EXPERIMENTAL PHYSIOLOGY, Issue 2 2000
S. Deborah Lucy
Neural mediation of the human cardiac response to isocapnic (IC) steady-state hypoxaemia was investigated using coarse-graining spectral analysis of heart rate variability (HRV). Six young adults were exposed in random order to a hypoxia or control protocol, in supine and sitting postures, while end-tidal PCO2 (PET,CO2) was clamped at resting eucapnic levels. An initial 11 min period of euoxia (PET,O2 100 mmHg; 13.3 kPa) was followed by a 22 min exposure to hypoxia (PET,O2 55 mmHg; 7.3 kPa), or continued euoxia (control). Harmonic and fractal powers of HRV were determined for the terminal 400 heart beats in each time period. Ventilation was stimulated (P < 0.05) and cardiac dynamics altered only by exposure to hypoxia. The cardiac interpulse interval was shortened (P < 0.001) similarly during hypoxia in both body positions. Vagally mediated high-frequency harmonic power (Ph) of HRV was decreased by hypoxia only in the supine position, while the fractal dimension, also linked to cardiac vagal control, was decreased in the sitting position (P < 0.05). However, low-frequency harmonic power (Pl) and the HRV indicator of sympathetic activity (Pl/Ph) were not altered by hypoxia in either position. These results suggest that, in humans, tachycardia induced by moderate IC hypoxaemia (arterial O2 saturation Sa,O2, 85%) was mediated by vagal withdrawal, irrespective of body position and resting autonomic balance, while associated changes in HRV were positionally dependent. [source]

The Relationship between Hospital Volume and Mortality in Mechanical Ventilation: An Instrumental Variable Analysis

HEALTH SERVICES RESEARCH, Issue 3 2009
Jeremy M. Kahn
Objective. To examine the relationship between hospital volume and mortality for nonsurgical patients receiving mechanical ventilation. Data Sources. Pennsylvania state discharge records from July 1, 2004, to June 30, 2006, linked to the Pennsylvania Department of Health death records and the 2000 United States Census. Study Design. We categorized all general acute care hospitals in Pennsylvania (n=169) by the annual number of nonsurgical, mechanically ventilated discharges according to previous criteria. To estimate the relationship between annual volume and 30-day mortality, we fit linear probability models using administrative risk adjustment, clinical risk adjustment, and an instrumental variable approach. Principle Findings. Using a clinical measure of risk adjustment, we observed a significant reduction in the probability of 30-day mortality at higher volume hospitals (,300 admissions per year) compared with lower volume hospitals (<300 patients per year; absolute risk reduction: 3.4%, p=.04). No significant volume,outcome relationship was observed using only administrative risk adjustment. Using the distance from the patient's home to the nearest higher volume hospital as an instrument, the volume,outcome relationship was greater than observed using clinical risk adjustment (absolute risk reduction: 7.0%, p=.01). Conclusions. Care in higher volume hospitals is independently associated with a reduction in mortality for patients receiving mechanical ventilation. Adequate risk adjustment is essential in order to obtained unbiased estimates of the volume,outcome relationship. [source]

Larger tidal volume increases sevoflurane uptake in blood: a randomized clinical study

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2010
B. ENEKVIST
Background: The rate of uptake of volatile anesthetics is dependent on alveolar concentration and ventilation, blood solubility and cardiac output. We wanted to determine whether increased tidal volume (VT), with unchanged end-tidal carbon dioxide partial pressure (PETCO2), could affect the arterial concentration of sevoflurane. Methods: Prospective, randomized, clinical study. ASA physical status 2 and II patients scheduled for elective surgery of the lower abdomen were randomly assigned to one of the two groups with 10 patients in each: one group with normal VT (NVT) and one group with increased VT (IVT) achieved by increasing the inspired plateau pressure 0.04 cmH2O/kg above the initial plateau pressure. A corrugated tube added extra apparatus dead space to maintain PETCO2 at 4.5 kPa. The respiratory rate was set at 15 min,1, and sevoflurane was delivered to the fresh gas by a vaporizer set at 3%. Arterial sevoflurane tensions (Pasevo), Fisevo, PETsevo, PETCO2, PaCO2, VT and airway pressure were measured. Results: The two groups of patients were similar with regard to gender, age, weight, height and body mass index. The mean PETsevo did not differ between the groups. Throughout the observation time, arterial sevoflurane tension (mean±SE) was significantly higher in the IVT group compared with the NVT group, e.g. 1.9±0.23 vs. 1.6±0.25 kPa after 60 min of anesthesia (P<0.05). Conclusion: Ventilation with larger tidal volumes with isocapnia maintained with added dead-space volume increases the tension of sevoflurane in arterial blood. [source]

Hepatic effects of an open lung strategy and cardiac output restoration in an experimental lung injury

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2010
M. KREDEL
Background: Ventilation with high positive end-expiratory pressure (PEEP) can lead to liver dysfunction. We hypothesized that an open lung concept (OLC) using high PEEP impairs liver function and integrity dependent on the stabilization of cardiac output. Methods: Juvenile female Pietrain pigs instrumented with flow probes around the common hepatic artery and portal vein, pulmonary and hepatic vein catheters underwent a lavage-induced lung injury. Ventilation was continued with a conventional approach (CON) using pre-defined combinations of PEEP and inspiratory oxygen fraction or with an OLC using PEEP set above the lower inflection point of the lung. Volume replacement with colloids was guided to maintain cardiac output in the CON(V+) and OLC(V+) groups or acceptable blood pressure and heart rate in the OLC(V,) group. Indocyanine green plasma disappearance rate (ICG-PDR), blood gases, liver-specific serum enzymes, bilirubin, hyaluronic acid and lactate were tested. Finally, liver tissue was examined for neutrophil accumulation, TUNEL staining, caspase-3 activity and heat shock protein 70 mRNA expression. Results: Hepatic venous oxygen saturation was reduced to 18 ± 16% in the OLC(V,) group, while portal venous blood flow decreased by 45%. ICG-PDR was not reduced and serum enzymes, bilirubin and lactate were not elevated. Liver cell apoptosis was negligible. Liver sinusoids in the OLC(V+) and OLC(V,) groups showed about two- and fourfold more granulocytes than the CON(V+) group. Heat shock protein 70 tended to be higher in the OLC(V,) group. Conclusions: Open lung ventilation elicited neutrophil infiltration, but no liver dysfunction even without the stabilization of cardiac output. [source]

Mechanical Ventilation Exacerbates Alveolar Macrophage Dysfunction in the Lungs of Ethanol-Fed Rats

ALCOHOLISM, Issue 8 2005
Pradip P. Kamat
Background: Patients with alcohol abuse have a two- to three-fold increased risk of acute lung injury and respiratory failure after sepsis or trauma but are also at increased risk of nosocomial pneumonia. Mechanical ventilation exacerbates lung injury during critical illnesses. In this study we tested whether mechanical ventilation of the alcoholic lung promotes on balance a proinflammatory phenotype favoring ventilator-induced lung injury or an immunosuppressive phenotype favoring ventilator-associated pneumonia. Methods: Lungs from rats fed an isocaloric diet with or without ethanol (six weeks) were isolated and ventilated ex vivo with a low-volume (protective) or high-volume (injurious) strategy for two hours with or without prior endotoxemia (two hours). In other experiments, rats were subjected to high-volume ventilation in vivo. Airway levels of the proinflammatory cytokines tumor necrosis factor-,, macrophage inflammatory protein-2, and interleukin-1, were determined after mechanical ventilation ex vivo and compared with edematous lung injury after high-volume ventilation in vivo. In parallel, alveolar macrophage phagocytosis of bacteria and secretion of interleukin-12 during ventilation ex vivo and endotoxin-stimulated alveolar macrophage phagocytosis and tumor necrosis factor-, secretion in vitro were determined. Results: Ethanol ingestion suppressed the proinflammatory response to injurious mechanical ventilation and did not increase experimental ventilator-induced lung injury. In parallel, ethanol ingestion blunted the innate immune response of alveolar macrophages during injurious ventilation ex vivo and after endotoxin stimulation in vitro. Conclusions: Ethanol ingestion dampens ventilator-induced inflammation but exacerbates macrophage immune dysfunction. These findings could explain at least in part why alcoholic patients are at increased risk of ventilator-associated pneumonia. [source]

Optimal control and design of a cold store using dynamic optimization

OPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 1 2009
Leo Lukasse
Abstract The design of controlled processes is a combined optimal control and design problem (OCDP). Literature on solving large OCDPs is rare. This paper presents an algorithm for solving large OCDPs. For this algorithm system dynamics, objective function and their first-order derivatives must be continuous in the state, control and design parameters. The algorithm is successfully applied to the combined control and design problem of a cold store with three possible refrigeration technologies: mechanical refrigeration, ventilation and evaporative cooling. As a result, insight into cost effectiveness of the refrigeration technologies is generated. It is concluded that for this cold store in the Netherlands evaporative cooling is too expensive. Ventilation is economically viable if the cold store is to be used in January only. In case the cold store is to be operated all year then it is most economical to rely on mechanical refrigeration only and use the overcapacity during most part of the year to shift refrigeration to low-tariff hours. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Ventilatory strategies for the extremely premature infant

PEDIATRIC ANESTHESIA, Issue 5 2008
ANNE GREENOUGH
Summary Bronchopulmonary dysplasia (BPD), which has long-term adverse outcomes, is common following extremely premature birth. BPD has a multifactorial etiology, including a high level or prolonged use of mechanical ventilation. Numerous research studies, therefore, have attempted to identify ventilatory techniques which reduce the likelihood of baro/volutrauma and hence BPD; these have been critically examined in this review, particularly with regard to their relevance to the extremely prematurely born infant. This has highlighted that few randomized studies of ventilatory strategies have concentrated exclusively on those high-risk infants. Overall, in prematurely born infants, advantages have been suggested by the results of studies examining pressure support, proportional assist and volume-targeted ventilation. In addition, High-Frequency Oscillatory Ventilation (HFOV) may reduce the deterioration seen in lung function of prematurely born infants over the first year after birth. In conclusion, more randomized studies are required which concentrate exclusively on the extremely prematurely born population who are at highest risk of BPD. It is essential in such studies that long-term follow-up assessment is inbuilt so that the benefits/adverse effects can be appropriately identified. [source]

Rituximab (B-cell depleting antibody) associated lung injury (RALI): A pediatric case and systematic review of the literature

PEDIATRIC PULMONOLOGY, Issue 9 2009
Martin Bitzan MD
Abstract Introduction Pulmonary toxicity of delayed onset is a rare complication of B-lymphocyte depleting antibody therapy and has been almost exclusively reported in older patients with B-cell malignancies. Aims To describe a pediatric patient with rituximab-associated lung injury (RALI), to systematically analyze previous reports of pulmonary complications, and to summarize common clinico-pathological features, treatment, and outcome. Results A teenage boy with focal segmental glomerulosclerosis (FSGS) presented with progressive dyspnea, fever, hypoxemia and fatigue 18 days after the completion of a second course of rituximab infusions for calcineurin inhibitor-dependent nephrotic syndrome. Respiratory symptoms started while he received high-dose prednisone for persistent proteinuria. Bilateral, diffuse ground-glass infiltrates corresponded to the presence of inflammatory cells in the bronchioalveolar lavage fluid. Empiric antibiotic treatment including clarithromycin was given, but the microbiological work-up remained negative. Serum IgE, C3, and C4 concentrations were normal. He recovered within 3 weeks after onset. We systematically reviewed 23 reports describing 30 additional cases of rituximab-associated lung disease. Twenty eight patients had received rituximab for B-cell malignancies, one for graft-versus-host disease and one for immune thrombocytopenia. Median age was 64 years (interquartile range [IQR] 58,69 years). Seventy one percent received concomitant chemotherapy. Time to onset from the last rituximab dose was 14 days (IQR 11,22 days). Eleven of 31 patients required mechanical ventilation, and 9 died (29%). Ventilation was a significant predictor of fatal outcome (odds ratio 46.7; confidence interval 9.5,229.9). High dose glucocorticoid therapy did not improve survival or prevent severe lung disease or death. Conclusions With the expanding use of rituximab for novel indications, additional cases of RALI affecting younger age groups are expected to emerge. Mechanical ventilation predicts poor outcome. Glucocorticoids may not be protective. Pediatr Pulmonol. 2009; 44:922,934. © 2009 Wiley-Liss, Inc. [source]

Mechanical ventilation with high tidal volume or frequency is associated with increased expression of nerve growth factor and its receptor in rabbit lungs

PEDIATRIC PULMONOLOGY, Issue 7 2009
Rashmi A. Mittal MD
Abstract Objective Nerve growth factor (NGF), a neurotrophin, is induced in lung cells by proinflammatory cytokines, and has a role in bronchial hyperreactivity and lung tissue repair. Ventilation induced lung injury, on the other hand, is known to increase the levels of proinflammatory cytokines in the lungs. We investigated whether, and to what extent, various degrees of lung injury induced by short-term ventilation affect NGF levels in the lung tissue of adolescent rabbits. Methods The rabbits were randomized to different modes of ventilation: (1) CON: normal ventilation for 30,min; (2) NVT: normal ventilation for 6,hr; (3) HFQ: ventilation for 6,hr at double frequency, but normal tidal volume (VT); and (4) HVT: 6,hr ventilation at double VT but normal frequency. Results NGF protein was detected in bronchoalveolar lavage fluid (BALF) and lung tissue in all animals. Ventilation for 6,hr significantly increased NGF levels, in both BALF and lung tissue, in the HFQ and HVT groups as compared to control (P,<,0.05). The maximum increase in BALF NGF was seen in the HVT group (P,=,0.02 vs. CON and NVT groups, and P,=,0.05 vs. HFQ). A parallel increase in interleukin 1-, (IL1-,) was observed. Expression of the high-affinity NGF-receptor, tropomyosin-related kinase A (TrkA), was also upregulated in these two groups. Conclusion Injurious modes of mechanical ventilation upregulate NGF and its receptor TrkA in rabbit lungs, and IL1-beta may be a mediator for this response. We speculate that this increase in NGF level may translate into the development of bronchial hyperreactivity. Pediatr Pulmonol. 2009; 44:713,719. © 2009 Wiley-Liss, Inc. [source]

Ventilation induced pneumothorax following resolved empyema

PEDIATRIC PULMONOLOGY, Issue 1 2008
A.G. Nyman MRCPCH
Abstract We report a case of pneumothorax as a result of positive pressure ventilation in a child previously treated for empyema. Three months following discharge for successful treatment of empyema our patient received a general anesthetic for an elective MRI of the brain for investigation of nystagmus. During recovery from the anesthetic he developed respiratory distress and was found to have a loculated pneumothorax. We propose that pleural fragility in childhood empyema possibly persists even after clinical resolution and in this case for up to 3 months. The complication of pneumothorax should be considered in all patients receiving positive pressure ventilation following resolved empyema. Pediatr Pulmonol. 2008; 43:99,101. © 2007 Wiley-Liss, Inc. [source]

Influence of successive bouts of fatiguing exercise on perceptual and physiological markers during an incremental exercise test

PSYCHOPHYSIOLOGY, Issue 1 2009
Jeremy B.J. Coquart
Abstract The purpose of this study was to examine the effects of a succession of fatiguing stages, on ratings of perceived exertion (RPE) and estimated time limits (ETL) during an incremental exercise test. Twenty-seven cyclists performed a continuous incremental test and a discontinuous test with randomized workloads. A linear mixed model was used to compare the RPE, ETL, respiratory gas, heart rate, and blood data obtained during the two exercise tests. RPE and ETL were not significantly different between the tests. Ventilation, breathing frequency, heart rate, and blood lactate concentration were significantly higher during the last incremental test workloads. In conclusion, although the incremental exercise test generated higher cardiorespiratory and muscular workloads than observed during the randomized exercise test, most likely due to a greater fatiguing process, these higher workloads did not influence the perceptual response. [source]

Mechanisms by which systemic salbutamol increases ventilation

RESPIROLOGY, Issue 2 2006
Antony E. TOBIN
Background and objective: Salbutamol (SAL) has systemic effects that may adversely influence ventilation in asthmatic patients. The authors sought to determine the magnitude of this effect and mechanisms by which i.v. SAL affects ventilation. Methods: A prospective study of nine healthy subjects (eight men, one woman; age 23 ± 1.4 years (SD)) was undertaken. Each subject received i.v. SAL at 5, 10 and 20 µg/min each for 30 min at each dose and was observed for 1 h post infusion. Minute ventilation (V,E), oxygen consumption (V,O2), CO2 production (V,CO2), occlusion pressure (P0.1), heart rate, blood pressure, respiratory rate, glucose, arterial blood gases, lactate and potassium (K+) were recorded at baseline and at 30-min intervals. The effect of 100% oxygen on V,E and P0.1 during SAL infusion at 20 µg/min was observed. Results are expressed as mean ± SEM. Results: V,E was significantly increased at 20 µg/min SAL (37.8 ± 12.1%, P = 0.01), as were V,O2 (22.5 ± 5.1%, P < 0.01) and V,CO2 (40.9 ± 10.6%, P < 0.01). Ventilation was in excess of metabolic needs as demonstrated by a rise in the respiratory exchange ratio (0.87 ± 0.03 to 0.99 ± 0.04, P < 0.05). Serum lactate rose by 124 ± 30.4% from baseline to 20 µg/min (1.1 ± 0.1 to 2.3 ± 0.25 mmol/L, P < 0.01) and base excess decreased (0.89 ± 0.56 to vs. ,1.75 ± 0.52 mmol/L, P < 0.01) consistent with a lactic acidosis contributing to the excess ventilation. There was no significant differences in V,E or P0.1 with FIO2 = 1.0, suggesting peripheral chemoreceptor stimulation was not responsible for the rise in V,E. At 20 µg/min SAL, K+ fell significantly from baseline (3.8 ± 0.06 to 2.8 ± 0.09 mmol/L, P < 0.001). Conclusion: Systemic SAL imposes ventilatory demands by increasing metabolic rate and serum lactate. This may adversely affect patients with severe asthma with limited ventilatory reserve. [source]

Nitric Oxide Ventilation of Rat Lungs from Non-Heart-Beating Donors Improves Posttransplant Function

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 12 2009
B. M. Dong
Lungs from non-heart-beating donors (NHBDs) would enhance the donor pool. Ex vivo perfusion and ventilation of NHBD lungs allows functional assessment and treatment. Ventilation of rat NHBD lungs with nitric oxide (NO) during ischemia, ex vivo perfusion and after transplant reduced ischemia-reperfusion injury (IRI) and improved lung function posttransplant. One hour after death, Sprague-Dawley rats were ventilated for another hour with either 60% O2 or 60% O2/40 ppm NO. Lungs were then flushed with 20-mL cold Perfadex, stored cold for 1 h, perfused in an ex vivo circuit with Steen solution and warmed to 37°C, ventilated 15 min, perfusion-cooled to 20°C, then flushed with cold Perfadex and stored cold. The left lung was transplanted and ventilated separately. Recipients were sacrificed after 1 h. NO-ventilation was associated with significantly reduced wet:dry weight ratio in the ex vivo circuit, better oxygenation, reduced pulmonary vascular resistance, increased lung tissue levels of cGMP, maintained endothelial NOS eNOS, and reduced increases in tumor necrosis factor alpha (TNF-,) and inducible nitric oxide synthase (iNOS). NO-ventilation had no effect on MAP kinases or NF-,B activation. NO administration to NHBDs before and after lung retrieval may improve function of lungs from NHBDs. [source]

Tracheal intubation in daylight and in the dark: a randomised comparison of the Airway Scope®, Airtraq®, and Macintosh laryngoscope in a manikin

ANAESTHESIA, Issue 7 2010
H. Ueshima
Summary Fifteen anaesthetists attempted to intubate the trachea of a manikin lying supine on the ground using the Airway Scope®, Airtraq® or Macintosh laryngoscope in three simulated conditions: (1) in room light; (2) in the dark and (3) in daylight. The main outcome measure was the time to ventilate the lungs after successful intubation; the secondary outcome was the success rate of ventilation within 30 s. In room light and in the dark, ventilation after successful tracheal intubation could always be achieved within 30 s for all three devices. There were no clinically meaningful differences in time to ventilate between the three devices. In daylight, time to ventilate the lungs for the Airway Scope was significantly longer than for the Macintosh blade (p < 0.0001; 95% CI for difference 27.5,65.0 s) and for the Airtraq (p < 0.0001; 95% CI for difference 29.2,67.6 s). Ventilation was always successful for the Macintosh and Airtraq laryngoscopes, but for the Airway Scope, only one of 15 participants could successfully ventilate the lungs (p < 0.0001). Therefore, the Airway Scope may have a role for tracheal intubation under room light or in darkness, but may not be so useful in daylight. In contrast, the Airtraq may have a role in both darkness and daylight. [source]

A comparison of the i-gelÔ with the LMA-UniqueÔ in non-paralysed anaesthetised adult patients

ANAESTHESIA, Issue 10 2009
H. Francksen
Summary This study assessed two disposable devices; the newly developed supraglottic airway device i-gelÔ and the LMA-UniqueÔ in routine clinical practice. Eighty patients (ASA 1,3) undergoing minor routine gynaecologic surgery were randomly allocated to have an i-gel (n = 40) or LMA-Unique (n = 40) inserted. Oxygen saturation, end-tidal carbon dioxide, tidal volume and peak airway pressure were recorded, as well as time of insertion, airway leak pressure, postoperative sore-throat, dysphonia and dysphagia for each device. Time of insertion was comparable with the i-gel and LMA-Unique. There was no failure in the i-gel group and one failure in the LMA-Unique group. Ventilation and oxygenation were similar between devices. Mean airway pressure was comparable with both devices, whereas airway leak pressure was significantly higher (p < 0.0001) in the i-gel group (mean 29 cmH2O, range 24,40) compared with the LMA-Unique group (mean 18 cmH2O, range 6,30). Fibreoptic score of the position of the devices was significantly better in the i-gel group. Post-operative sore-throat and dysphagia were comparable with both devices. Both devices appeared to be simple alternatives to secure the airway. Significantly higher airway leak pressure suggests that the i-gel may be advantageous in this respect. [source]

Core Topics in Mechanical Ventilation

ANAESTHESIA, Issue 9 2009
Chris Harber
No abstract is available for this article. [source]

Termination of Recurrent Ventricular Tachycardia by Continuous Positive Airway Pressure Ventilation

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2009
Yuichi J. Shimada M.D.
We report a case of hypertrophic cardiomyopathy with recurrent ventricular tachycardia that resolved after initiating continuous positive airway pressure therapy. [source]

Combination of Inhaled Nitric Oxide Therapy and Inverse Ratio Ventilation in Patients with Sepsis-Associated Acute Respiratory Distress Syndrome

ARTIFICIAL ORGANS, Issue 11 2000
Kazufumi Okamoto
Abstract: Inverse ratio ventilation (IRV) is a ventilatory technique that uses an inspiratory to expiratory ratio (I:E) greater than 1:1. We studied the effects of mechanical ventilation with an I:E of 1:3, 1:1, and 2:1 on arterial oxygenation in 10 patients with sepsis-associated acute respiratory distress syndrome (ARDS). At each I:E, patients received 0 and 4 ppm of inhaled nitric oxide (INO) in random order for 30 min. Respiratory and cardiovascular parameters were measured. Of the 10 patients studied, 7 responded to IRV and 3 did not. An increase in the I:E and the addition of INO significantly improved arterial oxygenation in the responders (p < 0.0001 and p < 0.006, respectively). The combination of an increase in the I:E and INO had an additive effect on arterial oxygenation. The combined use of IRV and INO is a more effective method of avoiding hypoxemia than either INO or IRV alone. [source]

Untersuchungen zum thermisch induzierten Luftwechselpotential von Kippfenstern

BAUPHYSIK, Issue 3 2004
Dipl.-Oec., Monika Hall Dr.-Ing.
Die sogenannte natürliche Lüftung , Lüftung infolge Temperatur- und Windeinwirkung über geöffnete Türen und Fenster , ist auch heute noch in Wohngebäuden die verbreitetste Form des Lüftens. Da die Lüftung über Kippfenster eine übliche Form des Lüftens ist, ist die Kenntnis des Luftwechsels über Kippfenster von großem Interesse. Der Vergleich von Ansätzen aus der Literatur zur Berechnung des Luftwechsels über Kippfenster zeigt, daß diese unter Verwendung gleicher Randbedingungen zu unterschiedlichen Ergebnissen führen. Aus diesem Grund wird aus eigenen Messungen ein Modellansatz abgeleitet, der die einseitige, thermisch induzierte Kippfensterlüftung besser beschreibt und gleichzeitig das Vorhandensein einer Laibung und/oder einer Heizung berücksichtigt. Investigations on Buoyancy Induced Ventilation through bottom hung Windows Natural ventilation , ventilation due to buoyancy and wind pressures , through windows and doors is the most common type of ventilation in dwellings in germany. Therefor, being able to predict the air change rate through bottom hung windows by simple models is important. A comparison between existing models to determine the air change rate through bottom hung windows shows, that in spite of using the same parameters the results are very different. The results from own measurements are used to formulate a modified model which describes buoyancy induced ventilation through bottom hung windows for one-sided ventilation. An internal embrasure and a heater is considered. [source]

Mechanical Ventilation Was Associated with Acidemia in a Case Series of Salicylate-poisoned Patients

ACADEMIC EMERGENCY MEDICINE, Issue 9 2008
Andrew I. Stolbach MD
Abstract Objectives:, Despite little empiric evidence, mechanical ventilation (MV) in the setting of salicylate poisoning is considered by many to be harmful. When salicylate-poisoned patients are ventilated at conventional settings, the respiratory alkalosis is abolished, more salicylate is able to pass into the central nervous system (CNS), and neurotoxicity worsens. The objective of this study was to identify a relationship between MV, acidosis, and outcome in salicylate-poisoned patients. Methods:, The authors electronically searched a poison control center (PCC) database (2001,2007) for patients with salicylate poisoning, defined as a serum concentration >50 mg/dL, who had MV listed as a therapy. For the 7-year study period, a total of 3,144 salicylate-poisoning cases were identified. Eleven patients met the inclusion criteria of having both salicylate concentrations >50 mg/dL and required MV; only 7 of them had post-MV data available. Results:, In all seven patients with post-MV blood gas data, the post-MV pH was <7.4. In five of six patients with recorded PCO2, the post-MV PCO2 was >50 mm Hg. Two of the seven patients in the study group died following intubation (two patients died within 3 hours [serum salicylate concentrations, 85 and 79 mg/dL, respectively]). Another patient sustained severe neurologic injury (serum salicylate concentration, 84 mg/dL). The other four patients were ultimately discharged home. In the three patients with the worst clinical outcome, deterioration was reported within hours of intubation. Conclusions:, Inadequate MV of patients with salicylate poisoning is associated with respiratory acidosis, acidemia, and clinical deterioration in this series of cases. This supports warnings about the danger of improper MV in patients with salicylate poisoning. A prospective study should be performed. [source]

Is ventilatory efficiency dependent on the speed of the exercise test protocol in healthy men and women?

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 2 2006
James A. Davis
Summary Indices of ventilatory efficiency have proven useful in assessing patients with heart and lung disease. One of these indices is the slope of the ventilation (V,E) versus carbon dioxide output (V,CO2) relationship during cardiopulmonary exercise testing (CPET) for work rates where the relationship is linear. However, this relationship is defined not only by the slope but also by the y -intercept. To examine whether this relationship is dependent on the speed of the CPET protocol, 30 healthy subjects (16 males) were administered a rapid CPET with 1-min increment duration (1-min CPET) to the limit of tolerance and a slow CPET with 4-min increment duration (4-min CPET) to the lactate threshold. Ventilation and the gas fractions for oxygen and CO2 were measured with a Vacumed metabolic cart. The average increment size of both protocols for both sexes was not significantly different (P>0·05). For the males, the mean (SD) slope for the 1- and 4-min CPET was 20·12 (2·61) and 20·37 (2·41), respectively. The corresponding values for the y -intercept were 4.·89 (2·08) and 5.·10 (2·00) l min,1. For the females, the mean (SD) slope for the 1- and 4-min CPET was 23·90 (2·38) and 24·16 (2·55), respectively. The corresponding values for the y -intercept were 3·93 (0·39) and 3·77 (0·71) l min,1. Paired t -test analysis demonstrated for both sexes that the slopes and y -intercepts were not different for the two protocols (P>0·05). The results of this study demonstrate that the V,E versus V,CO2 relationship is not dependent on the speed of the CPET protocol. [source]

Exercise test mode dependency for ventilatory efficiency in women but not men

CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 2 2006
James A. Davis
Summary Ventilatory efficiency is commonly defined as the level of ventilation V,E at a given carbon dioxide output (V,CO2). The slope of the V,E versus V,CO2 relationship and the lowest V,E/V,CO2 are two ventilatory efficiency indices that can be measured during cardiopulmonary exercise testing (CPET). A possible CPET mode dependency for these indices was evaluated in healthy men and women. Also evaluated was the relationship between these two indices as, in theory, V,E/V,CO2 falls hyperbolically towards an asymptote that numerically equals the V,E versus V,CO2 slope at exercise levels below the ones that cause respiratory compensation for metabolic acidosis. Twenty-eight healthy subjects (14 men) underwent treadmill and cycle ergometer CPET on different days. Ventilation and the gas fractions for oxygen and CO2 were measured with a vacumed metabolic cart. In men, paired t -test analysis failed to find a mode difference for either ventilatory efficiency index but the opposite was true in the women as each woman had higher values for both indices on the treadmill. For men, the lowest V,E/V,CO2 was larger than the V,E versus V,CO2 slope by 1·3 on the treadmill and 0·8 on the cycle ergometer. The corresponding values for women were 1·7 and 1·4. We conclude that in healthy subjects, women, but not men, demonstrate a mode dependency for the two ventilatory efficiency indices investigated in this study. Furthermore, our results are consistent with the theoretical expectation that the lowest V,E/V,CO2 has a numerical value just above the asymptote of the V,E/V,CO2 versus V,CO2 relationship. [source]

RISK FACTORS IN SURGICAL MANAGEMENT OF THORACIC EMPYEMA IN ELDERLY PATIENTS

ANZ JOURNAL OF SURGERY, Issue 6 2008
Ming-Ju Hsieh
Background: Although elderly patients with thoracic disease were considered to be poor candidates for thoracotomy before, recent advances in preoperative and postoperative care as well as surgical techniques have improved outcomes of thoracotomies in this patient group. The aim of this study was to investigate surgical risk factors and results in elderly patients (aged ,70 years) with thoracic empyema. Methods: Seventy-one elderly patients with empyema thoracis were enrolled and evaluated from July 2000 to April 2003. The following characteristics and clinical data were analysed: age, sex, aetiology of empyema, comorbid diseases, preoperative conditions, postoperative days of intubation, length of hospital stay after surgery, complications and mortality. Results: Surgical intervention, including total pneumonolysis and evacuation of the pleura empyema cavity, was carried out in all patients. Possible influent risk factors on the outcome were analysed. The sample group included 54 men and 17 women with an average age of 76.8 years. The causes of empyema included parapneumonic effusion (n = 43), lung abscess (n = 8), necrotizing pneumonitis (n = 8), malignancy (n = 5), cirrhosis (n = 2), oesophageal perforation (n = 2), post-traumatic empyema (n = 2) and post-thoracotomy complication (n = 1). The 30-day mortality rate was 11.3% and the in-hospital mortality rate was 18.3% (13 of 71). Mean follow up was 9.4 months and mean duration of postoperative hospitalization was 35.8 days. Analysis of risk factors showed that patients with necrotizing pneumonitis or abscess had the highest mortality rate (10 of 18, 62.6%). The second highest risk factor was preoperative intubation or ventilator-dependency (8 of 18, 44.4%). Conclusion: This study presents the clinical features and outcomes of 71 elderly patients with empyema thoracis who underwent surgical treatment. The 30-day surgical mortality rate was 11.3%. Significant risk factors in elderly patients with empyema thoracis were necrotizing pneumonitis, abscess and preoperative intubation/ventilation. This study also suggested that surgical treatment of empyema thoracic in elderly patients is recommended after failed conservative treatment because of the acceptably postoperative complication and mortality rate. [source]

Neurological features in Gaucher's disease during enzyme replacement therapy

ACTA PAEDIATRICA, Issue 2 2001
H Ono
This report describes two patients with Gaucher's disease who had unusual clinical symptoms during enzyme replacement therapy. One patient was a female with type 3 Gaucher's disease. She developed a pericardial effusion at 7 y of age, which contained many Gaucher cells despite enzyme replacement therapy. She died from neurological deterioration during enzyme replacement therapy, despite an improvement in her visceral manifestations. The other patient is a male with type 2 Gaucher's disease, who has achieved long-term survival after being supported by mechanical ventilation and enzyme replacement therapy. While on enzyme replacement therapy at the age of 4y, he suffered a generalized cutaneous disease which was clinically diagnosed as ichthyosis. Conclusion: These cases suggest that ordinary enzyme replacement therapy is insufficient for some of the non-neurological manifestations of severe types of Gaucher's disease. [source]

Budesonide delivered by dosimetric jet nebulization to preterm very low birthweight infants at high risk for development of chronic lung disease

ACTA PAEDIATRICA, Issue 12 2000
B Jónsson
We investigated the effect of an aerosolized corticosteroid (budesonide) on the oxygen requirement of infants at high risk for developing chronic lung disease (CLD) in a randomized, double-blind study. The study objective was to attain a 30% decrease in FiO2 levels in the budesonide treatment group after 14 d of therapy. Thirty very low birthweight (VLBW) infants (median (range)) gestational age 26 wk (23,29) and birthweight 805 g (525,1227) were randomized. Inclusion criteria were mechanical ventilation on day 6 of life, or if extubated on nasal continuous positive airway pressure with FiO2± 0.3. The budesonide (PulmicortÔ dose was 500 ,g bid, or placebo. The aerosol was delivered with a dosimetric jet nebulizer, with variable inspiratory time and breath sensitivity. Inhalations were started on day 7 of life. Twenty-seven patients completed the study. A significant lowering of the FiO2 levels at 21 d of life was not detected. Infants who received budesonide were more often extubated during the study period (7/8 vs 2/9) and had a greater relative change from baseline in their oxygenation index (budesonide decreased 26% vs placebo increased 60%). Subsequent use of intravenous dexamethasone or inhaled budesonide in the treatment group was significantly less. All patients required O2 supplementation on day 28 of life. At 36 wk postconceptual age, 61% of infants in the budesonide group needed supplemental O2 as opposed to 79% in the placebo group. No side effects on growth or adrenal function were observed Conclusion: We conclude that inhaled budesonide aerosol via dosimetric jet nebulizer started on day 7 of life for infants at high risk for developing CLD decreases the need for mechanical ventilation similar to intravenous dexamethasone, but without significant side effects. [source]

Randomized trial comparing natural and synthetic surfactant: increased infection rate after natural surfactant?

ACTA PAEDIATRICA, Issue 5 2000
AK Kukkonen
The efficacy of a natural porcine surfactant and a synthetic surfactant were compared in a randomized trial. In three neonatal intensive care units, 228 neonates with respiratory distress and a ratio of arterial to alveolar partial pressure of oxygen <0.22 were randomly assigned to receive either Curosurf 100mgkg,1 or Exosurf Neonatal 5 ml kg,1. After Curosurf, the fraction of inspired oxygen was lower from 15min (0.45 ± 0.22 vs 0.70 ± 0.22, p = 0.0001) to 6 h (0.48 ± 0.26 vs 0.64 ± 0.23,p= 0.0001) and the mean airway pressure was lower at 1 h (8.3 3.2 mmH2O vs 9.4 ± 3.1 mmH2O ,= 0.01). Thereafter the respiratory parameters were similar. The duration of mechanical ventilation (median 6 vs 5 d) and the duration of oxygen supplementation (median 5 vs 4 d) were similar for Curosurf and Exosurf After Curosurf, C-reactive protein value over 40 mg r1 occurred in 45% (vs 12%; RR 3.62, 95%CI 2.12-6.17, p = 0.001), leukopenia in 52% (vs 28%; RR 1.85, 95%CI 1.31-2.61, ,= 0.001) and bacteraemia in 11% (vs 4%; RR3.17, 95%CI 1.05-9.52, p < 0.05). We conclude that when given as rescue therapy Curosurf had no advantage compared with Exosurf in addition to the more effective initial response. Curosurf may increase the risk of infection. [source]

The Use of B-Type Natriuretic Peptides in the Intensive Care Unit

CONGESTIVE HEART FAILURE, Issue 2008
Christian Mueller MD
B-type natriuretic peptide levels are quantitative markers of cardiac stress and heart failure that summarize the extent of systolic and diastolic left ventricular dysfunction, valvular dysfunction, and right ventricular dysfunction. Initial observational pilot studies have addressed 7 potential indications in the intensive care unit: identification of cardiac dysfunction, diagnosis of hypoxic respiratory failure, risk stratification in severe sepsis and septic shock, evaluation of patients with shock, estimation of invasive measurements, weaning from mechanical ventilation, as well as perioperative and postoperative risk prediction. Although additional studies are required to better define the clinical utility of B-type natriuretic peptide values in the intensive care unit, current data suggest that the diagnosis of hypoxic respiratory failure and timing of extubation seem to be the most promising indications. Congest Heart Fail. 2008;14(4 suppl 1):43,45. ©2008 Le Jacq [source]

Impaired oxygen kinetics in beta-thalassaemia major patients

ACTA PHYSIOLOGICA, Issue 3 2009
I. Vasileiadis
Abstract Aim:, Beta-thalassaemia major (TM) affects oxygen flow and utilization and reduces patients' exercise capacity. The aim of this study was to assess phase I and phase II oxygen kinetics during submaximal exercise test in thalassaemics and make possible considerations about the pathophysiology of the energy-producing mechanisms and their expected exercise limitation. Methods:, Twelve TM patients with no clinical evidence of cardiac or respiratory disease and 10 healthy subjects performed incremental, symptom-limited cardiopulmonary exercise testing (CPET) and submaximal, constant workload CPET. Oxygen uptake (Vo2), carbon dioxide output and ventilation were measured breath-by-breath. Results:, Peak Vo2 was reduced in TM patients (22.3 ± 7.4 vs. 28.8 ± 4.8 mL kg,1 min,1, P < 0.05) as was anaerobic threshold (13.1 ± 2.7 vs. 17.4 ± 2.6 mL kg,1 min,1, P = 0.002). There was no difference in oxygen cost of work at peak exercise (11.7 ± 1.9 vs. 12.6 ± 1.9 mL min,1 W,1 for patients and controls respectively, P = ns). Phase I duration was similar in TM patients and controls (24.6 ± 7.3 vs. 23.3 ± 6.6 s respectively, P = ns) whereas phase II time constant in patients was significantly prolonged (42.8 ± 12.0 vs. 32.0 ± 9.8 s, P < 0.05). Conclusion:, TM patients present prolonged phase II on-transient oxygen kinetics during submaximal, constant workload exercise, compared with healthy controls, possibly suggesting a slower rate of high energy phosphate production and utilization and reduced oxidative capacity of myocytes; the latter could also account for their significantly limited exercise tolerance. [source]

Chest wall kinematics, respiratory muscle action and dyspnoea during arm vs. leg exercise in humans

ACTA PHYSIOLOGICA, Issue 1 2006
I. Romagnoli
Abstract Aim:, We hypothesize that different patterns of chest wall (CW) kinematics and respiratory muscle coordination contribute to sensation of dyspnoea during unsupported arm exercise (UAE) and leg exercise (LE). Methods:, In six volunteer healthy subjects, we evaluated the volumes of chest wall (Vcw) and its compartments, the pulmonary apposed rib cage (Vrc,p), the diaphragm-abdomen apposed rib cage (Vrc,a) and the abdomen (Vab), by optoelectronic plethysmography. Oesophageal, gastric and trans-diaphragmatic pressures were simultaneously measured. Chest wall relaxation line allowed the measure of peak rib cage inspiratory muscle, expiratory muscle and abdominal muscle pressures. The loop Vrc,p/Vrc,a allowed the calculation of rib cage distortion. Dyspnoea was assessed by a modified Borg scale. Results:, There were some differences and similarities between UAE and LE. Unlike LE with UAE: (i) Vcw and Vrc,p at end inspiration did not increase, whereas a decrease in Vrc,p contributed to decreasing CW end expiratory volume; (ii) pressure production of inspiratory rib cage muscles did not significantly increase from quiet breathing. Not unlike LE, the diaphragm limited its inspiratory contribution to ventilation with UAE with no consistent difference in rib cage distortion between UAE and LE. Finally, changes in abdominal muscle pressure, and inspiratory rib cage muscle pressure predicted 62% and 41.4% of the variability in Borg score with UAE and LE, respectively (P < 0.01). Conclusion:, Leg exercise and UAE are associated with different patterns of CW kinematics, respiratory muscle coordination, and production of dyspnoea. [source]

Mechanisms of genioglossus responses to inspiratory resistive load in rabbits

ACTA PHYSIOLOGICA, Issue 3 2002
N. P. ALEKSANDROVA
ABSTRACT The purpose of the present study has been to determine whether pharyngeal dilator muscles participate in inspiratory load compensatory responses and if so, to elucidate role of upper airway mechanoreceptors in these responses. The experiments were performed on anaesthetized rabbits. Each animal was tested in three ways by the imposition of inspiratory resistive load: (1) at upper airways via face mask, (2) at the tracheostomic cannula placed below larynx (all upper airway receptors were `bypassed') and (3) at the mouth after the section of the hypoglossus nerves (motor denervation of genioglossus muscle). The inspiratory load applied to the upper airways evoked significant increases in integrated genioglossus activity (to 129 ± 14.7% of control) and its inspiratory duration (to 113 ± 5% of control) already within the first loaded breath (P < 0.05). The increases in the inspiratory activity of musculius genioglossus were relatively greater than the simultaneous increases in the activity of the diaphragm. Motor denervation of the pharynx dilator muscles (including m. genioglossus) increased airway resistance to 184 ± 19% of control (P < 0.05) and induced obstructive alterations in the breathing pattern during unloaded breathing: decrease in maximal inspiratory flow (,13%) and increase in the level of negative oesophageal pressure (+14%) and the peak diaphragm activity (+6%). After nervi hypoglossus sections additional increases in motor and pressure outputs were required in order to maintain unaltered ventilation at the same degree of loading as before denervation. The results indicate that the pharyngeal dilator muscles have a role in compensation of added inspiratory load. Activation of these muscles facilitate the load compensating function of `pump' muscles by decreasing airway resistance. Tracheostomy did not reduce the genioglossus response to inspiratory loading, ruling out any role for upper airways receptors in the genioglossus response to inspiratory load compensations. [source]