Search

Introduction: The ergogenic effects of respiratory alkalosis induced by prior voluntary hyperventilation (VH) are controversial. This study examined the effects of prior VH on derived parameters from the 3-min all-out cycling test (3MT).\ud \ud Methods: Eleven men V̇O2max = 46 ± 8 mL⋅kg-1⋅min-1) performed a 3MT preceded by 15-min of rest (CONT) or voluntary hyperventilation (V˙E = 38 ± 5 L⋅min-1) with PETCO2 reduced to 21 ± 1 mmHg (HYP). End-test power (EP; synonymous with critical power) was calculated as the mean power output over the last 30-s of the 3MT, and the work done above EP (WEP; synonymous with W') was calculated as the power-time integral above EP.\ud \ud Results: At the start of the 3MT, capillary blood PCO2 and [H+] were lower in HYP (25.2 ± 3.0 mmHg, 27.1 ± 2.6 nmol⋅L-1) than CONT (43.2 ± 2.0 mmHg, 40.0 ± 1.5 nmol⋅L-1) (P < 0.001). At the end of the 3MT, blood PCO2 was still lower in HYP (35.7 ± 5.4 mmHg) than CONT (40.6 ± 5.0 mmHg) (P < 0.001). WEP was 10% higher in HYP (19.4 ± 7.0 kJ) than CONT (17.6 ± 6.4 kJ) (P = 0.006), whereas EP was 5% lower in HYP (246 ± 69 W) than CONT (260 ± 74 W) (P = 0.007). The ΔWEP (J·kg-1) between CONT and HYP correlated positively with the PCO2 immediately before the 3MT in HYP (r = 0.77, P = 0.006).\ud \ud Conclusion: These findings suggest that acid-base changes elicited by prior voluntary hyperventilation increase WEP but decrease EP during the all-out 3MT.

The goal of this experiment was to measure the physiological response of individual laying hens exposed to heat stress (HS). Performance, egg quality, body temperature (BT), and blood chemistry of laying hens were individually recorded before and after various intervals of daily cyclic HS. In total, 407 18-week-old W-36 parent-line laying hens (Hy-Line International, Dallas Center, IA) were housed individually in battery cages. After an acclimation period, baseline data were collected from 22 to 24-wk before the hens were subjected to a daily cyclic HS consisting of 7 h at 35°C returning to 30°C for the remaining 17 h/D from 24 to 28-wk of age. Eggs were collected and individually weighed daily. Feed intake (FI), egg production (EP), egg weights, egg mass, BW, and feed efficiency (FE) (g egg/kg FI) were calculated over 2-wk time periods. Eggs were collected for quality assessment the day before HS began, the 2nd day of HS, and on a weekly basis throughout the 4-wk HS. Blood was collected and BT measured the day before heat HS was initiated, on the first day of HS, and again at 2 and 4-wk of HS. Blood PCO2 and iCa decreased, and blood pH increased within 4 to 6 h of HS (P ≤ 0.01). Shell weights decreased with acute HS, possibly due to the reduction in blood iCa (P ≤ 0.01). After 4-wk of HS the blood pH returned to pre-HS levels but iCa remained decreased (P ≤ 0.01). Shell weights remained low and Haugh units decreased after 2 and 4-wk of HS (P ≤ 0.01). Feed efficiency was increased and FI, EP, and BW decreased by 2-wk of HS and remained low through 4-wk (P ≤ 0.01). The cyclic HS had a significant effect on the performance, egg quality, and blood chemistry over the 4-wk HS.

Background: Cor pulmonale in AECOPD results in increased morbidity and mortality, and constitutes a tremendous socioeconomic burden. Predicting the markers of cor pulmonale in AECOPD helps in preventing early morbidity and helps in planning for future therapies. Aim of Study: Predicting the markers of cor pulmonale in patients of AECOPD helps in planning the course of future treatment for averting the early morbidity. Methods: Study includes 138 patients of AECOPD admitted in the SSI hospital subjected to thorough history, clinical examination, all relevant examinations including ECG, 2-D ECHO with Colour Doppler of heart, ABG & other blood investigations like RFT, LFT, CBC, RBC etc were done and datas were analysed. Results: Most patients were elderly with mean age of 62.77 years. Cor pulmonale was present in 60.8 % (84/138) in patients of AECOPD. Mean Albumin of the patients with cor pulmonale was 3.29 gm% (SD±0.29) and those without cor pulmonale was 3.52gm% (SD±0.43). This difference between both groups was significant statistically (P=0.0360)(CI=0.445 – 0.0159). Mean blood PCO2 levels of the patients with cor pulmonale was 54.5 mmHg (SD±19.98) and those without cor pulmonale was 42.56mmHg (SD±11.16). This difference between both groups was significant statistically (P=0.026)(CI=1.517-22.37). Conclusion: Serum Albumin and blood PCO2 level are important markers of cor pulmonale in patients with AECOPD.

Soon after hatching, the osteoglossid fish Arapaima gigas undergoes a rapid transition from a water breather to an obligate air breather. This is followed by a gradual disappearance of gill lamellae, which leaves smooth filaments with a reduced branchial diffusion capacity due to loss of surface area, and a fourfold increase in diffusion distance. This study evaluated the effects these changes have on gill function by examining two size classes of fish that differ in gill morphology. In comparison to smaller fish (approximately 67.5 g), which still have lamellae, larger fish (approximately 724.2 g) without lamellae took up a slightly greater percentage of O2 across the gills (30.1% vs. 23.9%), which indicates that the morphological changes do not place limitations on O2 uptake in larger fish. Both size groups excreted similar percentages of CO2 across the gills (85%-90%). However, larger fish had higher blood PCO2 (26.51.9 vs. 16.51.5 mmHg) and HCO3(-) (40.2 +/- 2.9 vs. 33.6 +/- 4.5 mmol L(-1)) concentrations and lower blood pH (7.58 +/- 0.01 vs. 7.70 +/- 0.04) than did smaller fish, despite having lower mass-specific metabolisms, suggesting a possible diffusion limitation for CO2 excretion in larger fish. With regard to ion regulation, rates of diffusive Na+ loss were about 3.5 times higher in larger fish than they were in smaller fish, despite the lowered branchial diffusion capacity, and rates of Na+ uptake were higher by about the same amount despite 40% lower activity of branchial Na+/K+-ATPase. Kinetic analysis of Na uptake revealed an extremely low-affinity (K(m) = 587.9 +/- 169.5 micromol L(-1)), low-capacity (J(max) = 265.7 +/- 56.8 nmol g(-1) h(-1)) transport system. These data may reflect a general reduction in the role of the gills in ion balance. Renal Na+/K+-ATPase activity was 5-10 times higher than Na+/K+-ATPase activity in the gills, and urine: plasma ratios for Na+ and Cl(-) were very low (0.001-0.005) relative to that of other fish, which suggested an increased role for dietary salt intake and renal salt retention and which was representative of a more "terrestrial" mode of ion regulation. Such de-emphasis of branchial ion regulation confers greatly reduced sensitivity of diffusive ion loss to low water pH. Ammonia excretion also appeared to be impacted by gill changes. Rates of ammonia excretion in larger fish were one third less than that in smaller fish, despite larger fish having blood ammonia concentrations that were twice as high.

Ram-air ventilation (RAV) of the airspace in a fish hauling tank is achieved by equipping the tank with both forward-facing and rear-facing air scoops. To evaluate the benefits of RAV, we data-logged values every 5-min for dissolved oxygen (O2), pH, and temperature in hauling tanks with and without (control) RAV during a 6-h haul. Levels of CO2 were estimated from the pH–alkalinity relationship. To determine if RAV reduced hauling stress experienced by fingerling walleyes Stizostedion vitreum after a 6-h transport, blood samples were taken for measurement of physiological stress indicators, blood gases, and for assessment of acid–base status. Blood samples were collected before loading (preload), after loading (postload), and at the end of a 6-h trip (posthaul). The mean CO2 for the trip was substantially lower and the pH was higher in water of tanks equipped with RAV compared with water of the control tanks. At posthaul, blood pCO2 (partial pressure of CO2 in the blood) in fish from RAV tanks wa...

Wu, Eugene Y., Khalid W. Barazanji, and Robert L. Johnson, Jr. Sources of error in a-aDO2 calculated from blood stored in plastic and glass syringes. J. Appl. Physiol. 82(1): 196–202, 1997.—We studied the effects of time delay on blood gases, pH, and base excess in blood stored in glass and plastic syringes on ice and the effects of resulting errors on calculated alveolar-to-arterial [Formula: see text] difference (a-[Formula: see text]). Matched samples of dog whole blood were tonometered with gas mixtures of 5% CO2-12% O2-83% N2 ( mixture A), 10% CO2-5% O2-85% N2 ( mixture B), and 2.88% CO2-4% O2-93.12% N2 ( mixture C). Tonometered blood samples were transferred to 5-ml glass (5G), 5-ml plastic (5P), and 3-ml plastic (3P) syringes and stored on ice. Blood gases were measured every 1 h up to 6 h. In 5G,[Formula: see text] progressively decreased in blood tonometered with mixture A but rose in blood tonometered with mixtures B and C. O2 saturation progressively fell in all cases. In 5G, blood [Formula: see text]progressively rose regardless of which gas mixture was used, and pH as well as base excess progressively fell. The rise in[Formula: see text] was faster in plastic than in glass syringes, and O2 saturation always rose in plastic syringes. Differences between storage in plastic and glass syringes on [Formula: see text] change were greatest when initial blood [Formula: see text] was highest ( mixture A). At the highest[Formula: see text], O2 exchange was faster in 3P than in 5P. The rise of [Formula: see text] was just as fast in plastic as in glass syringes, but in both the rise in[Formula: see text] was faster at a higher initial[Formula: see text] ( mixture B) than at lower initial[Formula: see text] ( mixtures B and C). Rates of[Formula: see text] and[Formula: see text] change in matched samples were significantly faster in 3P than in 5P. Errors due to rises in[Formula: see text] and[Formula: see text] cause additive errors in calculateda-[Formula: see text], and when blood is stored in plastic syringes for >1 h significant errors result. Errors are greater in normoxic blood, in which estimateda-[Formula: see text]decreased by >10 Torr after 6 h on ice in plastic syringes, than in hypoxic blood.

O objetivo deste trabalho foi investigar os efeitos da solução de Ringer com lactato (SRL) sobre os equilíbrios hidroeletrolítico e acidobase de equinos, ovelhas e bezerros hígidos. Equinos adultos (n=6), ovelhas adultas (n=6) e bezerros (n=5) receberam a SRL em volume correspondente a 10% do peso corporal, administrada por infusão contínua intravenosa durante quatro (ovelhas e bezerros) ou seis (equinos) horas. Amostras de sangue venoso e de urina foram colhidas antes do início da infusão, na metade do volume infundido, ao término da infusão e duas (ovelhas e bezerros) ou três (equinos) horas após. Foram determinados valores de pH sanguíneo e urinário, de pCO2, HCO3- e BE no sangue, de Na+, K+, Cl- e SID no soro, de AG, PPT, Atot e lactato L no plasma e das excreções fracionadas urinárias de Na+, K+, Cl- e lactato L. A SRL provocou hemodiluição e não afetou os equilíbrios eletrolítico e acidobase nas três espécies estudadas, não sendo capaz de promover aumento da reserva alcalina. Por outro lado, deve ser considerada segura para a terapia de manutenção com infusão de grandes volumes porque não provoca desequilíbrios eletrolíticos. The effects of lactated Ringer's solution (LRS) on fluid, electrolyte and acid-base balances were investigated in healthy horses, ewes and calves. LRS was intravenously infused in six adult horses, six adult ewes and five calves in a volume corresponding to 10% of body weight, continously during four (ewes and calves) or six (horses) hours. Venous blood and urine samples were taken before the beginning, in the middle, at the end of the infusion and two (ewes and calves) or three (horses) hours after. Blood and urine pH, blood pCO2, HCO3- and BE, serum Na+, K+ and Cl-, and plasma TP and L lactate were measured. Na+, K+, Cl- and L lactate fractional clearance and plasma SID, AG, and Atot were calculated. In all species LRS caused hemodilution but didn't change electrolyte and acid-base balances. It was not able to increase alkali reserve. On the other hand, LRS must be considered safe for maintenance therapy with large volume infusions because it doesn't induce electrolyte imbalances.

The effects of supplemental alkaline salts on growth performance, blood chemistry, and stomach morphology were determined in two experiments using 248 finishing pigs fed finely ground diets. In Exp. 1, 128 pigs (56 kg average initial BW) were fed a corn-soybean meal-based diet (488-microns mean particle size) for 66 d. Treatments were control and 1, 2, or 3% added NaHCO3 in a randomized complete block design. Average daily gain (linear effect, P .11). In Exp. 2, 120 pigs (55 kg average initial BW) were fed a pelleted wheat-soybean meal-based diet (355-microns mean particle size) during a 64-d growth assay. Treatments were 1) control, 2) 1% NaHCO3, and 3) 1% KHCO3. Average daily gain, ADFI, gain/feed, backfat thickness, stomach keratinization score, blood pCO2, plasma urea N, and digestibilities of DM and N were not affected by treatment (P < .15). However, addition of NaHCO3 and KHCO3 tended to decrease (P < .10) the incidence of ulcers and increased (P < .05) the concentration of blood HCO3- and digestibility of GE. These data indicate that 1% addition of either NaHCO3 or KHCO3 may help to reduce the severity of gastric ulcers in finishing pigs without adversely affecting growth performance or nutrient digestibility.

1. The aim of this study was to investigate if genetic predisposition to ascites interacts with changed incubation conditions, and how this might affect the post-hatch performance and ascites susceptibility. 2. An ascites sensitive (A) and resistant (E) broiler line were incubated under standard or high CO(2) conditions (up to 4%) from embryonic d 10 onwards. After hatch, chicks were exposed to cold from the 15th day of the rearing period to increase the incidence of ascites. 3. The A line had a higher post-hatch body weight from week three, higher blood pCO(2) from d 21, higher haematocrit at d 35 and d 42, and higher plasma corticosterone concentration from d 21 onwards, compared with the E line, regardless of incubation conditions, supporting the given selection criteria. Ascites mortality did not, however, differ between lines. 4. Incubation under high CO(2) conditions during the second half of incubation increased the ascites mortality, decreased body weight from week 4 onwards, affected venous blood pCO(2), decreased blood pO(2) from d 31, increased haematocrit at d 35 and d 42, and lowered the thyroxine and triiodothyronine concentrations at most sampling days. These effects were observed in both lines. The results suggested a metabolic programming of CO(2) incubated chickens which affected ascites susceptibility.

The major objective was to determine in ponies whether factors in addition to changes in blood PCO2 contribute to changes in plasma [H+] during submaximal exercise. Measurements were made to establish in vivo plasma [H+] at rest and during submaximal exercise, and CO2 titration of blood was completed for both in vitro and acute in vivo conditions. In 19 ponies arterial plasma [H+] was decreased from rest 4.5 neq/l (P less than 0.05) during the 7th min of treadmill running at 6 mph, 5% grade (P less than 0.5). A 5.6-Torr exercise hypocapnia accounted for approximately 2.9 neq/l of this reduced [H+]. The non-PCO2 component of this alkalosis was approximately neq/l, and it was due presumably to a 1.7-meq/l increase from rest in the plasma strong ion difference (SID). Despite the arterial hypocapnia, mixed venous PCO2 was 2.7 Torr above rest during steady-state exercise. Nevertheless, mixed venous plasma [H+] was 1.2 neq/l above rest during exercise, which was presumably due to the increase in SID. Also studied was the effect of submaximal exercise on whole blood CO2 content (CCO2). In vitro, at a given PCO2 there was minimal difference in CCO2 between rest and exercise blood, but plasma [HCO3-] was greater for exercise blood than for rest blood. In vivo, during steady-state exercise, arterial plasma blood. In vivo, during steady-state exercise, arterial plasma [HCO3-] was unchanged or slightly elevated from rest, but CaCO2 was 4 vol% below rest.(ABSTRACT TRUNCATED AT 250 WORDS)

Para investigar o efeito da idade sobre o equilíbrio ácido-básico de bovinos neonatos, colheram-se amostras de sangue venoso de 300 bezerras sadias da raça Holandesa distribuídas por 15 grupos etários: do nascimento até 8 h; de 8 a 16 h; de 16 a 24 h; 2 d; 3 d; 4 d; 5 d; 6 e 7 d; 8 e 9 d; 10 e 11 d; 12 e 13 d; 14 e 15 d; 16 a 20 d; 21 a 25 d; e 26 a 30 d. Determinaram-se os valores de pH, pCO2, pO2, HCO3-, TCO2, BE, StB e SatO2, testando-se o efeito da idade por meio da Análise de Variâncias. Nas bezerras em seu primeiro dia de idade, estudaram-se as correlações das variáveis com o tempo de vida em horas; e a influência da condição de parto (espontâneos contra auxiliados ou distócicos). O pH e a pCO2 foram menor e maior, respectivamente, no primeiro grupo; e o BE e o StB mais reduzidos até 16 horas de vida, com uma tendência a aumentarem até o quinto dia. Ao longo do primeiro dia de vida o pH, o BE e o StB se elevaram e a pCO2 diminuiu. A condição do parto não atuou, em geral, como um fator adicional de variação. Tais resultados reforçam as evidências de que o estado de acidose mista exibido ao nascimento tende a se reverter nos primeiros dias de vida; e comprovam que os valores das variáveis hemogasométricas mantêm-se estabilizados ao longo de todo o período neonatal restante. Venous blood samples of 300 healthy female Holstein calves were used to study the effect of the age on the acid-base balance in the neonatal period. The calves were divided in 15 age groups: from birth to 8 h; 8 to 16 h; 16 to 24 h; 2 d; 3 d; 4 d; 5 d; 6 and 7 d; 8 and 9 d; 10 and 11 d; 12 and 13 d; 14 and 15 d; 16 to 20 d; 21 to 25 d; and 26 to 30 d. Blood pH, pCO2, pO2, HCO3-, TCO2, BE, StB and SatO2 values were measured and the results were analysed through ANOVA. The correlation between the variables and age in the first day of life was studied. The influence of the type of parturition (normal versus assisted or dystocic) on the acid-base status was compared. Blood pH and pCO2 values were respectivelly lower and higher in the first age group; BE and StB were reduced in the first 16 h of life, showing a trend to increase up to the 5th day of life. The older the calf, in the first day of life, the higher the blood pH, BE, and StB; the lower the blood pCO2. Few changes occurred in the acid-base status of calves born from different types of parturition. These results reforced the evidence that mixed acidosis presented at birth tend to be reverted during the first days of life. The acid-base vriables remained stable along the rest of the neonatal period.

the 1st set) were used to indirectly estimate the levels of central activation and peripheral excitability combined. Results: Peak and mean power outputs significantly declined with set number (p≤0.001).No conditioneffect or condition× time interaction existed for both variables. During exercise, neither HVshort orHVlong attenuated the fall in pHdespite lower blood PCO2 (p

The interface between acid-base physiology and blood gas interpretation is historically both stimulating and turbulent [1]. In 2009, most clinicians accept a bimodal categorization of acid-base disorders as either “respiratory” or “metabolic,” with arterial PCO2 (PaCO2) as the primary index of respiratory acid-base status. However, even today, there is no agreed method of defining and quantifying the metabolic component. An important milestone was passed nearly 50 years ago with the advent of “base excess” (BE), introduced by Siggaard-Andersen and Engel [2] after a series of experiments on the blood of Danish volunteers. Base excess was promoted as the ultimate measure of metabolic acid-base status. The subsequent debate was divisive [3], with practitioners separating into 2 “schools,” Boston or Copenhagen. Base excess became the flagship of the Copenhagen school. Base excess is determined from measurements of plasma pH, blood PCO2, and hemoglobin concentration. It can be defined as the concentration of titratable hydrogen ion required to return the pH of in vitro whole blood to 7.4 at 37°C, with PCO2 held at 40 mm Hg. For the first 17 years, BE was calculated empirically from the Danish nomogram. Then, Siggaard-Andersen [4] published a new equation, derived from expressions linking plasma and intraerythrocytic buffering and associated Gibbs-Donnan ionic distributions. He named it the Van Slyke equation, in honor of the American clinical chemist and acid-base pioneer, Donald Dexter Van Slyke. A prerequisite for any stand-alone metabolic acid-base parameter is “CO2 invariance.” By this, we mean that pure respiratory acid-base fluctuations have no distorting effect. Unfortunately, although the Van Slyke equation displays admirable CO2 invariance when applied to blood ex vivo [5], it falls short in the living patient [6]. The problem is that neither the nomogram nor the subsequent Van Slyke

1. Genetically fat and lean adult broiler breeder females were fed ad libitum or restricted throughout life. At one year of age, comparisons of blood viscosity and haematology and changes in blood chemistry after exposure to thermal stress were conducted. 2. Whole blood viscosity was more than twice as high, and plasma triglyceride and haemoglobin concentrations were over 30% higher in fat line than in lean line females fed ad libitum or in restricted birds of both genotypes. 3. Mean cell haemoglobin concentration was higher and mean cell volume lower in fat compared with lean line females. 4. Food restriction was associated with lower plasma triglyceride concentrations, lower numbers of heterophils and monocytes and a lower heterophil-lymphocyte ratio. 5. Fat line birds had a higher blood pCO2 and lower pH than lean line birds. 6. Thermal stress was associated in ad libitum-fed birds with a rise in blood pH and a decrease in pCO2, and in restricted birds with a decline in blood pH and an increase in pCO2. 7. Blood creatine kinase activity increased in all groups under thermal stress.

A new mass spectrometer inlet system for transcutaneous measurement of capillary blood PCO2 is described. The system is constructed to allow calibration in a gas mixture of known composition. The accuracy and precision of the system is demonstrated in human experiments, in which the PCO2 measured by the new probe is shown to be highly correlated with arterialized capillary PCO2 measured by Astrup's equilibration technique.

1. 1. The ambient temperature of embryos of pipped eggs was reduced from 38 to 28°C for a period of 45 min. 2. 2. The blood PCO2 was lower and the blood more alkaline at 28°C than at 38°C. 3. 3. At 28°C plasma [HCO3−] ] was lower than predicted from the blood buffer line determined in vitro. 4. 4. The plasma concentrations of strong ions and lactate were the same at both temperatures. 5. 5. After the ambient temperature had been returned to 38°C for a period of 45 min, blood pH was more acidic than before cooling, but there was no difference in blood PCO2. 6. 6. The plasma [HCO3−] was the same as that at 28°C and plasma [K+] was higher than before cooling. 7. 7. The results arc discussed in relation to the factors affecting blood pH in embryos at this stage of development.

Effect of nasal packing on respiration as studied mainly from the view point of blood gas analysis and respiratory rate. The subjects were fifteen patients underwent SMR, conchotomy and turbinectomy because of longlasting nasal obstruction and/or headache. All of them were packed in the nose after operation. As a control grcup, six patients, who were operated for chronic otitis media, chronic tonsillitis, and cervical lymphncde pathology, were tested. No nasal packing was placed on this group. Blood pCO2 was measured one day before the operation and 24 hours after the operation. In addition, respiratory rate was counted prior to the operation and also on the next morning of the operation. After statistical study on the changes of pCO2 and of respiratory rate in these two groups, the following results were obtained; 1) Before operation, pCO2 in the group with nasal obstruction was higher than that in the group free from nasal obstruction. 2) Twenty-four hours after the operation, pCO2 reduced in the group of anterior nasal packing. On the other hand, increase of pCO2 was observed in the group free from nasal obstruction. 3) After the operation, respiratory rate increased in the nasal packing group. However it de-creased in the group with no nasal packing.=

The remarkable combination of physical and chemical properties displayed by carbon dioxide has enabled the development of a very wide variety of analytical methods for its measurement in blood or blood plasma. Both for historical and technical reasons, the gasometric method of Van Slyke and Neill is preeminent, but great skill is needed to realize its full precision and accuracy. The microgasometer of Natelson, however, has served the clinical laboratory well as a practicable manual means of microanalysis for total carbon dioxide. So far as automated analysis is concerned, it is highly significant that one of the first applications of Skegg's continuous flow principle was to the titrimetric determination of total carbon dioxide in serum; the AutoAnalyzer technique remains the most widely used of its kind, in spite of inherent difficulties in specimen handling, instrumental standardization, and quality control. At the same time, it has been pointed out that the routine determination of total carbon dioxide in serum does not offer a useful screening procedure for identifying or characterizing patients with acid-base disorders; full assessment of acid-base status, including pCO2 in selected patients is much more rewarding. The credit for bringing pCO2 measurements within the scope of the clinical laboratory, by means of the interpolation technique, is largely due to Astrup and his colleagues. Nevertheless, continual improvements have been made in the design and performance of the Severinghaus type of pCO2 electrode, so that reliable instruments offering direct readout of blood pCO2 are available from several manufacturers. The more elaborate versions of these instruments are rugged and work-simplified, and they offer automated self-calibration and end-point detection for pH and pO2, as well as pCO2. It will be surprising if such instruments do not come into widespread use.

The avian respiratory system is a crosscurrent gas exchange system. One of the aspects of this type of gas exchange system is that end-expired PCO2 is greater than arterial PCO2, the highest possible value being equal to mixed venous PCO2. We made steady-state measurements of arterial, mixed venous, and end-expired PCO2 in anesthetized, spontaneously breathing chickens during inhalation of room air or 4–8% CO2. We found end-expired PCO2 to be higher than both arterial and mixed venous PCO2, the sign of the differences being such as to oppose passive diffusion. The observation that end-expired PCO2 was higher than arterial PCO2 can be explained on the basis of crosscurrent gas exchange. However, the observation that end-expired PCO2 exceeded mixed venous PCO2 must be accounted for by some other mechanism. The positive end-expired to mixed venous PCO2 gradients can be explained if it is postulated that the charged membrane mechanism suggested by Gurtner et al. (Respiration Physiol. 7: 173–187, 1969) is present in the avian lung.

Decreased ventilatory responses to hypoxia and hypercapnia have been demonstrated in a variety of disorders; however, the etiology of these decreased drives remains virtually unknown. Recent observations have suggested a familial influence on hypoxic and hypercapnic ventilatory response, but it is unclear whether this influence is the result of hereditary or environmental influences. Therefore we measured the ventilatory response to isocapnic hypoxia (HVR) and hyperoxic hypercapnia in 12 pairs of identical and 12 pairs of nonidentical twins. Significant correlation (P less than 0.01) was found for HVR within identical twin pairs but not within nonidentical twin pairs. Identical twins resembled each other more closely with respect to HVR than was the case for nonidentical twins (P less than 0.0125). This was independent of body size, blood PCO2, or pH. No such correlation could be found for ventilatory response to hyperoxic hypercapnia. It is concluded that hereditary influences affect HVR and it is speculated that such influences may play a role in clinical conditions characterized by decreased hypoxic ventilatory responses.

IN the normal subject, an increment in the partial pressure of carbon dioxide (Pco2) in arterial blood of only a few millimeters of mercury suffices to double or even triple minute and alveolar ventilation. However, analysis of this relation in terms of a simple stimulus-response pattern is complicated by several factors: changes in blood pH accompany the changes in blood Pco2; intracellular buffers are interposed between the arterial blood and the respiratory center; and the magnitude of the ventilatory response seems to be conditioned, in some obscure way, by factors such as the level of total-body . . .

The accuracy of the Astrup interpolation method for determining blood P CO2 has been examined using oxygen-desaturated adult and cord blood. It has been found that the interpolation method, without correction for oxygen desaturation, gives values in good agreement with those obtained by both the Henderson-Hassel-balch equation and the Severinghaus electrode. Application of the correction resulted in an overestimate of P CO2 proportional to the degree of undersaturation. Possible reasons why the correction is misleading are discussed.

The reliability of three methods commonly used for blood P co 2 measurements (CO 2 -electrode, whole-blood C CO 2 /pH method, Astrup method) was evaluated by analysis of human blood samples tonometered at known CO 2 pressures. P CO 2 , was in the physiological region (38–53 mm Hg); S O 2 ranged from 93% to 16%. The COa-electrode yielded the most satisfactory results (smallest scat- ter, no directional error). The whole-blood C CO 2 /pH method was likewise devoid of directional error, but its scatter was appreciably larger. The Astrup method showed, along with an intermediate scatter, a desaturation-dependent systematic error. This error could be attributed to two factors affecting the desaturation correction: 1. the presence of small but not negligible amounts of non-oxygenable Hb in the samples (COHb+metHb), and 2. an overestimation of the Haldane effect in terms of BB change.

The influence of hemoglobin deoxygenation on the P co 2 determination by the Astrup interpolation method was studied in the range of 28 to 86 mm Hg P co 2 . Blood samples drawn from subjects with different acid-base status were tonometered at known CO 2 pressures. The differences between the actual and the “uncorrected” (measured) P co 2 per g reduced hemoglobin, were studied in function of the P co 2 ; and the pH. These differences in P co 2 , which we called the “P co 2 correction factors”, were approximately half of these determined when using the Siggaard-Andersen nomogram. The study of the pH differences between partially and fully oxygenated blood showed that this discrepancy can be explained by the extra amount of CO 2 bound to hemoglobin in the carbamate form when the hemoglobin is freed of O 2 .

Fetal well-being during labour is usually evaluated by fetal heart rate monitoring. Fetal blood sampling and analysis (FBS) of fetal acid-base status are very important supplements to this monitoring, but these procedures are invasive only giving discontinuous information. Tissue-pH monitoring is continuous (Weber,1982), but this method is also invasive and because of technical problems with the electrode not applicable for routine monitoring at present. Transcutaneous carbon dioxide (tc-pCO2) monitoring is the only acid-base parameter which can be measured continuously and non-invasively. In previous studies fetal tc-pCO2 has demonstrated a significant correlation to fetal capillary blood pCO2 and to umbilical artery blood pCO2 (Schmidt et al.,1984; Nickelsen et al.,1986).

The exchanges and chemical reactions of CO2 within the blood are not complete during its transit time through the alveolar capillaries, so that theoretically alveolar PCO2 cannot exactly equal end-capillary blood PCO2. However, as a practical matter, the technical errors in determining alveolar and peripheral arterial PCO2 are so large in comparison with the difference between pulmonary arterial PCO2 and pulmonary venous PCO2, owing to the large effective solubility of CO2 in blood, that for this reason alone any difference between alveolar and end-capillary PCO2 can be neglected. The hypothetical mechanism that was originally proposed by Gurtner, Song, and Farhi for the production of an alveolar PCO2 greater than end-capillary PCO2 during rebreathing and depends on the existence of a radial gradient of H+ X HCO3- in the capillary blood near the wall appears unlikely because a) it would require a significant separation of charged ions over a large proportion of the capillary length and for a large proportion of the blood transit time and b) it would require a large radial gradient of PCO2 within the blood which on thermodynamic grounds would in turn require an unreasonable amount of energy to maintain.

Hubbard cockerels (2.8 to 3.6 kg) with chronically implanted electromagnetic blood flow probes placed on the celiac artery were used to determine the effect of elevated ambient temperature on postprandial intestinal hyperemia. Celiac mean blood flow (MBF) increased (P less than .05) from approximately 25 to 50 ml/min in response to feeding. When a thermoneutral temperature of 25 C was maintained, celiac MBF remained above 40 ml/min up to 210 min but fell below 25 ml/min by 300 min postprandial. In response to an acute heat exposure of 37 C, postprandial celiac MBF was reduced by approximately 50% in comparison to thermoneutral control values. Changes in celiac MBF during heat exposure were significantly (P less than .05) correlated (.60) with blood CO2 partial pressure (PCO2). To determine if flood PCO2 affected postprandial celiac MBF, cockerels were subjected to successive elevated ambient temperature and ambient CO2 treatments. Although cockerels exposed to 2.8% CO2 exhibited an increase in blood PCO2 regardless of temperature treatment, postprandial celiac MBF changes in these ambient CO2 experiments were only moderately correlated (P less than .05) with blood PCO2 (.34) but inversely correlated (-.83) with celiac vascular resistance (P less than .001). This study indicates that acute heat exposure reduces postprandial intestinal hyperemia and that this hemodynamic alteration was coincident with, but not necessarily dependent upon, changes in blood PCO2.

The exercise responses to two different progressive, upright cycle ergometer tests were studied in nine healthy, young subjects either with no drug (ND) or following 48 h of oral propranolol (P) (40 mg q.i.d.). The ergometer tests increased work rate by 30 W either every 30 s or every 4 min. Propranolol caused a significant (p −1[Formula: see text]; 30-s P, 3408 ± 778 mL∙min−1; 4-min ND, 4058 ± 409 mL∙min−1; 4-min P, 3725 ± 573 mL∙min−1). There was no difference between 30-s ND and 4-min ND for peak [Formula: see text]. The ventilatory anaerobic threshold was not significantly different between any test (30-s ND, 2337 ± 434 mL O2∙min−1; 30-s P, 2174 ± 406 mL O2∙min−1; 4-min ND, 2433 ± 685 mL O2∙min−1; 4-min P, 2296 ± 604 mL O2∙min−1). The [Formula: see text] at which blood lactate had increased by 0.5 mM above resting levels was significantly lower than the ventilatory anaerobic threshold for the 4-min ND (1917 ± 489) and the 4-min P (1978 ± 412) tests, but was not different for the 30-s ND and 30-s P tests. At exhaustion in the progressive tests, the blood [Formula: see text] was higher (p

The effect of an exercise-induced reduction in blood O2-carrying capacity on ventilatory gas exchange and acid-base balance during supramaximal exercise was studied in six males [peak O2 consumption (VO2peak), 3.98 +/- 0.49 l/min]. Three consecutive days of supramaximal exercise resulted in a preexercise reduction of hemoglobin concentration from 15.8 to 14.0 g/dl (P less than 0.05). During exercise (120% VO2peak) performed intermittently (1 min work to 4 min rest); a small but significant (P less than 0.05) increase was found for both O2 consumption (VO2) (l X min) and heart rate (beats/min) on day 2 of the training. On day 3, VO2 (l/min) was reduced 3.2% (P less than 0.05) over day 1 values. No changes were found in CO2 output and minute ventilation during exercise between training days. Similarly, short-term training failed to significantly alter the changes in arterialized blood PCO2, pH, and [HCO-3] observed during exercise. It is concluded that hypervolemia-induced reductions in O2-carrying capacity in the order of 10–11% cause minimal impairment to gas exchange and acid-base balance during supramaximal non-steady-state exercise.

New mathematical formulas are presented to calculate directly the change in blood pH during CO2 and O2 exchange with blood. pH changes are calculated from changes in blood Pco2 and saturation values or from changes in blood PCO2 and blood PO2 values. Computational results agree well with information obtained from a Dill nomogram. These new formulas have applicability to the modelling of gas exchange in blood oxygenators as well as to estimating blood acid-base parameters following the mixing of blood samples.

Ventilation and blood gases were measured in unanesthetized ducks at various levels of inspired CO2 partial pressure (PICO2). Ventilation was markedly augmented with increasing PICO2, whereas arterial and mixed venous PCO2 stayed essentially constant up to a PICO2 of about 20 torr and changed only slightly between that and the highest level tested (34 torr). After carbonic anhydrase had been blocked, blood PCO2 was elevated at all levels of PICO2 but the ventilatory response to increases in PICO2 were attenuated. The response to CO2 in the normal bird (before administration of acetazolamide) shows similarities to that in mammals. Qualitative differences between both classes of vertebrates after blockade of carbonic anhydrase may, however, suggest differences in their systems that control ventilation.

The influence of blood carbon dioxide pressure on growth index values yielded by the Bactec NR 660 system was evaluated. Growth index values of 1,175 Bactec blood culture vials collected from 293 patients were related to blood pCO2 and leukocyte concentrations. Thirty-three blood cultures were considered false-positive. These were significantly more frequently encountered in hypercapnia patients (5.4 %) than in hypocapnia patients (1.7 %) or normal patients (2.5 %). There was no relationship between the growth index values and leukocyte concentrations.

The effect of different dilutions with heparin solutions or saline on blood Pco2, pH and standard bicarbonate was investigated. Blood was first equilibrated to give about 40 or 60 mmHg Pco2. The solutions were in equilibrium with room air. The effect on blood Pco2 etc. could be fully explained by the dilution with a medium having a much lower Pco2. Thus, correction of the heparin solution to pH 7.40 and Pco2 40 mmHg eliminated the effect on Pco2, pH and standard bicarbonate. With ordinary procedure for blood heparinization (about 2% dilution) the effect is practically negligible.

Summary1. An attenuated initial hemodynamic response to endotoxin was observed in adult mongrel dogs under conditions of low blood pCO2 at both high and low pH. 2. No change in vascular responsiveness to histamine was found under these same conditions. 3. No change in the later phase of progressive systemic hypotension and death was observed.

The alveolar to blood P CO 2 difference during rebreathing, which abolished CO 2 exchange in the lung, has been studied in 3 children aged 9 to 10 years and 3 adults 23 to 24 years. The blood P CO 2 was measured from an arterialised ear lobe sample taken after recirculation had begun. The gas P CO 2 was measured from the end-tidal record at the mid point of blood sampling, with appropriate allowance for the time lag from lung to ear. Alveolar P CO 2 was consistently higher than blood P CO 2 by an amount which increased with the work load. The cardiac output calculated by using the uncorrected gas equilibrium P CO 2 gave the most reasonable results in all subjects. There were no differences in alveolar to blood gradient or in cardiac output for a given oxygen consumption between children and adults. The reason for the large gas to blood differences using the present technique is discussed and the problem posed by these studies is noted.

It is demonstrated that the most accurate and precise method of determining whole blood pCO2 is with the Severinghaus modification of the pCO2 electrode. The coefficient of variation is only ± 0.33 per cent. Experiments show that the pCO2 may not be stable for more than 30 min. when whole blood is stored at O° when whole blood is diluted with saline, the pCO2 falls in exact proportion to the dilution. The pH/log pCO2 curves of separated plasma and of whole blood have the same slope when temperature is changed. The pCO2 of cold-separated plasma is lower than the pCO2 plasma separated at body temperature. The variation of pCO2 with temperature appears to follow pari passu the variation of pH with temperature. The mean pK' of 18 patient samples equilibrated at 37.5° was 6.103. The standard deviation was ± 0.012. Calculated pCO2, utilizing the Henderson-Hasselbalch equation, can have a coefficient of variation of ± 2.5 per cent if proper temperature corrections are made. If temperature corrections are not made, calculated pCO2 may have a coefficient of variation greater than ± 5 per cent.