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PubMed1999

Clinical decisionmaking based on venous versus capillary blood gas values in the well-perfused child.

STUDY OBJECTIVE: In children aged 1 month to 18 years, we sought to examine the correlation between venous and arterialized capillary blood gas values, and to determine whether the source of blood sample influenced the interpretation of the acid-base status and clinical management. METHODS: In a cross-sectional study, venous and capillary blood gas values were simultaneously obtained in acutely ill well-perfused patients treated in a pediatric emergency department. Intraclass correlation coefficients for capillary and venous measured gas values were calculated. Crude agreement and intraobserver concordance were calculated for responses of 2 intensivists to the interpretation and clinical management questions, based on capillary and venous gas results. RESULTS: Intraclass correlation coefficients for 78 capillary and venous paired measured gas values were.92 (pH), .80 (PCO 2 ), and .67 (PO 2 ). The alpha of concordance values between capillary and venous blood gas values, with 95% confidence intervals (CIs) were as follows, respectively, for physician A and B: interpretation, .61 (.47 to .73) and .48 (.41 to .55); need for bicarbonate,.85 (.73 to.97) and.80 (.72 to.88); and need for intubation .73 (.64 to .82), and .83 (.75 to .91). CONCLUSION: In the well-perfused patient, we believe that venous samples are an acceptable alternative to capillary blood samples for determination of blood gas values and for making clinical management decisions.

Acid-Base Equilibrium↗
PubMed2003

The cytotoxic effect of volatile organic compounds of the gas phase of cigarette smoke on lung epithelial cells.

Health effects of cigarette smoke (CS) in humans are well known from both clinical and epidemiological studies. However, the mechanism behind CS toxicity and carcinogenicity remains mainly unknown. Recent studies have pointed to the major importance of the gas phase of CS in generating its cytotoxic effects. In the current study, an exposure system capable of introducing the gas phase of mainstream cigarette smoke deprived of its volatile organic constituents (VOCs) was used to study the role of the nonorganic components of the gas phase on the cytotoxicity of smoke to monolayer cultures of mouse lung epithelial cells. Cell viability was measured by Wst-1 and the lactate dehydrogenase (LDH) assays. In cells treated with increasing doses of mainstream cigarette smoke gas phase (one to nine puffs), a dose-dependent increase in cytotoxicity was observed (one puff, 95% viability; nine puffs, 40% viability). Cell viability of cultures exposed to gas phase with only the nonorganic components was found to be equivalent to control, unexposed cultures, indicating that removal of VOCs resulted in almost eliminating the cytotoxic ability of the gas phase of CS. Furthermore, the removal of VOCs seems to reduce the effects of protein tyrosine nitration mediated through the gas phase constituents. The results obtained suggest the important and decisive role of VOCs in inducing cytotoxic effects.

Animals↗
PubMed2002

Effects of prone and supine posture on cardiopulmonary function after experimental chlorine gas lung injury.

BACKGROUND: Chlorine gas may induce severe acute lung injury. Improvement of pulmonary gas exchange in patients and animals with acute lung injury nursed in the prone position was observed in recent years. The purpose of this study was to evaluate the effects of prone and supine positions on pulmonary and cardiovascular functions following experimental chlorine gas lung injury. METHODS: Twenty anesthetized and mechanically ventilated pigs were exposed to chlorine gas (400 p.p.m. in air) for 20 min in the supine position, then assigned randomly to ventilation in the supine or prone positions (n=10 in each group). Hemodynamics, gas exchange, lung mechanics and oxygen transport were evaluated for 5 h. RESULTS: All animals showed severe pulmonary dysfunction immediately after chlorine gassing with a threefold increase in pulmonary vascular resistance index, a drop in arterial oxygenation (12.3+/-1.3 kPa to 5.4+/-0.7 kPa) and a fall in lung-thorax compliance (22+/-1 ml cmH2O-1 to 8+/-2 ml cmH2O-1). Venous admixture (Qs/Qt) improved in animals in the prone position while there was no change in the supine position (prone 32+/-11% vs. supine 42+/-9% at 5 h,P<0.05). Lung-thorax compliance improved significantly with time in the prone group only (P<0.01). Oxygen delivery increased significantly in prone animals compared with animals nursed in the supine posture (P<0.001). CONCLUSION: Immediate prone positioning after chlorine gas injury not only inhibited deterioration of gas exchange but was also associated with improved pulmonary function and oxygen transport.

Administration, Inhalation↗
PubMedDate not supplied

Continuous blood gas monitoring using an in-dwelling optode method: clinical evaluation of the Neotrend sensor using a luer stub adaptor to access the umbilical artery catheter.

INTRODUCTION: Arterial blood gases are essential in the management of critically ill neonates. A new technology using the Neotrend system (Diametrics Medical) allows for continuous measurement of pH, PaCO(2), and PaO(2), and calculates oxygen saturation, bicarbonate, and base excess. OBJECTIVE: To evaluate and compare the results of continuous blood gas measurement using the Neotrend system with a standard system of blood gas analysis in our intensive care unit. DESIGN: Prospective, controlled, interventional study. SETTING: The neonatal intensive care unit of a tertiary referral center. PATIENTS: Neonates with respiratory distress who required respiratory support and frequent arterial blood gas sampling and had a UAC. RESEARCH DESIGN AND METHOD: To enable Neotrend sensor access to an existing Argyle umbilical artery catheter (UAC) the catheter was cut at the 25-cm mark and connected to an 18-gauge blunt needle luer stub adaptor (Vygon 95440). The study began with the insertion of the Neotrend sensor. Subjects remained on the study until the UAC was discontinued and/or frequent blood gases were no longer needed. The blood gas results from the Neotrend system were not used in clinical management of the patient. BLOOD GAS MEASUREMENT: During the study period, with each blood sample drawn for laboratory analysis, a printout from the Neotrend monitor was recorded for comparison. RESULTS: A total of 217 pairs of blood gas samples were collected from seven neonates. The mean bias/precision for pH was 0.01/0.04; for PaO(2) 0.72/18.5 mm Hg; and for PaCO(2) 3.96/2.63 mm Hg. The correlation (r value) between the sensor reading and the blood gases were 0.85 for pH, 0.96 for PaO(2), and 0.92 for PaCO(2). CONCLUSION: The blood gases compared in the two methods had a strong correlation for pH, PaCO(2), PaO(2), and oxygen saturation. Although the bicarbonate and base excess values showed suboptimal statistical correlation, the difference was not clinically relevant. Results of this study indicate that this technology provides an accurate means of monitoring continuous blood gas parameters in neonatal patients. It also allows reduced healthcare provider exposure to blood and decreased patient iatrogenic blood loss.

Blood Gas Analysis↗
PubMed2005

Performance characteristics of gas analysis systems: what we know and what we need to know.

It is important that sources of variation in gas analysis measurements are identified and described in an accurate and informative manner. In this paper, we discussed the potential sources of error, which should be considered in any measurement study on gas analysis systems. We then covered how errors in various terms associated with gas laws propagate to outcome measurements of gas exchange to help quantify the relative importance of sources of error. Finally, we performed a literature survey to explore the statistical methods researchers have employed to arrive at conclusions on the performance characteristics of gas analysis methods. We found examples of excellent practice in the literature, but there were also gaps in the knowledge of error in gas analysis systems. Consequently, we supplied guidelines for future method comparison studies. These guidelines included (i) a sample size of at least 40 participants and the citation of confidence intervals, (ii) a description of the relationships between systematic and random errors and the size of measured value, (iii) the parallel examination of test-retest error within a method comparison study, and (iv) an a priori-made judgement on how much systematic and random error between methods is acceptable for practical applications. We stressed that this judgement should be based on expert-agreed position statements about acceptable error, which unfortunately have yet to be formulated for gas analysis systems.

Breath Tests↗
PubMed2004

Use of a directional spray system design to control respirable dust and face gas concentrations around a continuous mining machine.

A laboratory study assessed the impacts of water spray pressure, face ventilation quantity, and line brattice setback distance on respirable dust and SF6 tracer gas concentrations around a continuous mining machine using a sprayfan or directional spray system. Dust levels were measured at locations representing the mining machine operator and the standard and off-standard shuttle car operators, and in the return airway. The results showed that changes in all three independent variables significantly affected log-transformed dust levels at the three operator sampling locations. Changes in setback distance impacted return airway dust levels. Laboratory testing also identified numerous variable interactions affecting dust levels. Tracer gas levels were measured on the left and right sides of the cutting drum and in the return. Untransformed gas levels around the cutting drum were significantly affected by changes in water pressure, face ventilation quantity, and setback distance. Only a few interactions were identified that significantly affected these concentrations. Gas levels in the return airway were grouped by face ventilation quantity. Return gas levels measured at the low curtain quantity were generally unaffected by changes in water pressure or curtain setback distance. At the high curtain quantity, return airway gas levels were affected by curtain setback distance. A field study was conducted to assess the impact of these parameters in an actual mining operation. These data showed that respirable dust levels may have been impacted by a change in water pressure and, to a lesser extent, by an increase in curtain setback distance. A series of tracer gas pulse tests were also conducted during this study. The results showed that effectiveness of the face ventilation was impacted by changes in curtain flow quantity and setback distance. Laboratory testing supported similar conclusions.

Caustics↗
PubMed1986

Gaseous homeostasis and the circle system. Factors influencing anaesthetic gas exchange.

A mathematical model of a subject breathing from a circle system has been used to follow the course of anaesthetic uptake during the simulated administration of 60% nitrous oxide, 2% halothane and 2% methoxyflurane, under non-rebreathing conditions and with fresh gas flows to the circle system of between 8 and 0.25 litre min-1. Compared with the non-rebreathing state, the use of a circle system reduced the initial rate of increase of alveolar towards fresh gas anaesthetic concentration, and the rate of increase in body anaesthetic content. The degree of reduction became more marked as fresh gas flow was reduced, and as agents of increasing blood solubility were used. These effects of a circle system were influenced by the volume of the circle system and the composition of gas initially present within the system. When the circle system was in use there were increases in the magnitude of both the concentration effect and the second gas effect which were related to the magnitude of fresh gas flow. The use of a circle system augmented the effects of changes in cardiac output and reduced the effects of changes in ventilation on the alveolar concentrations of the anaesthetic. These influences of a circle system were also dependent on the magnitude of fresh gas flow. The degree of augmentation of the effects of cardiac output decreased with increasing blood solubility of the agent in use, whilst the limitation of the effects of ventilation was greatest with the agent of highest blood solubility. Both under non-rebreathing conditions and with the circle system in use, the effects of cardiac output and ventilation were greater with 2% nitrous oxide than with 60% nitrous oxide, and were also greater when gases were given separately than when administered in combination.

Anesthesia, Closed-Circuit↗
PubMed1984

Distribution of expiratory gas and rebreathing in a T-piece modification combined with a PEEP valve.

T-piece modifications with PEEP valves are often used in weaning from mechanical ventilation or for intubated patients not requiring ventilatory support. Distribution of expiratory gas and the extent of rebreathing in a T-piece modified with an inspiratory reservoir (ICR) and with a PEEP valve were studied in a model with various fresh gas flows (FGF), tidal volumes and frequencies at three valve settings: 0 cmH2O (ZEEP) and PEEP of 5 and 10 cmH2O (0.490-0.981 kPa). Two types of distribution of expiratory gas were delineated: type one with expiratory gas in the inspiratory limb (IL) and a high ratio of the maximum CO2 content and corresponding end-expiratory CO2 concentration in the expiratory limb (EL) (FmaxCO2/FECO2) and a type 2 with no detectable alveolar gas in the IL and a low ratio of FmaxCO2/FECO2. The use of PEEP did not increase the amount of alveolar gas in the system, and no increase occurred in the end-expiratory CO2 concentration. The investigated system is in fact a Mapleson A system. The ratio of FGF to minute ventilation just preventing rebreathing during spontaneous ventilation is approximately 1, in contrast to 3 in other modifications. These advantages minimize the risk of rebreathing, even when the minute ventilation rises to that of the fresh gas flow. The T-system with a compliant inspiratory reservoir and a PEEP valve can, in most clinical weaning situations, satisfy the inspiratory peak flow of different respiratory patterns with a standard FGF of 15 l X min-1.

Carbon Dioxide↗
PubMed1998

Effects of propofol vs isoflurane on respiratory gas exchange during laparoscopic cholecystectomy.

BACKGROUND: Respiratory function and pulmonary gas exchange are affected in laparoscopic procedures where a pneumoperitoneum is introduced using CO2. Previous studies have shown differing results concerning pulmonary gas exchange during laparoscopic procedures: Whereas in patients undergoing isoflurane anaesthesia decreases in PaO2 are demonstrated, this factor remains unchanged in patients undergoing propofol anaesthesia. In the present study, the effects of propofol on pulmonary gas exchange were compared with those of isoflurane in patients undergoing elective laparoscopic cholecystectomy in a prospective randomised manner. METHODS: Twenty ASA patients with physical status I and II were divided randomly between isoflurane (IG) and propofol groups (PG). After induction of anaesthesia patients were moderately hyperventilated. Respirator settings remained unchanged during pneumoperitoneum (PP) until 10 min after deflation of the peritoneal cavity. Blood gas analyses were performed at 5 time points: 15 min after induction of anaesthesia (giving pre-PP values), immediately before carbon dioxide insufflation (0 min PP), after both 30 and 60 min of PP and 10 min post PP. Inspiration plateau pressure (Pplat), compliance of the respiratory system, and both ins- and expiratory gas concentrations were continuously recorded by an Ultima V monitor (Datex Corp., Helsinki, Finland). The difference between arterial and end-tidal CO2 partial pressure (P(a-et)CO2) was calculated so as to allow assessment of physiological dead space by the modified Bohr equation. RESULTS: Pulmonary gas exchange differed significantly after 30 min of PP between the IG and the PG. At this time, PaO2 was 19.5 +/- 2.9 kPa (mean +/- SD) in the IG and 23.1 +/- 1.8 kPa in the PG (P < 0.01), whereas PaCO2 was 5.5 +/- 0.37 kPa in the IG and 4.9 +/- 0.27 kPa in the PG (P < 0.01). These discrepancies remained until after carbon dioxide desufflation. At 10 min post PP, PaO2 was 18.3 +/- 2.6 kPa in the isoflurane group and 21.9 +/- 2.2 kPa in the propofol group (P < 0.01), whereas PaCO2 was 5.4 +/- 0.46 kPa in the IG and 4.8 +/- 0.22 kPa in the PG (P < 0.01). During carbon dioxide insufflation the P(a-et)CO2 increased significantly in the IG from 0.47 +/- 0.13 kPa to 0.76 +/- 0.37 kPa (P < 0.05), while the values in the PG remained constant. CONCLUSION: This study demonstrates that pulmonary gas exchange in patients with laparoscopic cholecystectomy is affected by the choice of anaesthetic procedure. During and after laparoscopic cholecystectomy using isoflurane as the anaesthetic, the PaCO2 is significantly higher and the PaO2 significantly lower than they are with propofol.

Adult↗
PubMedDate not supplied

A mathematical model of gas exchange in an intravenous membrane oxygenator.

Acute respiratory distress syndrome (ARDS) is a pulmonary edemic condition which reduces respiratory exchange in 150,000 people per year in the United States. The currently available therapies of mechanical ventilation and extracorporeal membrane oxygenation are associated with high mortality rates, so intravenous oxygenation represents an attractive, alternative support modality. We are developing an intravenous membrane oxygenator (IMO) device intended to provide 50% of basal oxygen and carbon dioxide exchange requirements for ARDS patients. A unique aspect of the IMO is its use of an integral balloon to provide active mixing. This paper describes a mathematical model which was developed to quantify and optimize the gas exchange performance of the IMO. The model focuses on balloon activated mixing, uses a lumped compartment approach, and approximates the blood-side mass transfer coefficients with cross-flow correlations. IMO gas exchange was simulated in water and blood, for a variety of device geometries and balloon pulsation rates. The modeling predicts the following: (1) gas exchange efficiency is reduced by a buildup of oxygen in the fluid near the fibers; (2) the IMO gas exchange rate in blood is normally about twice that in water under comparable conditions; (3) a balloon diameter of about 1.5 cm leads to optimal gas exchange performance: and (4) in vivo positioning can affect gas exchange rates. The numerically predicted gas transfer rates correlate closely with those experimentally measured in vitro for current IMO prototypes.

Counterpulsation↗
PubMed2004

Thin-section CT abnormalities and pulmonary gas exchange impairment in workers exposed to asbestos.

PURPOSE: To evaluate the relationship between abnormalities at thin-section computed tomography (CT) and indexes of pulmonary gas exchange impairment at rest and during moderate exercise in workers exposed to asbestos. MATERIALS AND METHODS: Eighty-two workers with long-term exposure to asbestos and abnormal thin-section CT findings underwent respiratory physiologic measurements at rest (lung diffusing capacity, Dlco) and during exercise (oxygen uptake-corrected alveolar-arterial pressure difference for oxygen, DeltaP[A-a]O(2)/VO(2)). CT results were compared with physiologic measurements of impairment in gas exchange (Dlco < 70% predicted value and/or DeltaP[A-a]O(2)/VO(2) > 20 mm Hg. L. min(-1)). The CT findings were divided into five categories by using a previously described method. Odds ratios and 95% CIs for gas exchange defects were calculated for patients grouped according to CT findings. Logistic regression analysis was performed with gas exchange as the dependent response and CT abnormalities as independent variables. RESULTS: A significant association was found between extent of disease at CT and impairment of gas exchange (P <.01). Probability of functional impairment was increased with multifocal (class II) and diffuse (class III) CT abnormalities, particularly when several lesion types were found concomitantly. Logistic regression analysis demonstrated significant association of parenchymal bands (odds ratio, 6.20; 95% CI: 1.99, 19.22) and subpleural nodules (odds ratio, 3.83; 95% CI: 1.23, 11.89) with functional impairment. Presence and number of pleural plaques did not improve model accuracy for gas exchange impairment prediction (P >.05). CONCLUSION: Thin-section CT grading of interstitial lung disease is useful in assessing the likelihood of pulmonary gas exchange impairment at rest (Dlco) and during exercise (DeltaP[A-a]O(2)/VO(2)) in workers with long-term asbestos exposure.

Adult↗
PubMed1983

Gas mixing within the acinus of the lung.

The subject is reviewed with an emphasis on recent developments in model analyses. Application of computer technology has facilitated the study of simultaneous convection and diffusion within a complex geometry approximating the airways and air spaces of the lung. During an inspiration of fresh gas the diffusion front separating inspired from "alveolar" gas is stationed within a portion of the acinus where the magnitudes of gas transport by convection and diffusion are similar. This constitutes the peripheral boundary of the Fowler dead space. Asymmetry of intra-acinar branching results in an inequality of gas concentrations within alveolar gas, despite homogeneous volume expansion. This is due to an interaction between diffusion and convection at branch points subtending units of unequal lengths. During a respiratory cycle a "diffusive Pendelluft" between these units results in a "first in-first out" pattern and a sloping alveolar plateau on the expired tracing, despite synchronous and homogeneous volume changes. Experimental results suggest that incomplete alveolar gas mixing constitutes a measurable limitation to gas exchange in the normal lung.

Animals↗
PubMed1983

A model evaluation of estimates of breath-to-breath alveolar gas exchange.

A mathematical model has been implemented for evaluation of methods for estimating breath-to-breath alveolar gas exchange during exercise in humans. This model includes a homogeneous alveolar gas exchange compartment, a dead space compartment, and tissue spaces for CO2 (alveolar and dead space). The dead space compartment includes a mixing portion surrounded by tissue and an unmixed (slug flow) portion which is partitioned between anatomical and apparatus contributions. A random sinusoidal flow pattern generates a breath-to-breath variation in pulmonary stores. The Auchincloss algorithm for estimating alveolar gas exchange (Auchincloss et al., J. Appl. Physiol. 21: 810-818, 1966) was applied to the model, and the results were compared with the simulated gas exchange. This comparison indicates that a compensation for changes in pulmonary stores must include factors for alveolar gas concentration change as well as alveolar volume change and thus implies the use of end-tidal measurements. Although this algorithm yields reasonable estimates of breath-to-breath alveolar gas exchange, it does not yield a "true" indirect measurement because of inherent error in the estimation of a homogeneous alveolar gas concentration at the end of expiration.

Evaluation Studies as Topic↗
PubMed1991

Kinetic measurements of gas exchange in the intact pulmonary microcirculation.

The kinetics of gas exchange are monitored in an isolated perfused lung preparation contained within a plethysmograph. The lungs are perfused with buffer, and there is no gas exchange until a 2.0-ml bolus of reactant is injected into the perfusion system. Subsequent gas exchange produces a pressure transient that is related to the corresponding volume of exchanged gas. The observed rate of volume change is the result of two separate processes: 1) the rate of gas exchange during transit through the capillary bed and 2) the distribution of vascular transit times between the point of injection and the capillary bed. The latter is assessed by a control injection containing a dissolved inert gas that is liberated in the alveoli as the bolus enters the capillary bed. Analysis of the experimental curves permits the separation of these two processes. A model of exchange kinetics indicates that this method has the capability of measuring kinetic events occurring during gas exchange in the microcirculation under physiological conditions.

Animals↗
PubMed2004

Soluble gas exchange in the pulmonary airways of sheep.

We studied the airway gas exchange properties of five inert gases with different blood solubilities in the lungs of anesthetized sheep. Animals were ventilated through a bifurcated endobronchial tube to allow independent ventilation and collection of exhaled gases from each lung. An aortic pouch at the origin of the bronchial artery was created to control perfusion and enable infusion of a solution of inert gases into the bronchial circulation. Occlusion of the left pulmonary artery prevented pulmonary perfusion of that lung so that gas exchange occurred predominantly via the bronchial circulation. Excretion from the bronchial circulation (defined as the partial pressure of gas in exhaled gas divided by the partial pressure of gas in bronchial arterial blood) increased with increasing gas solubility (ranging from a mean of 4.2 x 10(-5) for SF6 to 4.8 x 10(-2) for ether) and increasing bronchial blood flow. Excretion was inversely affected by molecular weight (MW), demonstrating a dependence on diffusion. Excretions of the higher MW gases, halothane (MW = 194) and SF6 (MW = 146), were depressed relative to excretion of the lower MW gases ethane, cyclopropane, and ether (MW = 30, 42, 74, respectively). All results were consistent with previous studies of gas exchange in the isolated in situ trachea.

Animals↗
PubMed1996

Former poison gas workers and cancer: incidence and inhibition of tumor formation by treatment with biological response modifier N-CWS.

Mustard gas is known to have mutagenic and carcinogenic effects on animal and human cells. In this report, 1,632 male Japanese who worked in poison gas factories at some time between the years 1927 and 1945 were studied to determine comparative risk for development of cancer, the reference population being data on Japanese males overall. The standardized mortality ratio (SMR) for lung cancer in workers directly and indirectly involved in the production of mustard gas was significantly elevated. In addition, SMR for lung cancer in worker who had worked for more than 5 years was also significantly elevated. Thus, poison gas workers who had engaged in the production of mustard gas or related work for more than 5 years are a high-risk group for lung cancer. Under the cancer preventive program, Nocardia rubra cell-wall skeleton (N-CWS) was administered to 146 former poison gas workers. During a 4.5 year observation period, development of cancers was found in 7 treated workers and 17 untreated controls. After elimination of the influence of smoking level, a significant suppression of development of cancers was noted in the N-CWS-treated workers as compared to the untreated controls. Although the molecular mechanisms of carcinogenesis in former poison gas workers remains unclear, our study proposes the possible effect of biological response modifiers in the prevention of cancer development in high-risk human subjects.

Arsenicals↗
PubMed1992

Use of arm crank exercise in the detection of abnormal pulmonary gas exchange in patients at low altitude.

BACKGROUND: The measurement of arterial blood gases, P(A-a)O2 and VD/VT, during cycle ergometry is the "gold standard" for the assessment of pulmonary gas exchange. However, some patients are unable to perform cycle ergometry because of other medical problems. STUDY OBJECTIVE: To determine whether arm crank exercise could be used to reliably detect gas exchange abnormalities compared to cycle ergometry. PARTICIPANTS: Fifteen patients with a variety of pulmonary disorders, who were referred for exertional dyspnea. DESIGN: All patients performed maximal arm crank and cycle exercise. Arterial blood gases, VO2, VCO2, and VE were measured at rest and during exercise. RESULTS: Compared to peak cycle exercise (mean +/- SD), PaO2 (85 +/- 14 vs 75 +/- 13 mm Hg), SaO2 (94 +/- 2 vs 91 +/- 4 percent), VD/VT (0.21 +/- 0.07 vs 0.19 +/- 0.08), and pH (7.37 +/- 0.04 vs 7.34 +/- 0.03) were significantly higher during peak arm crank exercise. The P(A-a)O2 (18 +/- 13 vs 29 +/- 12 mm Hg) was narrower, and PaCO2 (29 +/- 3 vs 29 +/- 4 mm Hg) and PAO2 (104 +/- 4 vs 103 +/- 4 mm Hg) were similar. Six patients had normal gas exchange during cycle exercise at low altitude (P[A-a]O2 less than or equal to 27 mm Hg, PaO2 greater than or equal to 65 mm Hg, VD/VT less than or equal to 0.18) and nine were abnormal. Utilizing criteria specific for arm crank at low altitude, the same six patients had normal gas exchange (P[A-a]O2 less than or equal to 13 mm Hg, PaO2 greater than or equal to 85 mm Hg, VD/VT less than or equal to 0.26), and the remaining nine were abnormal. The P(A-a)O2 during peak arm crank was the most useful criterion in identifying patients with abnormal gas exchange. CONCLUSION: Proposed criteria for arm crank exercise testing accurately identified all patients with normal and abnormal pulmonary gas exchange during cycle exercise. The data from the present study suggest that arm crank can be an acceptable alternative exercise testing modality for the assessment of pulmonary gas exchange.

Adult↗
PubMed1993

Does implementing pulse oximetry in a critical care unit result in substantial arterial blood gas savings?

OBJECTIVES: To examine the impact of pulse oximetry on the use of arterial blood gas and other laboratory determinations and to examine predictors of the use of arterial blood gas measurements. DESIGN: Before (preoximetry)/after (postoximetry) study. SETTING: Thirty-bed multidisciplinary critical care unit. PATIENTS: Consecutive admissions of 300 patients (150 before and 150 after oximetry). MEASUREMENTS: For each patient examined, the number of arterial blood gas determinations, serum electrolyte levels, complete blood chemistries, arterial lactate levels, and creatinine samples were recorded for the initial 9 days of the stay in the critical care unit. These data were stratified by nursing shift (day vs night) and by the source of the admission (medical vs surgical). Other information collected included demographic variables, the severity of illness, the length of stay in the critical care unit, and various ventilatory parameters. RESULTS: Introducing pulse oximetry was associated with a marginal (10.3 percent; p < 0.025) reduction in the use of arterial blood gas determinations. This decrease was accounted for by changes occurring on the night shift and in the surgical patient. These findings were also observed for serum electrolyte determinations. No significant differences in the use of arterial blood gas measurements were found for medical patients. No significant differences were found in the use of arterial lactate levels, complete blood chemistries, or creatinine determinations. Significant predictors of arterial blood gas determinations included the number of days intubated, the number of ventilator orders, the number of days on an inspired oxygen content (FIO2) greater than 50 percent, and the acute physiology and chronic health evaluation II (APACHE II) score. CONCLUSIONS: The implementation of pulse oximetry in this manner gives an idea how effective the technology will be in reducing the use of arterial blood gas determinations without guidelines for the use of pulse oximetry. As only a marginal decrease was observed in the total population of medical and surgical patients, and only on the night shift, formal and standardized guidelines for the most efficient use of pulse oximetry should be considered. If these were considered, pulse oximetry may indeed make a significant contribution to improving the efficiency of care services.

Blood Chemical Analysis↗