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1.
Summary Static relationships between arterial, transcutaneous[/p] and end-tidal PCO2 (P aCO2, P tc CO 2, P etCO2) as well as the dynamic relationship between P etCO2 and P tcCO2 were studied during moderate bicycle ergometer exercise with and without external C02 loading. The exercise pattern consisted of 5-min intervals of constant power at 40 W and 100 W and 900 s of randomised changes between these two power levels. The external CO2 loading was achieved by means of controlled variations of inspiratory gas compositions aimed at a constant P etCO2 of 6.5 kPa (49 mm Hg). The PetO2 was regulated at 17.3 kPa (130 mm Hg). Under steady-state conditions all PCO2 parameters showed close linear relationships. P aCO2/P tcCO2 was near to identity while the P etCO2 systematically overestimated changes in P aCO2. No relationship showed a significant influence of the exercise intensity. Transients of P tcCO2 are considerably slower than P etCO2 transients. The dynamic relationship between both parameters was found to be independent of whether internal or external C02 loadings were applied. It is concluded that the combination of P etCO2 and P tcCO2 measurements allows an improved non-invasive assessment of P aCO2. While P etC02 better reflects the transients, P tcCO2 can be employed to determine slow changes of the absolute P aCO2.  相似文献   

2.
APCO2 electrode working on the principle of electrical conductivity is described. The calibration curve can be linearized according to the formula . This linearity has been tested in thePCO2 range of 0.93–9.33 kPa (7–70 Torr). For the experiments electrodes are used which have conductivity values of about 50 nS and drifts of maximally 5%/h at aPCO2 of 5.33 kPa (40 Torr). The response time (T 90) is about 20 s. The temperature sensitivity is 2.4 nS/1 K between 298K–310K. The standard error of the measurements is =0.33 nS. With these electrodes tissuePCO2 can be measured on the surface of various organs.  相似文献   

3.
We describe here the construction and properties of a double-barrelled microelectrode (tip diameter 4–10 m) which permits simultaneous measurements of PCO2 and pH, and which has a 90% response time of only one or a few seconds for a step change in PCO2. The fast response of the CO2-sensitive barrel is due to (i) the use of a PVC-gelled (tridodecylamine-containing) membrane solution which enables the construction of extremely short ( 4 m), yet mechanically stable, membrane columns, and (ii) the presence of carbonic anhydrase in the filling solution. Recordings made in the pyramidal layer of area CA1 in rat hippocampal slices showed that the deviation in the acid direction of the basal interstitial pH (pH0) from that of the perfusion solution was attributable to a higher PCO2 level within the tissue. Most of the late acid shift evoked by stimulation of the Schaffer collaterals (5- to 20-s trains at 10 Hz) could also be explained on the basis of an accumulation of interstitial CO2 at a constant HCO 3 concentration. This conclusion was supported by the finding that inhibition of extracellular carbonic anhydrase activity by 10 M benzolamide completely abolished the activity-induced fall in pH0, but not the increase in PCO2. The initial stimulus-induced alkalosis was accompanied by a slight decrease in PCO2 only, implying a parallel increase in the interstitial HCO 3 concentration. Benzolamide produced a dramatic enhancement of the early alkaline shift as well as of the simultaneous fall in PCO2. The latter effect of the drug unmasks a cellular CO2 sink that is induced by neuronal activity.  相似文献   

4.
A new device was developed for rapid assessment of PO2 values in viable tissue, such as the brain, using a multiwire surface electrode. The instrument utilizes a phonograph-like construction with weightless suspension of the electrode which thus minimizes surface pressure and allows for compensation of brain movements. The new and original component of the present device is the motor-driven, servo-controlled rotation of the PO2 electrode around its vertical axis. This enables PO2 measurements from precisely defined locations. From values measured on rabbit brain surface a PO2 histogram was constructed. The mean PO2 and distribution histogram were similar to those obtained with a needle electrode. The novel device, therefore, enables accurate and fast tissue PO2 measurements with minimal risk of brain damage.  相似文献   

5.
Some membrane electrical properties of muscle cells from the middle cerebral artery of the rat were recorded with intracellular microelectrodes. The resting membrane potential (E m) of this preparation was –63 mV. Reduction of extracellular pH to 7.0 in the face of a constantP CO 2of 40 mm Hg had no significant effect onE m. Similarly the slope of the steady-state voltage/current curves was not different at pH 7.0 compared to control at pH 7.4. In marked contrast, whenP CO 2was elevated to around 60 to 70 mm Hg there was a rapid hyperpolarization and reduction in the slope of the voltage current curve suggesting an increased conductance for one or more ionic species. In addition elevation ofP CO 2increased the slope of theE m vs. log[K]0 curve from 46 mV/decade to 59 m V/decade which is in good agreement with a Nernstian potential for a K+ selective membrane. These data suggest that while the smooth muscle cells of rat cerebral arteries are relatively insensitive to a small reduction in extracellular pH; reduction of intracellular pH by elevatingP CO 2induces hyperpolarization by increasing K+ conductance (g k). However, it is not clear from these experiments if theP CO 2effects are mediated entirely by changes in pH or if there is a direct membrane action of CO2.This work is supported by Grant no. HL27862  相似文献   

6.
Summary In 11 adult cats, lightly anesthetized with chloralose-urethane, blood from both common carotid arteries was led into a plastic chamber of 15–20 ml and returned to the carotids at a point 1.5 cm more cranial. By doing so arterial blood was assumed to pool within the chamber and lose itsP CO 2 oscillations which are normally known to exist as a result of the respiratory cycle. In control periods blood bypassed the chamber, thus maintaining respiratoryP CO 2 oscillations. Spontaneous ventilation was measured spirometrically. The animals were breathing pure O2.Results. 1. When the sinus (carotid) nerves were intact or sectioned there was no significant difference in ventilation before or after switching from non-oscillating to oscillatingPa CO 2. 2. When the vertebral arteries were ligated a drop in ventilation occurred after turning to oscillatingPa CO 2 which was followed by a slight rise above control values after 30–50 sec. This phenomenon was independent of sinus nerve integrity. Thus in hyperoxie condition the smallPa CO 2 oscillations known to occur in phase with respiration do not seem to provide a respiratory stimulus to resting ventilation above that generated by the mean level ofPa CO 2. The ventilatory depression after vertebral artery ligation must at this time remain unexplained.  相似文献   

7.
On reaching the respiratory compensation point (RCP) during rapidly increasing incremental exercise, the ratio of minute ventilation (VE) to CO2 output (VCO2) rises, which coincides with changes of arterial partial pressure of carbon dioxide (P aCO2). Since P aCO2 changes can be monitored by transcutaneous partial pressure of carbon dioxide (PCO2,tc) RCP may be estimated by PCO2,tc measurement. Few available studies, however, have dealt with comparisons between PCO2,tc threshold (T AT) and lactic, ventilatory or gas exchange threshold (V AT), and the results have been conflicting. This study was designed to examine whether this threshold represents RCP rather than V AT. A group of 11 male athletes performed incremental excercise (25 W · min–1) on a cycle ergometer. The PCO2,tc at (44°C) was continuously measured. Gas exchange was computed breath-by-breath, and hyperaemized capillary blood for lactate concentration ([la]b) and P aCO2 measurements was sampled each 2 min. The T AT was determined at the deflection point of PCO2,tc curve where PCO2,tc began to decrease continuously. The V AT and RCP were evaluated with VCO2 compared with oxygen uptake (VO2) and VE compared with the VCO2 method, respectively. The PCO2,tc correlated with P aCO2 and end-tidal PCO2. At T AT, power output [P, 294 (SD 40) W], VO2 [4.18 (SD 0.57)l · min–1] and [la] [4.40 (SD 0.64) mmol · l–1] were significantly higher than those at V AT[P 242 (SD 26) W, VO2 3.56 (SD 0.53) l · min–1 and [la]b 3.52 (SD 0.75), mmol · l–1 respectively], but close to those at RCP [P 289 (SD 37) W; VO2 3.97 (SD 0.43) l · min and [la]b 4.19 (SD 0.62) mmol · l–1, respectively]. Accordingly, linear correlation and regression analyses showed that P, VO2 and [la]b at T AT were closer to those at RCP than at V AT. In conclusion, the T AT reflected the RCP rather than V AT during rapidly increasing incremental exercise.  相似文献   

8.
Summary The differences inP O 2readings between gas and blood were studied with a Clark-type electrode in the range of 38.5 to 713 mm HgP O 2.The tonometered blood samples were taken in two different ways. The results showed that the gas-blood ratior b(equilibrating gasP O 2reading/equilibrated bloodP O 2reading) depended not only on the sampling method but also on theP O 2range: it varied from 1.005 to 1.032 for aP O 2of 96.5 mm Hg, and from 1.040 to 1.081 for aP O 2of 713 mm Hg according to the sampling procedure.A theoretical analysis demonstrated that the variation ofr bwith the bloodP O 2can be attributed to the influence of the degree of oxygen saturation of the hemoglobin on theP O 2gradient existing in the blood diffusion boundary layer adhering to the electrode membrane.This work was supported by grants from the High Authority of the European Coal and Steel Community and from the Fonds de la Recherche Scientifique Médicale, Belgium.  相似文献   

9.
Summary It is possible to perform continuous quantitativeP O 2 measurements on vasodilated skin by means of surface Pt electrodes according to Clark when the electrode is fixed to the skin with a synthetic plastic material and in situ calibration is performed. A new in situ calibration of theP O 2 electrode is described. At first the skinP O 2 increases with O2 inspiration. After perfusion stop the skinP O 2 shows a linear decrease because of the skin respiration, down to aP O 2 at which hemoglobin liberates chemically bound O2. As thisP O 2 value of hemoglobin is known it is possible to use it for calibrating the electrode. TheP O 2 of normal skin is about 0–7 Torr. After vasodilation obtained by rubbing with a nicotinic acid derivate (Finalgon®, Anasco, Wiesbaden),P O 2 increases to a mean value of 38.1 (±8.1) Torr (n=77). Under these conditions, skinP O 2 reaches arterial values never in adults and rarely in new-born babies.Part of the results have been reported during the Workshop on Oxygen Transport in Tissue, 19–22 July, 1971, in Dortmund and at the 4. Deutsche Kongress für Perinatale Medizin, 4–6 Nov. 1971, in Berlin. The study was carried out with partial support from the German Research Council (DFG).  相似文献   

10.
Summary In rabbits rebreathing oxygen one carotid sinus nerve was stimulated repeatedly by electrical stimuli of constant intensity, both before and after inactivation of vagi by cold blocking or sectioning. In animals with intact vagi the reflex hyperpnea elicited by the nerve stimulation decreased only slightly with increasing hypercapnia. After inactivation of the vagi the stimulatory effect was, at normalP A CO 2, mostly greater than in the intact condition. But with increasing hypercapnia the decrease of the reflex hyperpnea was generally steeper than in the intact preparation, sometimes reaching even lower values than before inactivation. The depressant effects of the stimulation on systemic blood pressure and heart rate were not distinctly changed by the increase ofP A CO 2, neither with intact nor with inactivated vagi. It is concluded that the ventilatory effect of chemoreceptor afferents is modified both by centralP CO 2 and by vagal afferents.
Mit Unterstützung der Deutschen Forschungsgemeinschaft (Wi 165).  相似文献   

11.
These studies were undertaken to determine the effect of reducing aPCO2 below physiological levels on cat middle cerebral artery. Upon reduction ofPCO2 from 37 to 14 torr (pH 7.4) we observed membrane depolarization and force development. ReducingPCO2 decreased the slope of theE m vs. log [K]o curve and increased the slope of the steady-state I/V relationship suggesting that the change inE m was due to reduction of outward K+ conductance (g k). Elevation of pH from 7.37 to 7.6 had a very similar effect on these cerebral arterial muscle cells, depolarizing the muscle membrane (reducing theE m vs. log [K]o curve) and increasing the slope of the I/V relationship to statistically equivalent values as reduction ofPCO2. ReturningPCO2 from 14 to 37 torr rapidly relaxed these preparations, but only transiently. This relaxation was followed by a rebound contraction within 3 min, demonstrating a transient nature for the action of elevatingPCO2 in cerebral arteries. The response to changing pHo followed a slower time course but did not change with time. These studies demonstrate that both elevated pHo and reducedPCO2 activate cerebral arterial muscle by a mechanism which includes reduction ing k. However, it can not be determined if these similar responses and reduction, ofg k are mediated by changing pHi or mediated through different mechanisms. It is possible that pHo andPCO2 can modify cerebral arterial tone by direct mechanisms and not necesarily by their effect on pHi. It is clear, however, that reduction ofPCO2 and elevation of pHo both activate cerebral arterial muscle by a mechanism which includes reduction ofg k.This study was supported by NIH grant no. HL-32871. Dr. Harder is an established investigator of the American Heart Association  相似文献   

12.
Mass spectrometry was used for the continuous, simultaneous and quantitative measurement of oxygen (PO2) and carbon dioxide (PCO2) partial pressures in the subendocardial and subepicardial layers of the left ventricle in 11 anaesthetized ventilated dogs. Under control conditions,PO2 was significantly lower in the subendocardium (13.5±4.5 mm Hg) than in the subepicardium (20.7±2.3 mm Hg), whereasPCO2 did not differ significantly (43±8.8 and 51±9.2 mm Hg respectively). These variables were not correlated with blood pressure or coronary blood flow. Subendocardial and subepicardialPO2 decreased less than 5 s after coronary occlusion. These changes were more rapid and severe in the subendocardium. After occlusion for 90 s: subendocardialPO2 was 4.1±6.3 mm Hg while subepicardialPO2 was 6.7±15.0 mm Hg (P<0.05).PCO2 reached peak values of 56±25 mm Hg subendocardial and 82±22 mm Hg subepicardial at 2.67±0.71 min and 3.43±0.93 min after coronary clamping. A reactive hyperemia occurred after coronary unclamping with different time courses and amplitudes for systolic and diastolic stroke flows whilePO2 recovered with different kinetics. SubendocardialPO2 increased with a lower initial slope, probably in relation with the delay in the diastolic hyperemia. The observed delayed subendocardial hyperoxia, unrelated to the hyperemia, may indicate a delay in the recovery of normal work and metabolism in the inner layers of the myocardium.  相似文献   

13.
We attempted to analyze how is regulated during progesterone-induced hyperventilation in the luteal phase. A model for the CO2 control loop was constructed, in which the function of the CO2 exchange system was described as and that of the CO2 sensing system as . Using this model, we estimated (1) the primary increase in produced by progesterone stimulation and (2) the effectiveness (E) of the loop to regulateP A CO 2, defined as P A CO 2 (op)/P A CO 2 (cl) in which op signifies open-loop and cl, closed-loop. These respiratory variables were investigated throughout the menstrual cycle in 8 healthy women. During the luteal phase, on average, increased by 9.4% andP A CO 2,B andH decreased by 0.33 kPa (2.5 mm Hg), 0.47 kPa (3.5 mm Hg) and 13.6%, respectively, whileS and did not change significantly. (op) increased progressively on successive days of the luteal phase whileE remained unchanged at a value of 7.9, thus there was a progressive decrease inP A CO 2. The decrease inH was considered to lessen P A CO 2 (op) and so reduce the final deviation ofP A CO 2 (P A CO 2 (cl)) during the luteal phase. The decrease inB was found to be dependent on (op).  相似文献   

14.
Summary The purpose of this study was to determine the effect of fitness and work level on the O2 uptake and CO2 output kinetics when the increase in work rate step is adjusted to the subject's maximum work capacity. Nine normal male subjects performed progressive incremental cycle ergometer exercise tests in 3-min steps to their maximum tolerance. The work rate step size was selected so that the symptom-limited maximum work rate would be reached in four steps at 12 min in all subjects. Oxygen consumption (VCO2) and carbon dioxide production VCO2 were calculated breath by breath. For the group, the time (mean, SEM) to reach 75% of the 3-min response (T 0.75) for VO2 increased significantly (P<0.01) at progressively higher work rate steps, being 53.3 (5.5) s, 63.5 (4.6) s, 79.5 (5.0) s, and 94.5 (5.8) s, respectively. In contrast, T 0.75 for VCO2 did not change significantly [74.9 (7.4) s,. 75.6 (5.0) s, 85.1 (5.3) s, and 89.4 (6.3) s, respectively]. VCO2 kinetics were slower than VO2 kinetics at the low fractions of the subjects' work capacities but were the same of faster at the high fractions because of the slowing of VO2 kinetics. The first step showed the fastest rise in VO2. While VO2 kinetics slowed at each step, they were faster at each fraction of the work capacity in the fitter subjects. The step pattern in VO2 disappeared at high work rates for the less fit subjects. The heart rate response paralleled that of VO2. We conclude that VO2 and VCO2 kinetics are slower in the less fit subjects but only VO2 kinetics are significantly attenuated in response to proportional step increases in work rate.  相似文献   

15.
A commercially available catheter type electrode with whichP CO2 can be continuously measured in vivo and in vitro gave progressively less accurate results the longer the measuring period was extended. This proved to be due to temperature effects and a change in sensitivity with time. A correction procedure for these effects was developed which was based on two observations. 1. The relationship between temperature and the logarithm of the sensitivity of the electrodeamplifier combination was linear and virtually identical for 9 electrodes: 8% change in sensitivity for a deviation of 1° C from the temperature during calibration. 2. The change in sensitivity due to drift of the electrode output is approximately a logarithmic function of time: 1 h after calibration all electrodes exhibited a decreased sensitivity, varying between 0.3 and 16.7%. The drift effect can be dealt with by repeated calibrations, preferably at 11/2 h intervals.The adequacy of the correction procedure was assessed in in vivo measurements in cats and dogs. The meanP CO2 difference between the in vivo measurement, corrected for temperature and drift, and samples analyzed with a conventional electrode, was 0.005 kPa (0.04 mm Hg) with a standard deviation of 0.187 kPa (1.39 mm Hg).  相似文献   

16.
The hypothesis that sympathoexcitatory neurones within the rostroventrolateral medulla (RVLM) may be chemosensitive was tested in chloralose-anaesthetized cats by artificial perfusion of the RVLM via the left vertebral artery. The baroreceptors and peripheral chemoreceptors were denervated by bilaterally dissecting the carotid sinus and vagus nerves. Either white ramus T3 (WR-T3) or the renal nerve was recorded to monitor sympathetic activity. Perfusion with saline or Ringer solution bubbled with CO2 (10%–100%) produced a rapid and pronounced increase in sympathetic activity and blood pressure. Solutions adjusted to the same pH (pH 5.2 for 100% CO2) with HCl resulted in a much weaker excitation. A linear relationship between PCO2 and sympathetic activity was demonstrated. During prolonged perfusion (90 s) sympathetic activity returned to the control level after initial excitation and fell below control levels when perfusion ceased. The sympathetic activity response to CO2-bubbled solutions was unaffected by blockade of synaptic input by microinjection of CoCl2 into the RVLM, whereas spontaneous sympathetic activity and the supraspinal somato-sympathetic reflex from intercostal nerve T4 to WR-T3 were markedly reduced. It is therefore concluded that sympathoexcitatory bulbospinal neurones in the RVLM are directly chemosensitive to changes in arterial PCO2 and pH.This paper is dedicated to Prof. Dr. H. P. Koepchen on the occasion of his 65th birthday  相似文献   

17.
This study tested three possible mechanisms that could explain the prolonged breath-holds (BH) previously observed in humans during submersion in 35°C (thermoneutral) water, including a reduced metabolism, a decreased CO2 sensitivity, and an increased CO2 storage capacity. During immersed BH (n = 13), maximal BH time was prolonged by 20.3% (P < 0.05), the rate of rise of end tidal partial pressure of carbon dioxide (P ETCO2) was slower (P < 0.05) by 31 % (compatible with increased CO2 storage capacity), but the breaking-pointP ETCO2 (CO2 sensitivity) and the rate of decrease of end tidal partial pressure of oxygen (metabolism) were unchanged. During air breathing (n = 5), immersion resulted in a significant decrease in tidal volume (11%), but did not affect O2 uptake, CO2 elimination , or respiratory exchange ratio (R). During a 4-min CO2-rebreathing (n = 9), the slope of the hypercapnic ventilatory response curve (CO2 sensitivity index) was unchanged by immersion, but the significantly decreased ,R, and rate of rise inPETCO2 during immersed rebreathing indicated an increase in the acute CO2 storage capacity (SC). The estimated SC (n = 9), based on an assumed cellular respiratory quotient of 0.8, were 0.52 (SEM 0.03) ml · kg−1 · mmHg−1 for control and 0.66 (SEM 0.04) ml · kg−1 · mmHg−1 for immersion. A proposed mechanism for the increased SC during immersed BH and during immersed rebreathing is that immersion accelerated CO2 redistribution in the body by increasing perfusion to some low-perfused, low-metabolism, and high-capacity tissues, such as resting skeletal muscle. The increased SC during immersion, however, did not correlate with the prolonged BH duration (n = 9,P > 0.05). The mechanism of the latter remains unclear.  相似文献   

18.
The stability of arterial PCO2 (PaCO2) during moderate exercise in humans suggests a CO2-linked control that matches ventilation (E) to pulmonary CO2 clearance (CO2). An alternative view is that E is subject to long-term modulation (LTM) induced by hyperpnoeic history. LTM has been reported with associative conditioning via dead-space (VD) loading in exercising goats (Martin and Mitchell 1993). Whether this prevails in humans is less clear, which may reflect differences in study design (e.g. subject familiarisation; VD load; whether or not E is expressed relative to CO2; choice of PaCO2 estimator). After familiarisation, nine healthy males performed moderate constant-load cycle-ergometry (20 W-80 W-20 W; <lactate threshold, L): day 1, pre-conditioning, n=3; day 2, conditioning (VD=1.59 l, doubling E at 20 W and 80 W), n=8 with 10 min rest between tests; and, after 1 h rest, post-conditioning, n=3. Gas exchange was determined breath-by-breath. Post-conditioning, neither the transient [phase 1, phase 2 (1, 2)] nor steady-state E exercise responses, nor their proportionality to CO2, differed from pre-conditioning. For post-conditioning trial 1, steady-state E was 28.1 (4.7) l min–1 versus 29.1 (3.8) l min–1 pre-conditioning, and mean-alveolar PCO2 (a validated PaCO2 estimator) was 5.53 (0.48) kPa [41.5 (3.6) mmHg] versus 5.59 (0.49) kPa [41.9 (3.7) mmHg]; the 1 E increment was 4.2 (2.9) l min–1 versus 5.2 (1.9) l min–1; the 2 E time-constant () was 64.4 (24.1) s versus 64.1 (25.3) s; E/CO2 was 1.12 (0.04) versus 1.10 (0.04); and the E-CO2 slope was 21.7 (3.4) versus 21.2 (3.2). In conclusion, we could find no evidence to support ventilatory control during moderate exercise being influenced by hyperpnoeic history associated with dead-space loading in humans.  相似文献   

19.
CO2 responsivity in the mouse measured by rebreathing   总被引:1,自引:0,他引:1  
We have modified the rebreathing method to study CO2 responsivity in very small mammals. Tidal volume (V T) and frequency (f) of pentobarbital-anesthetized mice were measured during rebreathing from a closed circuit, primed with 95% O2, 5% CO2, through which the gas was constantly circulated at 0.5 l·min–1. The circuit consisted of T-tube from a plethysmograph, Tygon tubing with compliant element, CO2 analyzer and pump, in series. CircuitPCO2 (PctCO2), which was recorded continuously during spontaneous breathing, rapidly equilibrated with end-tidalPCO2. CO2 response curves were constructed from extrapolated minute ventilation ( ),V T,f and parameters of breath-to-breath timing, respectively, onPctCO2. Analyses of slopes of the response curves, change from onset of rebreathing to peak response, andPctCO2 at which the response peaked revealed that CO2 stimulates by increasingf andV T and that this is effected by facilitation of central inspiratory-expiratory phase switching and inspiratory drive mechanisms. However, the stimulatory effect of CO2 on phase switching was not sustained, with maximal effect occurring before peak . The advantages and facility of the modified rebreathing method make it suitable for studies of other small mammals, including neonates.  相似文献   

20.
Zusammenfassung Um zu untersuchen, wie ein Tauch- oder Atemanhalte-manöver den Sauerstoffverbrauch und die CO2-Abgabe des Menschen beeinflußt, hielten 6 männliche Versuchspersonen 30, 60, 90, 120 und 165 sec ruhig an der Wasseroberfläche und an Land liegend den Atem an. In einer Vergleichsserie tauchten sie in 80 cm Tiefe gleich lange.Nach der Apnoe wurden der endexspiratorischeP O 2 undP CO 2, und die Sauerstoffaufnahme und die CO2-Abgabe pro Atemzug mit Hilfe eines Massenspektrometers und eines Pneumotachographen ermittelt.Es zeigte sich, daß die Sauerstoffschuld, die während der Apnoe eingegangen wird, beim Atemanhalten im Wasser bis zu 29%, an Land bis zu 38% unter der O2-Schuld lag, die zu erwarten wäre, wenn die gemessene Ruheaufnahme angehalten hätte. Beim Tauchen sank die O2-Schuld bis etwa 28% unter die erwartete Schuld. Der endexspiratorischeP O a in der ersten Exspiration fiel mit Zunahme der Apnoezeit ab, lag jedoch bei gleich langen Apnoezeiten nach Tauchen signifikant unter dem Wert nach Atemanhalten.Die CO2-Abgabe nach der Apnoe entsprach bis zu einer Apnoezeit von 90 sec etwa der in der Apnoe gebildeten Menge. Bei längeren Apnoezeiten trat eine deutliche CO2-Retention ein. Beim Atemanhalten wurde bis zu 60% weniger CO2 abgegeben als zu erwarten war.Der endexspiratorischeP CO 2 im ersten Exspirationsgas lag unabhängig von der Apnoezeit ziemlich konstant bei 45 mm Hg, die CO2-Abgabe in der ersten Exspiration konstant bei etwa 150 ml ohne wesentlichen Unterschied zwischen Tauchen und Atemanhalten.  相似文献   

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