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The ventilatory anaerobic threshold (VAT) occurs when there is an isolated increase in the slope for ventilatory equivalent for oxygen consumption (VE/VO2) with no change in the slope for ventilatory equivalent for carbon dioxide production (VE/VCO2) when both are plotted against time. The concept of anaerobic threshold remains controversial. However, it is a clinically useful tool in evaluating the exercise capacity of children. This paper will review the history, biochemistry, and methodology involved in determining the anaerobic threshold, as well as the ventilatory anaerobic threshold, in children. [ABSTRACT FROM AUTHOR]

Objective: There are conflicting data regarding the use of end-tidal carbon dioxide (PetCO2) measurement in preterm infants. The aim of this study was to evaluate the effects of different dead space to tidal volume ratios (VD/VT) on the correlation between PetCO2 and arterial carbon dioxide pressure (PaCO2) in ventilated preterm infants with respiratory distress syndrome (RDS). Methods: We enrolled ventilated preterm infants (with assist control mode or synchronous intermittent mandatory mode) with RDS who were treated with surfactant in this prospective study. Simultaneous PetCO2 and PaCO2 data pairs were obtained from ventilated neonates monitored using mainstream capnography. Data obtained before and after surfactant treatment were also analyzed. Results: One-hundred and one PetCO2 and PaCO2 pairs from 34 neonates were analyzed. There was a moderate correlation between PetCO2 and PaCO2 values (r = 0.603, P < 0.01). The correlation was higher in the post-surfactant treatment group (r = 0.786, P < 0.01) than the pre-surfactant treatment group (r = 0.235). The values of PaCO2 and PetCO2 obtained based on the treatment stage of surfactant therapy were 42.4 ± 8.6 mmHg and 32.6 ± 7.2 mmHg, respectively, in pre-surfactant treatment group, and 37.8 ± 10.3 mmHg and 33.7 ± 9.3 mmHg, respectively, in the post-surfactant treatment group. Furthermore, we found a significant decrease in VD/VT in the post-surfactant treatment group when compared to the pre-surfactant treatment group (P = 0.003). Conclusions: VD/VT decreased significantly after surfactant therapy and the correlation between PetCO2 and PaCO2 was higher after surfactant therapy in preterm infants with RDS. [ABSTRACT FROM AUTHOR]

The respiratory effort in hyperbaric conditions is of particular nature, leading to an increase of the respiratory flow of the diver and to the change of their pulmonary volumes. There are important criteria in the selection process of the most suitable divers. Some of these criteria are related to the respiratory function. In order to evaluate the divers respiratory function an examination of the pulmonary volumes is performed in regards to their variations measured by spirometry, of the increased oxygen consumption in hyperbaric conditions and of the production of carbon dioxide during the unitary dive at the depth of work using air as a respiratory mixture. The physical and physiological phenomena invol ved in the hyperbaric respiration have been studied in cooperation with "Ovidius" University of Constanta, Faculty of Medicine. A specific medical method of evaluation of the pulmonary ventilation, spirometry, the measurement of forced expiratory volume in the first second of a forced expiration, Tiffneau index, have been adapted to the under pressure breathing environment. The parameters have been studied as experimental determinations on diver groups, during simulated diving, using air as a respiratory mixture, at 50 [mH2O] in the Hyperbaric Complex of the Diving Centre. [ABSTRACT FROM AUTHOR]

The present paper shows, by means of single-cell recordings, responses of antennal sensory neurons of the damselfly Ischnura elegans when stimulated by air streams at different CO 2 concentrations. Unlike most insects, but similarly to termites, centipedes and ticks, Odonata possess sensory neurons strongly inhibited by CO 2 , with the magnitude of the off-response depending upon the CO 2 concentration. The Odonata antennal sensory neurons responding to CO 2 are also sensitive to airborne odors; in particular, the impulse frequency is increased by isoamylamine and decreased by heptanoic and pentanoic acid. Further behavioral investigations are necessary to assign a biological role to carbon dioxide detection in Odonata. [ABSTRACT FROM AUTHOR]

Background: Cachexia affects most patients with incurable cancer. We hypothesize that in metastatic cancer the mass of the tumor as well as its level of anaerobic energy metabolism play a critical role in describing its energetic cost, which results in elevated resting energy expenditure and glucose utilization, leading to cachexia. Prior models of cancer cachexia may have underestimated the specific energetic cost of cancer as they have not taken the range of tumor mass and anaerobic energy metabolism fully into account. Methods: We therefore modelled the energetic cost of cancer as a function of the percentage of energy the cancer produces anaerobically, based on resting energy expenditure, glucose turnover, glucose recycling, and oxygen consumption in cancer patients found in previous studies. Results: Data from two clinical studies where tumor burden was estimated and resting energy expenditure or oxygen consumption were measured lead to a broad range of estimates of tumor cost from 190 to 470 kcal/kg tumor/day. These values will vary based of the percentage of energy the cancer produces anaerobically (from 0 to 100 %), which in and of itself can alter the cost over a 2 to 3-fold range. In addition to the tumor cost/kg and the degree of anaerobic metabolism, the impact on a given individual patient will depend on tumor burden, which can exceed 1 kg in advanced metastatic disease. Considering these dimensions of tumor cost we are able to produce a 2-dimensional map of potential values, with an overall range of 100-1400 kcal/day. Conclusions: Quantifying the energetic cost of cancer may benefit an understanding of the tumor's causation of cachexia. Our estimates of the range of tumor cost include values that are higher than prior estimates and suggest that in metastatic disease the tumor cost could be expected to eclipse attempts to stabilize energy balance through nutrition support or by drug therapies. Tumor mass and the percentage of anaerobic metabolism in the tumor contribute to the cost of the tumor on the body and potentially lead directly to negative energy balance and increased muscle wasting. [ABSTRACT FROM AUTHOR]

Migratory fishes encounter a variety of environmental conditions, including changes in salinity, temperature and dissolved gases, and it is important to understand how these fishes are able to acclimate to multiple environmental stressors. The gill is the primary site of both acid–base balance and ion regulation in fishes. Many ion transport mechanisms involved with acid–base compensation are also required for the regulation of plasma Na+ and Cl+, the predominant extracellular ions, potentially resulting in a strong interaction between ionoregulation and acid–base regulation. The present study examined the physiological interaction of elevated dissolved CO2 (an acid–base disturbance) on osmoregulation during seawater acclimation (an ionoregulatory disturbance) in juvenile white sturgeon (Acipenser transmontanus). Blood pH (pHe), plasma [HCO3−], [Na+], [Cl−] and osmolality, white muscle water content, and gill Na+/K+-ATPase (NKA) and Na+/K+/2Cl− co-transporter (NKCC) abundance were examined over a 10 day seawater (SW) acclimation period under normocarbia (NCSW) or during prior and continued exposure to hypercarbia (HCSW), and compared with a normocarbic freshwater (NCFW) control. Hypercarbia induced a severe extracellular acidosis (from pH 7.65 to pH 7.2) in HCSW sturgeon, and these fish had a 2-fold greater rise in plasma osmolarity over NCSW by day 2 of SW exposure. Interestingly, pHe recovery in HCSW was associated more prominently with an elevation in plasma Na+ prior to osmotic recovery and more prominently with a reduction in plasma Cl− following osmotic recovery, indicating a biphasic response as the requirements of osmoregulation transitioned from ion-uptake to ion-excretion throughout SW acclimation. These results imply a prioritization of osmoregulatory recovery over acid–base recovery in this period of combined exposure to acid–base and ionoregulatory disturbances. [ABSTRACT FROM AUTHOR]

Serotonin (5-hydroxytryptamine, 5-HT) neurons from the mouse and rat rostral medulla are stimulated by increased CO2 when studied in culture or brain slices. However, the response of 5-HT neurons has been variable when animals are exposed to hypercapnia in vivo. Here we examined whether halogenated inhalational anesthetics, which activate TWIK-related acid-sensitive K+ (TASK) channels, could mask an effect of CO2 on 5-HT neurons. During in vivo plethysmography in mice, isoflurane (1%) markedly reduced the hypercapnic ventilatory response (HCVR) by 78-96% depending upon mouse strain and ambient temperature. In a perfused rat brain stem preparation, isoflurane (1%) reduced or silenced spontaneous firing of medullary 5-HT neurons in situ and abolished their responses to elevated perfusate PCO2. In dissociated cell cultures, isoflurane (1%) hyperpolarized 5-HT neurons by 6.52 ± 3.94 mV and inhibited spontaneous firing. A subsequent decrease in pH from 7.4 to 7.2 depolarized neurons by 4.07 ± 2.10 mV, but that was insufficient to reach threshold for firing. Depolarizing current restored baseline firing and the firing frequency response to acidosis, indicating that isoflurane did not block the underlying mechanisms mediating chemosensitivity. These results demonstrate that isoflurane masks 5-HT neuron chemosensitivity in vitro and in situ and markedly decreases the HCVR in vivo. The use of this class of anesthetic has a particularly potent inhibitory effect on chemosensitivity of 5-HT neurons. [ABSTRACT FROM AUTHOR]

Bumblebees are facultative endotherms, having the ability to elevate thorax temperature above ambient temperature by elevating metabolism. Here, we investigated the influence of hypoxia on metabolic demands and thermoregulatory capabilities of the bumblebee Bombus terrestris. We measured thorax temperature, rates of oxygen consumption and carbon dioxide production, and abdominal pumping rates of bees randomly exposed to oxygen levels of 20, 15, 10 and 5kPa at 26°C. Under normoxia, bumblebees maintained an elevated mean thorax temperature of 35.5°C. There was no significant change in thorax temperature at 15kPa O2 (33.4°C). Mean thorax temperature decreased significantly at 10 kPa O2 (31.6°C) and 5kPa O2 (27.3°C). Bees were able to maintain an elevated metabolic rate at 15 and 10kPa O2. In normoxia, endothermic bees exhibited periods of rapid abdominal pumping (327 min-1) interspaced by periods of no abdominal pumping. At 10kPa O2, abdominal pumping rate decreased (255 min-1) but became more continuous. Upon exposure to 5kPa, metabolic rate and abdominal pumping rate (152 min-1) decreased, although the animals continued abdominal pumping at the reduced rate throughout the exposure period. Bumblebees are able to meet the energetic demands of endothermy at 15 kPa O2, but become compromised at levels of 10 kPa O2 and below. [ABSTRACT FROM AUTHOR]

Purpose: The aim is to provide better understanding of carbon dioxide ( $$\mathrm{CO}_2$$ ) elimination during ventilation for both the healthy and atelectatic condition, derived in a pressure-controlled mode. Therefore, we present a theoretical analysis of $$\mathrm{CO}_2$$ elimination of healthy and diseased lungs. Methods: Based on a single-compartment model, $$\mathrm{CO}_2$$ elimination is mathematically modeled and its contours were plotted as a function of temporal settings and driving pressure. The model was validated within some level of tolerance on an average of 4.9 % using porcine dynamics. Results: $$\mathrm{CO}_2$$ elimination is affected by various factors, including driving pressure, temporal variables from mechanical ventilator settings, lung mechanics and metabolic rate. Conclusion: During respiratory care, $$\mathrm{CO}_2$$ elimination is a key parameter for bedside monitoring, especially for patients with pulmonary disease. This parameter provides valuable insight into the status of an atelectatic lung and of cardiopulmonary pathophysiology. Therefore, control of $$\mathrm{CO}_2$$ elimination should be based on the fine tuning of the driving pressure and temporal ventilator settings. However, for critical condition of hypercapnia, airway resistance during inspiration and expiration should be additionally measured to determine the optimal percent inspiratory time (%TI) to maximize $$\mathrm{CO}_2$$ elimination for treating patients with hypercapnia. [ABSTRACT FROM AUTHOR]

Objective To determine the association between 5-min Apgar score and umbilical cord artery carbon dioxide tension ( pCO2). Design Observational study. Setting European hospital labor wards. Population Data from 36 432 newborns ≥36 gestational weeks were obtained from three sources: two trials of monitoring with fetal electrocardiogram (the Swedish randomized controlled trial and the European Union Fetal ECG trial) and Mölndal Hospital data. After validation of the acid-base values, 25 806 5-min Apgar scores were available for analysis. Methods Validation of the umbilical cord acid-base values was performed to obtain reliable data. 5-min Apgar score was regressed against cord artery pCO2 in a polynomial multilevel model. Main outcome measures Five-min Apgar score, umbilical cord pCO2, pH, and base deficit. Results Overall, a higher cord artery pCO2 was found to be associated with lower 5-min Apgar scores. However, among newborns with moderate acidemia, lower umbilical cord artery pCO2 (≤median pCO2 for the specific cord artery pH) was associated with lower 5-min Apgar scores, with a relative risk of 2.0 (95% confidence interval: 1.4-2.8) for 5-min Apgar scores 0-6. Conclusions Metabolic acidosis affects the newborn's vitality more than respiratory acidosis. In addition, elevated levels of pCO2 may be beneficial for fetuses with moderate acidemia, and thus cord artery pCO2 is a factor that should be considered when assessing the compromised newborn. [ABSTRACT FROM AUTHOR]

Abstract: This study quantified the impact of the well-known physiologic noise correction algorithm RETROICOR applied to a pain functional magnetic resonance imaging (FMRI) experiment at two field strengths: 1.5 and 3.0 T. In the 1.5-T acquisition, there was an 8.2% decrease in time course variance (σ) and a 227% improvement in average model fit (increase in mean R 2 a). In the 3.0-T acquisition, significantly greater improvements were seen: a 10.4% decrease in σ and a 240% increase in mean R 2 a. End-tidal carbon dioxide data were also collected during scanning and used to account for low-frequency changes in cerebral blood flow; however, the impact of this correction was trivial compared to applying RETROICOR. Comparison between two implementations of RETROICOR demonstrated that oversampled physiologic data can be applied by either downsampling or modification of the timing in the RETROICOR algorithm, with equivalent results. Furthermore, there was no significant effect from manually aligning the physiologic data with corresponding image slices from an interleaved acquisition, indicating that RETROICOR accounts for timing differences between physiologic changes and MR signal changes. These findings suggest that RETROICOR correction, as it is commonly implemented, should be included as part of the data analysis for pain FMRI studies performed at 1.5 and 3.0 T. [Copyright &y& Elsevier]

Abstract: Carbonic anhydrase (CA) is a zinc metalloenzyme that catalyzes the reversible hydration–dehydration reactions of CO2. It is present in high abundance in the cytoplasm of vertebrate red blood cells, where it contributes to CO2 excretion. A membrane-bound CA isoform (CA IV) is also present in the lungs of mammals and reptiles, but plays little role in CO2 excretion. The gills of teleost fish appear to lack plasma-accessible CA activity. In elasmobranchs, however, evidence gathered using a variety of physiological, biochemical and molecular approaches suggests that CA IV is present in the gills, and that at least in dogfish, this CA IV makes a significant contribution to CO2 excretion by catalyzing the dehydration of plasma HCO3 −. The contribution of CA IV to CO2 excretion is favoured by unusually high relative plasma buffering that aids in the provision of protons for HCO3 − dehydration. Moreover, reduced emphasis on HCO3 − flux through the red blood cell may reflect the occurrence of a slower turnover cytosolic CA in dogfish. This model of CO2 excretion, in which HCO3 − dehydration in the red blood cell catalyzed by cytosolic CA and HCO3 − dehydration in the plasma catalyzed by membrane-bound CA IV are of comparable importance, has been described for the dogfish. Further work is required to determine whether it applies to elasmobranch fish as a group. [Copyright &y& Elsevier]

Abstract: The monitoring of dissolved oxygen and carbon dioxide in blood or organic tissues is extremely useful for respiratory studies and can be valuable in determining the physiologic status of the critically ill patients. The measurement quantity for both O2 and CO2 sensors is the luminescence lifetime by phase modulation fluorometry. The properties and accuracy of both types of sensors have been firstly characterised in vitro using physiological solutions to demonstrate the fulfilment of the defined requirements for clinical applications. The presented sensors enable the measurement of pO2 in the range 0–300mmHg and of pCO2 in the range 0–150mmHg, respectively, with a resolution better than 1mmHg and accuracy better than 1mmHg. To verified the operating function of developed sensors in in vivo and to analyse the changes of interstitial pO2 and pCO2 in adipose tissue as indicators of critical ill conditions, several in vivo tests on animal and healthy volunteer have been successfully carried out using a microdialysis catheter CMA 60 for the extraction of interstitial fluid (ISF) from the subcutaneous adipose tissue. Critical conditions similar to intensive care patients have been provoked using two different models: an animal model of haemorrhagic shock and subministration of adrenaline, which causes a local vasoconstriction in the case of experiment with human subjects, respectively. Our results proved that changes in the interstitial pCO2 and pO2 are informative metabolic parameters for critical condition of the patients. [Copyright &y& Elsevier]

Abstract: Oxygen and carbon dioxide move passively between the alveoli and the pulmonary blood down concentration gradients, as described by Fick’s law of diffusion. Lungs are thin enough and offer a sufficiently large surface area for equilibrium to be achieved well before the blood has left them. As a result, the exchange of these gases is normally limited by the cardiac output. Both ventilation and perfusion of the lungs show gradients in the upright individual, with lower values at the apex than at the base. These gradients are caused by gravity, though the details of these effects differ between ventilation and perfusion. There is a ventilation-perfusion gradient down the lung, with the highest values at the apex; apical alveoli are over-ventilated and basal ones over-perfused. Such imbalances are normally minimized by local reflexes involving airway constriction (apex) and vascular constriction (base). One of the main functions of haemoglobin is to transport oxygen from the lungs to the tissues. The properties of this molecule are such that: small falls in the partial pressure of alveolar oxygen do not reduce the saturation of blood leaving the lungs; increased release of oxygen to the tissues is accomplished with small falls below the normal partial pressure of oxygen; and raised acidity and temperature in exercising tissues promote oxygen unloading. Haemoglobin is also involved in the carriage of carbon dioxide, directly (by the formation of carbaminohaemoglobin) and indirectly (by acting as a buffer for hydrogen ions produced during the formulation of carbaminohaemoglobin and by dissociation of carbonic acid formed at the erythrocyte membrane). [Copyright &y& Elsevier]

To investigate the effects of carbon dioxide (CO[sub 2]) hot spring baths on physiological functions, head-out immersion of urethane-anesthetized, fursheared male Wistar rats was performed. Animals were immersed in water (30 or 35°C) with high-CO[sub 2] content (∼1,000 parts/million; CO[sub 2]water). CO[sub 2]-water for bathing was made by using an artificial spa maker with normal tap water and high-pressure CO[sub 2] from a gas cylinder. When a human foot was immersed for 10 min in the CO[sub 2]-water at 35°C, the immersed skin reddened, whereas skin color did not change in normal tap water at the same temperature. Arterial blood pressure, heart rate (HR), underwater skin tissue blood flow, and temperatures of the colon and immersed skin were continuously measured while animals were immersed in a bathtub of water for ∼30 min at room temperature (26°C). Immersed skin vascular resistance, computed from blood pressure and tissue blood flow, was significantly lower in the CO[sub 2]-water bath than in tap water at 30°C, but no differences were apparent at 35°C. HR of rats in CO[sub 2]-water was significantly slower than in tap water at 35°C. Decreased HR in CO[sub 2]-water was inhibited by infusion of atenolol (β[sub 1]adrenoceptor blocker), but it was unaffected by atropine (muscarinic cholinoceptor blocker). Theses results suggest that bradycardia in CO[sub 2] hot spring bathing is caused by inhibition of the cardiac sympathetic innervation. This CO[sub 2]-water maker should prove a useful device for acquiring physiological evidence of balneotherapy. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the maximum acceptable work duration (MAWD) for high-intensity work. Thirty young individuals participated in this study. Their maximum oxygen uptake (VO2max) and maximum work rate (MWR) were assessed first. Each subject then performed two cycling tests (60% and 70% MWR) on two separate days. Oxygen uptake and heart rate data were collected throughout the test. The results indicate that the MAWD in the 60% MWR test (18.8 mm) was about threefold greater than the MAWD in the 70% MWR test (6.5 mm). The MAWD was inversely correlated with the relative workload indices: relative oxygen uptake (RVO2 r =-0.82, P <0.001) and relative heart rate (RHR; r = -0.79, P <0.001). The RVO2 was defined as the elevation in oxygen uptake from the resting level as a percentage of the difference between maximum and resting oxygen uptake. The RHR was defined as the elevation in heart rate from the resting level as a percentage of the difference between maximum and resting heart rate. Furthermore, more than 80% of the variations were explained by the exponential decrease regression model for predicting MAWD using the above two variables. The findings of this study can provide useful information for the design of high-intensity jobs. [ABSTRACT FROM AUTHOR]

Investigates the applicability of the bicarbonate stable isotope dilution technique for accurate determination of 24-hr energy expenditure in humans and in reference to the conduct of short term metabolic studies. Overview on studies done with [I-13 C]leucine tracer; Twenty-four-hour tracer infusion protocol.

Determines whether the intracellular fluid compartment contributes to the changes in carbon dioxide stores in undisturbed resting cane toads or Bufus marinus. Body temperature; Oxygen consumption; Respiratory exchange ratio (RE); Acid-base balance; Extracellular versus intracellular carbon dioxide stores.

Studies the effects of extracellular pH, carbon dioxide pressure (PCO2), and bicarbonate concentration (HCO3-) on taste receptor cell (TRC) intracellular pH (pHi) in taste bud fragments (TBF) isolated from rat taste buds. TRC viability and 2',7'-bis(2-carboxyethyl) 5(6)-carboxyfluorescein (BCECF) loading; Effect of weak acids and bases on TRC pH.

Reports on the continuous measurement of the production of 45 CO2 from 13-C labeled pyruvate in a guinea pig liver mitochondrial suspension and O2 consumption at 37 degrees Centigrade and pH 7.4. Mechanism of CO2/HCO3- effect; Effects of pyruvate metabolism; Relation of O2 consumption to CO2 production.

Despite widespread use of transcutaneous PCO[sub 2] (TcPCO[sub 2]) monitoring, the precise relationship between TcPCO[sub 2] and PaCO[sub 2] remains unclear. It has been widely assumed that theoretical correction of TcPCO[sub 2] (combining temperature correction with a constant metabolic factor of 4 mm Hg) accounts for the elevation of TcPCO[sub 2] over PaCO[sub 2]. To test this assumption, TcPCO[sub 2] was measured with a 44 Celsius electrode and compared to PaCO[sub 2] in 60 normotensive infants with cardiorespiratory disease during the first four +/- six days of life (mean +/- SD) (range one to 36 days). During hypocapnea, theoretically corrected TcPCO[sub 2] did not differ significantly from PaCO[sub 2]. In contrast, during normocapnea, theoretically corrected TcPCO[sub 2] exceeded PaCO[sub 2] by 5 +/- 4 mm Hg (P < .001), and similarly during hypercapnea, theoretically corrected TcPCO[sub 2] exceeded PaCO[sub 2] by 9 +/- 6 mm Hg (P < .001). These data suggest that, as PaCO[sub 2] increases, there may be an imbalance between tissue CO[sub 2] production and removal, resulting in a progressively increasing gradient between TcPCO[sub 2] and PaCO[sub 2]. Clarification of the relationship between TcPCO[sub 2] and PaCO[sub 2] should enhance the interpretation of TcPCO[sub 2] measurements in infants. Pediatrics 1988;81:684-687; transcutaneous carbon dioxide tension, arterial carbon dioxide tension. [ABSTRACT FROM AUTHOR]

ABSTRACT. Decreased ventilatory response to carbon dioxide is often present in lung disease. This can be due to a reduction in the output of the respiratory center or an inability of the respiratory pump to respond to a normal output because of the size or impedence of the pump. To separate these mechanisms we have measured the isometric force developed by the respiratory muscle during brief airway occlusion, by measuring the pressure generated at 100 msec (P[sub M100]). We studied 43 subjects ranging in age from 6 to 50 years, and nine neonates. We found a linear rise of P[sub M100] with rising PAco[sub 2] during carbon dioxide rebreathing maneuvers. Our results also show that although there are wide variations in slopes of P[sub M100] to carbon dioxide tension (SP[sub M100]/PAco[sub 2]) between individuals, in a given subject this slope remains constant even following repeated studies. It also remains constant for age and size, indicating that the neuromechanical output of the respiratory apparatus does not change with growth. In contrast the ventilatory response either assessed as V[sub E]/PAco[sub 2] or V[sub T]/PAco[sub 2] depended on age and lung size. The results suggest that throughout growth, comparison of P[sub M100]/PAco[sub 2] and V[sub E]/PAco[sub 2] can distinguish between abnormalities of neuromuscular output from other causes of ventilatory impairment. Pediatrics, 56:972-980, 1975, CARBON DIOXIDE RESPONSE, MOUTH OCCLUSION PRESSURE, RESPIRATORY CENTER OUTPUT. [ABSTRACT FROM AUTHOR]

Although polycystic ovary syndrome is associated with hypertension, hyperlipidaemia, and insulin resistance, mortality from cerebrovascular disease is not increased. We previously reported lower downstream resistance in the internal carotid artery in women with polycystic ovary syndrome. This study was designed to assess vascular reactivity by measuring the response to inhalation of 5% carbon dioxide. We studied 34 young women with polycystic ovary syndrome, 15 with symptomless polycystic ovaries, and 18 controls. [ABSTRACT FROM AUTHOR]

Presents a patient in whom the combination of pulse oximetry and end-tidal carbon dioxide (ETCO2) monitoring helped to determine the etiology of a cardiorespiratory arrest during transesophageal echocardiography (TEE). ETCO2 as a valuable adjunct to other monitors during sedation; Factors that alter the correlation between end-tidal and arterial carbon dioxide.

The article discusses the malfunctioning of the Pediatric Anesthesia Breathing Circuit as a cause of hypercapnia during the induction of anesthesia. It looks at the proximal hypospadias repair on an eight-month-old child wherein the trachea was intubated easily and the CO2 concentrations were elevated. During further examinations, the inner blue tubing of the Pediatric Anesthesia Breathing Circuit has became disconnected and the CO2 has decreased to normal levels upon changing of the device.

The inspiratory sinusoidal flow of Scherer et al' model (J. Appl. Physiol. 64:1022,1988) is here modified to study its effect upon the alveolar CO2 fraction as a function of alveolar generation. An exponential function was developed to produce a new flow model (figure 1). A tidal volume of 750 mL was used at 1.5s, 2s and 2.5s time of inspiration. FACO2 was normalized with the mean inspiratory CO2 fraction. Results of these models on alveolar CO2 during inspiration are shown in figure 2 (for clarity only 1.5s and 2.5s are shown). In conclusion, the faster the flow the curve is shifted to the left and the plateau is more diluted. [ABSTRACT FROM AUTHOR]

Presents an abstract of the article entitled `Maternal and Fetal Effects of a Prolonged CO2 Peritoneum in the Gravid Ewe,' by J. Barnard et al.

Presents an abstract of the article entitled `Maternal Oxygen Consumption and CO2 Production During the Peripartum Period in Normal Gestation,' by W. Kramer et al.