Respiratory Gas Concentrations Research Articles

Aerial ventilatory responses of the mudskipper, Periophthalmodon schlosseri, to altered aerial and aquatic respiratory gas concentrations

Periophthalmodon schlosseri is a mudskipper which uses the vascularized buccopharyngeal cavity as a respiratory organ. The fish construct mud burrows that contain hypoxic water, but store air inside the burrows. Because the burrow gas is frequently hypoxic and hypercapnic, the effects of altered respiratory gas concentrations on the aerial ventilation frequency (VF), inspiratory tidal volume (VT) and minute volume (VM=VF×VT) of P. schlosseri were studied by pneumotachography. Both total buccopharyngeal gas volume (VBP) and VT scaled significantly with body mass (mass exponents=1.10 and 1.03, respectively), and VT/VBP was 0.54±0.05 (S.E.M., n=6). VBP, expressed as a percentage of body volume, was much higher (16%) than in other air-breathing gobies (2–4%). When fish respired in normoxic air and water, VF was 0.25±0.04 breaths min−1, VT 7.6±0.6 ml 100 g−1, and VM 1.80±0.18 ml 100 g−1 min−1. Aquatic hypoxia did not significantly affect VF, VT, or VM. In both moderate (PO2=10 kPa) and severe (PO2=5 kPa) aerial hypoxia, VF and VM increased significantly. VT increased significantly only during severe aerial hypoxia. In aerial hypercapnia, VF and VM increased significantly.

Respiration Rate of a Dry Coleslaw Mix Affected by Storage Temperature and Respiratory Gas Concentrations

ABSTRACTThe respiration rate of dry coleslaw mix at different concentrations of O2 and CO2 was determined in an open flow‐through respirometer at 5°C. Product O2 consumption rate fitted an enzyme kinetics model. Vm and Km values of 22.72 mlkg‐1h‐1 and 1.083 %O2, respectively were calculated. CO2 had an inhibitory effect on respiration rate. The effect of CO2 on respiration gave a good fit with an uncompetitive inhibition enzyme kinetics model (E = 5.11%). Product respiration rate increased with temperature by an Arrhenius type relationship. Activation energies for O2 consumption and CO2 evolution were 74.8 kJ/kg and 84.2 kJ/kg respectively. These results provide information essential for the design and optimization of modified atmosphere packs for this product.

Measuring pulmonary CO2 elimination--studies with the lung model using various mixed gases

One way of determining pulmonary CO2 elimination during anaesthesia is the breath-by-breath method. With this technique, CO2 analysis is carried out using either the mainstream method (MSM), that is, directly in the expired air flow, or in samples of expired air. A disadvantage of MSM is the lack of sensor signal correction for changes in the composition of the gas mixture and barometric pressure. Sidestream systems (SSM) measure respiratory gas flow and gas concentration with adequate accuracy, and also correct the measured values for gas composition and ambient parameters. Disadvantages of breath-by-breath analysis are the SSM-system-related delay and distortion of the CO2 curves. In the present study, a computer-assisted comparative analysis of CO2 elimination measurement by the sidestream and mainstream methods was carried out using different mixtures of gases in a lung model. Under the selected conditions simulated in the lung model, evaluation of CO2 elimination using SSM and MSM is possible with an error of between 0 and 10% versus reference systems. Measuring accuracy of the MSM system in particular is found to depend directly on the composition of the gas mixture. Using the method described here, the measuring error of an SSM system in terms of delay and response time can be compensated with adequate accuracy.

Invasive pressure monitoring of patients during magnetic resonance imaging.

The purpose of this paper is to describe a system for monitoring patients who require general anaesthesia, profound sedation or intensive care while undergoing high field (> or = 1.5 T) magnetic resonance (MR) imaging. Continuous evaluation of invasive and noninvasive pressures, inspired and end-tidal respiratory gas concentrations, body temperature, heart rate, ECG and pulse oximetry were measured successfully during the MR examination. Diagnostic quality MR images were acquired on all 15 monitored patients. The calculated signal-to-noise ratios were not different between the control and monitored patients. Commonly encountered technical problems and their solutions are described. This study demonstrates that invasive monitoring can be safely performed in critically ill patients who are undergoing high field MR examinations.

The Effects of Altered Aquatic and Aerial Respiratory Gas Concentrations on Air-Breathing Patterns in a Primitive Fish (Amia Calva)

ABSTRACT The mechanisms and physiological control of air-breathing were investigated in an extant halecomorph fish, the bowfin (Amia calva). Air flow during aerial ventilation was recorded by pneumotachography in undisturbed Amia calva at 20–24°C while aquatic and aerial gas concentrations were independently varied. Separation of aquatic and aerial gases was used in an attempt to determine whether Amia calva monitor and respond to changes in the external medium per se or to changes in dissolved gases within the body. Air flow measurements revealed two different types of ventilatory patterns: type I air-breaths were characterized by exhalation followed by inhalation; type II air-breaths, which have not been described previously in Amia calva, consisted of single inhalations with no expiratory phase. Expired volume (Vexp) for type I breaths ranged from 11.6±1.1 to 26.7±2.9mlkg−1 (95% confidence interval; N=6) under normoxic conditions and was unaffected by changes in aquatic or aerial gases. Gas bladder volume (VB), determined in vitro, was 80mlkg−1; the percentage of gas exchanged for type I breaths ranged from 14 to 33% of VB in normoxia. Fish exposed to aquatic and aerial normoxia , or aerial hypercapnia in normoxic water, used both breath types with equal frequency. Aquatic or aerial hypoxia significantly increased air-breathing frequency in four of eight fish and the ventilatory pattern changed to predominantly type I air-breaths (75–92% of total breaths). When fish were exposed to 100% O2 in the aerial phase while aquatic normoxia or hypoxia was maintained, air-breathing frequency either increased or did not change. Compared with normoxic controls, however, type II breaths were used almost exclusively (more than 98% of total breaths). Type I breaths appear to be under feedback control from O2-sensitive chemoreceptors since they were stimulated by aquatic or aerial hypoxia and were nearly abolished by aerial hyperoxia. These results also indicate that Amia calva respond to changes in intravascular ; however, externally facing chemoreceptors that stimulate air-breathing in aquatic hypoxia cannot be discounted. Type II air-breaths, which occurred in aerial hyperoxia, despite aquatic hypoxia, appear to be stimulated by reductions of VB, suggesting that type II breaths are controlled by volume-sensitive gas bladder stretch receptors. Type II breaths are likely to have a buoyancy-regulating function.

Seasonal Variation in the Microclimate and Gas Composition of Beaver Lodges in a Boreal Environment

Seasonal changes in the microenvironment of Castor canadensis in the Canadian Shield of southeastern Manitoba, Canada, are described. The construction and occupation of lodges by family groups of beavers provided these animals with year-round access to a thermoneutral microclimate. Between June 1988 and March 1989, air temperatures at sampling sites ranged from −41.4 to 32.4°C, while temperatures recorded from within the chambers of occupied lodges varied from 0 to 35.6°C. Mean monthly chamber temperature consistently exceeded mean monthly air and water temperature. Despite the large metabolic mass of resident animals, lodge occupancy resulted in only limited disturbance to the respiratory gas concentrations inside lodges. The CO2 levels of occupied lodges ranged from 0.03 to 1.8%, with no evidence of seasonal variation in either CO2 accumulation or O2depletion in these shelters. Before freeze-up, the gaseous composition and mean internal temperature of occupied and unoccupied lodges were similar. Following freeze-up, mean CO2 accumulation, O2 depletion, and chamber temperature were all significantly higher in occupied houses. During the open-water season, water temperature accounted for 90% of the variation in chamber temperature of occupied lodges. Following freeze-up, none of the meteorological or physical variables measured were significant predictors of chamber temperature.

Respiratory gas monitoring in patients with chronic respiratory failure during intensive positive pressure ventilation vs aerosol therapy

The aim of this study is to evaluate the variations of respiratory gas concentration with transcutaneous blood gas measurements (tcm PO2; tcm PCO2) during intermittent positive pressure ventilation (I.P.P.V.) and aerosol therapy in patients (5 female, 5 male; 43–75 years) with chronic obstructive pulmonary diseases (COPD) with haemo gas analysis values PO2<76 mmHg. The subjects underwent transcutaneous blood gas monitoring, 16 minutes during therapy (I.P.P.V. or aerosol) and 14 minutes of recovery. ANOVA analysis of variance was used for statistical analysis. During I.P.P.V. tcm PO2 increase from the base value (60.6±9 mmHg) already after 2 minutes until the 16th minute (69.7±9); 2 minutes after the end of I.P.P.V. tcm PO2 falls below the basic one (57.6±7) and then exceeds the basic value until the 14th minute (63.5±10) (p=ns). The base tcm PCO2 (41.2±7) decreases reaching the maximum decrement at the 16th minute of therapy (32±6.6); at the end of I.P.P.V. it increases without exceeding the base value (39.5±7) (p<0.01). During aerosol therapy, tcm PO2 increases from the basic one (62.4±10) (maximum after 16 minutes 70±9.5), then it decreases (64±11) and increases againg reaching the maximum growth after 14 minutes of recovery (65.7±11) (p=ns). The tcm PCO2 values show a decrement below the base value (42.7±4.5) reaching its maximum at the 16th minute of therapy (38.8±7); at the end of aerosol the tem PCO2 increases (42.5±4.6) (p=ns). The tcm PO2 variations (I.P.P.V. vs aerosol) did not show any significant statistical difference. At the end of the therapies the tcm PO2 falls a little more after I.P.P.V. than after aerosol (57.6±7.3 vs 64±11, p=ns); the tcm PCO2 base values are similar during the two therapies (41.2±7 vs 42.7±4.5, p=ns), but the tcm PCO2 decrements reach a significant statistical difference after 8–10–12–16 minutes (p<0.05); during the recovery time after 2 minutes (34±6.5 vs 40±6.3, p<0.05) and this difference disappeared at the last recording. We calculate the tcm PO2 increment and the tcm PCO2 decrement from the base value. The tcm PO2 increment is higher during I.P.P.V. than during aerosol therapy. The tcm PCO2 decrement shows how the tcm PCO2 falls during I.P.P.V. and how these values remain below the base one until the end of the rest time. Data reported here demonstrate that mechanical physiokinesi therapy improves COPD ventilation so that the respiratory pattern could be ameliorated and preserved.

高圧ヘリオックス環境下の呼吸気の連続分析

An N2 washout measurement was applied in the hyperbaric heliox environment to estimate lung ventilation distribution. In this procedure, N2 lung content was flushed by the inhalation of an N2 free gas. The purpose of the measurement was to investigate change in ventilation distribution in a hyperbaric environment which was created by the use of a deep diving simulator. Physiological parameters measured were respiratory gas concentrations (FN2, FAr, FCO2, FO2, FHe and FH2O), respiratory flow rate and temperature.The respiratory gas concentrations, flow, and temperature were simultaneously measured in a breath-by-breath fashion in the full pattern and digitally recorded with high accuracy and response. Concentration and flow of each breath were examined on a CRT and corrected as required prior to recording on a data base system. The corrections were made to compensate for gas leakage to and from the gas circuit, the electronic drift and noise.In this experiment, a mass spectrometer to analyze respiratory gas concentrations and an amplifier to enhance readings, were placed outside the hyperbaric chamber for reading of a Fleish pheumotachometer and thermistor sensors.In order to be analyzed, it was necessary to introduce the respiratory gas sample through the large pressure difference. Concentrations of physiological gases were decreased with the increased ambient pressure of He balance.Other technical points to be resolved were mass spectrometer and flow meter calibrations under hyperbaric conditions. The computer-assisted measurement was also used to conduct the complex procedure. The technical problems which were encountered are discussed in this study.The experimental results obtained at 12, 18 and 31 ATA (equivalent to depths of 110, 170 and 300m) are shown in comparison with results in the atmospheric environment.

Respiratory gas concentrations and temperatures within nest cavities of the northern flicker (Colaptes auratus)

We measured respiratory gas concentrations and air temperatures within nest cavities occupied by the northern flicker. (Colaptes auratus). The means of all measurements of carbon dioxide and oxygen concentrations were 0.37 and 20.42%, respectively. The maximal carbon dioxide level recorded was 2.56%, while the minimal oxygen level was 18.04%. There was a diel cycle in the levels of respiratory gases in nest cavities, with peak carbon dioxide and minimal oxygen levels occurring between 22:00 and 24:00. However, the gaseous conditions within nest cavities remained essentially unchanged throughout the nestling period. Cavity air temperature averaged 21.2 °C, ranging from 10.2 to 33.8 °C, and nearly always exceeded the outside air temperature. The mean difference between inside and outside air temperatures was 7.1 °C and is comparable with those reported in other studies of cavity microenvironments. The elevated cavity temperatures may reduce energy requirements of developing young and also may induce a convective transfer of air between the cavity and free atmosphere that would moderate gaseous conditions within the cavity.

Continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases is difficult and potentially unsafe.

One essayist suggests that continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases has little or no positive effect on patient outcome and may even be detrimental to patients. Such monitoring, he says, tends to remove anesthesiologists from personal contact with their patients. He recommends careful monitoring of fresh gas concentrations leaving the anesthetic machine, careful monitoring of inspired gas in a circle absorption breathing system, and improved training of anesthesiologists to prevent human error. Another essayist suggests that continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases is cost-effective and relatively simple. He says that such monitoring, without being a source of legal problems for its users, improves the quality of patient care.

Continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases is safe, simple, and cost-effective.

Continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases is safe, simple, and cost-effective.

Respiratory gas concentrations in the microhabitats of some florida arthropods

1. 1. The concentrations (dry gas %) of oxygen and carbon dioxide were measured in a variety of microhabitats of arthropods in Florida: at the ends of the burrows of three spider species ( Sphodros abboti, Geolycosa micanopy, Cyclocosmia torreya) and a tiger beetle ( Megacephala carolina) larva, within ant ( Solenopsis invicta) mounds, within stumps inhabited by termites ( Reticulitermes flavipes), and within and under decaying hardwood logs. 2. 2. Hypoxia and hypercarbia occurred in all microhabitats, with the ratio of oxygen decrement to carbon dioxide increment close to one. Changes for both gases were minor in the spider burrows, under decaying logs, and within ant mounds (<2.3% for O 2 and 1.1% for CO 2) and are probably physiologically unimportant to their inhabitants. 3. 3. In contrast, %O 2 fell to as low as 12–14%, and CO 2 rose to as high as 6–8%, in the burrows of tiger beetle larvae, within decaying logs, and inside decaying stumps inhabited by termites. 4. 4. Such changes, particularly for CO 2 may present a challenge to organisms living in these microenvironments. 5. 5. Approximately 20–25% of the changes in the concentrations of respiratory gases in the burrows of tiger beetle larvae are attributable to the metabolism of the larva, the remainder being due to diffusional exchanges with the soil.

Continuous pulmonary capillary blood flow estimation from measurements of respiratory anesthetic gas concentration.

A noninvasive, on-line estimation scheme has been developed for continuous determination of pulmonary capillary blood flow (PCBF) and related cardiopulmonary parameters from measurements of anesthetic gas concentration based on a gas uptake and distribution model of the body and the lungs. Two moving window algorithms, one based on the well-known off-line maximum likelihood algorithm, and the other based on a frequency response technique, have been investigated for this purpose. Special consideration was given to the sensitivity to various error sources that affect each estimation algorithm. Both computer simulations and in vivo experiments demonstrate that the proposed estimation procedures can be used for on-line PCBF determination provided that the nonestimated system parameters can be measured with sufficient accuracy.

A new method for multi-dimensional analysis of circulation and metabolism. Application of respiratory mass spectrometer and computer system.

An improved mass spectrometer-computer system has been developed for a simultaneous measurement of multi-variables and multi-dimensional analysis of the respiration, circulation and metabolism functions.The system is composed of a respiratory mass spectrometer, a pneumotachometer, a heart rate meter, a microcomputer system which is combined with a specially designed analogue processor. A bicycle ergometer and a treadmill are used for exercise test. Measurable factors are instantaneous change of respiratory gas concentrations, breathing flow, heart rate, ventilation rate VE, oxygen uptake rate VO2, carbon dioxide output rate VCO2, cardiac output Qe, all kinds of lung volumes and thier derivatives. VE, VO2, VCO2 are calculated in breath by breath with an improved precision by means of real time processing of gas concentrations and breathing flow. Qc and its derivatives can be intermittently measured by means of C2H2 rebreathing method. With employing the present system, almost all kinds of respiration factors can be simultaneously measured together with circulation and metabolism factors, and especially the analysis of transient response to the applied exercise became accessible. Thus the more advanced measurement was attained for the study of respiration physiology and for the clinical applications.

OPTIMIZATION OF PARAMETERS FOR PACKAGING OF FRESH PEACHES IN POLYMERTIC FILMS1

ABSTRACTFresh produce packaged in polymeric films represents a dynamic respiration‐permeation model. Control of equilibrium concentrations of respiratory gases is an important variable in extending the shelf life if critical vectors of quality deterioration and transport properties of packaging materials are known.Fresh peaches were stored at 5 × 1° C under various modified atmospheres for a period of up to thirty days. Samples were removed at ten day intervals for chemical and physical analyses of vulnerable quality factors. Parameters evaluated include soluble solids, titratable acidity, and texture and profile parameters such as hardness, elasticity, and cohesiveness.An internal atmosphere of 10 to 15% O2 and 15 to 25% CO2 inside the package provided better retention of quality attributes such as hardness and cohesiveness than any other treatments. Springiness did not provide any significant index of quality. Soluble solids decreased over time as did the amount of acid present in the fruit. Anaerobic fermentation did not occur under any storage conditions.Subsequent to establishing the optimal gaseous concentrations, respiration rates were determined as a function of time and gas composition. Permeability of polymeric films were determined using ASTM method. Analytical equations were employed to optimize packaging parameters or to estimate transient and equilibrium gas concentrations in polymeric packages. Equations were set up to estimate transient and steady state time values for oxygen and carbon dioxide concentrations inside a package. This approach is applicable in extending the storage quality of other fresh produce.

Influence of lipid infusion (0.4 g/kg/hr) and positive end expiratory pressure (8 cm H2O) on pulmonary function and hemodynamics in healthy anesthetized pigs.

Fat emulsions are used increasingly for parenteral nutrition in premature infants suffering from various disorders, including respiratory insufficiency necessitating artificial ventilation with positive end expiratory pressure (PEEP). Both PEEP and lipid infusions (LI) may alter pulmonary hemodynamics. The simultaneous effect of LI and PEEP were therefore investigated. Five adult anesthetized Göttinger minipigs were infused with a 20% LI at a high rate of 0.4 g/kg/hr for 30 min, followed by PEEP of 8 cm H2O for 15 min. Catheters were inserted into the upper vena cava, the pulmonary artery, the right and left atrium, and the aorta, and pressures recorded continuously. Ventilation volume, respiratory fractional gas concentrations of O2 and CO2 (mass spectrometer), and blood gases were measured. The following parameters were calculated: total peripheral resistance, pulmonary arteriolar resistance, right-to-left shunt (QS/QT) dead space ventilation (VD/VT) and effective compliance. Total peripheral resistance remained unchanged. Pulmonary arteriolar resistance increased significantly during PEEP, PEEP + LI, but not during LI alone. QS/QT increased significantly during LI and returned to normal when PEEP was applied. VD/VT and effective compliance did not change during LI. The increased right to left shunt, caused by LI, is reduced by means of PEEP, while the pulmonary arteriolar resistance increased with PEEP and LI.

Active branchial and ram gill ventilation in fishes.

1. Characteristics of cyclic breathing movements have been examined in a number of fish species at rest and during swimming acceleration to velocities above those sufficient to induce transfers from active to passive gill ventilation (ram gill ventilation). They were trained to swim in one of several types of swimming tunnels after electrode implants to permit recording of ECG's and ventilatory muscle EMG's.2. Transfer to the ram mode of gill breathing is marked by a drop-out of individual cyclic breathing movements as swimming increases from rest. When the swimming speed reaches about 65 cm· sec-1, most fish that use ram gill ventilation complete conversion to the ram mode (35 to 82 cm·sec-1, range of all fish tested). This is equivalent to an across-gill differential pressure of 2.1 cm H2O as measured with a combined impact-reverse pitot tube as an approximate model. Generally, a fish must be swimming to ram gill ventilate, but some exceptions are noted such as the shark-riding remoras.3. Control of the transfer between gill ventilation modes appears basically to be a reflex shut-down of rhythmic breathing initiated by mechanoreceptive detection of water flow-velocity and the detection of swimming movements. Reflex transitions between active and passive breathing seem to happen too rapidly for a sufficient change of respiratory gas concentrations to occur and allow triggering of chemoreceptors.4. No unusual events are detectable in the ECG's of swimming fish as they reach and surpass speeds sufficient to maintain the ram mode. Cardioacceleration varies as between sluggish and active swimmers, but seems to be independent of the mode of gill ventilation used.5. Generally, demersal fishes that depend mainly upon the opercular phase for active gill ventilation, strongly aided by a well-developed branchiostegal system, do not ram ventilate. Conversely, nearly all species in which the work share of active ventilation is about equally buccal and opercular, probably use ram gill ventilation when they reach the requisite swimming speed. These are mostly midwater to pelagic in habits so for them, transfer of the muscular work of gill ventilation from the branchial to the swimming musculature seems to serve a dual function—a reduction in the cost of breathing, and an improvement in swimming efficiency.

The distribution and movements of carbon dioxide, carbonic acid and bicarbonate between blood and milk in the goat.

1. A-V differences and milk concentrations of respiratory gases, pH, HCO3 and H2CO3 have been measured in lactating goats and cows. 2. The pH and [HCO3 minus] of milk were significantly lower than those of plasma while milk PCO2 was virtually identical to that of mammary venous blood. [H2CO3+ dissolved CO2] was similar in milk and blood. 3. 14-C (from injected [14-C]HCO3 minus was found to cross the mammary epithelium in both directions. 14-C also passed across the duct epithelium and since this epithelium has previously been shown to be impermeable to ions it is argued that 14-C crossed in an unionized form, i.e. as CO2 and/or H2CO3. 4. Hourly milking with the aid of oxytocin raised milk pH, [HCO3 minus], [H2CO3], [Na] and E1Cl], and lowered [K], [lactose] and [phosphate]. These effects are discussed in relation to the hypothesis proposed previously for the action of oxytocin on milk composition. 5. A scheme for the distribution and movements of CO2, H2CO3 and HCO3 minus between extracellular fluid and milk is suggested, and discussed in relation to Cl minus transport.

Effect of changes in inspired oxygen tension on wound metabolism.

This work was prompted by earlier findings of the beneficial effect of increased oxygen supply on wound healing. Enzyme activities in the limiting step of glycolysis, citric acid cycle and pentose phosphate cycle were determined in cellulose sponge implants of rats chronically, breathing 12% O(2), air or 55% O(2.) Respiratory gas tensions and concentrations of pyruvate and lactate were measured in wound fluid aspirated from the implants. Significant portions of repair tissue exist in conditions of extremely low oxygen tension. Probably because all added oxygen is readily consumed, the wound fluid PO(2) increased only slightly in hyperoxic environment. The wound PCO(2) increased in parallel with the inspired PO(2), probably due to enhanced production of carbon dioxide. Hyperoxia shifted the wound metabolism from anaerobic towards aerobic glycolysis. This occurred concurrently with activation of citric acid cycle. Succinic dehydrogenase, a linking enzyme between citric acid cycle and electron transfer chain, also increased with increasing oxygen tension. This oxygen-induced metabolical change has been previously observed in many other tissues.

Respiratory Monitoring: Recent Developments in Automatic Monitoring of Gas Concentration, Flow, Pressure, and Temperature

Advances in instrumentation and programming techniques have resulted in the expansion of a previously reported 12-bed respiratory gas-concentration monitoring system to now include automatic calibrated measurements of bidirectional airflow, airway pressure, and airway temperature as well as other vital signs (rectal temperature, arterial blood pressure, central venous pressure, and heart rate). The more expensive hardware, including a programmable digital desk calculator, interfacing, a mass spectrometer, signal conditioners, and a major portion of the airflow instrumentation, are time-shared to provide an acceptable per-bed cost. Calculated and edited measurements of pulmonary mechanics (tidal and minute volume, mean and end-expiratory airway pressures, compliance, resistance, respiratory rate) and gas exchange (oxygen consumption, carbon dioxide production, respiratory exchange ratio, alveolar P O 2 , and alveolar P CO 2 ) are printed out and stored in an extended memory. The memory is accessed by a second calculator, which prints out summaries of data every 8 hours, correlates off-line blood gases and other measurements with automatically acquired data, and communicates with a commercial time-sharing system for more sophisticated data processing.