Biomedical subjects

O Stenqvist

Publications and source records attributed to O Stenqvist.

At least 19 recordsLinked to original sources

PubMed1999

Decreased respiratory depression during emergence from anesthesia with sevoflurane/N2O than with sevoflurane alone.

PURPOSE: To investigate ventilation and gas elimination during the emergence from inhalational anesthesia with controlled normoventilation with either sevoflurane/N2O or sevoflurane alone. METHODS: Twenty-four ASA I-II patients scheduled for abdominal hysterectomy were randomly allocated to receive either 1.3 MAC sevoflurane/N2O (n = 12) or equi-MAC sevoflurane (n = 12) in 30% oxygen (O2). Expired minute ventilation volumes (V(E)), end-tidal (ET) concentrations of O2, carbon dioxide (CO2), sevoflurane and N2O as well as pulse oximetry saturation (SpO2) and CO2 elimination rates (VCO2) were measured. The ET concentrations of sevoflurane and N2O were converted to total MAC values and gas elimination was expressed in terms of MAC reduction. Time to resumption of spontaneous breathing and extubation were recorded and arterial blood gas analysis was performed at the end of controlled normoventilation and at the beginning of spontaneous breathing. RESULTS: Resumption of spontaneous breathing and extubation were 8 and 13 min less, respectively, in the sevoflurane/N2O than in the sevoflurane group. Spontaneous breathing was resumed in both groups when pH had decreased by 0.07-0.08 and PaCO2 increased by 1.3-1.5 kPa. Depression of V(E) and VCO2 were less, and MAC reduction more rapid in the sevoflurane/N2O than in the sevoflurane group. CONCLUSIONS: Respiratory recovery was faster after sevoflurane/N2O than sevoflurane anesthesia. Changes in pH and PaCO2 rather than absolute values were important for resumption of spontaneous breathing after controlled normoventilation. In both groups, the tracheas were extubated at about 0.2 MAC.

Adult↗

PubMed1999

Intraoperative glucose administration influences respiratory quotient during paediatric anaesthesia.

BACKGROUND: Oxidation of carbohydrates and fat yields respiratory quotients (RQ) of 1.0 and 0.7 respectively. Maintained or increased blood glucose concentrations are usually seen during paediatric anaesthesia and surgery even without glucose administration. The aim of the present study was to evaluate whether an intraoperative glucose infusion influences the RQ as an indication of a different metabolic preference in comparison to a glucose-free fluid regime. METHODS: Eighteen children between 0.5 and 24 months of age were studied during anaesthesia with controlled ventilation, oxygen in air, isoflurane, thiopentone, atracurium and fentanyl. Oxygen consumption and carbon dioxide production were measured using indirect calorimetry All children received Ringer acetate as needed; in addition, nine children were given glucose 10%, 3 ml.kg-1.h-1, corresponding to 300 mg.kg-1.h-1. Blood samples for analyses of glucose, lactate, free fatty acids and ketones were taken before and during surgery. RESULTS: RQ was significantly higher in the children given glucose 0.92 +/- 0.08, compared to 0.81 +/- 0.06 in the children without glucose (P < 0.01). Oxygen consumption tended to be higher, although not significantly so, in patients without glucose infusion. Energy expenditure was 1.70 +/- 0.29 kcal.kg-1.h-1, without significant group differences. Higher blood glucose concentrations during surgery were found in the children given glucose. CONCLUSIONS: Our results indicate a higher glucose oxidation rate in patients given glucose during surgery.

Anesthesia↗

PubMed1999

A simplified method for separate measurements of lung and chest wall mechanics in ventilator-treated patients.

BACKGROUND: Airway pressure measurements above the endotracheal tube will be distorted because of endotracheal tube resistance. To separate lung and chest wall compliance, esophageal pressure is conventionally measured with an air-filled balloon catheter, which is difficult to insert in unconscious patients. We have developed a methodology with fluid-filled catheters for intratracheal and esophageal pressure measurements. METHODS: Twelve anesthetized patients were studied. Tidal volumes were measured by side-stream spirometry. Airway pressures were measured at the Y-piece and in the trachea with fluid-filled pressure lines. Esophageal pressure was measured via the narrow lumen in a fluid-filled Salem double-lumen stomach tube, which was slowly retracted from the stomach up through the esophagus until maximal respiratory pressure readings and minimal cardiac artifacts were obtained. Lung mechanics were measured at different tidal volumes (TV) and positive end-expiratory pressure (PEEP). RESULTS: There was a significant difference between airway pressures at the Y-piece and in the trachea. Total compliance significantly increased with increasing TV and decreased with increasing PEEP. Chest wall compliance increased significantly with increasing TV, while lung compliance did not change significantly. Two patients showed repeatedly marked increase in lung compliance at one specific ventilatory setting, an increase the proportion of which was not reflected by changes in total compliance. CONCLUSIONS: Y-piece pressures are not representative of intratracheal pressures, which can be measured by inserting a fluid-filled pressure line through the tube. Esophageal pressure is easily recorded with a fluid-filled Salem double-lumen catheter. Large changes in lung compliance may pass unnoticed when only total compliance is monitored. Monitoring of lung compliance may offer an improved basis for decisions about ventilator settings.

Adult↗

PubMed1999

Luxury lung perfusion in end-stage liver disease during liver transplantation.

BACKGROUND: End-stage liver disease is accompanied by a hyperkinetic circulation sometimes combined with hypoxaemia. Nitric oxide overproduction has been described as a possible cause by dilating the vasculature and decreasing cardiac afterload. The aim of this study was to evaluate haemodynamics, ventilation/perfusion matching, alveolar and alveolar dead space ventilation and resistance of systemic and pulmonary vasculature during liver transplantation. METHODS: Ten liver transplantation patients were studied. Cardiac output, CO, was measured with thermodilution technique. Pulmonary shuntflow was calculated from standard formulas. Effective cardiac output, COeff, was defined as the CO in contact with alveolar ventilation, VA. Effective alveolar ventilation, VAeff, was defined as VA in contact with pulmonary circulation. Measurements were performed during dissection, anhepatic and reperfusion phases. RESULTS: During the dissection phase the shunt was 23 +/- 3%, COeff was 7.9 +/- 0.6 l/min, SVR was 620 +/- 67 dyn.s/cm5, VAeff was 3.4 +/- 0.5 l/min, SaO2 was 98 +/- 1% and SvO2 was 86 +/- 2%. Corresponding values during the anhepatic phase were 16 +/- 2%, 5.6 +/- 0.4 l/min, 931 +/- 78 dyn.s/cm5, 3.1 +/- 0.2 l/min, 99 +/- 1% and 88 +/- 1%. During the reperfusion phase the values returned to levels close to that of the dissection phase. The reduction of COeff between the dissection and the anhepatic phase was significant (P < 0.01). CONCLUSIONS: The low vascular resistance is accompanied by a high cardiac output. In spite of the high shunt fraction, these patients were not hypoxaemic. This is explained by the fact that the increased cardiac output leads to a decrease in arterio-mixed venous oxygen content difference and an increase in mixed venous oxygenation level, SvO2 86-88%, normal value approximately 70%. The VAeff/COeff in this study was approximately 0.5, i.e. the effective cardiac output, COeff is 235, 180 and 197% of the effective alveolar ventilation, VAeff during the three phases. Thus, about twice the amount blood is oxygenated as compared to a normodynamic situation, which compensates for the effect of the shunt flow on oxygenation.

Adult↗

PubMed1998

Evaluation of a Pitot type spirometer in helium/oxygen mixtures.

OBJECTIVE: Mixtures of helium and oxygen are regaining a place in the treatment of obstruction of the upper and lower respiratory tract. The parenchymal changes during the course of IRDS or ARDS may also benefit from the reintroduction of helium/oxygen. In order to monitor and document the effect of low-density gas mixtures, we evaluated the Datex AS/3 Side Stream Spirometry module with D-lite (Datex-Engstrom Instrumentarium Corporation, Finland) against two golden standards. METHODS: Under conditions simulating controlled and spontaneous ventilation with gas mixtures of He (approx. 80, 50, and 20%)/O2 or N2(approx. 21 and 79%)/02, simultaneous measurements using Biotek Ventilator Tester (Bio-Tek Instr., Vermont, USA) or body plethysmograph (SensorMedics System, Anaheim, USA) were correlated with data from the spirometry module. Data were analyzed according to a statistical regression model resulting in a best-fit equation based on density, voltage, and volume measurements. RESULTS: As expected, the D-lite (a modified Pitot tube) showed density-dependent behaviour. Regression equations and percentage deviation of estimated versus measured values were calculated. CONCLUSION: Measurements with the D-lite using low-density gases are satisfactorily contained in best-fit equations with a standard deviation of less than 5% during all ventilatory modes and mixtures.

Airway Obstruction↗

PubMed1998

Respiration during emergence from anaesthesia with desflurane/N2O vs. desflurane/air for gynaecological laparoscopy.

BACKGROUND: The complications related to anaesthesia usually occur in the early postoperative period. Hypercapnia and hypoxaemia may result from any persistent depression of the respiratory drive relative to the metabolic demand. The purpose of this study was to compare the respiratory effects of desflurane anaesthesia with or without nitrous oxide during the period of emergence. METHODS: Twenty patients scheduled for a standardised surgical procedure, laparoscopic hysterectomy, were randomly allocated to anaesthesia with 1.3 MAC of desflurane/N2O (Group 1) or desflurane alone (Group 2), with 10 patients in each group. Times of resumption of spontaneous breathing and extubation were recorded and elimination rates of carbon dioxide, end-tidal concentrations of desflurane and N2O, and blood gases were measured. RESULTS: Spontaneous breathing was resumed in both groups when pH had decreased by about 0.07 and PaCO2 increased by about 1.4 kPa compared with the values at the end of 1.3 MAC anaesthesia with controlled normoventilation. There were no significant differences between the groups with regards to extubation time, 6 vs. 13 min, or total MAC value at extubation, 0.20 vs. 0.19 in Group 1 and 2, respectively. Neither did the groups differ in minute ventilation, end-tidal carbon dioxide, oxygen concentrations, or blood gases. CO2 elimination decreased in both groups from about 220 ml 70 kg-1 min-1 at the end of anaesthesia to a lowest value of about 160 ml 70 kg-1 min-1. CONCLUSION: The respiratory profiles during recovery from gynaecological laparoscopy with either desflurane/N2O or desflurane anaesthesia were similar with fast resumption of spontaneous breathing, short time to extubation, and no signs of CO2 retention.

Adult↗

PubMed1997

A study of mixing conditions during nitric oxide administration using simultaneous fast response chemiluminescence and capnography.

We have evaluated the mixing properties of nitric oxide in inspired gases for five different administration techniques. Nitric oxide and carbon dioxide were delivered to the ventilator system before the ventilator or after the ventilator as a continuous flow, either directly into the inspiratory limb or into a mixing chamber positioned in the inspiratory limb. Both gases were delivered as above but synchronized with inspiration. Mixing conditions were evaluated using fast response chemiluminescence for nitric oxide and capnography for carbon dioxide analysis. Administration of nitric oxide and carbon dioxide directly into the inspiratory limb as a continuous flow or with a magnetic valve-controlled synchronized flow resulted in peak concentrations of 236% and 220%, respectively, of expected values. The use of a mixing chamber reduced these values to 104% and 102%, respectively. Administration of nitric oxide as a continuous flow into the tubing of an intermittent flow ventilator resulted in highly fluctuating inspiratory peak concentrations, which could be avoided with a mixing chamber.

Capnography↗

PubMed1997

A retrospective analysis of nitric oxide inhalation in patients with severe acute lung injury in Sweden and Norway 1991-1994.

BACKGROUND: Patients with severe acute lung injury (ALI) have been treated compassionately on doctors' initiative with inhaled nitric oxide (INO) in Sweden and Norway since 1991. In 1994 the previously used technical grade nitric oxide was replaced by medical grade nitric oxide. METHODS: We have carried out a retrospective data collection on all identified adult patients treated with INO for >4 h during the period 1991-1994 focusing on safety aspects and patient outcome. We used the following exclusion criteria (1) Age <18 years, (2) Simultaneous treatment with extracorporeal removal of CO2 (3) NO inhalation period <4 h, (4) Incomplete or missing patient charts, (5) Use of INO in order to treat pulmonary hypertension following cardiac surgery, with little or no acute lung injury. RESULTS: Inclusion criteria were met by 56 out of 73 identified patients. Mean age was 48+/-19 years and the median duration of INO treatment was 102 h. PaO2/FIO2 ratio at start of treatment was 85 +/- 33 mm Hg with a lung injury score (LIS) of 3.2+/-0.8. The aetiology of the lung injury was pneumonia (n= 27), sepsis (n=12) and trauma (n=8). Survival to hospital discharge was 41% and survival after 180 d was 38%. Three serious adverse events were identified, two from technical failures of the INO delivery device and one withdrawal reaction necessitating slow weaning from INO. No methaemoglobin values >5% were reported during treatment. CONCLUSION: The overall mortality did not differ dramatically from historical controls with high mortality. Only a randomised study may determine whether INO as an adjunct to treatment alters the outcome in severe ALI. One cannot at present advocate the routine use of INO in patients with ALI outside such studies.

Administration, Inhalation↗

PubMed1997

Should nitrous oxide be discontinued before desflurane after anaesthesia with desflurane/N2O?

BACKGROUND: The appearance of hypoxaemia immediately after anaesthesia with nitrous oxide may be partially explained by diffusion hypoxia. This study was undertaken to evaluate circulatory and respiratory variables during emergence after desflurane/nitrous oxide anaesthesia, and whether there are any differences depending on which gas is discontinued first. METHODS: 20 patients were studied after gynaecological laparoscopic surgery. The depth of anaesthesia was reduced 10 min prior to the emergence by stopping the administration of one of the two inhalational agents. Desflurane was discontinued first in Group 1, nitrous oxide in Group 2. Ventilation was controlled with E'CO2 maintained at 5% until the administration of the second anaesthetic gas was discontinued. Thereafter, the patients breathed spontaneously. RESULTS: The PaCO2 at which the respiratory drive reappeared after controlled normoventilation was similar in both groups, 6.1-6.5 kPa, and extubation was performed after 10-11 min. At extubation, the end-tidal CO2 and total MAC were similar in the groups, about 6.2 vol% and 0.16, respectively. Mean arterial blood pressure was significantly higher in Group 1. The cardiac output increased in both groups from about 6 l/min at the conclusion of anaesthesia to 9.0 and 7.6 l/min at 15 min in the recovery period. End-tidal O2 decreased and CO2 increased in both groups during the first 10 min in the recovery period. pH was reduced at 15 and 30 min in both groups. CONCLUSION: Irrespective of which agent was discontinued first there was an increase in cardiac output decrease in oxygenation and a modest acidosis in the first 30-min recovery period. The only significant difference between the groups was in mean arterial blood pressure in the early emergence phase with a greater MAP when N2O had been used until the conclusion of anaesthesia.

Adult↗

PubMed1997

Emergence from isoflurane/N2O or isoflurane anaesthesia.

BACKGROUND: The first goal of anaesthetic recovery is return of the patient's ability to independently maintain respiratory and circulatory functions. Nitrous oxide remains popular due to minor effects on the cardiovascular and respiratory systems. However, diffusion hypoxaemia can occur during recovery and there is a potential advantage of providing the patient with only a potent vaporised agent. METHODS: This randomised study of 20 gynaecological patients evaluated respiratory and circulatory variables during emergence after anaesthesia with equipotent mixtures of isoflurane/nitrous oxide or isoflurane. Inspired, end-tidal and mixed expired gas concentrations, expired minute volume, pulse oximetry saturation and arterial blood gases were registered. Monitoring of cardiac output was performed by transthoracic bioimpedance. RESULTS: Patients anaesthetised with isoflurane/N2O resumed their spontaneous breathing 16 min earlier and were extubated 22 min earlier than those anaesthetised with only isoflurane. At extubation, total MAC and end-tidal CO2 were similar in both groups, 0.22-0.26 and 5.5-5.9 vol%, respectively. The isoflurane/ N2O group had greater minute ventilation and CO2 excretion rates than the isoflurane group throughout the emergence period. There were no significant differences between the groups in blood gas variables or in heart rate, mean arterial blood pressure or cardiac index. Cardiac index was between 3.4 and 3.9 l m(-2) min(-1) throughout the emergence period in both groups. CONCLUSION: Patients anaesthetised with only isoflurane had a longer delay until resumption of spontaneous breathing and extubation in the emergence period. Minute ventilation and carbon dioxide elimination were also significantly more suppressed throughout emergence after anaesthesia with isoflurane as compared with isoflurane/N2O.

Adult↗

PubMed1997

Nitric oxide administration after the ventilator: evaluation of mixing conditions.

BACKGROUND: Because of the potential toxicity of nitric oxide (NO) and its oxidising product nitrogen dioxide (NO2), any system for the delivery of inhaled NO must aim at stable and predictable levels of NO and as low concentrations as possible of NO2. METHODS: In a laboratory set-up, we have evaluated mixing conditions in a system where NO is added after the ventilator with continuous flow. Mixing was studied by using carbon dioxide (CO2) as a tracer gas since capnography has a short response time (360 ms) in comparison with measurements of NO with electrochemical fuel cells (response time of 18 s). CO2 (in volumes corresponding to an ideal mixture of 1, 3 and 6%) was fed, after the ventilator, either into plain breathing tubing, into one or two soda lime absorbers, or into an empty and a soda lime-filled canister, at different ventilatory rates and different I:E ratios. Samples were drawn from the inspiratory limb close to the Y-piece. NO was added in the same way and in the same volume as the highest concentration of CO2. RESULTS: CO2 added to plain tubing resulted in peak levels up to five times the set levels, while addition to a mixing box with an empty and a soda lime-filled canister resulted in even mixing with gas concentrations close to the ideal. When NO was fed into plain tubing, low levels were measured at the Y-piece, indicating poor mixing. Gas supply to a mixing chamber resulted in even concentrations. CONCLUSION: Even and predictable levels of NO can be obtained with continuous flow of NO to the inspiratory limb, after the ventilator, if a mixing chamber is used. To obtain adequate mixing, the volume of the mixing box should be greater than the tidal volume.

Carbon Dioxide↗

PubMed1997

Uptake of inhaled nitric oxide in acute lung injury.

BACKGROUND: Despite the widespread use of inhaled nitric oxide (NO), little is known of its pulmonary uptake in patients with acute respiratory failure. METHODS: Fourteen patients with acute lung injury (ALI) and ongoing NO therapy were studied. Three doses of NO (5, 10 and 40 ppm) were given for 20 min and at each dose level the following parameters were recorded: minute ventilation, inspiratory NO conc., mixed expired NO conc., end-tidal NO conc., mixed expired CO2 conc., end-tidal CO2 conc, and arterial CO2 tension. Total uptake was calculated and correlated to the total amount of NO inhaled, the amount of NO administered to the alveolar space, and the amount of NO administered to the perfused alveolar space. RESULTS: About 35% of the total amount of NO delivered is taken up by the lungs, 70% of NO administered to the alveolar space is taken up, and 95-100% of the NO administered to perfused alveolar space is taken up. The size of the alveolar dead space varied between 10 and 60% of the alveolar space. At 40 ppm of inhaled NO there was no difference between inspired and mixed expired NO2 concentration, indicating that there is no significant NO2 formation taking place in the lungs during NO inhalation at the concentrations studied. CONCLUSIONS: Practically all NO administered to the perfused alveolar space is taken up. The total uptake differs from that of healthy persons probably because of differences in the alveolar dead space.

Administration, Inhalation↗

PubMed1996

Response to nitric oxide inhalation in early acute lung injury.

OBJECTIVE: To evaluate the dose response of inhaled nitric oxide (NO) on gas exchange and central haemodynamics in patients with early acute lung injury (ALI). DESIGN: Prospective, multicentre clinical study. SETTING: General ICUs in university and regional hospitals. PATIENTS: 18 Patients with early ALI according to specified criteria. INTERVENTIONS: During controlled ventilation an inhalation system was used to deliver NO (1000 ppm in N2) and O2/air to the low pressure fresh gas inlet of a Siemens 900C ventilator. Haemodynamics and pulmonary gas exchange variables were measured at baseline and at stepwise increased inspiratory NO concentrations of 0.1, 0.3, 1, 3, 10, 30 and 100 ppm, each dose being maintained for 15 min. Dose testing was repeated the next day, and the response to prolonged (2 h) NO inhalation at 1 and 10 ppm was also tested. MEASUREMENTS AND RESULTS: Inhalation of NO produced a significant increase in PaO2 (P < 0.0025). The degree of response, as well as the optimal NO dose varied in individual patients and between different days. Venous admixture (QVA/QT) was reduced (P < 0.02) from 38% (31-46%) to 33% (26-41%). In our patients with early acute lung injury and only a moderate elevation in pulmonary arterial pressure NO inhalation did not reduce mean pulmonary artery pressure significantly, being 27.0 (21-30) mmHg at baseline and 26.0 (21-30) mm Hg at 100 ppm. CONCLUSIONS: This study shows that improvements in arterial oxygenation in response to inhaled NO may show great inter- as well as intraindividual variability, and that improvements in arterial oxygenation occur without any measurable lowering of the pulmonary artery pressure.

Administration, Inhalation↗

PubMed1996

Gas kinetics during nitrous oxide analgesia for labour.

Hypoxaemia may occur after hyperventilation with nitrous oxide during labour. The purpose of this study was to assess whether diffusion hypoxia is a contributory factor. Twenty-four parturients were randomly allocated to receive 50 or 70% nitrous oxide in oxygen. The median nitrous oxide inhalation time per contraction was 58 s and 33 s, respectively. The end-tidal carbon dioxide and the minute ventilation remained unchanged. The end-tidal oxygen concentration was lowest at 120 s, reaching 15.4% in both groups. The oxygen saturation did not differ between the groups with a lowest median value of 96% before the start of nitrous oxide inhalation. Two parturients had episodes of desaturation. Both had low end-tidal oxygen concentrations in association with the desaturation but, as the end-tidal nitrous oxide concentrations were low, the desaturations could not be attributed to diffusion hypoxia.

Adult↗

PubMed1996

Safety aspects of delivery and monitoring of nitric oxide during mechanical ventilation.

In the presence of oxygen NO is oxidised to NO2, which is toxic in higher concentrations. In this technical investigation, we evaluated a dosage system, modified from Stenqvist et al. 1993 (1), regarding NO and NO2 levels. NO was administered before the ventilator and NO2 scavenged using a soda little absorber in the inspiratory limb close to the ventilator. NO/NO2 levels were measured using fuel cell technique. We tested the duration of soda lime scavenging, put in additional soda lime absorbers, used charcoal as absorber and exchanged tubing material. NO was delivered after the ventilator and we studied effect of interruption of ventilation. With concentrations of NO at or below 40 parts per million (ppm) at F1O2 0.9, NO2 levels were 1.2 ppm or lower. Corresponding values for 20 and 10 ppm were 0.4 and 0.2 ppm, respectively. Duration of the soda lime absorber was at least 72 hours. Additional soda lime absorbers did not further reduce NO2 levels. Charcoal absorbers reduced NO2, but also NO by 45% from set value. Tubing materials had no influence on NO and NO2 levels. When administering NO at the Y-piece, levels of NO were increased by 35-60% and NO2 levels by 110-230% compared to set values. Oxidation of NO to NO2 is continuously taking place in the breathing system. Doses of up to 40 ppm NO should be considered safe regarding NO2 levels. Administration of NO at the Y-piece gives high and unpredictable levels of NO2.

Absorption↗

PubMed1996

Continuous non-invasive monitoring of energy expenditure, oxygen consumption and alveolar ventilation during controlled ventilation: validation in an oxygen consuming lung model.

BACKGROUND: We have developed a combined indirect calorimetric and breath-by-breath capnographic device (GEM) for respiratory monitoring: oxygen consumption (VO2), carbon dioxide excretion (VCO2), respiratory quotient (RQ), energy expenditure (EE), alveolar ventilation (VA) and dead space/total ventilation (VD/VT). METHODS: The device was tested in a lung model in which VO2 was achieved by combustion of hydrogen. VCO2 was achieved by delivering CO2 into the single alveolus combustion chamber. VO2, VCO2, compliance, and anatomical dead space could be varied independently. RESULTS: Measured VO2 was 101 +/- 3% (SD) of set value at a F1O2 < 0.6 and 101 +/- 7% at a F1O2 > 0.6 during 15 hours of testing. The corresponding VCO2 values were 99 +/- 2% and 102 +/- 7%. The GEM could with good accuracy measure accumulated energy expenditure (EE) during simulated unstable patient conditions up to a F1O2 of 0.8. At F1O2 above 0.8 VCO2 and VO2 could be estimated using a default RQ value of 0.85. On-line estimated VA and VD/VT values could be obtained at any F1O2 up to 1.0. In a test sequence with stable VO2 and VCO2 the GEM adequately followed changes in VA, induced by changes in anatomical dead space, breathing frequency and compliance. CONCLUSION: The overall performance of the device is satisfactory and well comparable with any equipment tested. It allows near-continuous non-invasive monitoring of EE, VO2, VCO2, VA, VD/VT in ventilated, critically ill patients, providing a rationale for ventilator settings and nutritional support.

Capnography↗

PubMed1995

Do changes in cardiac output affect the inspiratory to end-trial oxygen difference?

BACKGROUND: The paramagnetic technique has made it possible to monitor the end-tidal oxygen concentration and P(1-ET)O2, i.e. inspiratory to end-tidal oxygen difference, breath-by-breath. Little is known about the implications of a changing P(1-ET)O2, but so far studies have shown it to be a quick and sensitive variable to detect hypoventilation. This study was designed to observe the circulatory effects on P(1-ET)O2 in an experimental setting but monitored as in a clinical situation. METHODS: We assessed the oxygen difference during changes in cardiac output induced by intravenous ephedrine-hydrochloride in 12 healthy male volunteers. P(1-ET)O2 was measured with a fast-response paramagnetic differential oxygen sensor. Cardiac output was measured with non-invasive transthoracic electrical bioimpedance. As simultaneous changes in metabolism and ventilation will also influence P(1-ET)O2 oxygen uptake and expired minute volume were monitored. After a rest period, the subjects had an intravenous injection of ephedrine-hydrochloride 0.1 mg.kg-1 followed by a 30-min observation period. RESULTS: Cardiac output increased significantly as did the oxygen uptake and the ventilation. We found no biological significant correlation between cardiac output and P(1-ET)O2. The P(1-ET)O2 was influenced by ventilation and metabolism.

Adult↗

PubMed1995

Conversion of inhaled nitric oxide to nitrate in man.

1. Nitric oxide (NO) is potentially useful as a selective vasodilator drug in infants and adults with pulmonary hypertension. In vitro and in vivo observations demonstrate that NO may be converted to nitrate in the blood, to be further excreted into the urine. The aim of the present study was to assess quantitatively the importance of this pathway for inhaled NO in human subjects. 2. Healthy subjects inhaled 15NO (25 p.p.m.) for 1 h. The plasma and urine levels of 15NO3- were followed for 2 and 48 h, respectively. 3. The measured retention of 15NO in the lungs was 224 +/- 13 mumol, corresponding to 90 +/- 2% of the inhaled amount. Plasma 15NO3- increased during the inhalation of 15NO, to about 15 mumol l-1, and fell when inhalation of 15NO was terminated. 4. Urinary excretion of 15NO3- during the first 24 h after inhalation was 154 +/- 12 mumol. During the following 24 h another 8 +/- 2 mumol of 15NO3- appeared in the urine. 5. We conclude that conversion of inhaled NO to nitrate is a major metabolic pathway in man, covering more than 70% of its inactivation. The metabolic fate of the remaining NO inhaled requires further study.

Administration, Inhalation↗