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Biomedical subjects

T Kolobow

Publications and source records attributed to T Kolobow.

At least 19 recordsLinked to original sources
PubMed1994

Design and development of ultrathin-walled, nonkinking endotracheal tubes of a new "no-pressure" laryngeal seal design. A preliminary report.

BACKGROUND: Endotracheal tubes (ETTs) of conventional design and manufacture greatly increase the air-flow resistance of the upper airways. This increase in upper-airway resistance can lead to a significant increase in the work of breathing and may necessitate the use of assisted mechanical ventilation. Current ETTs are relatively stiff and contribute greatly to patient discomfort. The inflatable cuffs now mounted onto the ETTs function well in short-term use but impart significant morbidity when used over longer periods. These issues were addressed by the designing of a low-resistance ETT. METHODS: Using new techniques, we developed ultrathin-walled, wire reinforced ETTs of conventional configuration and ETTs the oropharyngeal-section diameter of which was a few millimeters larger than the diameter of the tracheal section. The wall thickness was a constant 0.20 mm. The wire reinforcement was stainless steel flat wire or superelastic nickel-titanium alloy. The superelastic nickel-titanium alloy reinforcement made those ETTs crush-proof; after forceful manual compression, recovery was complete. To obtain a seal with the upper airways, we first shaped a short section of the oropharyngeal section of the ETT from round to oval (or egg-shaped) to conform better to the larynx. We then attached to this segment numerous soft, pliable, 0.025-0.075-mm-thick rings of polyurethane to occlude voids for potential air leaks from within the larynx. RESULTS: In vitro pressure-flow studies showed a decrease by as much as four- or fivefold in air-flow resistance in the adult ETT range, effectively increasing the internal diameter by 2.3-3.7 mm, compared with conventional ETTs of the same outside diameter. In vivo studies for 24 h in sheep showed no air leaks at airway pressures to 30 cmH2O and minimal leak at greater pressures. The gross appearance of the trachea was normal. CONCLUSIONS: Although the new tubes appear to offer advantages to those currently used, testing in humans is required to assess the clinical utility of the tube-cuff design.

Anesthesia, Endotracheal↗
PubMed1994

Intratracheal pulmonary ventilation (ITPV): control of positive end-expiratory pressure at the level of the carina through the use of a novel ITPV catheter design.

A new mode of pulmonary ventilation called intratracheal pulmonary ventilation (ITPV) was studied. Briefly, a continuous flow of air/oxygen is introduced through a small catheter, the tip of which is positioned at the carina, with a diffuser mounted at its distal end. A timed expiration valve, when closed, provides for inspiration; when open, it provides for expiration. The system as first described had a potential for significant back pressure at the level of the carina, which was more at rapid gas flows and with smaller endotracheal tubes. We have now mounted a venturi on the tip of the catheter (reverse thrust catheter [RTC]) that avoids back pressure, and which facilitates expiration. At respiratory rates from 10 to 120/min, the ITPV system with the RTC maintained end-expiratory pressure at the level of the carina at, or near 0 cm H2O. Compared to conventional mechanical ventilation, at identical respiratory rates, this system reduced tidal volume by one half at the lowest respiratory rates, and by as much as two thirds at the highest respiratory rates, with a proportional decrease in peak inspiratory pressure. ITPV has the smallest minute volume ventilation of any conventional or nonconventional mode of pulmonary ventilation.

Animals↗
PubMed1993

How to ventilate lungs as small as 12.5% of normal: the new technique of intratracheal pulmonary ventilation.

We wished to determine in a laboratory animal model how much residual lung was needed to sustain total gas exchange. In a series of young, healthy lambs weighing approximately 10 kg that were sedated and paralyzed, we progressively excluded from gas exchange all the left lung (a total of 43%), plus the right lower and cardiac lobes (81%), plus the right middle lobe (87.5%). In some studies, the respective lobes were surgically removed; in others, the bronchi and the pulmonary arteries to the respective lobes were ligated. We provided pulmonary ventilation using the pressure control mode (Servo 900 C) at a tidal volume of 20 mL/kg multiplied by the fraction of the remaining lungs, a respiratory rate up to 120/min, a peak inspiratory pressure of 12-15 cm H2O, and a positive end-expiratory pressure of 3 cm H2O. Those lambs with at least both the right upper lobe (RUL) and right middle lobe remaining (19% of total lungs) were weaned to room air on mechanical ventilation within 48 h. Ventilating RUL (12.5% of remaining lung) with the same ventilator required a substantially higher tidal volume and peak inspiratory pressure to result in adequate alveolar ventilation but led to respiratory failure and death within 8 h. We then applied a newly developed system of intratracheal pulmonary ventilation to ventilate the RUL (12.5% of remaining lung) alone. A continuous flow of humidified mixture of air and oxygen was directly passed into the trachea at the level of the carina through a diffuser at a tidal volume of 2.5 mL/kg. A single valve controlled expiration and respiratory rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

[Acute respiratory failure--support of gas exchange using extracorporeal or implanted oxygenators--present status and future development].

In acute respiratory failure gas exchange can be supported or even maintained in an "alternative" way to mechanical ventilation using extracorporeal techniques (extracorporeal membrane oxygenation ECMO, extracorporeal CO2-removal ECCO2R), or intravenacaval oxygenators (IVOX). These techniques, which are currently in use in neonatology, pediatrics, and adult intensive care medicine, or techniques at present in clinical evaluation (IVOX), are reviewed with their indications, contraindications, differences, problems, worldwide results, and possible future applications.

Acute Disease↗
PubMed1991

Histopathologic pulmonary changes from mechanical ventilation at high peak airway pressures.

We investigated the histopathologic pulmonary changes induced by mechanical pulmonary ventilation (MV) with a high peak airway pressure and a large tidal volume in healthy baby pigs. Eleven animals were mechanically ventilated at a peak inspiratory pressure (PIP) of 40 cm H2O, a respiratory rate (RR) of 20 min-1, a positive end-expiratory pressure (PEEP) of 3 to 5 cm H2O, and an FIO2 of 0.4. High airway pressure MV was terminated in 22 +/- 11 h because of severe hypoxemia in the animals. Five of the baby pigs were killed for gross and light microscope studies. The pulmonary changes consisted of alveolar hemorrhage, alveolar neutrophil infiltration, alveolar macrophage and type II pneumocyte proliferation, interstitial congestion and thickening, interstitial lymphocyte infiltration, emphysematous change, and hyaline membrane formation. Those lesions were similar to that seen in the early stage of the adult respiratory distress syndrome (ARDS). The remaining six animals were treated for 3 to 6 days with conventional respiratory care with appropriate ventilator settings. Prominent organized alveolar exudate in addition to lesions was also found in the five animals. These findings were indistinguishable from the clinical late stage of ARDS. Six control animals were mechanically ventilated at a PIP of less than 18 cm H2O, a RR of 20 min-1, a PEEP of 3 to 5 cm H2O, and an FIO2 of 0.4 for 48 h. They showed no notable changes in lung functions and histopathologic findings. Aggressive MV with a high PIP is often applied to patients with respiratory distress to attain adequate pulmonary gas exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Acute lung injury from mechanical ventilation at moderately high airway pressures.

We have explored adverse pulmonary effects of mechanical ventilation at a peak inspiratory pressure of 30 cmH2O in paralyzed and anesthetized healthy sheep. A control group of eight sheep (group A) was mechanically ventilated with 40% oxygen at a tidal volume of 10 ml/kg, a frequency of 15 breaths/min, a peak inspiratory pressure less than 18 cmH2O, and a positive end-expiratory pressure of 3-5 cmH2O. During the ensuing 48 h, there were no measurable deleterious changes in lung function or arterial blood gases. Another 19 sheep were ventilated with 40% oxygen at a peak inspiratory pressure of 30 cmH2O under a different set of conditions and were randomly assigned to two groups. In group B, the respiratory rate was kept near 4 breaths/min to keep arterial PCO2 in the normal range; in group C, the frequency was kept near 15 breaths/min by including a variable dead space in the ventilator circuit to keep arterial PCO2 near baseline values. There was a progressive deterioration in total static lung compliance, functional residual capacity, and arterial blood gases. After some hours, there were abnormal chest roentgenographic changes. At time of death we found severe pulmonary atelectasis, increased wet lung weight, and an increase in the minimum surface tension of saline lung lavage fluid.

Air Pressure↗
PubMed1990

Long-term cardiopulmonary bypass by peripheral cannulation in a model of total heart failure. The decompression of the left heart through a percutaneous helical spring positioned within the lumen of the tricuspid and pulmonary artery valves.

We performed long-term closed-chest cardiopulmonary bypass in an animal model of total heart failure (induced ventricular fibrillation). The extracorporeal system included a venous reservoir, a roller pump, a membrane lung, and a blood pulsator system. We cannulated the right external jugular vein for venous drainage and the right subclavian artery for arterial return. To decompress the left heart we passed by percutaneous cannulation a special helical spring mounted on a Swan-Ganz catheter (Baxter Edwards Divisions, Irvine, Calif.) and positioned it to rest within the pulmonary artery and tricuspid valves, which rendered them partly incompetent. After induced ventricular fibrillation, blood flow was raised to keep the central venous pressure at baseline values. The lungs were ventilated with 5% carbon dioxide in room air. During bypass, mean pulmonary artery pressure was 10.0 +/- 1.7 mm Hg, mean wedge pressure 11.9 +/- 1.8 mm Hg, and mean blood pressure 95.2 +/- 5.6 mm Hg. After 2 days (four animals) and 3 days (two animals) the hearts were defibrillated. There was immediate ejection from both sides of the heart. All sheep were weaned from bypass within 29 +/- 11 minutes and their lungs were ventilated with room air within 42 +/- 34 minutes. At autopsy hearts and lungs grossly appeared normal. We conclude that the percutaneous helical spring resting within right heart valves provided excellent decompression throughout the study, with full recovery of heart and lung function on defibrillation.

Animals↗
PubMed1989

A stopped-flow mixer device for a batch microcalorimeter application to NAD-NADase reaction.

A new molded polypropylene, diamond-like carbon (DLC)-coated mixing cell has been developed for use in the batch microcalorimeter. Reagent volume can be varied from 25 microliters to 100 microliters. A 10 microcalorie reaction heat can be measured to 5%. Repeat reactions can be done as often as every 10 min for a fast reaction. Reactions can be started within 1 h or less after loading. A pre-equilibrator and a temperature-controlled syringe drive unit permit solutions to be stored at 4 degrees C while being run at any temperature from -20 degrees C to 40 degrees C. The kinetics and enthalpy of reaction of NAD-NADase have been measured. delta H is about 21 kcal/mol endothermic.

Calorimetry↗
PubMed1988

Acute respiratory failure following pharmacologically induced hyperventilation: an experimental animal study.

The pulmonary effects of hyperventilation following infusion of sodium salicylate into the cisterna magna was studied in 16 spontaneously breathing adult sheep. We found a fall in PaO2, a decrease in the static compliance of the respiratory system, abnormal chest roentgenographic films, and grossly abnormal lungs following 3.5 to 13 h of hyperventilation. A control group of 15 sheep (10 sheep similarly injected with sodium salicylate, but then sedated and paralyzed and ventilated at normal tidal volume and respiratory rate on a mechanical ventilator, and 5 sheep infused with saline alone and breathing spontaneously) showed no pulmonary or arterial blood gas abnormalities. We conclude that prolonged hyperventilation under the conditions of this experiment precipitated events that resulted in acute lung injury.

Animals↗
PubMed1988

Severe acute respiratory failure managed with continuous positive airway pressure and partial extracorporeal carbon dioxide removal by an artificial membrane lung. A controlled, randomized animal study.

Using an animal model of acute respiratory failure (ARF), we evaluated two treatments: conventional mechanical pulmonary ventilation (MV) and continuous positive airway pressure (CPAP) with extracorporeal removal of CO2 by an artificial membrane lung. We developed a model of "mild" ARF and a model of "severe" ARF after ventilating healthy sheep at a peak inspiratory pressure of 50 cm H2O for various lengths of time. Sheep from either injury models were randomly assigned to one of the above treatment groups. All 16 sheep from the model with "severe" ARF died, with progressive deterioration in pulmonary function and multiorgan failure irrespective of the treatment. Of 11 sheep from the model with "mild" ARF treated by MV, only three survived, whereas all 11 sheep from the model with "mild" ARF treated with CPAP and extracorporeal removal of CO2 responded well, and nine sheep ultimately recovered. We conclude that CPAP with extracorporeal removal of CO2 provided a better environment for the recovery in our model with "mild" ARF than the conventional arrangement centered on MV alone. Our studies also suggest that lung injury can progress (i.e., model with "severe" ARF) to where neither of the two treatments can succeed.

Acute Disease↗
PubMed1987

Enhancement of lung conditioning by acetylcholine in the prevention of respiratory distress syndrome in the preterm fetal lamb.

We exposed 128- to 130-day-gestation fetal lambs by cesarean section leaving the umbilical cord and placenta undisturbed, and we then treated the lungs with pulmonary conditioning (i.e., repeated prolonged inflations to 35 cm H2O, followed by a continuous positive airway pressure of 15 cm H2O). To investigate the added effect of pulmonary vasodilation upon the increase of total compliance and pulmonary oxygen uptake, we also administered acetylcholine intravenously at a rate of 80 micrograms min-1. Eleven of 13 lambs met the endpoint criteria of either compliance (0.5 ml [cm H2O]-1 kg-1; 1 animal), or pulmonary oxygen uptake (6 ml kg-1 min-1; 6 animals), or both (4 animals), and were delivered within 0.6 +/- 0.3 h. This time was significantly (p less than 0.05) shorter than previously seen in similar studies without the infusion of a vasodilator; all animals so delivered survived 24 h of mechanical ventilation in excellent health. We suggest that pharmacologic pulmonary vasodilation, in addition to deep sustained pulmonary insufflation and distension, is an effective and rapid means of transforming stiff immature lungs into lungs that can sustain normal ventilation and gas exchange.

Acetylcholine↗
PubMed1987

Severe impairment in lung function induced by high peak airway pressure during mechanical ventilation. An experimental study.

We explored the pulmonary effects of continuous mechanical ventilation (MV) at a peak inspiratory pressure of 50 cm H2O in healthy, paralyzed, and anesthetized adult sheep during a period of 48 h. The 9 control sheep (Group A) were ventilated with 40% oxygen at a tidal volume of about 10 ml/kg and a peak inspiratory pressure of 15 to 20 cm H2O. All these animals remained stable throughout the 48 h of MV with no change in lung function. The 7 sheep in Group B were ventilated with 40% oxygen using a pressure-controlled ventilator at 50 cm H2O peak inspiratory pressure, at a VT of 50 to 70 ml/kg. All sheep in Group B developed severe respiratory failure and died or were killed within 2 to 35 h, and showed parenchymal consolidation at autopsy. The 9 sheep in Group C were ventilated as in Group B, except that 3.8% CO2 was added to the inspired gases: the Group C animals deteriorated more slowly, with little change in PaO2 but with a severely reduced FRC, VT, total static lung compliance, and grossly abnormal lungs at autopsy. We conclude that in this model, mechanical ventilation at peak airway pressure of 50 cm H2O will lead to progressive impairment in pulmonary mechanics, lung function, acute respiratory failure, and alveolar cellular dysfunction, as demonstrated by highly abnormal minimal surface tension values of saline lung lavage fluid in both study groups.

Animals↗
PubMed1987

ECMO revisited.

Explore the source record for details and available documents.

Humans↗
PubMed1986

Successful treatment of experimental neonatal respiratory failure using extracorporeal membrane lung assist.

A total of 44 preterm fetal lambs at great risk of developing respiratory failure were delivered by Cesarean section, and were then managed on conventional mechanical pulmonary ventilation. Fifteen animals initially fared well, and 14 of these were long term survivors. Twenty-nine other lambs showed a progressive deterioration in arterial blood gases within 30 minutes of delivery, of which 10 lambs were continued on mechanical pulmonary ventilation (20% survival), while the remaining 19 lambs were placed on an extracorporeal membrane lung respiratory assist (79% survival). Extracorporeal membrane lung bypass rapidly corrected arterial blood gas values, and permitted the use of high levels of CPAP instead of the continuation of mechanical pulmonary ventilation at high peak airway pressures. Improvement in lung function was gradual, and predictable. Early institution of extracorporeal respiratory assist using a membrane artificial lung rapidly corrected arterial blood gas values and significantly improved on neonate survival.

Animals↗