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S A Loer

Publications and source records attributed to S A Loer.

At least 19 recordsLinked to original sources
PubMed2006

Closed system anaesthesia--historical aspects and recent developments.

Closed circuit anaesthesia was described decades ago but did not achieve wide popularity among anaesthesiologists mainly because reliable control of inspiratory gas concentrations was not possible. Recent innovations including fast gas analysers, electronically controlled dosage systems and algorithms for feedback control have made possible the development of sophisticated closed circuit ventilators designed for routine clinical practice. The main advantages comprise economic use of medical gases and volatile anaesthetics, reduction of anaesthetic gas loss into the atmosphere, improved airway acclimatization as well as estimations of oxygen consumption. This article reviews historical aspects, recent developments as well as advantages and limitations of closed system anaesthesia.

Anesthesia, Closed-Circuit↗
PubMed2006

Partial liquid ventilation: effects of closed breathing systems, heat-and-moisture-exchangers and sodalime absorbers on perfluorocarbon evaporation.

BACKGROUND AND OBJECTIVES: During partial liquid ventilation perfluorocarbons are instilled into the airways from where they subsequently evaporate via the bronchial system. This process is influenced by multiple factors, such as the vapour pressure of the perfluorocarbons, the instilled volume, intrapulmonary perfluorocarbon distribution, postural positioning and ventilatory settings. In our study we compared the effects of open and closed breathing systems, a heat-and-moisture-exchanger and a sodalime absorber on perfluorocarbon evaporation during partial liquid ventilation. METHODS: Isolated rat lungs were suspended from a force transducer. After intratracheal perfluorocarbon instillation (10 mL kg(-1)) the lungs were either ventilated with an open breathing system (n = 6), a closed breathing system (n = 6), an open breathing system with an integrated heat-and-moisture-exchanger (n = 6), an open breathing system with an integrated sodalime absorber (n = 6), or a closed breathing system with an integrated heat-and-moisture-exchanger and a sodalime absorber (n = 6). Evaporative perfluorocarbon elimination was determined gravimetrically. RESULTS: When compared to the elimination half-life in an open breathing system (1.2 +/- 0.07 h), elimination half-life was longer with a closed system (6.4 +/- 0.9 h, P 0.05) when compared to a closed system. CONCLUSIONS: Evaporative perfluorocarbon loss can be reduced effectively with closed breathing systems, followed by the use of sodalime absorbers and heat-and-moisture-exchangers.

Absorption↗
PubMed2006

[Carbon monoxide: toxic molecule with antiinflammatory and cytoprotective properties].

Carbon monoxide arises during incomplete combustion of organic material, is incorporated into the circulation via the lungs and displaces oxygen from hemoglobin. Consecutively, symptoms of intoxication such as headache, vertigo, nausea, seizures and coma may result in a dose dependent fashion. Carbon monoxide is however also generated endogenously during heme degradation catalysed by heme oxgenase enzymes. The isoform hemeoxygenase-1 is inducible by oxidative stress and may mediate cytoprotection mainly attributable to endogenously produced carbon monoxide. Exogenous applied carbon monoxide has also been shown to confer protection in experimental studies. Meanwhile, in addition to the toxicological properties, antiinflammatory and cytoprotective effects of carbon monoxide have moved into the focus of scientific interest.

Animals↗
PubMed2005

Transfusion-related acute lung injury: lack of recognition because of unawareness of this complication?

BACKGROUND AND OBJECTIVE: Transfusion of blood components can trigger immunological reactions which may result in a transfusion-related acute lung injury (TRALI). The reported incidence is low; however, there is increasing evidence that the true incidence of this complication may be much higher. One reason for underdiagnosing TRALI could be a deficiency of knowledge about this complication. Therefore, we studied the level of knowledge concerning TRALI among clinicians working on intensive care units (ICU) of an university teaching hospital. METHODS: A total of 65 clinicians were asked to complete a confidential questionnaire designed to evaluate their knowledge about incidence, pathophysiology, clinical symptoms, therapy and outcome of TRALI. This questionnaire consisted of 13 questions which could be assessed by 'yes', 'no' or 'do not know'. RESULTS: Only 42 +/- 18% (mean +/- SD) of all answers were correct, while 33 +/- 17% were wrong and 25 +/- 8% unanswered ('do not know'). The 95% confidence interval for the correct answers was 30.8-53.8% implying that there was no significant difference compared to the probability of arbitrary guessing (33.3%). CONCLUSIONS: Our survey uncovered a marked deficit of knowledge about TRALI suggesting that the low reported incidence of this complication may be in part due to a lack of awareness for TRALI. We conclude that training programmes for clinicians should alert them to the symptoms, diagnosis and treatment options of TRALI.

Blood Component Transfusion↗
PubMed2005

Partial liquid ventilation in acute salt water-induced lung injury.

BACKGROUND AND OBJECTIVES: Salt-water aspiration results in pulmonary oedema and hypoxia. We tested the hypothesis that partial liquid ventilation has beneficial effects on gas exchange and rate of survival in acute and extended salt water-induced lung injury. METHODS: Anaesthetized, ventilated rats (tidal volume 6 mL kg(-1), PEEP 5 cmH2O) received a tracheal salt-water instillation (3%, 8 mL kg(-1) body weight) and were randomly assigned to three groups (n = 10 per group). While lungs of Group 1 were gas-ventilated, lungs of Group 2 received a single perfluorocarbon instillation (30 min after the injury, 5 mL kg(-1) perfluorocarbon) and lungs of Group 3 received an additional continuous perfluorocarbon application into the treachea (5 mL kg(-1) h(-1)) Arterial blood gases were measured with an intravascular blood gas sensor. RESULTS: Salt-water instillation resulted in a marked decrease in PaO2 values within 30 min (from 432 +/- 65 to 83 +/- 40 mmHg, FiO2 = 1.0, P < 0.01). Arterial oxygenation improved in all three groups irrespective of treatment. We observed no significant differences between groups in peak PaO2 and PaCO2 values. CONCLUSIONS: Our results suggest that partial liquid ventilation has no additional beneficial effects on gas exchange after life-threatening salt water-induced lung injury when compared to conventional gas ventilation with positive end-expiratory pressure.

Anesthesia↗
PubMed2004

Continuous intra-arterial blood gas monitoring in rats.

Studies on lung injury and its treatment options are often performed on small animals like rats. Because conventional blood gas analyses may not detect rapid changes in gas exchange during respiratory distress syndrome and intermittent blood withdrawal can result in hypo-volaemia and anaemia, we tested the applicability and accuracy of a continuous intravascular blood gas monitor (Paratrend 7+). Anaesthetized and ventilated rats with a body weight of 398 +/-45 g (n =22) had a 20-gauge cannula inserted in both carotid arteries. A photochemical blood gas sensor for continuous measurement (Paratrend 7+) was advanced into the aorta via the left carotid artery. Blood was sampled for intermittent blood gas analysis by means of the right carotid artery. Arterial pO(2) was varied by applying different inspiratory oxygen concentrations, and arterial pCO(2) by applying different respiratory rates. Paired blood gas measurements (n =136) were analysed over a wide range of pO(2) values (5.3-76.8 kPa). We found an acceptable correlation for pO(2) (r(2)=0.98), pCO(2) (r(2)=0.96) and pH (r(2)=0.92). The calculated bias and imprecision for pO(2) was -1.0 +/- 3.3 kPa, for pCO(2) 0.04 +/- 0.28 kPa and for hydrogen ion concentration -0.05 +/-2.2 nmol/l. We conclude that in rats, continuous blood gas monitoring with a photochemical blood gas sensor provides pO(2), pCO(2) and pH measurements with acceptable accuracy.

Animals↗
PubMed2002

Nasal CPAP therapy: effects of different CPAP levels on pressure transmission into the trachea and pulmonary oxygen transfer.

BACKGROUND: Nasal continuous positive airway pressure (nCPAP) is considered useful for prophylaxis and treatment of respiratory complications following major thoracic surgery. It is unknown, however, which CPAP levels are required to avoid alveolar derecruitment and to consistently improve pulmonary oxygen transfer in patients following thoracotomy. We therefore studied the effects of different nCPAP levels on pressure transmission into the trachea as well as on pulmonary oxygen transfer. METHODS: In 10 consecutive patients after cardiac or thoracic vascular surgery, following extubation in the ICU, nCPAP was generated by means of a high-flow gas source and applied randomly at levels of 5 or 10 cm H2O. Airway pressure was recorded continuously in the nasal mask and the trachea. The PaO2/FiO2ratio was calculated from the tracheal oxygen concentration, and PaO2 was determined while breathing at an ambient and elevated airway pressure. Haemodynamic variables (heart rate, arterial blood pressure, central venous pressure) were also recorded. RESULTS: Mean pressures in the nasal mask were 5.4+/-0.1 and 9.7+/-0.3 cm H2O. Corresponding tracheal pressures were 2.8+/-1.0 vs. 7.2+/-1.1 cm H2O (P=0.007). With higher mask pressure, the fraction of pressure transferred from the nasal mask into the trachea was larger (0.75+/-0.03 vs. 0.52+/-0.05; P=0.04), and tracheal pressures remained positive during the entire respiratory cycle in all patients. In contrast, with 5.4 cm H20, negative pressure changes during inspiration occurred in five out of 10 patients. The PaO2/FiO2 ratio increased from 183+/-53 (ambient pressure) to 199+/-74 (nCPAP 5.4 cm H2O; P=0.25) and to 333+/-54 (nCPAP 9.7 cm H2O; P=0.003). Nasal CPAP did not alter hemodynamics. CONCLUSION: Nasal CPAP is an effective non-invasive means of increasing tracheal and thus intrathoracic pressure without adverse hemodynamic effects. Only mask pressures of 9-10 cm H2O were sufficient to consistently improve pulmonary oxygen transfer in patients following thoracotomy.

Aged↗
PubMed2002

Partial liquid ventilation: effects of liquid volume and ventilatory settings on perfluorocarbon evaporation.

During partial liquid ventilation perfluorocarbons are eliminated mainly by evaporation via the airways. The effects of intrapulmonary perfluorocarbon volume, respiratory rate, tidal volume, as well as the level of end-expiratory pressure on perfluorocarbon elimination from isolated lungs, were studied. Nonperfused rabbit lungs underwent partial liquid ventilation (2-15 mL x kg(-1) perfluorocarbon) with variable levels of end-expiratory pressure (0-10 cmH2O), respiratory rates (15-60 breaths x min(-1)) and tidal volumes (3.3-10.0 mL x kg(-1)). Evaporative loss of perfluorocarbon was determined gravimetrically as rate of change in lung weight. At constant respiratory settings, intrapulmonary liquid volume determined evaporative loss in a nonlinear fashion. Mean evaporation at a liquid volume of 5 mL x kg(-1) was 13% lower compared to evaporation at a liquid volume of 15 mL x kg(-1). Any increase in end-expiratory pressure reduced perfluorocarbon evaporation, e.g. by approximately 50% when end-expiratory pressure was increased from 0 to 10 cmH2O. At constant end-expiratory pressure and perfluorocarbon filling evaporation increased in a linear fashion with increasing respiratory rate and tidal volume. In summary, the experiments suggested that evaporative loss of perfluorocarbons during partial liquid ventilation of isolated lungs is increased with increasing intrapulmonary liquid volume, respiratory rate and tidal volume and is reduced in a level-dependent fashion by the application of positive end-expiratory pressure.

Animals↗
PubMed2001

Partial liquid ventilation reduces fluid filtration of isolated rabbit lungs with acute hydrochloric acid-induced edema.

BACKGROUND: Hydrochloric acid aspiration increases pulmonary microvascular permeability. The authors tested the hypothesis that partial liquid ventilation has a beneficial effect on filtration coefficients in acute acid-induced lung injury. METHODS: Isolated blood-perfused rabbit lungs were assigned randomly to one of four groups. Group 1 (n = 6) served as a control group without edema. In group 2 (n = 6), group 3 (n = 6), and group 4 (n = 6), pulmonary edema was induced by intratracheal instillation of hydrochloric acid (0.1 N, 2 ml/kg body weight). Filtration coefficients were determined 30 min after this injury (by measuring loss of perfusate after increase of left atrial pressure). Group 2 lungs were gas ventilated, and group 3 lungs received partial liquid ventilation (15 ml perfluorocarbon/kg body weight). In group 4 lungs, the authors studied the immediate effects of bronchial perfluorocarbon instillation on ongoing filtration. RESULTS: Intratracheal instillation of hydrochloric acid markedly increased filtration coefficients when compared with non-injured control lungs (2.3 +/- 0.7 vs. 0.31 +/- 0.08 ml.min(-1). mmHg(-1).100 g(-1) wet lung weight, P < 0.01). Partial liquid ventilation reduced filtration coefficients of the injured lungs (to 0.9 +/- 0.3 ml.min(-1).mmHg(-1).100 g(-1) wet lung weight, P = 0.022). Neither pulmonary artery nor capillary pressures (determined by simultaneous occlusion of inflow and outflow of the pulmonary circulation) were changed by hydrochloric acid instillation or by partial liquid ventilation. During ongoing filtration, bronchial perfluorocarbon instillation (5 ml/kg body weight) immediately reduced the amount of filtered fluid by approximately 50% (P = 0.027). CONCLUSIONS: In the acute phase after acid injury, partial liquid ventilation reduced pathologic fluid filtration. This effect started immediately after bronchial perfluorocarbon instillation and was not associated with changes in mean pulmonary artery, capillary, or airway pressures. The authors suggest that in the early phase of acid injury, reduction of fluid filtration contributes to the beneficial effects of partial liquid ventilation on gas exchange and lung mechanics.

Animals↗
PubMed2000

Effects of haemoconcentration and haemodilution on acute hypoxia-induced pulmonary hypertension and changes in vascular compliance of isolated rabbit lungs.

OBJECTIVE: Erythrocytes influence the magnitude of hypoxia-induced pulmonary artery pressure increase. It is, however, unknown to what extent haemoconcentration and haemodilution affect this response and whether intrapulmonary blood volume (and thus vessel dimensions) alters the magnitude of pressure increase. Furthermore, it is unclear whether the haemodilution/ haemoconcentration-dependent pressure increase is flow-related, via flow-dependent changes in vasomotor tone or rheologic effects, or can also be observed under no-flow conditions. DESIGN: Experimental study in isolated rabbit lungs (n = 12) perfused with autologous blood at constant flow (100 ml/min) and ventilated with 5% carbon dioxide in air. SETTING: Laboratory for experimental studies. INTERVENTIONS: Haemoconcentration (centrifugation) and haemodilution (Krebs-Henseleit/albumin) were carried out, resulting in haematocrits between 50% and 0%. During hypoxic ventilation, inspiratory oxygen fraction was reduced from 0.20 to 0.03. MEASUREMENTS AND RESULTS: Under constant flow conditions, haemodilution (from a Hct of 34-36% to 0-1%) decreased hypoxic pulmonary artery pressure response to one-third (from 10.8 +/- 2.3 cmH2O to 3.1 +/- 1.0 cmH2O, P < 0.05), while haemoconcentration did not affect the magnitude of hypoxic response (10.5 +/- 2.0 cmH2O). For all haematocrit values an increase in pulmonary blood volume (by 5 ml) decreased the magnitude of pressure response. Hypoxia-induced changes in static vascular filling pressure (double occlusion pressure) and vascular compliance were used to assess the strength of hypoxic vasoconstriction under static conditions. Neither haemoconcentration nor haemodilution altered hypoxia-induced changes in either variable. CONCLUSIONS: The magnitude of the acute hypoxic pressure response is not altered by haemoconcentration, but significantly reduced by haemodilution. In contrast, neither haemoconcentration nor haemodilution influenced hypoxia-induced changes in static vascular filling pressure and compliance. This suggests that the degree of hypoxic pulmonary vasoconstriction is not affected under static conditions and that the red blood cell-dependence of the magnitude of hypoxic pressure response is based on flow-related mechanisms.

Analysis of Variance↗
PubMed2000

Effects of ventilation and nonventilation on pulmonary venous blood gases and markers of lung hypoxia in humans undergoing total cardiopulmonary bypass.

OBJECTIVE: To assess the effects of lung oxygenation and ventilation vs. lung collapse on pulmonary markers of lung hypoxia. DESIGN: A prospective, nonrandomized, nonblinded comparative study. SETTING: University department of anesthesiology and cardiothoracic surgery. SUBJECTS: Twelve adult patients undergoing coronary bypass grafting requiring total cardiopulmonary bypass. INTERVENTIONS: Single lung ventilation during total cardiopulmonary bypass (tidal volume, 150 mL; respiratory rate, 6 breaths/min; inspiratory oxygen fraction, 0.5) while the contralateral lung was allowed to collapse completely without oxygenation. MEASUREMENTS AND MAIN RESULTS: At the beginning and at the end of total cardiopulmonary bypass (duration, 59-65 mins), blood was aspirated from the right and left pulmonary veins and the radial artery for measurement of blood gases and concentrations of endothelin-1, big-endothelin, thromboxane B2, lactate, and lactate dehydrogenase. Nonventilation during total cardiopulmonary bypass compared with ventilation resulted in lower pulmonary venous P(O2) values (57+/-15 torr [7.6+/-2.0 kPa] vs. 103+/-23 torr [13.7+/-3.1 kPa]) and higher thromboxane B2 concentrations (488+/-95 pg/mL vs. 434+/-92 pg/mL). The concentrations of endothelin-1, big-endothelin, lactate, and lactate dehydrogenase in the pulmonary veins did not differ significantly between nonventilated and ventilated lungs. CONCLUSIONS: Development of pulmonary tissue hypoxia during 1 hr of nonventilation and cardiopulmonary bypass with completely inhibited pulmonary arterial blood flow is unlikely, suggesting that enough oxygen is stored in or is provided to the collapsed lung. Thus, nonventilation during total cardiopulmonary bypass does not appear to contribute to postoperative respiratory dysfunction by causing pulmonary tissue hypoxia. These results, however, do not exclude that mechanical factors of ventilation might benefit the lung during cardiopulmonary bypass.

Adult↗
PubMed2000

Effects of partial liquid ventilation on regional pulmonary blood flow distribution of isolated rabbit lungs.

OBJECTIVE: Partial liquid ventilation with perfluorocarbons may increase alveolar hydrostatic transmural pressure and may result in a redistribution of pulmonary blood flow from dependent to nondependent lung regions. To test this hypothesis under controlled study conditions, we determined intrapulmonary blood flow distributions during gas and perfluorocarbon ventilation in isolated rabbit lungs. DESIGN: Controlled animal study with an ex vivo isolated lung preparation. SETTING: Research laboratory for Experimental Anesthesiology at the Heinrich-Heine-University of Düsseldorf. SUBJECTS: New Zealand White rabbits. INTERVENTIONS: The lungs were perfused with autologous blood at constant flow (150 mL/min) and ventilated with 5% C(O2) in air (positive end-expiratory pressure, 2 cm H2O; tidal volume, 10 mL/kg body weight; respiratory rate, 30 breaths/ min) without and with perfluorocarbon administered intratracheally (15 mL/kg). MEASUREMENTS AND MAIN RESULTS: Regional lung perfusion was measured with colored microspheres in apical, central, peripheral, and basal samples before and after bronchial instillation of perfluorocarbons. Compared with gas ventilation, intrapulmonary blood flow during perfluorocarbon ventilation was higher in apical samples (49.4+/-8.6 mL/min/g vs. 38.3+/-6.8 mL/min/g dry weight; p = .03) and lower in basal samples (22.2+/-5.1 mL/min/g vs. 39.9+/-8.2 mL/min/g; p = .04). CONCLUSIONS: Our findings suggest that during partial liquid ventilation, intrapulmonary blood flow is redistributed toward less-dependent lung regions. (Crit Care Med 2000; 28:1522-1525)

Animals↗
PubMed1999

Does bronchial thermodilution allow estimation of cardiac output?

OBJECTIVE: Transcapillary heat transfer after injections of cold saline into the right atrium generates bronchial thermodilution curves resembling those observed in the aorta. Under the assumption that no indicator is lost or gained within the pulmonary capillary bed and changes in blood temperature are instantaneously recorded in the bronchial system, we tested the hypothesis that flow rates calculated from bronchial temperature-time curves are similar to those from aortic curves. DESIGN: Comparative study of two cardiac output estimates in five dogs. SETTING: Research laboratory for Experimental Anaesthesiology. INTERVENTIONS: Cardiac output was decreased (repeated withdrawal of blood) and increased (infusion of colloids or dobutamine) in order to study a wide range of cardiac outputs. MEASUREMENTS AND RESULTS: Thermistors were placed in a bronchiole (wedge position) and in the ascending aorta of anaesthetized dogs. Bronchial and aortic thermodilution curves were recorded after injection of 5 ml ice-cold saline into the right atrium. We found that bronchial thermodilution yields flow estimates similar to those from aortic curves. Correlation between the two flow estimates was acceptable (r = 0.84) with a mean difference between the two of less than 2%. CONCLUSION: We conclude that the Stewart-Hamilton equation may be extended to bronchial temperature-time curves for estimations of cardiac output. At this time, however, we do not advocate bronchial thermistors as suitable and less invasive alternatives to pulmonary arterial catheters for routine cardiac output measurements in patients.

Animals↗
PubMed1998

Pulmonary blood volume and its effects on pressure/flow relations and flow resistance in isolated lungs of rabbits.

Quantitative information about the effects of pulmonary blood volume (Qp) on pulmonary haemodynamics is lacking since Qp changes inevitably with flow. To separate flow-dependent from volume-dependent changes in intravascular pressures we imposed changes in Qp (measured continuously) by altering outflow pressure in seven isolated, blood-perfused rabbit lungs and studied the effects of Qp on the relations between arteriovenous pressure gradient (DeltaP) and blood flow (Q.) under two conditions: flow-dependent volume changes were either permitted or compensated. In the latter circumstances, DeltaP changed more for a given change in Q.. The DeltaP/Q. relations were shifted to smaller DeltaP when Qp was increased. Hence, the calculated flow resistance (R = DeltaP/Q.) decreased with increasing Qp at a given Q.. Assuming constant viscosity, changes in R can be predicted from changes in vessel geometry and thus Qp. We found that R increased less than expected (by a factor of 3-7.5 instead of 9) when Qp was reduced to one-third. This discrepancy may be explained by a change in blood distribution within the lung despite constant Qp and by a change in apparent blood viscosity with Q.. Regardless of these speculations we have shown that Qp determines DeltaP at each flow and thus flow resistance.

Animals↗
PubMed1998

Effects of partial liquid ventilation with perfluorocarbons on pressure-flow relationships, vascular compliance, and filtration coefficients of isolated blood-perfused rabbit lungs.

OBJECTIVES: The density of perfluorocarbons is almost twice that of blood. Therefore, we hypothesized that partial liquid ventilation with these fluids markedly affects pulmonary hemodynamics and filtration coefficients. To test these hypotheses we studied pressure-flow relationships, vascular compliances, capillary pressures, and filtration coefficients in normal and perfluorocarbon-ventilated rabbit lungs. DESIGN: Controlled animal study with an ex-vivo isolated lung preparation. SETTING: Research laboratory for experimental anesthesiology at the Heinrich-Heine-University of Düsseldorf. SUBJECTS: Fourteen New Zealand White rabbits. INTERVENTIONS: The lungs were perfused under zone 3 flow conditions with autologous blood at various flow rates (50 to 250 mL/min, closed circuit, roller pump, 37 degrees C) and ventilated with 5% CO2 in air (positive end-expiratory pressure: 2 cm H2O, tidal volume: 10 mL/kg, respiratory rate: 30 breaths/min) without (control group, n=7) and with (n=7) perfluorocarbon administered intratracheally (15 mL/kg). MEASUREMENTS AND MAIN RESULTS: Pulmonary arterial, left atrial, and airway pressures, as well as blood reservoir volume (reflecting changes in pulmonary blood volume) and lung weight, were measured continuously. Inconsistent with our hypothesis, we found no significant differences between both groups in the slopes and intercepts of the pressure-flow relationships. There were no significant differences in capillary pressures determined by double occlusion (6.7+/-1.2 vs. 6.3+/-1.3 cm H2O for control group, p=.53), vascular compliances (0.51+/-0.10 vs. 0.47+/-0.09 mL/cm H2O for control group, p=.38), and filtration coefficients (0.33+/-0.06 vs. 0.37+/-0.07 mL/min/mm Hg/100 g wet weight for control group, p=.80, Mann-Whitney). CONCLUSIONS: Partial liquid ventilation with perfluorocarbons has no relevant effects on pulmonary filtration coefficients and global hemodynamic variables of isolated zone 3 lungs. These findings suggest that right ventricular afterload is not changed with partial liquid ventilation. It is likely, however, that intrapulmonary blood flow is redistributed toward less-dependent regions, although relevant global hemodynamic changes are absent during partial liquid ventilation.

Animals↗
PubMed1998

Bronchial temperature reflects transcapillary heat transport of isolated blood-perfused rabbit lungs.

The pulmonary capillaries are in such close proximity to the terminal airways that changes in capillary blood temperature should also cause changes in bronchial wall temperature. Therefore, we hypothesized that injection of cold solutions into the pulmonary artery would yield bronchial temperature-time curves similar to those in the pulmonary artery and left atrium. These bronchial curves should mainly represent the capillary bed. Isolated rabbit lungs (n=8) were ventilated (5% CO2 in air) and perfused (autologous blood, 37 degrees C) at various flow rates (50-200 mL x min[-1]). Thermistor probes (diameter 0.46 mm) registered temperature changes in the pulmonary artery, at the bronchial wall (wedge position) and in the left atrium after injection of 0.8 mL Ringer's lactate (0 degrees C) into the pulmonary artery. Bronchial temperature-time curves were found to resemble "dilution" curves located between pulmonary arterial and left atrial curves. Independent of flow rate, their appearance times, peaks and calculated mean transit times were between those from the pulmonary artery and the left atrium. We conclude that bronchial temperature-time curves reflect transcapillary heat transport and that this approach might be useful in gaining further information about vascular transport processes in the interior of the lung.

Animals↗
PubMed1997

Bronchial temperature as a key to the interior pulmonary capillary bed of anaesthetized dogs.

The terminal airways are separated from the surrounding pulmonary capillaries by a tissue layer of a few micrometers in thickness only. Therefore, it should be possible to gain information about in vivo transcapillary heat transport of the interior pulmonary vascular bed by recording the terminal bronchial temperature. For this purpose, we studied temperature-time curves in the pulmonary artery, bronchial system and the aorta of six anaesthetized dogs permanently instrumented for measuring pulmonary blood flow. Thermistors recorded temperature changes at the three locations after injection of 5 ml cold solution into the right atrium. From the observed temperature-time curves mean transit times between the three recording sites were calculated for various pulmonary blood flows (integral of delta Ttdt/integral of delta Tdt) (range 1.1-3.5 1/ min). We found that the temperature-time curves of the bronchial system resemble typical "dilution" curves and are interspaced between those in the pulmonary artery and those in the aorta. Regardless of pulmonary blood flow, mean transit times from the pulmonary artery to the distal bronchial system and from there to the aorta were about equal. We conclude that transcapillary heat transfer generates bronchial temperature-time curves which permit an estimation of the relation of precapillary to postcapillary mean transit times in the interior of the lung.

Animals↗