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1.
CANNON D.; KALSO E. J.; BURCHARDI H.; SYKES M. K. 《British journal of anaesthesia》1988,60(4):430-438
Electromagnetic flow probes were placed around the pulmonaryartery and left lower lobe artery in anaesthetized open-chestdogs in order to measure possible changes in the ratio of lobar-to-totalpulmonary blood flow (l/t) in response to changes in cardiacoutput produced by the opening of arterio-venous fistulae orfluid loading. Ventilation of the lobe with 7% oxygen or lobarcollapse reduced l/t by 35% and 42%, respectively, butthere were no significant changes in l/t in response to increases in t of 29133%. It is concludedthat the changes in t, pulmonary vascular pressures and mixed venous PO2 within the range studieddid not influence l/t. 相似文献
2.
The blood flow to the left lower lobe (L), and total (T) pulmonary blood flow, were measured in 10 open-chest dogs usingelectromagnetic flowmeters. Ventilation of the left lower lobewith 7% oxygen in nitrogen produced a greater reduction in L/T (41%) than lobar ventilation with 7% oxygen in nitrous oxide(33%). Lobar collapse reduced QL/QT by 65%, but there was nochange in L/T when 50% nitrous oxide was administered to theright lung. The i.v. infusion of lignocaine hydrochloride duringventilation of the lobe with 7% oxygen in nitrogen producedno change in L/T. However, lignocaine infusion during lobar ventilationwith 7% oxygen in nitrous oxide produced a further reductionin L/T to a value which was not significantly differentfrom that observed during ventilation with 7% oxygen in nitrogen.Lignocaine had no effect on L/T during lobar collapse whether theright lung was ventilated with 50% oxygen in nitrogen or 50%oxygen in nitrous oxide. It is concluded that lignocaine reversesthe depression of hypoxic pulmonary vasoconstriction producedby lobar ventilation with nitrous oxide. 相似文献
3.
Gas exchange was modelled by a Fortran program. Arterial blood-gastensions have higher resolution than inert gas retentions interms of distinguishing a single A/ compartment from a progressively broadeninglognormal distribution. The maximum number of compartments determinableby arterial blood-gas tensions is three; A/ distributions containing more compartments are non-unique. Without utilizing100% inspired oxygen, arterial blood-gas tensions cannot resolvethe relative perfusion in shunt and low-A/ compartments, but the total perfusion in these compartments is determinable.The way in which the arterial blood-gas tensions vary with thevariables of two and three-compartment distributions is described.Two-and three-compartments A/ distributions are derivable from eitherarterial blood-gas tensions or inert gas retentions. 相似文献
4.
AN EVALUATION OF REBREATHING WITH THE BAIN SYSTEM DURING ANAESTHESIA WITH SPONTANEOUS VENTILATION 总被引:1,自引:0,他引:1
Data from 12 anaesthetized patients breathing spontaneouslyfrom the Bain system were used to calculate the degree of rebreathingoccurring when the fresh gas flowrate(F) was equal to 2,1 and 0.7 times the estimated normalminute ventilation (tot)- Measurementsof the expired minute volume (E) and end-tidal carbon dioxide tension (PE'CO2) were made to determinethe effects of this rebreathing. No rebreathing occurred whenF was equal to twice tot. When F was equal to tot rebreathing was usually small in amount and produced no changes in E or PE'CO2. Changes attributable torebreathing occurred in only two patients when F was reduced to 0.7 tot.These results are explained by the presence of anaesthesia-inducedventilatory depression and favourable changes occurring in therespiratory wave forms in the majority of patients studied.In some patients, greater values of E and rebreathing occurred in response to strong surgical stimulation.The net result of increased ventilation in these patients wasa decrease in PE'CO2-,. It is concluded that during anaesthesia,when the Bain system is used with F equal to tot, any increasein PE'CO2 which may result from rebreathing is likely to besmall and seldom of clinical importance. 相似文献
5.
MEAKIN G.; JENNINGS A. D.; BEATTY P. C. W.; HEALY T. E. J. 《British journal of anaesthesia》1992,68(4):333-337
We have determined the minimum fresh gas flow rate (F) for use with the Ohmeda enclosedafferent reservoir breathing system (EAR) in 10 anaesthetizedchildren breathing spontaneously. First, we determined the F required to prevent rebreathing asdetected by increased total ventilation (E) and end-tidal carbon dioxide partial pressure.Second, we used a mathematical model to calculate the degreeof rebreathing occurring at each F.A F equal to the predictedalveolar ventilation was sufficient to prevent clinically detectablerebreathing in all pateints. From the model, no rebreathingoccurred when F//E was 0.78 or more. We have shown previously thatthe EAR functions efficiently during controlled ventilationwith a F = 0.6x weight0.5.As this F is slightly greaterthan the predicted alveolar ventilation, we suggest that theEAR may be used with a F =0.6 x weight 0.5 regardless of the mode of ventilation. 相似文献
6.
Ventilation (E), end-tidal (P')co2 mixed venous Pco2 (Pco2andthe ventilatory response to carbon dioxide (E/Pco2) were measured before and within 90 min asgtermorphine 0.15 mg kg1 i.m. given to 17 adult patientsundergoing elective surgery under general anaesthesia. The hypothesisthat pastients with a low ventilastory response to carbon dioxideare more susceptible to the ventilatory depressant effecstsof morphine was tested. Morephine induced increases in PE'co2andPco2 were not correlasted witheither the slope or the position of the preinjection responseto carbon dioxide. Mean E/Pco2was depressed after morphine (P <0.05), but individual responsesvaried widely. Seven pastients whose control E/Pco2 was 9.9 litre min1kPa1 or lessdecreased E/Pco2 after morphine.In four patients, E/Pco2 increasedafter morphine; however, in each case, PE'co2 and Pco2 increased also. Morphine disphine displaced thecarbon dioxide response to the right (P < 0.001) but no correlationwas found between either the magnitude of the displacement orchange in slope and control E/Pco2.The results suggest that patients with a low value for E/Pco2 are not more susceptible tothe ventilatory depressant action of morphine. 相似文献
7.
HENDERSON A. M.; FORRESTER P. C.; ARMSTRONG R. F.; MOSSE C. A.; HALSALL D. 《British journal of anaesthesia》1983,55(8):791-800
A continuous, non-invasive system is described for measuringoxygen uptake () and carbon dioxide output () in mechanically ventilated patients. Inspiratory and mixed expiratory gas sampleswere pumped through fine-bore tubing to a remote mass spectrometerfor analysis. The expiratory flow transducer of a Siemens Servo900B ventilator was used for expiratory flow measurement andinspiratory flow was calculated from this using the Haldanetransformation. A desk-top computer calculated , and respiratory quotient. The system has been validated against standard methodsof gas analysis and flow measurement ( mean difference lOml min1: SD9.13; mean difference 8.12ml min1:SD4.66). Comparison with Douglas bag measurements in patientshas been made ( mean difference 10.7ml min1: SD9.8; mean difference 1.07ml min1: SD4.7). 相似文献
8.
The fourth and sixth equations towards the bottom of the secondcolumn of this page should be amended, respectively, to: 相似文献
9.
The Bain circuit was studied in a model lung on the assumptionthat, in addition to the ratio of fresh gas flow to total ventilation(FG/E), different time fractions of the respiratory cycle might influencerebreathing. We found that the time fraction for active expiration(FEt) governed rebreathing for each FG/E value. With FEt, as an independentvariable, a theoretical formula was derived for rebreathing.Rearranging this formula made it possible to calculate the necessaryincrease in ventilation to keep end-tidal carbon dioxide constantfor each FG/E. Thus, at a fresh gas flow of 70 ml kg-1 min-1,I has to be increased 2.6 times. For spontaneously breathing patients inhalation anaestheticsthat do not depress carbon dioxide sensitivity seem to be bettersuited to use in the Bain circuit. The FECO2 can then kept constantthrough increased ventilation in spite of the concomitant increasein rebreathing 相似文献
10.
VENTILATORY EFFECTS AND PLASMA CONCENTRATION OF MORPHINE IN MAN 总被引:2,自引:0,他引:2
The relationship between the plasma concentration of morphineand morphine-induced changes in ventilation and the ventilatoryresponse to carbon dioxide was studied in 17 healthy adultsundergoing elective surgery under general anaesthesia. Eachsubject was given morphine sulphate 0.15 mg kg1 i.m.;ventilation (E), end-tidal Pco2(PE'CO2), mixed venous PVCO2(PCO2)and ventilatory response to carbon dioxide (E/PCO2) were measured before and within 90 min afterinjection. Mixed venous PCO2 and E/PCO2were measured by standard rebreathing methods; plasma morphineconcentration was measured by radioimmunoassay. Maximum plasmamorphine ranged from 30 to 120 ng ml1, between 4 and60 min after injection. There was a significant increase inmixed venous PE'CO2 (P<0.001), and PE'CO2 (P<0.01) aftermorphine while E decreased insignificantly. Morphine displaced the carbon dioxide responsecurve to the right (P<0.01) and E/PCO2decreased from 12.3 to 10.0 litre min1 kPa1 (P<0.05).The magnitude of changes in E and E/PCO2 were not relatedto the peak plasma concentration of morphine or to the meanconcentration immediately before and after the carbon dioxideresponse measurement. Plasma concentrations of morphine, underthe conditions of the present study, are not an objective indicatorof pharmacological activity between one patient and another.
Presented in part at the VI World Congress of Anaesthesiology,MexicoCity, Mexico, April 1976 相似文献
11.
The ability to assess changes in pulmonary blood flow, usinga modified ratio (), was evaluated in 12 infants withcongenital heart disease and complete intracardiac mixing whounderwent modified Blalock-Taussig shunt procedures. At thevarious measuring stages there were no major changes in meanarterial pressure or heart rate. Arterial oxygen tensions andsaturation increased (P < 0.01) and the arterial to end-tidalcarbon dioxide difference (PaCO2PE'CO2) was significantlyreduced (P < 0.001) after completion of the shunt procedure.There was a significant increase in mean after chest closure (P < 0.001), which was seento correlate well with early clinical outcome. Two patientswho did not demonstrate any increase in over the course of the procedure had failed shunts.The limitations of use of the are discussed. A modified ratio of less than unity after surgery is strongly indicativeof inadequate palliation.
Present address: Department of Anaesthesiology, University ofTexas Health Science Center at Dallas, 5323 Harry Hines Blvd,Dallas, Texas 75235, U.S.A. 相似文献
12.
An i.v. infusion regimen was developed to permit rapid attainmentof steady-state blood pethidine concentrations (Cp26). In 10adult volunteers (12 studies) the relationship of pethidineCp26 to the ventilatory effects of the drug were examined. Meanpethidine Cp26 ranged from 170 to 1320 ng ml1, with amedian Cp26 of 480 ng ml1. Increased end-tidal (PE' co2)and mixed venous and decreased slope (I/Pco2) and position(ISO-I) of the carbon dioxide response wereall significant (P<0.001) for CP26. (1) 480 and (2) >480ng ml-1. The averaged changes in PE'co2, ,I/Pco2, and ISO-I expressed as a per cent of respectivecontrol variables, were shown to be linear functions of CP26.It is concluded that, under conditions of CP26, significantventilarory depression occurs at blood pethidine concentrationsless than those required for analgesia. The possible significanceof these findings in volunteers is discussed in terms of thisapplication to the clinical setting of postoperative pain andits management after general anaesthesia. 相似文献
13.
A new group of breathing systems, namely the Enclosed AfferentReservoir (EAR) systems, is described. They allow for the selectiveelimination of alveolar gas in association with both spontaneousand controlled ventilation. A comparison with the Bain systemin controlled ventilation demonstrates greater efficiency ineliminating carbon dioxide. A fresh gas flow (F) of 70 ml kg1 min1 using an EAR systemgave mild hypocarbia which equated to a F of 100 ml kg1 min1 using the Bainsystem. Smaller minute volumes of ventilation are required foroptimal performance than with the Bain system. The minimum recommendedminute volume of ventilation (l) should equal F plus anatomical deadspace ventilation (Danat).The pattern of ventilation appears to have little influenceupon the efficiency of carbon dioxide elimination when usingan EAR system, whereas the Bain system does appear to be affected. 相似文献
14.
A SIMPLIFIED APPROACH TO THE EFFECT KINETICS OF ATRACURIUM 总被引:1,自引:0,他引:1
The combination of the Hill equation, which describes the concentrationeffectrelation, with the monoexponential function for the terminaldecline of plasma concentration, yields a compound time constant,. This constant is a combination of the terminal elimination half-life () and the exponent (s) of the Hill equation and maybe used to describe the time course of recovery from neuromuscularblock. The constant may be estimated by non-linear curve fittingto f, the effect expressed as fraction of maximal effect, orby linear regression of the logit function of f. The methodswere validated using plasma concentration and effect data fromseven patients administered atracurium. The two methods utilizingeffect data alone yielded values of 4.2 (0.7) min and 4.3 (0.5)min (mean (SEM)), respectively, for compared with 4.1 (0.6) min when the constant was calculatedusing plasma concentration data for and curve fitting to the concentrationeffect data todetermine s. These methods offer and objective measure of therate of recovery and a means of testing if redistribution orelimination is the primary process in the termination of drugeffect. 相似文献
15.
Background. Jugular bulb oxygen saturation () is a surrogate marker for global cerebral oxygenation. The effectof milrinone on and the cerebrovascular carbon dioxide reactivity (CCO2R) was investigated. Methods. Thirty patients scheduled for coronary artery bypassgraft surgery (CABG) were studied prospectively. After sternotomy,normoventilation (at T1; =4.75.0 kPa) and hyperventilation (at T2; =3.33.7 kPa) were induced and the changes in () and (), and (CCO2R) were measured. After normoventilationwas re-established (at T3), milrinone 50 µg kg1was given (at T4), followed by hyperventilation (at T5), and, and CCO2R were measured. Results. After milrinone administration at normoventilation(T3 and T4), cardiac index and mixed venous oxygen saturationincreased, while mean arterial pressure and systemic vascularresistance index decreased, without a significant change in. Before milrinone administration (T1 andT2), hyperventilation decreased and , and showed positive linear correlation with . After milrinone administration (T4 and T5), hyperventilation decreased and , and showed positive linear correlation with . There was no significant difference in CCO2R before and after milrinone administration(13.3 (5.7)% kPa1 and 12.3 (3.9)% kPa1, respectively). Conclusions. Although milrinone induced significant haemodynamicchanges, and CCO2R were unchanged duringits administration. 相似文献
16.
THE CONCEPT OF DEADSPACE WITH SPECIAL REFERENCE TO THE SINGLE BREATH TEST FOR CARBON DIOXIDE 总被引:10,自引:3,他引:7
We present a review and a theoretical analysis of factors determiningairway deadspace (VDaw) and alveolar deadspace (VDalv), thetwo constituents of physiological deadspace (VDphys). VDaw isthe volume of gas between the lips and the alveolar/fresh gasinterface, the location of which is determined by inspiratoryflow pattern and airway geometry. VDalv can be caused by incompletealveolar gas mixing and associated / mismatching within the terminal respiratoryunits, temporal / mismatching within units, spatial / mismatching between units, and venous admixture. Most causes of VDphys are influencedby inspiratory flow pattern and the time available for gas diffusionand distribution. Analysis can be made from the single breathtest for carbon dioxide (SBTCO2) which is the plot offraction of carbon dioxide in expired gas against expired volume.The common causes of VDalv are associated with a sloping SBT-CO2phase III. Combination of SBT-CO2 with PaCO2 yields VDphys andVDalv. A sloping phase III with a negative arterial-end-tidalPco2 gradient implies compensation by perfusion for early emptying,overventilated alveoli. 相似文献
17.
Four hundred and thirty blood samples from suxamethonium-sensitiveindividuals have been phenotyped by the Cholinesterase ResearchUnit following its transfer from Exeter to the Hammersmith Hospital.The distribution of genotypes has been shown to be similar tothat found in Exeter. Screening for the and genes has not yielded any major differences in the gene frequencies ofsensitive individuals, even during pregnancy. The uneven sexdistribution of the patients, as well as other unusual pointsthat have arisen, are discussed. A new gene for the biosynthesisof cholinesterase has probably been identified. 相似文献
18.
AMBIENT AIR CONTAMINATION IN A DENTAL OUTPATIENT THEATRE 总被引:1,自引:0,他引:1
THOMPSON J. M.; BARRATT R. S.; HUTTON P.; ROBINSON J. S.; BELCHER R.; STEPHEN W. I. 《British journal of anaesthesia》1979,51(9):845-855
The extent of air contamination by halothane in an operatingsession was correlated with the number of patients, the totalusage of halothane, refilling a vaporizer and the number ofhyperventilating patients per session. Trichloroethylene contentof theatre air correlated only with total usage and refillinga vaporizer. A very strong personal asssociation was found between the anaesthetist and the extentof air contamination with halothane. The association was weaker(0.05 <P<0.1) for trichloroethylcne. The median ambientair contamination with halothane in the vicinity of the facesof anaesthetists and dental surgeons was between six and ninetimes grater than the median air contamination at the fixedsampling sites . 相似文献
19.
The ventilatory response to carbon dioxide was studied in 12unpremedicated children, aged 2068 months, weighing between10 and 20 kg, under nitrous oxide-halothane anaesthesia. Tidalvolume (VT) and end-tidal carbon dioxide tension (PE'CO2) werecontinuously measured by pneumotachograph and capnograph. Minuteventilation (), respiratory rate (f), mean in-spiratory flow (VT) and effective inspiratorycycle (T1/Ttot) were calculated during anaesthesia at threedifferent inspired halothane concentrations (0.5, 7 and 1.5%).The ventilatory response to carbon dioxide was determined byrelating the increase in ventilation during exposure to 2% carbondioxide to the change in end-tidal carbon dioxide concentration.When the inspired concentration of halothane increased, therewere significant decreases in , VT, , and a significant increase in PE'CO2 The slope of the carbon dioxide response under lightnitrous oxide-halothane anaesthesia (0.5% halothane) was relativelyflat (18.64 ml min1 kg mm Hg-1) when comparedwith the mean values published for anaesthetized adults, childrenor neonates. When the inspired concentration of halothane wasincreased, the slope decreased significantly (39% of initialvalue at 1 % inspired halothane, 26% at 1.5%). The additionof carbon dioxide produced significant increases in , VT and but no change in respiratory rate. No statistical differencewas observed in the slope of carbon dioxide response betweenthe initial and "control" periods which were measured at thesame inspired halothane concentration (0.5%). 相似文献
20.
BENHAMOU D.; ECOFFEY C.; ROUBY J. J.; SPIELVOGEL C.; VIARS P. 《British journal of anaesthesia》1987,59(10):1257-1264
Fourteen critically ill patients with ventilatory failure wereventilated with HFJV using a constant driving pressure of 3atm and a constant I: E ratio of 0.43. In six (group I) HFJV,using a frequency of 100 b.p.m., was delivered via a proximalinjector cannula. Four injector cannulae (i.d. 1.8, 1.6, 1.4and 1.2 mm, respectively) were used at random. In eight patients(group II), HFJV using three frequencies (100, 300 and 600 b.p.m.)was administered either via a 1.8-mm i.d. proximal injectorcannula (proximal injection), or via a Hi-Lo jet tracheal tube(distal injection). The following indices were measured in vivo:mean airway pressure (Psw), mean pulmonary volume above apnoeicFRC (), mean alveolar pressure (clamps method) and arterial blood-gas tensions. Injected volume(Vinj), entrainment (E) and tidal volume (VT) were measuredin vitro using a water-sealed spirometer. Operating pressure(the pressure in the connecting tube) was measured directlyusing a high pressure calibrated transducer. In group I, Psw, Pao2 Vinj and VT significantly decreased whereas operating pressure and E significantly increasedwhen the internal diameter of the injector cannula was reduced.In group II, Psw, , E, VT and operating pressure significantly decreased, whereas Vinj increasedand Pao2 and Paco2 remained unchanged, when proximal injectionwas switched to distal injection. In both groups, a significantrelationship was found between operating pressure and E. Ata constant driving pressure, operating pressure increased withnarrow injector cannulae and increased frequency, and decreasedwhen proximal injection was switched for distal injection.
Presented in part at the Annual Meeting of the American Societyof Anesthesiologists, New Orleans, October 1984. 相似文献