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1.
The method ofsurfactant instillation into the lungs for treatment of neonatalrespiratory distress syndrome is an important attribute of delivery,and it may determine the overall efficacy of treatment. Previousstudies primarily focused on the rate at which the bolus is instilled.These findings show that rapid injections lead to a more homogenousdistribution, whereas slow infusions drain into the dependent lung withrespect to gravity, resulting in a heterogeneous deposition. Theseresults suggest that it is beneficial to form a meniscus, from which amore homogenous dispersal can proceed. The objective of the presentstudy was to develop a functional criterion for meniscus formationduring bolus injection. An in vitro experiment was used to examine theclinical setting of surfactant instillation. The physical variablesexamined were the bolus viscosity (µ) and density (), gravity(g), injection rate (Q), orientation of thetrachea with respect to gravity (), tracheal size(D), surface tension (), andcatheter size (d). All quantitieswere varied, except gravity and catheter size. Experimental resultsshow that a meniscus will form whenNSt > 0.004Re2/3, whereNSt is Stokesnumber and Re is Reynolds number,NSt = µQ/D4gsin,a ratio of viscous effects to gravitational effects, and Re = QD/d2µ,a ratio of inertial effects to viscous effects. Rapid injections, highviscosity, and small inclination with respect to gravity promotemeniscus formation. These results can be used to refine the guidelinesfor administration of surfactant replacement therapy. 相似文献
2.
Interferon-gamma has immunomodulatory effects with minor endocrine and metabolic effects in humans 总被引:1,自引:0,他引:1
de Metz J.; Sprangers F.; Endert E.; Ackermans M. T.; ten Berge I. J.M.; Sauerwein H. P.; Romijn J. A. 《Journal of applied physiology》1999,86(2):517-522
To evaluatewhether interferon- (IFN-) is involved in the interaction betweenthe immune and endocrine systems in vivo, we studied six healthysubjects twice in a placebo-controlled trial: once after administrationof recombinant human IFN- and, on another occasion, afteradministration of saline. The rate of appearance of glucose wasdetermined by infusion of[6,6-2H2]glucoseand resting energy expenditure by indirect calorimetry. Human leukocyteantigen-DR gene expression on monocytes and serum neopterin increased after administration of IFN-(P < 0.05 vs. control). IFN-increased serum interleukin-6 levels significantly. Levels of tumornecrosis factor- remained below detection limits. IFN- increasedplasma concentrations of ACTH and cortisol(P < 0.05 vs. control), IFN- didnot alter concentrations of growth hormone,(nor)epinephrine, insulin, C peptide, glucagon, or insulin-like growthfactor I. IFN- did not alter plasma concentrations of glucose andfree fatty acids nor the rate of appearance of glucose. IFN-increased resting energy expenditure significantly. We conclude thatIFN- is a minor stimulator of the endocrine and metabolic pathways.Therefore, IFN- by itself is probably not a major mediator in theinteraction between the immune and the endocrine and metabolic systems. 相似文献
3.
Treppo Steven; Mijailovich Srboljub M.; Venegas Jose G. 《Journal of applied physiology》1997,82(4):1163-1176
Treppo, Steven, Srboljub M. Mijailovich, and José G. Venegas. Contributions of pulmonary perfusion and ventilation toheterogeneity in A/measured by PET. J. Appl. Physiol. 82(4): 1163-1176, 1997. To estimate the contributions of the heterogeneity in regionalperfusion () and alveolar ventilation(A) to that of ventilation-perfusionratio (A/), we haverefined positron emission tomography (PET) techniques to image localdistributions of andA per unit of gas volume content(s and sA,respectively) and VA/ indogs. sA was assessed in two ways:1) the washout of 13NN tracer after equilibrationby rebreathing (sAi), and2) the ratio of an apneic image after a bolus intravenousinfusion of 13NN-saline solution to an image collectedduring a steady-state intravenous infusion of the same solution(sAp).sAp was systematically higher than sAi in allanimals, and there was a high spatial correlation betweens andsAp in both body positions(mean correlation was 0.69 prone and 0.81 supine) suggesting thatventilation to well-perfused units was higher than to those poorlyperfused. In the prone position, the spatial distributions ofs, sAp, and A/ were fairlyuniform with no significant gravitational gradients; however, in thesupine position, these variables were significantly more heterogeneous,mostly because of significant gravitational gradients (15, 5.5, and10%/cm, respectively) accounting for 73, 33, and 66% of thecorresponding coefficient of variation (CV)2 values. Weconclude that, in the prone position, gravitational forces in blood andlung tissues are largely balanced out by dorsoventral differences inlung structure. In the supine position, effects of gravity andstructure become additive, resulting in substantial gravitationalgradients in s andsAp, with the higherheterogeneity inA/ caused by agravitational gradient in s, only partially compensated by that in sA. 相似文献
4.
Li, M. H., J. Hildebrandt, and M. P. Hlastala.Quantitative analysis of transpleural flux in the isolated lung.J. Appl. Physiol. 82(2): 545-551, 1997.In this study, the loss of inert gas through the pleura of anisolated ventilated and perfused rabbit lung was assessed theoreticallyand experimentally. A mathematical model was used to represent an idealhomogeneous lung placed within a box with gas flow(box) surrounding the lung. Thealveoli are assumed to be ventilated with room air(A) andperfused at constant flow () containinginert gases (x) with various perfusate-air partition coefficients(p,x).The ratio of transpleural flux of gas(plx)to its total delivery to the lung via pulmonary artery( ),representing fractional losses across the pleura, can be shown todepend on four dimensionless ratios:1)p,x,2) the ratio of alveolar ventilation to perfusion(A/), 3) the ratioof the pleural diffusing capacity(Dplx) to the conductance ofthe alveolar ventilation (Dplx /Ag,where g is the capacitancecoefficient of gas), and 4) theratio of extrapleural (box) ventilation to alveolar ventilation(box/A).Experiments were performed in isolated perfused and ventilated rabbitlungs. The perfusate was a buffer solution containing six dissolvedinert gases covering the entire 105-fold range ofp,x usedin the multiple inert gas elimination technique. Steady-state inert gasconcentrations were measured in the pulmonary arterial perfusate,pulmonary venous effluent, exhaled gas, and box effluent gas. Theexperimental data could be described satisfactorily by thesingle-compartment model. It is concluded that a simple theoreticalmodel is a useful tool for predicting transpleural flux from isolatedlung preparations, with known ventilation and perfusion, for inertgases within a wide range of . 相似文献
5.
Labella John J.; Daood Monica J.; Koretsky A. P.; Roman Brian B.; Sieck Gary C.; Wieringa Be; Watchko Jon F. 《Journal of applied physiology》1998,84(4):1166-1173
Creatine kinase(CK) provides ATP buffering in skeletal muscle and is expressed as1) cytosolic myofibrillar CK (M-CK)and 2) sarcomeric mitochondrial CK(ScCKmit) isoforms that differ in their subcellular localization. Wecompared the isometric contractile and fatigue properties of1) control CK-sufficient (Ctl),2) M-CK-deficient (M-CK[/]), and3) combined M-CK/ScCKmit-deficientnull mutant (CK[/]) diaphragm (Dia) todetermine the effect of the absence of M-CK activity on Dia performancein vitro. Baseline contractile properties were comparable across groupsexcept for specific force, which was ~16% lower inCK[/] Dia compared withM-CK[/] and Ctl Dia. During repetitiveactivation (40 Hz, duty cycle), force declined in all threegroups. This decline was significantly greater inCK[/] Dia compared with Ctl and M-CK[/] Dia. The pattern of forcedecline did not differ between M-CK[/] andCtl Dia. We conclude that Dia isometric muscle function is notabsolutely dependent on the presence of M-CK, whereas the completeabsence of CK acutely impairs isometric force generation duringrepetitive activation. 相似文献
6.
Yan, Sheng, Pawel Sliwinski, and Peter T. Macklem.Association of chest wall motion and tidal volume responses during CO2 rebreathing.J. Appl. Physiol. 81(4):1528-1534, 1996.The purpose of this study is to investigate theeffect of chest wall configuration at end expiration on tidal volume(VT) response duringCO2 rebreathing. In a group of 11 healthy male subjects, the changes in end-expiratory andend-inspiratory volume of the rib cage (Vrc,E andVrc,I, respectively) and abdomen (Vab,E and Vab,I, respectively) measured by linearizedmagnetometers were expressed as a function of end-tidalPCO2(PETCO2). The changes inend-expiratory and end-inspiratory volumes of the chest wall(Vcw,E and Vcw,I,respectively) were calculated as the sum of the respectiverib cage and abdominal volumes. The magnetometer coils were placed atthe level of the nipples and 1-2 cm above the umbilicus andcalibrated during quiet breathing against theVT measured from apneumotachograph. TheVrc,E/PETCO2 slope was quite variable among subjects. It was significantly positive (P < 0.05) in fivesubjects, significantly negative in four subjects(P < 0.05), and not different fromzero in the remaining two subjects. TheVab,E/PETCO2slope was significantly negative in all subjects(P < 0.05) with a much smallerintersubject variation, probably suggesting a relatively more uniformrecruitment of abdominal expiratory muscles and a variable recruitmentof rib cage muscles during CO2rebreathing in different subjects. As a group, the meanVrc,E/PETCO2,Vab,E/PETCO2, andVcw,E/PETCO2slopes were 0.010 ± 0.034, 0.030 ± 0.007, and0.020 ± 0.032 l / Torr, respectively;only theVab,E/PETCO2 slope was significantly different from zero. More interestingly, theindividualVT/PETCO2slope was negatively associated with theVrc,E/PETCO2(r = 0.68,P = 0.021) and Vcw,E/PETCO2slopes (r = 0.63,P = 0.037) but was not associated withtheVab,E/PETCO2slope (r = 0.40, P = 0.223). There was no correlation oftheVrc,E/PETCO2 andVcw,E/PETCO2slopes with age, body size, forced expiratory volume in 1 s, orexpiratory time. The groupVab,I/PETCO2 slope (0.004 ± 0.014 l / Torr) was not significantlydifferent from zero despite theVT nearly being tripled at theend of CO2 rebreathing. Inconclusion, the individual VTresponse to CO2, althoughindependent of Vab,E, is a function ofVrc,E to the extent that as theVrc,E/PETCO2slope increases (more positive) among subjects, theVT response toCO2 decreases. These results maybe explained on the basis of the respiratory muscle actions andinteractions on the rib cage. 相似文献
7.
Vascular tree structure affects lung blood flow heterogeneity simulated in three dimensions 总被引:3,自引:0,他引:3
Parker James C.; Cave Chris B.; Ardell Jeffrey L.; Hamm Charles R.; Williams Susan G. 《Journal of applied physiology》1997,83(4):1370-1382
Parker, James C., Chris B. Cave, Jeffrey L. Ardell, CharlesR. Hamm, and Susan G. Williams. Vascular treestructure affects lung blood flow heterogeneity simulated in threedimensions. J. Appl. Physiol. 83(4):1370-1382, 1997.Pulmonary arterial tree structures related toblood flow heterogeneity were simulated by using a symmetrical,bifurcating model in three-dimensional space. The branch angle (),daughter-parent length ratio(rL), branchrotation angle (), and branch fraction of parent flow () for asingle bifurcation were defined and repeated sequentially through 11 generations. With fixed at 90°, tree structures were generatedwith between 60 and 90°,rL between 0.65 and 0.85, and an initial segment length of 5.6 cm and sectioned into1-cm3 samples for analysis. Bloodflow relative dispersions (RD%) between 52 and 42% and fractaldimensions (Ds)between 1.20 and 1.15 in 1-cm3samples were observed even with equal branch flows. When 0.5, RD% increased, butDs eitherdecreased with gravity bias of higher branch flows or increased withrandom assignment of higher flows. Blood flow gradients along gravityand centripetal vectors increased with biased flow assignment of higherflows, and blood flows correlated negatively with distance only when 0.5. Thus a recursive branching vascular tree structuresimulated Ds andRD% values for blood flow heterogeneity similar to those observedexperimentally in the pulmonary circulation due to differences in thenumber of terminal arterioles per1-cm3 sample, but blood flowgradients and a negative correlation of flows with distance requiredunequal partitioning of blood flows at branchpoints. 相似文献
8.
The relativelyrecent detection of nitric oxide (NO) in the exhaled breath hasprompted a great deal of experimentation in an effort to understand thepulmonary exchange dynamics. There has been very little progress intheoretical studies to assist in the interpretation of the experimentalresults. We have developed a two-compartment model of the lungs in aneffort to explain several fundamental experimental observations. Themodel consists of a nonexpansile compartment representing theconducting airways and an expansile compartment representing thealveolar region of the lungs. Each compartment is surrounded by a layerof tissue that is capable of producing and consuming NO. Beyond thetissue barrier in each compartment is a layer of blood representing thebronchial circulation or the pulmonary circulation, which are bothconsidered an infinite sink for NO. All parameters were estimated fromdata in the literature, including the production rates of NO in the tissue layers, which were estimated from experimental plots of theelimination rate of NO at end exhalation (ENO) vs. theexhalation flow rate (E). The modelis able to simulate the shape of the NO exhalation profile and tosuccessfully simulate the following experimental features of endogenousNO exchange: 1) an inverse relationship between exhaled NOconcentration and E, 2) the dynamic relationship between the phase III slope andE, and 3) the positiverelationship between ENO andE. The model predicts that theserelationships can be explained by significant contributions of NO inthe exhaled breath from the nonexpansile airways and the expansilealveoli. In addition, the model predicts that the relationship betweenENO and E can be used as anindex of the relative contributions of the airways and the alveoli toexhaled NO. 相似文献
9.
Gozal Evelyne; Roussel Anisha L.; Holt Gregory A.; Gozal Lyad; Gozal Yair M.; Torres Jose E.; Gozal David 《Journal of applied physiology》1998,84(6):1982-1990
This study aimedto determine the role of protein kinase C (PKC) in signal transductionmechanisms underlying ventilatory regulation in the nucleus tractussolitarii (NTS). Microinjection of phorbol 12-myristate 13-acetate intothe commissural NTS of nine chronically instrumented, unrestrained ratselicited significant cardiorespiratory enhancements that lasted for atleast 4 h, whereas administration of vehicle(n = 15) or the inactive phorbol ester 4-phorbol 12,13-didecanoate (n = 7)did not elicit minute ventilation (E)changes. Peak hypoxic Eresponses (10% O2-balanceN2) were measured in 19 additional animals after NTS microinjection of bisindolylmaleimide(BIM) I, a selective PKC inhibitor (n = 12), BIM V (inactive analog; n = 7),or vehicle (Con; n = 19). In Con,E increased from 139 ± 9 to 285 ± 26 ml/min in room air and hypoxia, respectively, and similarresponses occurred after BIM V. BIM I did not affect room airE but markedly attenuated hypoxia-induced E increases (128 ± 12 to 167 ± 18 ml/min; P < 0.02 vs. Con and BIM V). When BIM I was microinjected into the cerebellum(n = 4), cortex(n = 4), or spinal cord(n = 4),E responses were similar to Con.Western blots of subcellular fractions of dorsocaudal brain stemlysates revealed translocation of PKC, , , , , and isoenzymes during acute hypoxia, and enhanced overall PKC activity wasconfirmed in the particulate fraction of dorsocaudal brain stem lysatesharvested after acute hypoxia. These studies suggest that, in the adultrat, PKC activation in the NTS mediates essential components of theacute hypoxic ventilatory response. 相似文献
10.
Khimenko Pavel L.; Bagby G. J.; Fuseler J.; Taylor Aubrey E. 《Journal of applied physiology》1998,85(6):2005-2011
The effects ofboth recombinant rat tumor necrosis factor- (TNF-) and ananti-TNF- antibody were studied in isolated buffer-perfused ratlungs subjected to either 45 min of nonventilated[ischemia-reperfusion (I/R)] or air-ventilated(/R) ischemia followed by 90 min of reperfusion and ventilation. In the I/R group, the vascularpermeability, as measured by the filtration coefficient(Kfc),increased three- and fivefold above baseline after 30 and 90 min ofreperfusion, respectively (P < 0.001). Over the same time intervals, theKfc for the/R group increased five- and tenfold above baseline values, respectively (P < 0.001).TNF- measured in the perfusates of both ischemic modelssignificantly increased after 30 min of reperfusion. Recombinant ratTNF- (50,000 U), placed into perfusate after baseline measurements,produced no measurable change in microvascular permeability in controllungs perfused over the same time period (135 min), but I/R injury wassignificantly enhanced in the presence of TNF-. An anti-TNF-antibody (10 mg/rat) injected intraperitoneally into rats 2 h beforethe lung was isolated prevented the microvascular damage in lungsexposed to both I/R and /R (P < 0.001). These results indicatethat TNF- is an essential component at the cascade of events thatcause lung endothelial injury in short-term I/R and/R models of lung ischemia. 相似文献
11.
Liposome encapsulation attenuates hemoglobin-induced vasoconstriction in rabbit arterial segments 总被引:2,自引:0,他引:2
Rudolph Alan S.; Sulpizio Anthony; Hieble Paul; Macdonald Victor; Chavez Mark; Feuerstein Giora 《Journal of applied physiology》1997,82(6):1826-1835
Rudolph, Alan S., Anthony Sulpizio, Paul Hieble, VictorMacdonald, Mark Chavez, and Giora Feuerstein. Liposomeencapsulation attenuates hemoglobin-induced vasoconstriction in rabbitarterial segments. J. Appl. Physiol.82(6): 1826-1835, 1997.Free hemoglobin (Hb) induces a potentvasoconstrictor response that may limit its therapeutic application asa red blood cell replacement. We have investigated whetherencapsulation of stroma-free Hb (SFHb) or cross-linked Hb (-Hb)in liposomes modulates Hb vasoactivity in isolated blood vessels.Relaxation of rabbit thoracic vessels was measured before and afterexposure to acellular SFHb, -Hb, and liposome-encapsulated SFHbor -Hb. SFHb and -Hb caused significant inhibition ofcarbachol-induced relaxation at 0.5 mg/dl, whereas encapsulationinhibited vessel relaxation at 30- to 60-fold higher Hb concentrations.The contractile response of rabbit ear arterial segments to electricalstimulation in the presence of acellular -Hb resulted in a 150%increase (EC150) in contractileamplitude at 0.23 mg/dl, whereas theEC150 for encapsulated -Hbwas 13.7 mg/dl. Mechanistic studies of the vasoconstrictor activity ofHb demonstrated that acellular -Hb had no effect onnorepinephrine release in the rabbit ear artery. In addition, neitheracellular nor encapsulated -Hb preparations inhibited endothelialnitric oxide (NO) synthase activity isolated from bovine pulmonaryartery. However, inhibition of vessel relaxation by acellular orencapsulated -Hb was reversed by the NO donor S-nitrosylpenacillamine, implicatingHb-NO binding as a possible mechanism for the vasoconstrictor response.In vitro stopped-flow kinetic studies of Hb-NO binding showed similarrates of reaction for conversion of oxyhemoglobin to methemoglobin(metHb; <2 ms), followed by rapid conversion of metHb to NO-Hb (300 ms) for both acellular and encapsulated -Hb, demonstrating thatliposome encapsulation does not retard NO-Hb binding. The attenuatedvasoactivity of encapsulated Hb may, therefore, result from the limitedaccess of encapsulated Hb to NO imposed by the physical size of theliposome and reduced penetration of Hb across the vascular endothelium. 相似文献
12.
Interaction of cross-sectional area, driving pressure, and airflow of passive velopharynx 总被引:2,自引:0,他引:2
Isono Shiroh; Feroah Thom R.; Hajduk Eric A.; Brant Rollin; Whitelaw William A.; Remmers John E. 《Journal of applied physiology》1997,83(3):851-859
Isono, Shiroh, Thom R. Feroah, Eric A. Hajduk, Rollin Brant,William A. Whitelaw, and John E. Remmers. Interaction ofcross-sectional area, driving pressure, and airflow of passive velopharynx. J. Appl. Physiol. 83(3):851-859, 1997.Previous studies have shown that, when thepharyngeal muscles are relaxed, the velopharynx is a highly compliantsegment of the pharynx. Thus, under these circumstances,cross-sectional area of the velopharynx (AVP), drivingpressure across the velopharynx (P), and inspiratory airflow(I) willbe mutually interdependent variables. The purpose of the presentinvestigation was to describe the interrelation among these threevariables during inspiration. We studied 15 sleeping patients withobstructive sleep apnea/hypopnea when the pharyngeal muscles wererendered hypotonic by applying continuous positive airway pressure tothe nasal airway.AVP, determined by endoscopic imaging, was significantly greater at onset ofI limitationthan at minimum oropharyngeal pressure(P < 0.01). Snoring was neverobserved duringIlimitation. In a subgroup of six patients, values for P,I, andAVP were obtainedat 0.1-s intervals at various levels of mask pressure. For these sixpatients, the mathematical expressionI = 0.657(AVP/Amax) · P0.332,where Amax ismaximal AVP,described the relationship among the three variables(R2 = 0.962) forflow-limited and non-flow-limited inspirations. The impedance of thepassive velopharynx, defined asP0.33/,was inversely related toAVP and increaseddramatically when AVP was <0.3cm2. In summary, we observed aprogressive decrease inAVP during flow-limited inspiration in patients with obstructive sleep apnea. Thisconstriction of the velopharynx contributes to an increase invelopharyngeal impedance that, in turn, counterbalances the increase inP during flow limitation. 相似文献
13.
Griffin, M. Pamela. Role for anions in pulmonaryendothelial permeability. J. Appl.Physiol. 83(2): 615-622, 1997.-Adrenergic stimulation reduces albumin permeation across pulmonary artery endothelial monolayers and induces changes in cell morphology that aremediated by Cl flux. Wetested the hypothesis that anion-mediated changes in endothelial cellsresult in changes in endothelial permeability. We measured permeationof radiolabeled albumin across bovine pulmonary arterial endothelialmonolayers when the extracellular anion was Cl,Br,I,F, acetate(Ac), gluconate(G), and propionate(Pr). Permeability toalbumin (Palbumin)was calculated before and after addition of 0.2 mM of thephosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), whichreduces permeability. InCl, thePalbumin was 3.05 ± 0.86 × 106 cm/s andfell by 70% with the addition of IBMX. The initialPalbumin was lowest forPr andAc. InitialPalbumin was higher inBr,I,G, andF than inCl. A permeability ratiowas calculated to examine the IBMX effect. The greatest IBMX effect wasseen when Cl was theextracellular anion, and the order among halide anions wasCl > Br > I > F. Although the level ofextracellular Ca2+ concentration([Ca2+]o)varied over a wide range in the anion solutions,[Ca2+]odid not systematically affect endothelial permeability in this system.When Cl was theextracellular anion, varying[Ca2+]ofrom 0.2 to 2.8 mM caused a change in initialPalbumin but no changein the IBMX effect. The anion channel blockers4-acetamido-4-isothiocyanotostilbene-2,2-disulfonic acid(0.25 mM) and anthracene-9-carboxylic acid (0.5 mM) significantly altered initialPalbumin and the IBMXeffect. The anion transport blockers bumetanide (0.2 mM) and furosemide(1 mM) had no such effects. We conclude that extracellular anionsinfluence bovine pulmonary arterial endothelial permeability and thatthe pharmacological profile fits better with the activity of anionchannels than with other anion transport processes. 相似文献
14.
Tokics Leif; Hedenstierna Goran; Svensson Leif; Brismar Bo; Cederlund Torsten; Lundquist Hans; Strandberg Ake 《Journal of applied physiology》1996,81(4):1822-1833
Tokics, Leif, Göran Hedenstierna, Leif Svensson, BoBrismar, Torsten Cederlund, Hans Lundquist, and ÅkeStrandberg. / distributionand correlation to atelectasis in anesthetized paralyzed humans.J. Appl. Physiol. 81(4):1822-1833, 1996.Regional ventilation and perfusion were studiedin 10 anesthetized paralyzed supine patients by single-photon emissioncomputerized tomography. Atelectasis was estimated from twotransaxial computerized tomography scans. The ventilation-perfusion(/) distribution was alsoevaluated by multiple inert gas elimination. While the patients wereawake, inert gas / ratio wasnormal, and shunt did not exceed 1% in any patient. Computerizedtomography showed no atelectasis. During anesthesia, shunt ranged from0.4 to 12.2%. Nine patients displayed atelectasis (0.6-7.2% ofthe intrathoracic area), and shunt correlated with the atelectasis(r = 0.91, P < 0.001). Shunt was located independent lung regions corresponding to the atelectatic area. There wasconsiderable / mismatch, withventilation mainly of ventral lung regions and perfusion of dorsalregions. Little perfusion was seen in the most ventral parts (zone 1)of caudal (diaphragmatic) lung regions. In summary, shunt during anesthesia is due to atelectasis in dependent lung regions. The / distributions differ fromthose shown earlier in awake subjects. 相似文献
15.
Clark Justin S.; Lin Yuxiang J.; Criddle Michael J.; Cutillo Antonio G.; Bigler Adelbert H.; Farr Fred L.; Renzetti Attilio D. Jr. 《Journal of applied physiology》1997,83(3):884-896
Clark, Justin S., Yuxiang J. Lin, Michael J. Criddle,Antonio G. Cutillo, Adelbert H. Bigler, Fred L. Farr, and Attilio D. Renzetti, Jr. Cardiac output and mixed venous oxygen content measurements by a tracer bolus method: theory. J. Appl.Physiol. 83(3): 884-896, 1997.We present a bolus method ofinert-gas delivery to the lungs that facilitates application ofmultiple inert gases and the multiple inert-gas-exchange technique(MIGET) model to noninvasive measurements of cardiac output (CO) andcentral mixed venous oxygen contentReduction in recirculation error is made possible by 1)replacement of sinusoidal input functions with impulse inputs and2) replacement of steady-state analyses with transientanalyses. Recirculation error reduction increases the inert-gasselection to include common gases without unusually high (and difficultto find) tissue-to-blood partition coefficients for maximizing thesystemic filtering efficiency. This paper also presents a practicalmethod for determining the recirculation contributions to inert expiredprofiles in animals and determining their specific contributions toerrors in the calculations of CO and from simulationsapplied to published ventilation-perfusion ratio(/) profiles.Recirculation errors from common gases were found to be reducible tothe order of 5% or less for both CO and whereassimulation studies indicate that measurement bias contributions fromrecirculation, / mismatch, andthe / extractionprocess can be limited to 15% for subjects with severe/ mismatch and high inspiredoxygen fraction levels. These studies demonstrate a decreasinginfluence of / mismatch onparameter extraction bias as the number of inert gases are increased.However, the influence of measurement uncertainty on parameterextraction error limits improvement to six gases. 相似文献
16.
The object of this study was to investigatehow changes in the contractile state of smooth muscle would modifyoscillatory mechanics of tracheal muscle and lung parenchyma duringagonist challenge. Guinea pig tracheal and parenchymal lung strips were suspended in an organ bath. Measurements of length(L) and tension (T) were recordedduring sinusoidal oscillations under baseline conditions and afterchallenge with 1 mM ACh. Measurements were also obtained in stripspretreated with the calmodulin inhibitor calmidazolium (Cmz) orstaurosporine (Stauro), a protein kinase C inhibitor. Elastance (E) andresistance (R) were calculated by fitting changes in T,L, andL/tto the equation of motion. Hysteresivity () was obtained from thefollowing equation: = (R/E)2f,where f is frequency. Finally, maximalunloaded shortening velocity during electrical field stimulation wasmeasured in Cmz-pretreated and control tracheal strips. In trachealstrips, pretreatment with Cmz caused a significant decrease in the response to ACh challenge and in maximal unloaded shortening velocitymeasured during electrical field stimulation; Stauro decreased the T,E, and R response to ACh. In parenchymal strips, Cmz decreased the response, whereas Stauro had no effect. These results suggest thatmodifications in the contractile state of the smooth muscle arereflected in changes in the hysteretic behavior and that T and maybe controlled independently. Second, inasmuch as changes in weresimilar in parenchymal and tracheal strips, the contractile element isimplicated as the structure responsible for constriction-induced changes in the mechanical behavior of the lung periphery. 相似文献
17.
Combined heart rate and activity improve estimates of oxygen consumption and carbon dioxide production rates 总被引:1,自引:0,他引:1
Moon, Jon K., and Nancy F. Butte. Combined heart rateand activity improve estimates of oxygen consumption and carbon dioxideproduction rates. J. Appl. Physiol.81(4): 1754-1761, 1996.Oxygen consumption(O2) andcarbon dioxide production (CO2) rates were measuredby electronically recording heart rate (HR) and physical activity (PA).Mean daily O2 andCO2 measurements by HR andPA were validated in adults (n = 10 women and 10 men) with room calorimeters. Thirteen linear and nonlinear functions of HR alone and HR combined with PA were tested as models of24-h O2 andCO2. Mean sleepO2 andCO2 were similar to basalmetabolic rates and were accurately estimated from HR alone[respective mean errors were 0.2 ± 0.8 (SD) and0.4 ± 0.6%]. The range of prediction errorsfor 24-h O2 andCO2 was smallestfor a model that used PA to assign HR for each minute to separateactive and inactive curves(O2, 3.3 ± 3.5%; CO2, 4.6 ± 3%). There were no significant correlations betweenO2 orCO2 errors and subject age,weight, fat mass, ratio of daily to basal energy expenditure rate, orfitness. O2,CO2, and energy expenditurerecorded for 3 free-living days were 5.6 ± 0.9 ml · min1 · kg1,4.7 ± 0.8 ml · min1 · kg1,and 7.8 ± 1.6 kJ/min, respectively. Combined HR and PA measured 24-h O2 andCO2 with a precisionsimilar to alternative methods. 相似文献
18.
Carvalho Paula; Johnson Shane R.; Charan Nirmal B. 《Journal of applied physiology》1998,84(1):215-221
Carvalho, Paula, Shane R. Johnson, Nirmal B. Charan.Non-cAMP-mediated bronchial arterial vasodilation in response toinhaled -agonists. J. Appl.Physiol. 84(1): 215-221, 1998.We studied thedose-dependent effects of inhaled isoetharine HCl, a -adrenergicbronchodilator (2.5, 5.0, 10.0, and 20.0 mg), on bronchial blood flow(br) in anesthetized sheep. Isoetharine resulted ina dose-dependent increase in br. With atotal dose of 17.5 mg, br increased from baselinevalues of 22 ± 3.4 (SE) to 60 ± 16 ml/min(P < 0.001), an effect independentof changes in cardiac output and systemic arterial pressure. To furtherstudy whether synthesis of endogenous nitric oxide (NO) affects-agonist-induced increases in br, weadministered isoetharine (20 mg) by inhalation before and after theNO-synthase inhibitorN-nitro-L-argininemethyl ester (L-NAME).Intravenous L-NAME (30 mg/kg) rapidly decreased br by ~80% of baseline,whereas L-NAME via inhalation(10 mg/kg) resulted in a delayed and smaller (~22%) decrease.Pretreatment with L-NAME viaboth routes of administration attenuated bronchial arterialvasodilation after subsequent challenge with isoetharine. We concludethat isoetharine via inhalation increases br in adose-dependent manner and that -agonist-induced relaxation ofvascular smooth muscle in the bronchial vasculature is partiallymediated via synthesis of NO. 相似文献
19.
Zschauer A. O.A.; Sielczak M. W.; Smith D. A.S.; Wanner A. 《Journal of applied physiology》1997,82(6):1918-1925
Zschauer, A. O. A., M. W. Sielczak, D. A. S. Smith, and A. Wanner. Norepinephrine-induced contraction of isolated rabbit bronchial artery: role of 1-and 2-adrenoceptor activation. J. Appl. Physiol. 82(6):1918-1925, 1997.The contractile effect of norepinephrine (NE) onisolated rabbit bronchial artery rings (150-300 µm in diameter)and the role of 1- and2-adrenoceptors (AR) on smoothmuscle and endothelium were studied. In intact arteries, NE increasedtension in a dose-dependent manner, and the sensitivity for NE wasfurther increased in the absence of endothelium. In intact but not inendothelium-denuded arteries, the response to NE was increased in thepresence of both indomethacin (Indo; cyclooxygenase inhibitor) andNG-nitro-L-argininemethyl ester [L-NAME;nitric oxide (NO) synthase inhibitor], indicating that twoendothelium-derived factors, NO and a prostanoid, modulate theNE-induced contraction. The1-AR antagonist prazosinshifted the NE dose-response curve to the right, and phenylephrine(1-AR agonist) induced adose-dependent contraction that was potentiated byL-NAME or removal of theendothelium. The sensitivity to NE was increased slightly by the2-AR antagonists yohimbine andidazoxan, and this effect was abolished by Indo or removal of theendothelium. Similarly, contractions induced by UK-14304(2-AR agonist) were potentiatedby Indo or removal of the endothelium. These results suggest thatNE-induced contraction is mediated through activation of1- and2-ARs on both smooth muscle andendothelium. Activation of the1- and2-ARs on the smooth musclecauses contraction, whereas activation of the endothelial 1- and2-ARs induces relaxationthrough release of NO (1-ARs) and a prostanoid (2-ARs). 相似文献
20.
Muscle capillarization, O2 diffusion distance, and VO2 kinetics in old and young individuals 总被引:1,自引:0,他引:1
Chilibeck P. D.; Paterson D. H.; Cunningham D. A.; Taylor A. W.; Noble E. G. 《Journal of applied physiology》1997,82(1):63-69
Chilibeck, P. D., D. H. Paterson, D. A. Cunningham, A. W. Taylor, and E. G. Noble. Muscle capillarization,O2 diffusion distance, andO2 kinetics in old andyoung individuals. J. Appl. Physiol.82(1): 63-69, 1997.The relationships between muscle capillarization, estimated O2diffusion distance from capillary to mitochondria, andO2 uptake(O2) kineticswere studied in 11 young (mean age, 25.9 yr) and 9 old (mean age, 66.0 yr) adults. O2kinetics were determined by calculating the time constants () forthe phase 2 O2 adjustment to andrecovery from the average of 12 repeats of a 6-min, moderate-intensityplantar flexion exercise. Muscle capillarization was determined fromcross sections of biopsy material taken from lateral gastrocnemius.Young and old groups had similarO2 kinetics(O2-on = 44 vs. 48 s;O2-off = 33 vs. 44 s, for young and old, respectively), muscle capillarization, andestimated O2 diffusion distances.Muscle capillarization, expressed as capillary density or averagenumber of capillary contacts per fiber/average fiber area, and theestimates of diffusion distance were significantly correlated toO2-off kinetics in theyoung (r = 0.68 to 0.83;P < 0.05). We conclude that1) capillarization andO2 kinetics during exerciseof a muscle group accustomed to everyday activity (e.g., walking) arewell maintained in old individuals, and2) in the young, recovery of O2 after exercise isfaster, with a greater capillary supply over a given muscle fiber areaor shorter O2 diffusion distances. 相似文献