Carbon Dioxide Content Of Blood Research Articles

Association of end-tidal and venous carbon dioxide in intubated and ventilated children

Introduction: The end-tidal CO2 pressure (PetCO2) monitoring which is a non-invasive method than PvCO2 (venous pressure of carbon dioxide), could determinate a graph depicting the carbon dioxide concentration in blood. The aim of this study was to investigate the correlation between PetCO2-PvCO2 in ventilated children. Methods: All children intubated in the PICU of Children hospital Tabriz, Iran from 2019 to 2020 using the census method were assessed in terms of initial diagnosis, age, sex, PetCO2, and PvCO2 during a prospective cross-sectional study. Associations between variables were calculated for total patients and patients in the subgroups. Descriptive statistics were used to describe the quantitative analysis of data and the Pearson correlation coefficient and Linear Regression Test were used for the evaluation of the relationship between variables and for assessing the predictive values of PvCO2 using SPSS.26. A P value<0.05 was considered statistically significant. Results: Out of 61 samples, 42 (68.9%) patients were males with a median age of 48 months. The mean of PetCO2 and PvCO2 were 20.3±8.5 and 43±12.3 mm Hg, respectively. The correlation of PetCO2-PvCO2 was significant in total patients (P value=0.003, r=0.379) and group 1 (P value=0.009, r=0.374). Furthermore, the results presented the predictive values of PvCO2 for PetCO2 while for one unit increase in the PvCO2 variable, PetCO2 could increase 0.372 units (P value=0.005, Slope b=0.24, Beta coefficient=0.372). Conclusion: In most intubated children, PetCO2 may estimate the ventilation and change concentrations of CO2. It is necessary that the sample size of future studies will become large due to the weak correlation.

Systemic immune inflammation index and peripheral blood carbon dioxide concentration at admission predict poor prognosis in patients with severe traumatic brain injury.

Recent studies have shown that systemic inflammation responses and hyperventilation are associated with poor outcomes in patients with severe traumatic brain injury (TBI). The aim of this retrospective study was to investigate the relationships between the systemic immune inflammation index (SII = platelet × neutrophil/lymphocyte) and peripheral blood CO2 concentration at admission with the Glasgow Outcome Score (GOS) at 6 months after discharge in patients with severe TBI. We retrospectively analyzed the clinical data for 1266 patients with severe TBI at three large medical centers from January 2016 to December 2021, and recorded the GOS 6 months after discharge. The receiver operating characteristic (ROC) curve was used to determine the best cutoff values for SII, CO2, neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), and lymphocyte to monocyte ratio (LMR), and chi-square tests were used to evaluate the relationships among SII, CO2 and the basic clinical characteristics of patients with TBI. Multivariate logistic regression analysis was used to determine the independent prognostic factors for GOS in patients with severe TBI. Finally, ROC curve, nomogram, calibration curve and decision curve analyses were used to evaluate the value of SII and coSII-CO2 in predicting the prognosis of patients with severe TBI. And we used the multifactor regression analysis method to build the CRASH model and the IMPACT model. The CRASH model included age, GCS score (GCS, Glasgow Coma Scale) and Pupillary reflex to light: one, both, none. The IMPACT model includes age, motor score and Pupillary reflex to light: one, both, none. The ROC curves indicated that the best cutoff values of SII, CO2, PLR, NLR and LMR were 2651.43×109, 22.15mmol/L, 190.98×109, 9.66×109 and 1.5×109, respectively. The GOS at 6 months after discharge of patients with high SII and low CO2 were significantly poorer than those with low SII and high CO2. Multivariate logistic regression analysis revealed that age, systolic blood pressure (SBP), pupil size, subarachnoid hemorrhage (SAH), SII, PLR, serum potassium concentration [K+], serum calcium concentration [Ca2+], international normalized ratio (INR), C-reactive protein (CRP) and co-systemic immune inflammation index combined with carbon dioxide (coSII-CO2) (P < 0.001) were independent prognostic factors for GOS in patients with severe TBI. In the training group, the C-index was 0.837 with SII and 0.860 with coSII-CO2. In the external validation group, the C-index was 0.907 with SII and 0.916 with coSII-CO2. Decision curve analysis confirmed a superior net clinical benefit with coSII-CO2 rather than SII in most cases. Furthermore, the calibration curve for the probability of GOS 6 months after discharge showed better agreement with the observed results when based on the coSII-CO2 rather than the SII nomogram. According to machine learning, coSII-CO2 ranked first in importance and was followed by pupil size, then SII. SII and CO2 have better predictive performance than NLR, PLR and LMR. SII and CO2 can be used as new, accurate and objective clinical predictors, and coSII-CO2, based on combining SII with CO2, can be used to improve the accuracy of GOS prediction in patients with TBI 6 months after discharge.

FC 052ACID-BASE BALANCE DURING IN-SERIES EXTRACORPOREAL CARBON DIOXIDE REMOVAL AND CONTINUOUS VENOVENOUS HEMOFILTRATION: PREDICTIONS FROM A MATHEMATICAL MODEL

Abstract Background and Aims Critically ill acute kidney injury (AKI) patients may require treatment by extracorporeal carbon dioxide removal (ECCO2R) devices to allow protective or ultraprotective mechanical ventilation and avoid hypercapnic acidosis. Continuous venovenous hemofiltration (CVVH) and ECCO2R devices can be arranged in series to form a single extracorporeal circuit; such a circuit has been proposed to be optimal, based carbon dioxide removal efficacy, if the ECCO2R device is placed proximal to the CVVH device (Allardet-Servent et al, Crit Care Med 43:2570-2581, 2015). Method We developed a mathematical model of whole-body, acid-base balance during extracorporeal therapy using in-series ECCO2R and CVVH devices for treatment of mechanically ventilated AKI patients. Equilibrium acid-base chemistry in blood was assumed as reported previously (Rees and Andreassen, Crit Rev Biomed Eng 33:209-264, 2005). Published clinical data from Allardet-Servent et al of mechanically ventilated (6 mL/kg predicted body weight or PBW) AKI patients treated by CVVH without ECCO2R were used to adjust model parameters to fit plasma levels of arterial partial pressure of carbon dioxide (PaCO2) and arterial plasma bicarbonate concentration ([HCO3]). The effects of applying ECCO2R at an unchanged tidal volume and a reduced tidal volume (4 mL/kg PBW) on PaCO2 and [HCO3] were then simulated assuming carbon dioxide removal rates from the ECCO2R device measured in the clinical study (91 mL of CO2/min when ECCO2R was proximal and 72 mL of CO2/min when CVVH was proximal). Results Agreement of model predictions with the clinical data was good, and model predictions were relatively independent of the in-series position of the devices (see Table). Total carbon dioxide removal from the CVVH device via ultrafiltration predicted by the model was lower after applying ECCO2R at both the unchanged tidal volume (25 mL of CO2/min when ECCO2R was proximal and 39 mL of CO2/min when CVVH was proximal) and the reduced tidal volume (30 mL of CO2/min when ECCO2R was proximal and 44 mL of CO2/min when CVVH was proximal). The reduced removal of total carbon dioxide via ultrafiltration when ECCO2R was proximal resulted from the lower total carbon dioxide concentration in blood entering the CVVH device. Thus, independent of the in-series position of the devices, the magnitude of this difference in total carbon dioxide removal by the CVVH device (14 mL of CO2/min) approximately cancels out the relative greater efficacy of the ECCO2R device (19 mL of CO2/min). Conclusion The described mathematical model has quantitative accuracy. It suggests that overall acid-base balance when using ECCO2R and CVVH devices in a single, combined extracorporeal circuit will be similar, independent of their in-series position.

Principles, Utility and Limitations of Pulse Oximetry in Management of COVID-19

Pulse oximetry is an essential component of the standard care of COVID-19 patients. In the context of the spreading COVID-19 pandemic for which no targeted therapy or vaccines are yet available, early identification of the severe cases or cases with high risk of severe disease and appropriate supportive treatment are of paramount importance to save lives. Pulse oximetry is a cheap, fast, easy to use, noninvasive, painless and accurate tool that allows real-time monitoring of hypoxemia. As the primary target of the disease is the respiratory system pulse oximetry provides an unparalleled way to assess the severity of the disease, guide supportive therapies and monitor the clinical status and response to treatment with greater benefits in the low-resource settings. All settings from the quarantine facilities at the ground level to the ICUs in the highest level hospitals can utilize it to achieve their goals. To get the best of this tool, it needs to be used properly and the findings interpreted carefully. Role of basic understanding of the physiological principles and technology behind its use and awareness of its limitations cannot be overemphasized. The pulse oximetry readings are interpreted in the context of blood hemoglobin concentration, tissue perfusion, arterial blood carbon dioxide concentration and oxygen supplementation status.

Assessment of cerebral hemodynamic parameters using pulsatile versus non-pulsatile cerebral blood outflow models.

Prior methods evaluating the changes in cerebral arterial blood volume (∆CaBV) assumed that brain blood transport distal to big cerebral arteries can be approximated with a non-pulsatile flow (CFF) model. In this study, a modified ∆CaBV calculation that accounts for pulsatile blood flow forward (PFF) from large cerebral arteries to resistive arterioles was investigated. The aim was to assess cerebral hemodynamic indices estimated by both CFF and PFF models while changing arterial blood carbon dioxide concentration (EtCO2) in healthy volunteers. Continuous recordings of non-invasive arterial blood pressure (ABP), transcranial Doppler blood flow velocity (CBFVa), and EtCO2 were performed in 53 young volunteers at baseline and during both hypo- and hypercapnia. The time constant of the cerebral arterial bed (τ) and critical closing pressure (CrCP) were estimated using mathematical transformations of the pulse waveforms of ABP and CBFVa, and with both pulsatile and non-pulsatile models of ∆CaBV estimation. Results are presented as median values ± interquartile range. Both CrCP and τ gave significantly lower values with the PFF model when compared with the CFF model (p ≪ 0.001 for both). In comparison to normocapnia, both CrCP and τ determined with the PFF model increased during hypocapnia [CrCPPFF (mmHg): 5.52 ± 8.78 vs. 14.36 ± 14.47, p = 0.00006; τPFF (ms): 47.4 ± 53.9 vs. 72.8 ± 45.7, p = 0.002] and decreased during hypercapnia [CrCPPFF (mmHg): 5.52 ± 8.78 vs. 2.36 ± 7.05, p = 0.0001; τPFF (ms): 47.4 ± 53.9 vs. 29.0 ± 31.3, p = 0.0003]. When the CFF model was applied, no changes were found for CrCP during hypercapnia or in τ during hypocapnia. Our results suggest that the pulsatile flow forward model better reflects changes in CrCP and in τ induced by controlled alterations in EtCO2.

Aging of the respiratory system

Changes in the respiratory system caused by aging generally include structural changes in the thoracic cage and lung parenchyma, abnormal findings on lung function tests, ventilation and gas exchange abnormalities, decreased exercise capacity, and reduced respiratory muscle strength. Decreased respiratory system compliance caused by reduced elastic recoil of the lung parenchymaand thoracic cage is related to decreased energy expenditure by the respiratory system. Lung function, as measured by 1-second forced expiratory volume and forced vital capacity (FVC), decreases with age, whereas total lung capacity remains unchanged. FVC decreases because of increased residual volume and diffusion capacity also decreases. Increased physiological dead space and ventilation/perfusion imbalance may reduce blood oxygen levels and increase the alveolar-arterial oxygen difference. More than 20% decrease in diaphragmstrength is thought to beassociated withaging-related muscle atrophy. Ventilation per minute remains unchanged, and blood carbon dioxide concentration does not increase with aging. However, responses to hypoxia and hypercapnia are decreased. Exercise capacity also decreases, and maximum oxygen consumption decreases by &amp;gt;1%/year. Consequence of these changes, many respiratory diseases occur with aging. Thus, it is important to recognize these aging-related respiratory system changes.

Hemoglobin–oxygen-affinity and acid-base properties of blood from the fossorial mole-rat, Cryptomys hottentotus pretoriae

Oxygen affinity and other hematological parameters in strictly subterranean mole-rats, Cryptomys hottentotus (subspecies pretoriae) were measured immediately upon capture and after 14-21 days in captivity. The pH, hematocrit, hemoglobin (Hb) concentration, blood oxygen content, 2,3 bisphosphoglycerate (2,3 BPG) concentration and oxygen dissociation curves (ODC), as well as tonometric measurements, were determined using whole blood. Additionally ODCs were also determined for stripped hemolysates of individual animals. Compared to other mammals, blood of freshly caught animals had low pH (7.32+/-0.22), elevated hematocrits (48.4+/-3.8 %) and significantly lower P50 values for whole blood (21.1+/-1.6 mm Hg at pH 7.4) than those reported for other similar-sized fossorial and terrestrial mammals. Blood carbon dioxide content (22.4+/-3.9 mMol L(-1)), hemoglobin concentration (1.9+/-0.15 mMol L(-1)), oxygen content (164.8+/-26 mL L(-1)), bicarbonate concentrations (22.5+/-3.5 mMol L(-1)) were within the range of values reported for similar-sized mammals. We conclude that high blood-oxygen affinity, low body temperature and possibly also high hematocrit enable C. h. pretoriae to maintain an adequate oxygen supply to the tissues in a potentially hypoxic burrow atmospheres, but that the blood of this species shows no exceptional CO2 sensitivity or buffering capacity.

Measurement of carbon monoxide in simulated expired breath

Background: Environmental carbon dioxide (CO) detectors used as an early warning method have been adapted to measure CO concentration in expired breath. This technique has been validated in smokers with relatively low CO concentrations, but its applicability to poisoning has not been demonstrated. Objective: To compare the reliability of toxicologically significant CO measurements performed using a portable CO detector with those obtained using infrared spectrometry, the standard method for blood CO concentration determination. Design: Experimental study with a CO detector and infrared spectrometer. A balloon simulated respiratory movements and an expired breath. Balloon gas mixtures contained CO, in one of 21 different concentrations from 100 to 600 parts per million (ppm) in air. CO concentration was measured directly with the portable CO detector and two gas samples obtained at the beginning and end of the simulated expired breath were diluted, with validation, for spectrometric measures. Main outcome measures: Portable CO detector concentrations were compared with the mean value of the reference method. Simple linear regression was performed using ANOVA to evaluate the parallel between the model with the reference method. Results: Portable CO detector concentration measurements were perfectly linear ( R 2 = 0.989, P < 10 −3) over a concentration range of 46–645 ppm. The difference from the reference plot was significant ( P < 0.01). Conclusion: Given the linearity of the measurements, the underestimation by the portable CO detector at higher concentrations can be corrected mathematically. A portable CO detector should measure CO in expired breath efficiently and reliably.

EFFECTIVENESS OF NOVEL METHODS TO REDUCE HEAT STRESS IN BROILERS: CHILLED AND CARBONATED DRINKING WATER

The broiler industry is seeking effective and economical methods to minimize production heat losses. Poultry exposedto heat stress pant and experience reduced blood carbon dioxide concentration, suggesting that supplementing birdswith carbon dioxide would be beneficial. Chilled drinking water also has a potential to reduce heat stress. The present studiesseek to determine the effectiveness of offering carbonated or reducedtemperature water to two broiler flocks raised to 42 daysof age. Bird production performance data obtained from the two studies were combined since environmental temperaturesduring both studies were mild with little heat stress activity, except for a sudden increase in environmental temperatures on day38 in the second study. There were no significant differences in live weight, cumulative mortality, and feedtogain ratio atharvest when data obtained from the two studies were combined. Birds provided chilled drinking water showed a 1.2 L/birdgreater cumulative drinking water use than those provided tap water at ambient temperature. Ambient air temperatures werebetween 29. C and 37.C during the hottest periods in either study. Reducedtemperature carbonated drinking water had betterretention of dissolved carbon dioxide, as indicated by significantly lower pH (p < 0.001, at . = 0.050) when compared withambienttemperature carbonated drinking water.

Septicemia and septic shock in pediatric patients: 140 consecutive cases on a pediatric hematology-oncology service.

This report describes the incidence of septic shock in pediatric hematology-oncology patients with positive blood cultures and investigates parameters of potential use in early diagnosis of gram-negative (GN) bacteremia and septic shock. In a 12-month period, 140 consecutive episodes of septicemia (135 bacterial and 5 fungal) were seen in 100 patients. The absolute neutrophil count (ANC) was > 500/microl in 89 episodes (65%). Septic shock developed in patients with positive blood cultures with an overall incidence of approximately 19%. Of the 12 bacteremic patients who required transfer to the intensive care unit, 83% had a GN isolate recovered. The incidence of septic shock was not significantly lower in the group of patients with ANC > 500/microl. Low serum bicarbonate correlated with GN infection in patients with bacteremia. GN organisms were the major cause of septic shock in a group of pediatric hematology-oncology patients with positive blood cultures although they were recovered less frequently than gram-positive organisms. In our study, non-neutropenic patients with indwelling catheters were at approximately the same risk for GN shock as neutropenic patients. Monitoring blood carbon dioxide content may be useful in the early diagnosis of GN infection.

Prolonged pumpless arteriovenous perfusion for carbon dioxide extraction

A method of extracorporeal carbon dioxide extraction from the blood using an efficient microporous membrane oxygenator or membrane gas exchanger was evaluated during pumpless arteriovenous perfusions with a view to its application for partial respiratory support. The first study carried out in dogs revealed some increase in cardiac output, cardiac index, and cardiac work, although this increase was less than that normally expected from the added extracorporeal blood flow. In sheep during 3 to 7 days of continuous bypass, there was practically no hemolysis and relatively stable hemoglobin and hematocrit levels, and the platelet counts remained within safe levels. The maximum extracorporeal blood flow tended to decrease from a mean of 1.55 L/min on day 1 to 1.34 L/min on day 3 to 1.28 L/min on day 7. Carbon dioxide extraction remained efficient throughout the perfusion, but there was a minimal decrease from the first day (10.92 mmol/L) to the third day (8.46 mmol/L) at the higher blood carbon dioxide concentrations; it remained stable thereafter at 9.0 mmol/L.

Patterns of Morbidity and Mortality in Typhoid Fever Dependent on Age and Gender: Review of 552 Hopitalized Patients with Diarrhea

Features of typhoid fever were correlated with age and gender through a review of the charts of 552 hospitalized culture-positive patients with diarrhea in Bangladesh. Seizures occurred more frequently in children from birth through 10 years of age (5%-11%) and pneumonia more frequently in children from birth through 5 years of age (8%-15%) than in older age groups (P less than .05), whereas intestinal perforation occurred more frequently in patients greater than or equal to 11 years of age (5%-25%) than in younger age groups (P less than .005). Compared with older age groups, children from birth through 10 years of age were more anemic, those from birth through 5 years of age had a higher mean white blood cell count, and those from birth through 1 year of age had a lower mean blood carbon dioxide content (all P less than .05). Female patients were more severely anemic than male patients (P less than .05). The case-fatality rate was 4.3% overall, with the highest rates for children from birth through 1 year of age (11%) and adults greater than or equal to 31 years of age (10%). Female patients had a higher case-fatality rate (6%) than male patients (3%), although the difference was not significant (P greater than .05). Death was independently associated with seizures, intestinal perforation, pneumonia, and delirium or coma. These results indicated that the patients with typhoid fever who were at highest risk of complications and death were children from birth through 1 year of age and adults greater than or equal to 31 years of age.

Respiratory responses of the domestic fowl to low level carbon dioxide exposure

Respiratory function in the restrained, conscious domestic fowl was measured using a non-invasive technique and computer aided analysis to examine respiratory flow, and in-dwelling arterial catheters to monitor blood carbon dioxide levels. The effects of two low ranges of inspiratory carbon dioxide (0.2 to 1.0 per cent and 0.25 to 2.25 per cent) were studied, simulating levels of carbon dioxide that may occur in commercial poultry units and representing a mild environmental stress for the birds. A linear increase in minute volume with inspiratory carbon dioxide was observed, due primarily to increases in tidal volume. Arterial carbon dioxide (PaCO2) tension also rose as the inspiratory carbon dioxide concentration was raised, but higher inspiratory carbon dioxide levels were required to affect significantly blood carbon dioxide concentration than to modify respiratory parameters. Variation was observed in the individual bird's response to carbon dioxide (bird X carbon dioxide interaction), suggesting that resting values of the respiratory parameters measured were important in determining the bird's ventilatory response to carbon dioxide.

SECRETION OF NITROGEN INTO THE SWIMBLADDER OF FISH. I. SECRETION BY FISHES NEARLY LACKING CIRCULATING HEMOGLOBIN. ROLE OF THE RETE MIRABILE

Toadfish (Opsanus tau) essentially lacking circulating erythrocytes were pre pared by repeated exchange transfusion with serum. The rate of nitrogen secretion is not changed by removal of the erythrocytes. Oxygen secretion is slowed dras tically. This shows that nitrogen secretion does not require erythrocytes and is not driven by oxygen secretion. In the absence of circulating erythrocytes, oxygen and nitrogen are brought into the swimbladder in proportion to their concentrations in blood plasma. Carbon dioxide partial pressure in the secreted gas mixture is three to fourfold greater than the pressure generated by acidifying arterial blood. This implies counter-current multiplication of the small increment of carbon dioxide pressure brought about by acidification of the blood. In the presence of blood buffers, increased carbon dioxide pressure will increase blood bicarbonate. Three independent estimates indicate that, during gas secretion, gas gland blood is near pH 6.5. Total carbon dioxide (CO2, HCO3, CO3) is increased from the arterial value near 2 mM to about 14 mM, divided nearly equally between carbon dioxide and bicarbonate anion. The increment in total blood carbon dioxide concentration together with the well-known increment in lactate anion may serve to salt out inert gases from solution in blood plasma.

CO2 exchange in the blue crab, Callinectes sapidus (Rathbun)

AbstractThis study represents a first attempt to describe the pattern of carbon dioxide excretion in the gills of the blue crab, Callinectes sapidus. A computer simulation model was constructed, based on measurements of gill morphometry and blood carbon dioxide concentrations. Results of the simulation indicated that, although carbonic anhydrase is available in the gill epithelium for dehydration of HCO3−, it is probably not significantly involved in CO2 excretion. This conclusion was further supported by the observation that injection of a carbonic anhydrase inhibitor had no detectable effect on blood concentrations of CO2. Disequilibrium of the CO2‐HCO3− system is proposed as a significant factor in accounting for CO2 excretion.

In vitro blood carbon dioxide of the rainbow trout ( Salmo gairdneri)

1. 1. Rainbow trout were acclimated to 6, 15 and 20°C for at least 3 weeks; blood was removed and equilibrated in vitro at the acclimation temperature with CO 2 tensions in the range 1–8 mm Hg. Determinations of blood carbon dioxide content and pH were made. 2. 2. Increasing temperature caused a decrease in blood pH and CO 2 content, but the buffering capacity ( ΔC CO2 / ΔpH) appeared to be the same at all temperatures. 3. 3. Oxygenated blood contained less carbon dioxide than deoxygenated blood—the Haldane effect; this effect appeared to increase with decreasing temperature. 4. 4. The buffering properties of trout blood are compared with those of other species. The acid-base status of the blood is discussed in terms of the HendersonHasselbalch equation and the concept of relative alkalinity.

Determination of carbon dioxide content of blood by infrared analysis.

Determination of carbon dioxide content of blood by infrared analysis.

Oxygen and carbon dioxide content of blood in toad ( bufo melanostictus) during hibernation and non-hibernation

An increase in both oxygen and carbon dioxide concentration in blood of toad has been noted in hibernation compared to non-hibernation. The increase has been ascribed to be due to haemoconcentration during hibernation.

Changes in Levels of Hemoglobin, Oxygen, Carbon Dioxide, Pyruvate, and Lactate in Venous Blood of Rainbow Trout (Salmo gairdneri) During and Following Severe Muscular Activity

The effects of severe muscular exercise were studied in [Formula: see text]-year-old rainbow trout (Salmo gairdneri). Changes in the oxygen and carbon dioxide content of blood taken from the heart together with alterations in blood levels of pyruvate and lactate were followed in 14 separate conditions. Observations were also made on fish swimming steadily in a rotating annulus.

Hyperventilation in carbon-monoxide poisoning.

The recent revival of interest in the use of 5% or 7% carbogen in the treatment of carbon-monoxide poisoning has prompted the description of four unusual cases in which gross hyperventilation occurred. The investiga tion of these cases was not very thorough, but such cases are seen so seldom that it is felt that even this incomplete report may be of value in stimulating further research. Hyperventilation in carbon-monoxide poisoning was noted by Haldane (1895) in experiments performed upon himself, but Drinker (1938) concluded that increased breathing is not a prominent feature. He felt that those patients in whom it occurred would receive especial benefit from inhalation of carbon-dioxide mixtures because Haggard and Henderson (1921) had demonstrated a falling carbon-dioxide content of arterial blood in dogs poisoned with carbon monoxide. A low blood carbon-dioxide content may, however, be due to either respiratory alkalosis (as suggested by Drinker) or to non-respiratory acidosis, and the latter condition would be less likely to benefit from inhalation of carbon dioxide. The pH of the blood would distinguish between these two conditions, but this does not appear to have been measured either in animals or in man.