tonsillectomy were inquired. 676 parents of 440 children with FMF were surveyed in this study. Controls (n: 774) were selected as parents of healthy children. RESULTS: The presence of febrile episodes more than four per year, arthralgia, past diagnosis for acute rheumatic fever, rheumatoid arthritis and prophylaxis of penicillin, acute rheumatic fever, and rheumatoid arthritis were significantly higher in asymptomatic parents for the MEFV mutations compared to controls. The frequency of allergy was found to be significantly lower in the asymptomatic parents as compared to controls. There was no significant difference at the frequency of urinary tract infection and tonsillectomy between the parents of the patents and controls. CONCLUSIONS: We suggest that one MEFV mutation may indeed be conferring a heightened inflammation as suggested by the increased frequency in inflammatory symptoms. The carrier status for MEFV mutations seem to be unique, in that they cause an alteration in the state of "health".

In vitro and in vivo studies of ibuprofen-loaded biodegradable alginate beads.

The irritation effects of ibuprofen, a widely used non-steroidal anti-inflammatory drug (NSAID), were evaluated on mouse gastric and duodenal mucosa when suspended in 0.5% (w/v) sodiumcarboxymethylcellulose (NaCMC) solution and loaded in alginate beads. The ionotropic gelation method was used to prepare controlled release alginate beads of ibuprofen. The influence of various formulation factors on the encapsulation efficiency, as in vitro drug release and micromeritic properties, was investigated. Other variables included the alginate concentration, percentage drug loading and stirring speed during the microencapsulation process. Scanning electron micrographs of alginate beads loaded with ibuprofen showed rough surface morphology and particle sizes in the range of 1.15 +/- 0.4 - 3.15 +/- 0.6 mm. The yield of microspheres, as collected after drying, was generally 80-90%. Formulation code H showing t50% value of 3.5 h was chosen for in vivo trials because of the appropriate drug release properties. For in vivo trials, free ibuprofen (100 mg kg(-1)), blank and ibuprofen (100 mg kg(-1)) loaded alginate beads (formulation code H) were suspended in 0.5% (w/v) NaCMC solution and each group was given to six mice orally by gavage. NaCMC solution was used as a control in experimental studies. In vivo data showed that the administration of ibuprofen in alginate beads prevented the gastric lesions.

Effects of pneumoperitoneum created through CO2 insufflation and parameters of mechanical ventilation (PEEP application) on systemic dissemination of intraabdominal infections.

BACKGROUND: To examine whether CO2 pneumoperitoneum and positive end expiratory pressure (PEEP) in mechanical ventilation affect the systemic spread of intraabdominal infection. METHODS: Sprague-Dawley male rats weighing 200-300 g were allocated to three groups of 12 animals in each. All rats received mechanical ventilation under general anesthesia. An intraabdominal infection model was established by injecting with 1 ml of Escherichia coli (10(9) CFU/mL) intraperitoneally. Half of the animals in each group were exposed to PEEP (10 cmH2O). CO2 pneumoperitoneum at 13 mmHg was applied to the rats in group 1. Group 2 rats underwent laparotomy. Group 3 served as controls. In addition, TNF-alpha serum levels were measured at baseline and 3 h. A peritoneal specimen for histopathological examination were obtained after the rats were killed at the end of 3 h. For the assessment of data, descriptive statistical methods (mean, standard deviation) as well as Friedman test for repeated measurements in multiple groups, Kruskal-Wallis test for intergroup comparisons, Dunn's multiple comparison test for subgroup comparisons, Mann-Whitney U test for comparisons between paired groups, chi-square and Fisher's exact test for comparison of qualitative data, and McNemar's test for assessment of changes in group variables over time were used. The results were considered statistically significant if probability (p) values were <0.05. RESULTS: Grades of peritonitis in group 1 and 2 were seen to differ nonsignificantly. In group 1, baseline blood cultures were not included in the assessment between the subgroups that received PEEP or not, as there was no growth in any of the subgroups. No significant difference was detected between growth in blood cultures at 1, 2, and 3 h ( p > 0.05). Application of PEEP in subgroups did not alter the blood culture results ( p > 0.05). Significant differences were seen between the initial and final TNF-alpha values of groups (KW: 18.94, p < 0.0001). The values in control group were observed to be significantly lower than those in groups 1 and 2 ( p < 0.01, p < 0.001). Bacteremia and systemic spread of the intraabdominal infection did appear to be different according to the PEEP application. After the assessments of ventilation parameters in our study, significant reductions in pH and HCO3 levels were detected in group 1 as a result of pneumoperitoneum, which was consistent with the literature. There is a significant difference between pH values at baseline and at the end of 1 h because of pneumoperitoneum (Fr: 10.01, p < 0.05). PEEP application in subgroups did not create significant differences in terms of respiratory parameters ( p < 0.01). CONCLUSION: No difference was found between the applications of CO2 pneumoperitoneum and laparotomy with regard to bacteremia and infection-induced peritonitis. It was determined that pneumoperitoneum along with PEEP application had neither a positive nor a negative impact on intraabdominal infection.

Apoptosis in the developing human brain: a preliminary study of the frontal region.

BACKGROUND: Natural cell death due to apoptotic mechanisms has been described in various species. Relatively few studies examined this process in humans. AIM: To investigate the distribution of apoptosis in fetal brain tissue. DESIGN: We examined apoptosis in the frontal region of human fetal brain by the TUNEL method in nine fetuses with no neurological conditions, gestational age 14-26 weeks, and three fetuses with structural anomalies of the nervous system (lumbar meningomyeloceles, n=2, hydrocephalus, n=1). RESULTS: In normal fetuses, TUNEL-positive cells were most concentrated in the intermediate zone (IZ) and between 18 and 22 weeks of gestation; cortical apoptosis was not prominent. The fetus with hydrocephalus had increased numbers of TUNEL-positive cells while those with neural tube defects did not differ from normals. CONCLUSION: The definition of normally occurring apoptosis may provide a basis for further studies directed at central nervous system (CNS) malformations.

Reliability of procalcitonin as a severity marker in critically ill patients with inflammatory response.

Procalcitonin (PCT) is increasingly recognised as an important diagnostic parameter in clinical evaluation of the critically ill. This prospective study was designed to investigate PCT as a diagnostic marker of infection in critically ill patients with sepsis. Eighty-five adult ICU patients were studied. Four groups were defined on the basis of clinical, laboratory and bacteriologic findings as systemic inflammatory response syndrome (SIRS) (n = 10), sepsis (n = 16), severe sepsis (n = 18) and septic shock (n = 41). Data were collected including C-reactive protein (CRP), PCT levels and Sequential Organ Failure Assessment and Acute Physiology and Chronic Health Evaluation II scores on each ICU day. PCT levels were significantly higher in patients with severe sepsis and septic shock (19.25 +/- 43.08 and 37.15 +/- 61.39 ng/ml) than patients with SIRS (0.73 +/- 1.37 ng/ml) (P < 0.05 for each comparison). As compared with SIRS patients, plasma PCT levels were significantly higher in infected patients (21.9 +/- 47.8 ng/ml), regardless of the degree of sepsis (P < 0.001). PCT showed a higher sensitivity (73% versus 35%) and specificity (83% versus 42%) compared to CRP in identifying infection as a cause of the inflammatory response. Best cut-off levels were 1.31 ng/ml for PCT and 13.9 mg/dl for CRP. We suggest that PCT is a more reliable marker than CRP in defining infection as a cause of systemic inflammatory response.

Clinical applicability of the substitution of mixed venous oxygen saturation with central venous oxygen saturation.

OBJECTIVE: To examine the clinical applicability of substituting central venous oxygen saturation (ScvO2) for mixed venous oxygen saturation (SmvO2) in monitoring global tissue oxygenation. DESIGN: Prospective clinical investigation. SETTING: University hospital. PARTICIPANTS: Seventy-three adult patients. INTERVENTIONS: Venous oxygen saturation was recorded, and oxygen saturation difference between SmvO2 and ScvO2 (DeltaSmvcv) was calculated in 2 groups of patients (group I, sepsis patients [n = 41], and group II, general anesthesia for cardiovascular surgery patients [n = 32]) during initial placement of pulmonary artery catheters. MEASUREMENTS AND MAIN RESULTS: Patients were classified as follows: class A, patients having a DeltaSmvcv >-5%; class B, patients having a DeltaSmvcv between -5% and +5%; and class C, patients having a DeltaSmvcv >+5 %. Statistically significant differences were observed in cardiac index, oxygen delivery index, and oxygen extraction ratio between class A and B in both groups. Class C of group II showed the worst correlation between SmvO2 and ScvO2 and had significantly lower arterial carbon dioxide tension values than class A and B. CONCLUSION: Pulmonary artery blood sampling should not be replaced with central venous blood. Hypocapnia and increased oxygen extraction ratio seem to be the major factors that worsen the relationship between ScvO2 and SmvO2.

[The effect of pentaglobin therapy on prognosis in patients with severe sepsis]. / Agir sepsis hastalarinda Pentaglobin tedavisinin prognoz üzerine etkisi.

This study was designed to assess the effects of polyclonal immunoglobulin administration on septic shock incidence and prognosis in patients with severe sepsis. Patients with severe sepsis were randomly allocated into two groups. One group (n = 21) received 5 ml/kg/day IgM enriched immunoglobulin preparation (Pentaglobin) for 3 days. Other group did not receive immunoglobulins (n = 18). Simplified Organ Failure Assessment (SOFA) scores, leucocyte count, duration of mechanical ventilation, ICU stay, duration of severe sepsis did not show significant differences between the groups, as regards to septic shock incidence and mortality. However, a significant decrease in procalcitonin levels were detected only in patients who received pentaglobin (p = 0.001). Mortality rate was 5/21 (23.8%) in pentaglobin group and 5/18 (27.7%) in the control group. Although pentaglobin therapy could not achieve a statistically significant improvement in septic shock occurrence and mortality, the constant reduction in procalcitonin levels indicated the beneficial effects of immunotherapy on the severity of inflammatory response to infection in severe sepsis.

Static and dynamic pressure-volume curves reflect different aspects of respiratory system mechanics in experimental acute respiratory distress syndrome.

INTRODUCTION: A lower inflection point, an upper inflection (or deflection) point, and respiratory system compliance can be estimated from an inspiratory static pressure-volume (SPV) curve of the respiratory system. Such data are often used to guide selection of positive end-expiratory pressure (PEEP)/tidal volume combinations. Dynamic pressure-volume (DPV) curves obtained during tidal ventilation are effortlessly displayed on modern mechanical ventilator monitors and bear a theoretical but unproven relationship to the more labor-intensive SPV curves. OBJECTIVE: Attempting to relate the SPV and DPV curves, we assessed both curves under a range of conditions in a canine oleic acid lung injury model. METHODS: Five mongrel dogs were anesthetized, paralyzed, and monitored to assure a stable preparation. Acute lung injury was induced by infusing oleic acid. SPV curves were constructed by the super-syringe method. DPV curves were constructed for a range of PEEP and inspiratory constant flow settings while ventilating at a frequency of 15 breaths/min and tidal volume of 350 mL. Functional residual capacity at PEEP = 0 cm H2O was measured by helium dilution. The change in lung volume by PEEP at 8, 16, and 24 cm H2O was measured by respiratory inductance plethysmography. RESULTS: The slope of the second portion of the DPV curve did not parallel the corresponding slope of the SPV curve. The mean lower inflection point of the SPV curve was 13.2 cm H2O, whereas the lower inflection point of the DPV curve was related to the prevailing flow and PEEP settings. The absolute lung volume during the DPV recordings exceeded (p < 0.05) that anticipated from the SPV curves by (values are mean +/- SEM) 267 +/- 86 mL, 425 +/- 129 mL, and 494 +/- 129 mL at end expiration for PEEP = 8, 16, and 24 cm H2O, respectively. CONCLUSIONS: The contours of the SPV curve are not reflected by those of the DPV curve in this model of acute lung injury. Therefore, this study indicates that DPV curve should not be used to guide the selection of PEEP/tidal volume combinations. Furthermore, an increase in end-expiratory lung volume occurs during tidal ventilation that is not reflected by the classical SPV curve, suggesting a stable component of lung volume recruitment attributable to tidal ventilation, independent of PEEP.

Time required for partial pressure of arterial oxygen equilibration during mechanical ventilation after a step change in fractional inspired oxygen concentration.

OBJECTIVE: To determine the time required for the partial pressure of arterial oxygen (PaO2) to reach equilibrium after a 0.20 increment or decrement in fractional inspired oxygen concentration (FIO2) during mechanical ventilation. SETTING: A multi-disciplinary ICU in a university hospital. PATIENTS AND METHODS: Twenty-five adult, non-COPD patients with stable blood gas values (PaO2/FIO2 > or = 180 on the day of the study) on pressure-controlled ventilation (PCV). Following a baseline PaO2 (PaO2b) measurement at FIO2 = 0.35, the FIO2 was increased to 0.55 for 30 min and then decreased to 0.35 without any other change in ventilatory parameters. Sequential blood gas measurements were performed at 3, 5, 7, 9, 11, 15, 20, 25 and 30 min in both periods. The PaO2 values measured at the 30th min after a step change in FIO2 (FIO2 = 0.55, PaO2[55] and FIO2 = 0.35, PaO2[35]) were accepted as representative of the equilibrium values for PaO2. Each patient's rise and fall in PaO2 over time, PaO2(t), were fitted to the following respective exponential equations: PaO2b + (PaO2[55]-PaO2b)(1-e-kt) and PaO2[55] + (PaO2[35]-PaO2[55])(e-kt) where "t" refers to time, PaO2[55] and PaO2[35] are the final PaO2 values obtained at a new FIO2 of 0.55 and 0.35, after a 0.20 increment and decrement in FIO2, respectively. Time constant "k" was determined by a non-linear fitting curve and 90% oxygenation times were defined as the time required to reach 90% of the final equilibrated PaO2 calculated by using the non-linear fitting curves. RESULTS: Time constant values for the rise and fall periods were 1.01 +/- 0.71 min-1, 0.69 +/- 0.42 min-1, respectively, and 90% oxygenation times for rises and falls in PaO2 periods were 4.2 +/- 4.1 min-1 and 5.5 +/- 4.8 min-1, respectively. There was no significant difference between the rise and fall periods for the two parameters (p > 0.05). CONCLUSION: We conclude that in stable patients ventilated with PCV, after a step change in FIO2 of 0.20, 5-10 min will be adequate for obtaining a blood gas sample to measure a PaO2 that will be representative of the equilibrium PaO2 value.