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Background During severe sepsis, the existence of a pathologic oxygen supply dependency remains controversial. Study objective To evaluate the relationship between oxygen delivery (Do 2 ) and oxygen consumption ( V ˙ o 2 ) during severe sepsis and to compare, in this respect, survivors and nonsurvivors and patients with normal or increased concentration of plasma lactate. Study design Cohort analytic study. Setting Three European ICUs in university hospitals. Patients Seventeen mechanically ventilated patients with severe sepsis (six with high blood lactate levels) studied within the first day of diagnosis. Interventions and measurements Pulmonary elimination of carbon dioxide, or carbon dioxide production ( V ˙ Co 2 ) and V ˙ o 2 were measured by indirect calorimetry before and after two interventions designed to increase Do 2 (calculated from the Fick equation): inflation of a military antishock trouser (MAST) and infusion of dobutamine. Results During MAST inflation, Do 2 increased by 19% in patients with a normal concentration of plasma lactate (p 2 increased in both groups by 16% (p

Previous studies have described oxygen delivery ( V ˙ o 2 ) and oxygen consumption ( V ˙ o 2 ) relationships in patients with ARDS and other acute diseases that suggest occasions when V ˙ o 2 may be dependent on the supply of oxygen, ie, V ˙ o 2 . We studied 127 postoperative patients who developed ARDS to evaluate the relationship of V ˙ o 2 to V ˙ o 2 . We found a weak correlation between V ˙ o 2 and V ˙ o 2 in the total series (r = 0.49) as well as in several clinical subgroups of patients with ARDS. Moreover, we observed similar relationships in a concurrent group of 218 postoperative patients who did not develop ARDS. We also examined the V ˙ o 2 data of individual patients with ARDS to identify instances where flow-dependent V ˙ o 2 patterns developed into flow-independent V ˙ o 2 patterns. We were able to identify an apparent plateau in the V ˙ o 2 relationships in 29/50 (58 percent) patients where multiple measurements were obtained over a short period of time. Our data are consistent with the concept that the V ˙ o 2 relationship in acutely ill early postoperative patients with and without ARDS is affected by antecedent circulatory problems that may lead to tissue hypoxia and tissue oxygen deficiencies that are manifest by flow dependency.

The finding of a dependence of oxygen consumption on oxygen delivery in critically ill patients has encouraged interventions to increase oxygen delivery index (DO2I) to overcome tissue hypoxia. In individuals other factors may influence oxygen consumption index (VO2I) and DO2I and may cause an apparently dependent relationship. We studied the effects of sedation and temperature on the VO2I/DO2I relationship in 13 perioperative patients. Pooled data showed significant correlations between VO2I and DO2I (r greater than 0.6, p less than 0.05) but also between VO2I and sedation score (r greater than 0.7, p less than 0.05), but not VO2I and temperature (r less than 0.5). When VO2I was standardized for the effects of sedation score (SS), the relationship between VO2I and DO2I was lost (r less than 0.5). Seven of 13 patients had significant (p less than 0.05) correlations between VO2I and SS and six of 13 between VO2I and DO2I; when standardized for the effect of varying sedation, no relationships were significant. When interpreting oxygen transport data from critically ill patients, the effects of sedation but not temperature must be taken into account; otherwise a false impression of a dependent relationship between VO2I and DO2I may cause unnecessary treatment.

1991;100;1676-1684 Chest R Chiolero, J P Flatt, J P Revelly and E Jequier patients. consumption and oxygen delivery in critically ill Effects of catecholamines on oxygen http://chestjournal.chestpubs.org/content/100/6/1676.citation can be found online on the World Wide Web at: The online version of this article, along with updated information and services ) ISSN:0012-3692 http://chestjournal.chestpubs.org/site/misc/reprints.xhtml ( without the prior written permission of the copyright holder. reserved. No part of this article or PDF may be reproduced or distributed Chest Physicians, 3300 Dundee Road, Northbrook, IL 60062. All rights of been published monthly since 1935. Copyright1991by the American College is the official journal of the American College of Chest Physicians. It has Chest

Previous studies reporting pathologic oxygen supply dependency calculated VO2 as CO x C(a-v)O2. We investigated whether pathologic oxygen supply dependency exists in septic and postoperative patients if VO2 and DO2 are assessed independently. In septic patients, VO2 was 164 +/- 31 and DO2 was 633 +/- 209 ml/min/m2. The slope (b) of the VO2-DO2 regression line VO2 = b x DO2 + a ranged from -0.10 to 0.08 (mean, 0.02 +/- 0.01, p less than 0.05) and was statistically significant in two patients (b = 0.05 and b = 0.08, p less than 0.05). In postoperative patients VO2 was 136 +/- 19 and DO2 was 481 +/- 160 ml/min/m2; b ranged from -0.07 to 0.09 (mean, 0.04 +/- 0.01, p less than 0.001) and was statistically significant in one patient (b = 0.09, p less than 0.01). The lack of a close relationship between independently measured VO2 and DO2 may indicate that septic and postoperative patients in stable hemodynamic condition have no pathologic oxygen supply dependency. Analysis of the VO2-DO2 relationship may not be useful to guide therapy or predict outcome.

Pathologic dependency of V ˙ O2 on D ˙ O2 has been reported in postoperative and septic patients. We studied the influence of an artifact due to calculation of V ˙ O2 from CO and AV content difference. In 13 postoperative and seven septic patients, the relationships between D ˙ O2 and c V ˙ O2 and between D ˙ O2 and m V ˙ O2 were analyzed by linear regression. In ten patients, c V ˙ O2 and D ˙ O2 were significantly correlated, but in only two of these patients m V ˙ O2 also correlated with D ˙ O2. In two patients, there was a significant correlation between m V ˙ O2 and D ˙ O2. The main contribution to the correlation and to the slope of the regression line between c V ˙ O2 and D ˙ O2 may be due to mathematic coupling of c V ˙ O2 and D ˙ O2. With c V ˙ O2, erroneous conclusions concerning the V ˙ O2- D ˙ O2 relationship may be drawn. In four patients, D ˙ O2 and m V ˙ O2 were significantly related, reflecting either physiologic coupling or pathologic supply dependency of V ˙ O2.

Healthy individuals are able to tolerate profound, short-term decreases in hemoglobin levels and oxygen saturation without serious consequences, but critically ill patients in respiratory failure lack the necessary reserve capacity to preserve tissue oxygenation. The development of progressive anemia in ICU patients has led to much interest and debate about transfusion practices, yet optimal hemoglobin levels and how they should be achieved remain unclear. Animal and human studies regarding critical oxygen delivery provide the rationale for optimizing hemoglobin levels and supporting cardiovascular function during respiratory failure. Theoretically, the oxygen-carrying benefit of RBCs should hasten recovery from respiratory failure, and transfusions would therefore be expected to shorten the duration of mechanical ventilation. However, evidence to the contrary has been reported. Controversies related to transfusions and their inability to improve outcomes suggest that further research regarding transfusion alternatives is needed, especially in anemic patients with respiratory failure.

Aim: Demand oxygen delivery systems (DODSs) were developed to secure the mobility of patients requiring oxygen therapy. The aim of the present study was to compare the efficacy of two currently available DODS with continuous oxygen administration (CONT). Patients: Thirteen patients with COPD (mean [ SD] FEV1 ,2 8 5.2% predicted; mean PO2, 56.4 8.1 mm Hg [breathing room air]). Intervention: Treatment for 30 min with CONT at a flow rate of 2 L/min, with the DODSs Oxytron 3 (Weinmann; Hamburg, Germany) or DeVilbiss EX 3000 (Somerset, PA) in random sequence. Arterialized blood samples were obtained from a hyperaemized ear lobe after 15 and 30 min. Results: After 15 min, no significant differences in PO2 or arterial oxygen saturation (SaO2) were observed. In comparison with CONT (mean PO2, 70.5 10.4 mm Hg; mean SaO2, 94.8 2.13%), oxygenation with the Oxytron 3 (mean PO2, 66.3 10.3 mm Hg; mean SaO2, 93.5 2.6%) was significantly less after 30 min when measured independently by blood gas analysis and pulse oximetry. The DeVilbiss EX 3000 (mean PO2, 69.1 12.0 mm Hg; mean SaO2, 94.5 3.2%) and CONT showed no differences. Conclusions: PO2 did not reach equilibrium after 15 min of treatment with the DODSs. The titration of a patient to a DODS is recommended, since simply accepting the manufacturer’s information on oxygen equivalent does not guarantee an adequate supply of oxygen. (CHEST 2005; 128:2082–2087)

Objective Almost every country in the developed worldhas a domiciliary oxygen program. Whether recipients meet programcriteria has not been rigorously studied. Design Cross-sectional survey. Participants Two hundredthirty-seven patients receiving domiciliary oxygen in the OntarioMinistry of Health Home Oxygen Program (HOP). Methods A respiratory therapist visited the patients' homes and administeredquestionnaires, obtained resting arterial blood gas measurements, andconducted a standardized home exercise test while monitoring oxygensaturation using an oximeter. Measures of outcome Weevaluated the extent to which patients met HOP criteria that are basedon the inclusion criteria of randomized trials showing thelife-prolonging effects of domiciliary oxygen. We also assessed theextent to which the patients' oxygen prescription was consistent withthe results of rest and exercise testing. Results Ninety-six of 237 participants (40.5%; 95% confidence interval, 34.3to 46.8) did not meet criteria for home oxygen. Patients aged ≤ 70years were more likely to meet criteria (71 of 105 patients; 67.9%)than those > 70 years old (70 of 132 patients; 53.0%). Theproportion of patients meeting criteria was similar whether thereferring physician was a specialist (71 of 112 patients; 62.5%) or aprimary-care physician (69 of 123 patients; 56.1%). A very importanthealth benefit from oxygen was identified among 82% of those who metcriteria and 88% of those who did not. Patients received higher flowrates than our criteria suggested were appropriate. Agreement betweenthe independently assessed oxygen prescription at rest and thepatients' report of oxygen use was extremely poor (chance-correctedagreement [κ], 0.17), as was agreement concerning optimal exerciseflow rates (κ, 0.26). Conclusions Currentprocedures for administration and reimbursement of home oxygen resultin a large proportion of recipients not meeting criteria, as well asthe prescription of excessive oxygen flow rates. These results arelikely to apply to many jurisdictions and suggest a large potential formore efficient resource allocation.

Study objectives To determine if oxygen consumption/oxygen delivery ( V ˙ o 2 / D o 2 ) relationships derived using calorimetry (which are not influenced by shared measurement error) agreed with those obtained using the pulmonary artery (PA) catheter alone. To evaluate three strategies to reduce the influence of shared measurement error to determine if agreement between the two methods could be improved. Methods Twenty-seven patients were studied following coronary artery bypass surgery. Calorimetric V ˙ o 2 , six thermodilution cardiac outputs (COs), and arterial and mixed venous oxygen content measurements were made at baseline and were repeated 30 min following dobutamine administrations of 3 μg/kg/min and 5 μg/kg/min. Results Dobutamine produced a dose-dependent increase in Do 2 , from 378±65 mL/min/m 2 to 446±78 mL/min/m 2 (p

Objective Investigation of the hypothesis that the infusion of 10 ng/kg/min prostacyclin (epoprostenol) (PGI 2 ) improves O 2 uptake in patients with hyperdynamic septic shock. Design Prospective, single cohort design. Setting ICU, university hospital. Patients Fifteen postoperative patients with septic shock. Interventions Infusion of 10 ng/kg/min of PGI2 for 60 min. Measurements Complete hemodynamic profile with O 2 transport-related variables (simultaneous measurements of Vo 2 from the respiratory gases and by cardiovascular Fick) and blood lactate levels before start of the PGI 2 -infusion and 60 min thereafter. Main results Oxygen delivery increased significantly (14 percent) from its already high value, 750±238 to 852±214 ml/min/m 2 . The O 2 extraction ratio remained unchanged. When Vo 2 was measured from the respiratory gases, it was unchanged. When Vo 2 was measured by cardiovascular Fick, it increased slightly (p Conclusions We conclude that in this O 2 challenge test with PGI2 in patients with septic shock, an increase in O 2 delivery was not matched by an increase in Vo 2 . We believe that the adequate conventional support of these patients may have prevented the PGI2 from revealing a "covert" O 2 debt. The PGI2 test did not predict mortality by O 2 supply dependency. The small increase in Vo 2 as calculated indirectly suggests a degree of mathematical coupling of O 2 delivery and uptake.

Five different oxygen-conserving devices were tested in each of ten oxygen-dependent patients with COPD who had met the NOTT criteria for continuous oxygen use. They were tested on room air, their prescribed continuous oxygen flow and then on each of the five devices. The devices which delivered a bolus of oxygen during early inspiration or increased oxygen delivery as the respiratory rate increased did better than those devices which delivered oxygen at a normal flow rate during inspiration or a fixed portion of inspiration. In at least one of the subjects each device was associated with desaturation to less than 80 percent during a 12-min walk. It is concluded that oxygen-conserving devices vary in their ability to maintain SaO2 levels during exercise. It is recommended that a home oxygen evaluation include measurement of an exercise SaO2 utilizing the prescribed oxygen delivery system.

Forty-four critically ill patients with or without adult respiratory distress syndrome (ARDS) were studied in an attempt to define critical levels of oxygen delivery. Blood lactate was used as the indicator of tissue hypoxia independent of cardiac output. Survival was good (55 percent) and blood lactate near normal for those with oxygen delivery more than 8 ml/kg/min. Below this level, survival was poor (14 percent) and blood lactate markedly increased. There were significant nonlinear correlations of lactate with O 2 delivery (r = – .735, p

Over a six-year period, 200 patients requiring long-term oxygen therapy for hypoxemic lung disease underwent insertion of the micro-trach transtracheal catheter and were evaluated for one to seven years. The catheter requires no removal for cleaning; it is designed to function undisturbed within the trachea for six months between replacements. Transtracheal oxygen delivery and saline instillation were instituted immediately after inserting the device. Oxygen administration at a rate of 0.25 to 3 L/min was equivalent to 1 to 8 L/min delivered nasally. By the end of one year of follow-up, 12.5 percent of patients had dropped out of the study. Most patients comply with prescribed 24-hour-a-day oxygen use; in keeping with the NOTT study, life expectancy of emphysema patients may therefore be increased.

Nine hypoxemic patients with COLD, whose hypoxemia is aggravated by minimal exercise, volunteered for this study. Each subject underwent two treadmill exercise trials at two oxygen delivery settings, each on the DODS and SF delivery systems for a total of four exercise trials. We measured SaO2 via ear oximetry and recorded oxygen usage per minute. We compared the oxygen usage required for the two techniques to achieve an SaO2 of 90 percent. The results indicate that the mean oxygen requirement using the DODS to achieve an SaO2 of 90 percent was 211.4 ml/min as compared to SF delivery which required 1,610.9 ml/min. This implies an oxygen savings advantage of the DODS over SF of 7:1. The fact that the DODS oxygen savings extends to exercise conditions lends support to its use in portable oxygen therapy. Widespread use of this and other oxygen savings techniques could result in significant cost savings while maintaining the desired benefits of supplemental oxygen administration.

We evaluated the effects of fluid challenges on oxygen delivery (DO2) and oxygen consumption (VO2) in nine patients receiving immunotherapy with interleukin-2. Fluid resuscitation produced an increase in DO2 from 15.7 +/- 3.1 to 17.4 +/- 3.5 ml/min/kg (mean +/- SD, p less than 0.001), which was associated with a corresponding increase in VO2, from 2.8 +/- 0.7 to 3.1 +/- 0.6 ml/min/kg (p less than 0.01). These results suggest that oxygen consumption may be dependent on oxygen delivery in patients on IL-2 therapy. The presence of oxygen supply dependency may contribute to the multiple organ failure observed with IL-2 administration.

The efficacy of long-term oxygen therapy for hypoxemic COPD patients is well established. However, oxygen is expensive and the portability of home oxygen is limited by the weight and bulk of the oxygen source. As a result, there has been a recent surge of interest in creating oxygen-conserving devices and methods. The efficiency of oxygen therapy can be improved over steady flow delivery by focusing oxygen delivery to early inspiration. Three methods for improving oxygen delivery efficiency—transtracheal catheter, reservoir cannula and demand-pulse oxygen delivery—are currently available for patient use. Each has its own set of advantages and disadvantages. By using oxygen conservation methods, the oxygen required to achieve adequate blood oxygenation can be reduced by a factor of 2:1 to 7:1 compared to steady flow. Thus, the cost of oxygen can be substantially reduced while increasing the portability and range of home oxygen therapy.

Recent heightened concern about the costs of medical care has stimulated research and development in devices and schemes for saving costs while retaining quality of care. Consistent with that concern is the fact that standard steady-flow oxygen delivery is so wasteful. Almost its entire benefit occurs at the very beginning of inspiration. We compared the efficacy of nasal oxygen delivery via a new demand oxygen delivery system (DODS) with the standard steady-flow (SF) method. The DODS incorporates a valve and sensor interposed between the oxygen reservoir and the patient, which meters oxygen to the patient only during early inspiration. Twelve COPD subjects with hypoxemia at rest received oxygen at flow settings of 1 to 4 L/min via SF and at various breath interval settings via the DODS method, calculated to match the above spectrum of the SF. We measured oxygen delivery using an ear oximeter. The results indicate that significantly less oxygen was required to provide equivalent saturations using the DODS compared with the SF method (p less than .001). The mean comparative savings in oxygen is better than seven to one favoring the DODS over the SF method. Further study is warranted, since the widespread use of such a device could result in substantial cost saving while increasing the range of portable oxygen delivery.

The effects of increasing oxygen delivery (DO2) on oxygen consumption (VO2) in eight patients with septic shock and five patients with hypovolemic shock were studied during fluid resuscitation. In the septic shock group, DO2 increased from 315 +/- 29 to 424 +/- 25 ml/min/m2 (p less than 0.01) and VO2 increased from 134 +/- 8 to 151 +/- 7 ml/min/m2 (p less than 0.01). In the hypovolemic shock group, DO2 increased from 239 +/- 26 to 386 +/- 48 ml/min/m2 (p less than 0.01) and VO2 increased from 96 +/- 9 to 135 +/- 6 ml/min/m2 (p less than 0.01). There was no significant difference in either the increase in DO2 or VO2 between the septic shock and hypovolemic shock patients. We conclude that increasing DO2 by fluid resuscitation increases VO2 during both hypovolemic and septic shock.

The demand oxygen delivery system has been reported to improve oxygen delivery 7:1 vs steady flow during rest and exercise in COPD patients. The present study evaluates the DODS during rest and exercise in eight patients with restrictive lung disease. It was concluded that the DODS provides substantial oxygen savings in RLD patients, particularly during exercise.

ncreased blood 02 affinity was found in an I asymptomatic 55-year-old man with a Hct of 70 percent. An abnormal hemoglobin was found which had greater cathodal mobility than Hb A on agar gel electrophoresis at pH 6.0, but did not separate from Hb A on starch gel electrophoresis at pH 7.0, 7.7 and 8.6. Hb Little Rock was heat stable and normally sensitive to alkali. The p-Little Rock chain is abnormal as indicated by its separation from PA on CMC chromatography of whole hemolysate treated with p-chloromecuribenzoate so as to dissociate the a and p chains. The 02 equilibrium of red cells suspended in phosphate buffer at 37OC showed a log of P5002 of 1.03 at pH 7.40 (normal 1.34-1.40), normal Bohr effect, and an "n" value of 1.6. At 02 saturations 80 percent, however, "n" approached 2.5. The log P5002 of cells depleted of DPG and ATP by an in vitro incubation procedure was 0.80 (normal 1.041.07). The in viuo effects of Hb Little Rock on oxygen delivery were assessed by measuring red cell mass - 51 mllkg; plasma volume - 35 ml/kg; plasma iron turnover-two times normal; urine erythropoietin-high normal; red cell DPG-12.2 pM/g Hb (normal 11.9-18.0); red cell ATP-3.7 pM/g Hb