Blood Gas Data Research Articles

A Case of Chronic Mountain Sickness Diagnosed by Routine Pulmonary Function Tests

In summary, this is a patient who presented with respiratory acidosis and cor pulmonale. The major diagnostic challenge was in differentiating primary cardiopulmonary disease from a central abnormality of ventilatory drive. The arterial blood gases showed a normal A-a gradient suggesting hypoventilation as the etiology of his hypoxemia. Pulmonary function testing showed air trapping, but a relatively normal FEV1/FVC and airways resistance. The literature suggests that most altitude natives have depressed hypoxemic and hypercapnic drives with a distinct subset demonstrating a profoundly depressed drive to ventilation. This latter group has been labeled as having chronic mountain sickness or Monge's disease. As one might expect, ventilatory control during sleep is also abnormal in these patients with CMS. Our patient indeed showed typical frequent severe desaturations with hypopnea. The diagnosis of CMS in our patient was made with routine arterial blood gases and standard pulmonary function tests. Additional tests of ventilatory responsiveness to oxygen and carbon dioxide could have been performed, but are not necessary to make the diagnosis.

Temporal reasoning in blood gas diagnosis

Abstract: The aim of this paper is to describe a system whereby an intensive care unit patient's condition can be monitored and assessed over time using mostly blood gas analysis data. The first six sections analyse some major temporal reasoning approaches (with limited examples from other related areas) with the aim of selecting one for the task at hand. The last sections describe the PONJIP temporal blood gas analysis expert system with its main components, including user interfaces customised to the doctor's requirements. Since the overall aim of this paper is to describe an expert system used for the evaluation of the possible contribution of temporal medical reasoning from blood gas data, research specific to other application areas or data will not be covered here.

Cocaine-induced respiratory depression in urethane-anesthetized rats: A possible mechanism of cocaine-induced death

Urethane-anesthetized rats were used to study the mechanism of cocaine-induced death. Continuous recording of the changes in five physiological parameters, including respiratory rate (RR), electroencephalogram (EEG), blood pressure (BP), electrocardiogram (ECG), and body temperature (BT), were conducted after intraperitoneal (IP) administration of a single dose of cocaine HCl (70 mg/kg). In the control group (normothermic with core body temperature 37.7±0.1°C spontaneously breathing), the death rate was 88% (15/17), and the average time to respiratory arrest was 12.99±1.40 min (mean±SEM). The first set experiments investigated the contribution of hypothermia to cocaine-induced death. The hypothermic group (core body temperature 33.9±0.3°C and spontaneously breathing) had a death rate of 81.5% (22/27), and an average time to respiratory arrest of 16.70±1.24 min, which was significantly ( p<0.05) prolonged. A substantial decrease in respiratory rate was seen in normothermic group, while all the other measured parameters remained relatively stable until respiratory arrest. Sequential arterial blood gas data in this group showed a decrease in PaO 2 from 116.0±5.7 mmHg to 57.7±4.6 mmHg, and increase in PaCO 2 from 27.7±2.2 mmHg to 42.7±3.0 mmHg, and a decrease in pH from 7.467±0.039 to 7.357±0.003. To confirm that respiratory depression was an important mechanism of cocaine-induced death in this model, ten normothermic rats underwent mechanical ventilation, and all survived cocaine exposure. This study points to the important role of respiratory depression as a cause of cocaine-induced death.

A study on the effectiveness of pulmonary flushing for lung preservation

The effect of pulmonary flushing prior to lung preservation was studied using an ex vivo perfusing rabbit model. The grafts were divided into the following five groups : Group I ; surface cooling without flushing (n=6), Group II ; flushed in vivo with intracellular solution (A solution) (n = 6), Group III ; flushed ex vivo with A solution (n = 6), Group IV ;flushed in vivo with extracellular (B solution) (n=6), Group V : flushed ex vivo with B solution (n=6). After 18 hours' preservation at 8°C, the function of preserved grafts was examined for 60 minutes with a closed circuit system.In flushing with A solution, the pressure increased after 2 minutes (p <0.01) and the perfusion volume decreased after 4 minutes (p<0.01), while the flow of the B solution groups was constant throughout. The cooling effect, shown by the effluent temperature, and the flushing effect, measured in the in vivo group compared with the ex vivo groups (p<0.050.01). The flushing of Group V was most effective from the three points of view of perfusion, cooling and washing out.In the functional assessment of preserved grafts, Groups, II, III and IV dropped out due to permeability injury within 20 minute. Group V had better graft function in blood gas data, perfusion pressure, tidal volume, the perfusate decrement, and wet-dry ration (p < 0.050.01), compared with Group I.We conclude that the ex vivo flushing with extracellular solution in the best lung preservation method, and is more useful than surface cooling only.

Improvement in Pulmonary Function in Mitral Stenosis after Percutaneous Transvenous Mitral Commissurotomy

Before and after percutaneous transvenous mitral commissurotomy (PTMC), pulmonary function studies were performed in 25 patients with mitral stenosis, in order to determine the effects of pulmonary hemodynamics on pulmonary function in patients with mitral stenosis. After PTMC, dramatic improvements in pulmonary hemodynamics were seen in all patients. With regard to pulmonary function data, the VC as percent predicted value increased from 87.6 +/- 16.1 percent to 94.7 +/- 14.4 percent (p less than 0.001). Although the ratio of FEV1/FVC was unchanged, the MVV as percent predicted value increased, and the ratio of RV/TLC, CV, and the difference in nitrogen concentration between 750 ml and 1,250 ml of expired volume decreased significantly. According to the maximum expiratory flow-volume curves, V ax 50% and Vmax 25% improved. Despite marked improvements in pulmonary ventilatory function soon after PTMC, the percent predicted diffusing capacity of the lung for carbon monoxide decreased significantly after PTMC. Arterial blood gas data, such as the partial pressure of oxygen and carbon dioxide in arterial blood and the alveolar-arterial differences in partial pressure of oxygen, did not improve within one or two weeks after PTMC. We conclude that in mitral stenosis, the majority of ventilatory function impairments are caused by hemodynamic alterations that are mainly reversible.

Decision support alerts for clinical laboratory and blood gas data

We have designed and implemented a computerized Intensive Care Unit (ICU) decision support alerting system which analyzes all incoming laboratory and blood gas data for critically abnormal values and trends. A computerized patient data management system (HP 78709A PDMS, Hewlett-Packard Co., Waltham, MA) serving 20 Surgical ICU beds is networked to a Clinical Laboratory Information System and a blood gas computer system. The ALERTS subsystem operates on the PDMS as an automatic program triggered by the receipt of fresh laboratory data. Three types of ALERTS are detected: (1) high and low critical values, (2) calculation-adjusted critical values, and (3) critical trends. Once detected, a specific ALERT message is displayed at the bottom of the patient's bedside PDMS terminal and at the central station. Over an eight month period a total of 1,515 ALERTS were detected from amongst approximately 115,000 laboratory data results transmitted to the Surgical Intensive Care Unit (SICU). Slightly over half of all ALERTS were caused by critical blood gas values. ALERTS were found to be a sensitive indicator of severity of illness: patients with one or more ALERTS suffered an ICU mortality of 9.52%, compared to 0% mortality in patients with no ALERTS. We conclude that automated laboratory data ALERTS represent a valuable decision support tool for the management of high risk ICU patients.

THE USE OF A PROSTACYCLIN ANALOG, ILOPROST, AS AN ADJUNCT TO PULMONARY PRESERVATION WITH EURO-COLLINS SOLUTION

The addition of prostaglandin to the single-flush technique of lung preservation is considered to enhance subsequent graft function. We have evaluated the use of the prostacyclin analog, Iloprost, in an animal model of unilateral lung transplantation. Group 1 (n = 5) received Iloprost as a pretreatment intravenously (20 ng/kg/min) and as an additive (20 ng/L) to 20 ml/kg of modified Euro-Collins solution. Group 2 (n = 5) received no Iloprost, either as pretreatment or added to the perfusate. Perfusate distribution within the lungs during flush perfusion was assessed using 99mTc-labelled microaggregates of albumin. After the initial preservation technique the lungs in both groups were stored for 6 hr in Euro-Collins solution at 4 degrees C. Thereafter, left lung transplantation was followed by ligation of the contralateral pulmonary artery and bronchus, rendering the animal completely dependent on the transplanted, stored lung. Preservation was assessed by animal survival, measurement of hemodynamic and blood gas data for 24 hr at a fixed FiO2 (0.4) and tidal volume (10 ml/kg), and at sacrifice by measurement of transplanted lung water. By these criteria, both group 1 and 2 lungs were well preserved. The addition of Iloprost to group 1 animals appeared to confer no measureable benefit in terms of lung cooling, perfusate distribution, postoperative graft function, or total lung water.

The oxygen status algorithm: A computer program for calculating and displaying pH and blood gas data

Input parameters for the program are the arterial pH, pCO2, and pO2 (measured by a blood gas analyzer), oxygen saturation, carboxy-, met-, and total hemoglobin (measured by a multi-wavelength spectrometer), supplemented by patient age, sex, temperature, inspired oxygen fraction, fraction of fetal hemoglobin, and ambient pressure. Output parameters are the inspired and alveolar oxygen partial pressures, pH,pCO2 and pO2 referring to the actual patient temperature, estimated shunt fraction, half-saturation tension, estimated 2,3-diphosphoglycerate concentration, oxygen content and oxygen capacity, extracellular base excess, and plasma bicarbonate concentration. Three parameters related to the blood oxygen availability are calculated: the oxygen extraction tension, concentration of extractable oxygen, and oxygen compensation factor. Calculations of the 'reverse' type may also be performed so that the effect of therapeutic measures on the oxygen status or the acid-base status can be predicted. The user may choose among several different units of measurement and two different conventions for symbols. The results are presented in a data display screen comprising all quantities together with age, sex, and temperature adjusted reference values. The program generates a 'laboratory diagnosis' of the oxygen status and the acid-base status and three graphs illustrating the oxygen status and the acid-base status of the patient: the oxygen graph, the acid-base chart and the blood gas map. A printed summary in one A4 page including a graphical display can be produced with an Epson or HP Laser compatible printer. The program is primarily intended for routine laboratories with a blood gas analyzer combined with a multi-wavelength spectrometer. Calculating the derived quantities may enhance the usefulness of the analyzers and improve patient care. The program may also be used as a teaching aid in acid-base and respiratory physiology. The program requires an IBM PC, XT, AT or similar compatible computer running under DOS version 2.11 or later. A VGA color monitor is preferred, but the program also supports EGA, CGA, and Hercules monitors. The program will be freely available at the cost of a discette and mailing expenses by courtesy of Radiometer Medical A/S, Emdrupvej 72, DK-2400 Copenhagen NV, Denmark (valid through 1991). A simplified algorithm for a programmable pocket calculator avoiding iterative calculations is given as an Appendix.

Prediction of arterial oxygen partial pressure from intrapulmonary venous admixture.

A short program was developed to predict the PaO2 at a given FIO2 by using arterial and mixed venous blood gas data obtained at an FIO2 of 1.0. Our program resolves Adair's equation and the shunt equation inversely, on the assumption that intrapulmonary venous admixture and the arteriovenous oxygen content difference remain constant during the study. The study was conducted on 19 patients with respiratory failure who were intubated and mechanically ventilated. According to linear regression analysis, regression coefficients of 0.91 and 0.97 were obtained between the measured PaO2 values and those estimated by the arterial/alveolar oxygen tension ratio (PaO2/PaO2) and our program, respectively (n = 23). The PaO2 values were predicted more accurately by our program than those calculated by PaO2/PaO2. Because our program is simple enough to be carried out with a pocket computer, it may be helpful in a bedside decision of lowering FIO2, especially in patients who require a high FIO2 level to maintain sufficient arterial oxygenation.

Decreased O2 consumption and cardiac output during normobaric hyperoxia in conscious dogs.

Recent reports indicate that under certain restricted conditions hyperoxia may decrease tissue O2 consumption. However, this effect has not been established for whole body O2 consumption in the intact healthy conscious state. The goal of the present study was to document the effect of hyperoxia on resting whole body O2 consumption and hemodynamics under these latter more general physiological conditions. The inspired gas was delivered by mask to six fasted resting conscious dogs and alternated hourly between air and O2-enriched air (hyperoxia) for 5 h, while hemodynamics and blood gas data were obtained every 20 min. Compared with air breathing, hyperoxia increased the mean arterial O2 tension from 95 to 475 Torr and decreased heart rate, cardiac output, pulmonary vascular resistance, and right and left ventricular work rates and thus, presumably, myocardial O2 consumption. Hyperoxia also increased systemic vascular resistance and right atrial pressure but did not change stroke volume or systemic arterial pressure. The increase in arterial O2 content during hyperoxia was counterbalanced by the decrease in cardiac output, so that O2 delivery was unchanged by hyperoxia. Surprisingly, hyperoxia decreased the arterial-to-mixed venous difference in O2 content; this decrease together with the decrease in cardiac output produced a decrease in resting whole body O2 consumption from 5.88 +/- 0.68 to 4.80 +/- 0.62 ml O2.min-1.kg-1 (P = 0.0002). It is concluded that under physiological conditions normobaric hyperoxia may decrease metabolic rate in addition to cardiac output, which may have important implications for the metabolic regulation of O2 utilization as well as for the medical and nonmedical uses of O2.

Heparin Free Long-term Extracorporeal Circulation Using Bioactive Surfaces

As already shown, a single bolus injection of heparin is sufficient to perform extracorporeal circulation (ECC) for long-term lung support if bioactive surfaces (HBS) are used. In the present study whether complete avoidance of systemic heparinization using HBS is possible was studied. Seven conscious sheep (50-60 kg) underwent venovenous bypass under standardized conditions using a Maxima capillary membrane oxygenator. Drug administration, surgery, and other conditions, such as priming volume and blood flow rates, were identical in all experiments. All blood contacting surfaces (oxygenator, catheters, etc.) were HBS. The ECC periods were set for 24 hr (n = 3) and 5 days (n = 4). At no time was heparin administered. No complications occurred in any experiment. Partial thromboplastin time, activated clotting time, and other coagulation parameters remained within physiologic ranges. Platelets did not drop below 80% of baseline values, and hemolysis rates were negligible. Blood gas data and other vital parameters were normal during the entire ECC period. Results show that HBS can be applied to long-term ECC, without the necessity for heparin administration.

Pressure Indices of Myocardial Oxygen Consumption During Pulsatile Ventricular Assistance

Left ventricular (LVP) and intramyocardial (IMP) pressure indices were compared with left ventricular myocardial oxygen consumption (MVO2) during pulsatile ventricular assistance to determine if MVO2 can be predicted under conditions of ventricular support. During five acute anesthetized calf experiments, IMP and LVP were recorded for control and six conditions of support. The assisted conditions were asynchronous and synchronous, 1:1 or 1:2; each control mode with atrial uptake only or combined atrial and ventricular uptake. IMP was measured by implantation of a miniature pressure transducer in the midanteriolateral wall of the left ventricle. MVO2 was determined using the radioactive microsphere blood flow technique and blood gas data. Mean values of peak systolic pressure, maximum dP/dt, and integral of Pdt were calculated for IMP and LVP for each condition. Pressure indicators of left ventricular function were found to correlate well with MVO2 during conditions of pulsatile support.

Flow velocity waveforms in the fetal internal carotid artery relative to fetal blood gas and acid-base measurements in normal pregnancy

Flow velocity waveforms in the fetal internal carotid artery during fetal behavioural state 2F were compared with blood gas and acid-base data from fetal scalp blood samples immediately following artificial rupture of the membranes in 17 normal term pregnancies. The pulsatility index in the fetal internal carotid artery was positively related to PO 2 and base excess suggesting that also under physiological conditions fetal cerebral vascular resistance may respond to changes in fetal oxygenation.

Mechanical ventilation for status asthmaticus in children

We retrospectively reviewed the time course of recovery of pediatric patients in status asthmaticus who were undergoing mechanical ventilation for life-threatening respiratory failure to evaluate the results with current medications and technology. Ten patients between 2 and 18 years of age underwent intubation on 20 occasions. Mechanical ventilation was maintained for a mean of 2 days. Positive end-expiratory pressure was introduced in the recovery phase to prevent hypoxemia. Twelve episodes (Group 1) involved intubation less than 48 hours; in eight episodes (group 2) the patients required ventilatory support greater than 48 hours. The two groups did not differ in regard to age, pharmacologic therapy, preintubation arterial blood gas data, or initial ventilator settings, but the rise in pH and fall in Paco2 differed significantly over the first 12 hours of therapy. In the group 2 patients, peak pressures were not increased greater than 60 cm H2O despite elevated Paco2 values, and aggressive sodium bicarbonate therapy for pH correction was not pursued. Complications were few and all patients survived. We conclude that asthma patients have variable resolution of airway obstruction during mechanical ventilation and that controlled hypoventilation can be a safe therapy for the patients with more severe obstruction.

A slide–rule for assessment of venous admixture

Determination of venous admixture (physiological shunt, Qva/Qt) requires analysis of both arterial and mixed venous blood. When a pulmonary arterial catheter is not in use, the pulmonary oxygenating capacity may be assessed from arterial blood gas data, the fraction of inspired oxygen (FIO2) and an assumed value of the arterial-mixed venous oxygen content difference. To facilitate this process, a slide-rule based on the "virtual shunt" concept is presented. It permits rapid assessment of Qva/Qt from known values of arterial oxygen tension (PaO2) or saturation (SaO2) and FIO2 and may promote the choice of appropriate FIO2. The limitations of the slide-rule were studied theoretically and its validity was tested by comparing 100 determinations of virtual shunt with the corresponding Qva/Qt values. The slide-rule was found to estimate Qva/Qt more accurately than commonly used oxygenation indices such as the PaO2/FIO2 ratio.

Skin flap circulation. Simultaneous monitoring with laser Doppler and electromagnetic flowmeters in the pig island buttock flap.

Twenty-two island skin flaps based on the deep circumflex iliac vessels were elevated in pigs. A comparative study of Laser Doppler flowmetry (LDF) and electromagnetic flowmetry (EMF) was undertaken. Flow values were compared during selective arterial and venous occlusion, nerve stimulation and intra-arterial noradrenaline or papaverine injection. The effectiveness of flap temperatures and blood gas data in monitoring vascular occlusions was also investigated. Similar and simultaneous responses in LDF and EMF values were noted during the different experimental manipulations, but for single simultaneous LDF/EMF observations from different animals the correlation coefficients were poor. The accuracy of EMF measurements in monitoring total flap inflow was confirmed by a high correlation with total venous outflow values. Major vascular occlusions also resulted in significant changes in the flap temperatures, and in the flap blood gases.

Assessment of the efficiency of pulmonary oxygenation. The choice of oxygenation index.

Oxygen-derived indices are often used as alternatives to determination of venous admixture (Qva/Qt) when a pulmonary arterial catheter is not in use, but the question of which more accurately indicates the efficiency of oxygenation is controversial. The theoretical relationships between six measures of oxygenation (PaO2, SaO2, P(A-a)O2, PaO2/FIO2, P(A-a)O2/PaO2, PaO2/PAO2) and venous admixture were analyzed with special reference to the influence of the concentration of inspired oxygen (FIO2). In addition, the predictability of Qva/Qt was evaluated on the basis of 100 authentic sets of arterial and mixed venous blood gas data. Of the above six indices, PaO2/FIO2 was most accurate (r = 0.88), but was far from independent of the FIO2 used. However, a direct Estimate of Venous Admixture (EVA) - based on arterial blood analysis and with C(a-v)O2 assigned a value of 50 ml.l-1 - predicted Qva/Qt still better (r = 0.95). It is concluded that when mixed venous blood gas data are lacking, EVA is the preferable measure of oxygenation.

The PDMS as a focal point for distributed patient data.

Distributed data links are essential requirements for a successful patient data management system (PDMS). These links funnel clinically needed data into bedside ICU workstations. We have constructed four data links which acquire most of the objective data required for direct patient care. Data from bedside monitors is acquired via a standard HP Signal Distribution Network. Urine volumes and core bladder temperatures are acquired over a link to 20 electronic urimeters. Clinical laboratory data is obtained over an HP General Purpose Data Link (GPDL) to a VAX 11/785 laboratory system. Blood gas data is obtained over a second GPDL link to a DEC 11/23 computer. The ICU staff is notified of incoming lab results with bedside video messages. Combined with automated calculations, these data links eliminate thousands of data entry keystrokes daily and allow the PDMS to serve as the focal point for real-time patient care.

Thrombolytic treatment of pulmonary embolism with APSAC

BRL 26921 (Eminase registered trade mark in Belgium, Germany and The Netherlands) is the p-anisoyl derivative of the primary (human) lys plasminogen-streptokinase activator complex (APSAC). The acyl-enzyme has the theoretical advantage of causing fibrinolysis in situ in the presence of fibrin clotbound plasminogen. It was administered to 34 patients with severe pulmonary embolism (PE) in an open multicentre study. PE was suspected on clinical, blood gas, ECG, and radiographic data. Pulmonary angiograms performed pre- and post-treatment confirmed the diagnosis and were assessed using the Miller Index (MI). Fibrinogen, plasminogen, alpha-2-antiplasmin, fibrinogen degradation products (FDP), activated partial thromboplastin time (APTT), partial thromboplastin time (PTT) were closely monitored before and after each administration of APSAC. Median angiographic improvement was 50% (range 0-94%). The following adverse events were reported: bleeding at puncture sites (n = 12), haematuria (n = 1), epistaxis (n = 3), fever (n = 2). A blood transfusion was given in one patient with an inguinal haematoma. Systemic fibrinogenolysis occurred in 20/28 patients.

Cricothyroid membrane puncture

A method for pediatric airway support was evaluated for the situation when mask ventilation or intubation is impossible. Mongrel dogs were sedated, intubated, and allowed to breathe room air for 30 min. Baseline variables were recorded, and the airway obstructed. After 2 to 3 min of hypoxia, arterial blood gas and hemodynamic data were again recorded. A percutaneous cricothyroid membrane puncture (PCMP) was then performed with a 12-ga iv catheter. Studies were carried out both in the presence and absence of spontaneous ventilatory efforts. With spontaneous ventilation, continuous low flow (1.0 L/min) oxygen insufflation provided oxygenation for 30 min and reversed increases in mean arterial pressure, pulmonary artery pressure (PAP), and systemic and pulmonary vascular resistance that had been produced by the obstruction. Respiratory acidosis occurred but was well tolerated. With paralyzed animals, whose ventilation was supported by a self-inflating bag with 10.0 L/min of oxygen, all hemodynamic variables except PAP returned to normal, oxygenation was excellent, and PaCO2 values were maintained at steady, but elevated levels. Complications included bilateral tension pneumothorax in one animal. This experimental study supports anecdotal experiences where PCMP has been used and has proven lifesaving when standard resuscitative measures to establish a clear airway have failed.