Micro sequential injection: fermentation monitoring of ammonia, glycerol, glucose, and free iron using the novel lab-on-valve system.

Using an integrated lab-on-valve manifold in a microfluidic sequential injection format (microSI), automated sample processing has been developed for off-line and on-line monitoring of small-scale fermentations. Spectrophotometric assays of ammonia, glucose, glycerol, and free iron were downscaled to use micro-quantities of commercial reagents. By monitoring the reaction rate, the response curves in a stopped-flow mode generate linear calibration curves for ammonia [r2 = 1.000 (0.9% SE)], glycerol [r2 = 0.999 (1.1% SE)], glucose [r2 = 0.999 (1.1% SE)], and free iron [r2 = 0.999 (1.5% SE)]. Since sample dilution and reagent quantities are easily adjusted within the programmable SI format, the lab-on-valve system can accommodate samples over a wide concentration range (ammonia: 3-1200 ppm; glycerol: 20-120 ppm; glucose: 35-1000 ppm; and free iron: 80-400 ppm). This work demonstrates the key advantages of miniaturization through the reduction of sample and reagent use, minimizing waste and providing a compact yet reliable instrument. The lab-on-valve manifold uses a universal hardware configuration for all analyses, only requiring changes in software protocol and choice of reagents. All of these features are of particular importance to small-scale experimental fermentation where multiple analyte analyses are needed in real-time using small sample volumes. It is hoped that this first real-life application of the lab-on-valve manifold will serve not only as a model system to downscale assays in a practical fashion, but will also inspire and promote the use of the integrated microSI manifold approach for a wider range of biotechnological applications.

Esophagitis in scleroderma. Prevalence and risk factors.

Of 53 patients with scleroderma (43 women and 10 men) evaluated by esophagoscopy and biopsy, 32 (60%) had erosive esophagitis. Symptoms of heartburn and dysphagia were significantly more frequent in the patients who had erosive esophagitis but often were present in those without this condition. Abnormal motility characterized by loss of peristalsis in the distal esophagus was present in all patients with erosive esophagitis, including the 5 who were asymptomatic. No patient with normal esophageal motility had erosive esophagitis at endoscopy. The patients with erosive esophagitis also had significantly diminished lower esophageal sphincter pressures and increased frequency and duration of gastroesophageal reflux episodes. Stricture was present in 13 of 32 patients with erosive esophagitis and was absent in the other 21 patients. The duration of disease, rate of gastric emptying, and fungal smear and culture were not significantly different in those with or without esophagitis. Treatment of fungal infection for a month had little beneficial effect. The pattern of esophageal motility in scleroderma identifies high and low risk groups for esophagitis and stricture, and can be used to select those who require further investigation, irrespective of symptoms.

Unilateral lung lavage: blood flow manipulation by ipsilateral pulmonary artery balloon inflation in dogs.

The authors attempted to favorably manipulate the distribution of pulmonary blood flow during unilateral atelectasis and during unilateral lung lavage by nonocclusive inflation of an ipsilateral pulmonary artery catheter balloon (PAB). Six mongrel dogs were anesthetized, intubated with a double-lumen endotracheal tube, and following a thoracotomy, pulmonary artery and left lung blood flows (Qt and QLL/Qt, respectively) were measured electromagnetically; right lung blood flows (QRL/Qt) were derived by difference. A PAB was positioned in the right main pulmonary artery. The experimental sequence consisted of seven steps: 1) both lungs ventilated; 2) ventilation of the left lung (LL vent), right lung (RL) atelectatic, PAB deflated; 3) LL vent, RL atelectatic, PAB inflated; 4) LL vent, RL lavaged, PAB deflated; 5) LL vent, RL lavaged, PAB inflated; 6) LL vent, RL drained, PAB deflated; and 7) LL vent, RL drained, PAB inflated. At each step the shunt fraction (Qs/Qt) was determined. Inflation of the PAB during LL vent and RL atelectatic (step 3) caused QRL/Qt and Qs/Qt to decrease and QLL/Qt and PaO2 to increase significantly (compared to step 2). There were no significant differences in QRL/Qt, QLL/Qt, Qs/Qt, and PaO2 during RL lavage with the PAB deflated (step 4) compared to RL lavage with the PAB inflated (step 5). Inflation of the PAB during RL drainage (step 7) caused QRL/Qt to decreased and QLL/Qt to increase significantly compared to their values during periods of RL drainage with the PAB deflated (step 6). This resulted in a significant increase in PaO2 and decrease in Qs/Qt. These results demonstrate that the distribution of pulmonary blood flow in dogs can be favorably manipulated by nonocclusive ipsilateral PAB inflation and support a trial of use in selected patients during one-lung anesthesia and ventilation.

Description and clinical evaluation of a new continuous positive airway pressure device.

A new CPAP device is described which is simple, lightweight, easily constructed, and not functionally dependent on gravity or valves. The device consists of a conventional T-piece into which a small nozzle is placed opposite, but projecting towards, the patient connection. When a flow of oxygen is delivered through the nozzle, continuous positive pressure within the airway results. The device was evaluated with a mechanical lung model, in human volunteers using various breathing patterns and in intubated patients requiring transport within the hospital. In all three situations, the device provided 7-15 torr end-expiratory pressure and an FIO2 of 0.40-0.90 using oxygen flow rates of 10-30 L/min. The device is safe, reliable, and can be easily adapted to provide IMV when required. Clinical applications are discussed.