Intra-arterial Blood Gas Monitoring System Research Articles

A system for integrated measurement of ventilator settings, lung volume change and blood gases during high-frequency oscillatory ventilation

To describe and validate a system for integrated measurement of ventilator settings and dependent physiological variables during high-frequency oscillatory ventilation (HFOV). A custom interface was built for data acquisition. Lung volume change was determined by respiratory inductive plethysmography (RIP), modified to sampling rates of 140 Hz. Blood gas analysis was obtained using a continuous intra-arterial blood gas monitoring system. FIO2 was measured by means of an electrochemical sensor. Pressure at the airway opening and trachea (microtip transducer) were sampled. The data acquired were sent to a laptop computer for analysis, display and storage. The system was tested during a lung recruitment procedure in an animal model of respiratory distress. Linearity of the RIP was checked by gas volume injection using a supersyringe. The system operated succesfully. Agreement between RIP-measured volume with injected volume was excellent; bias was 5 ml; limits of agreement were 1-9 ml. Graphs were obtained, showing the relationship between imposed mean airway pressure and lung volume change, and oxygenation. The integration of ventilator settings and dependent physiological variables may provide useful information for clinical, instructional and research application.

Continuous intra-arterial blood gas monitoring during thoracic surgery.

This study was undertaken to assess the clinical usefulness of a continuous intra-arterial blood gas (CIABG) monitoring system, Paratrend 7, during thoracic surgery. A sensor of the CIABG monitoring system was inserted into the radial artery in 50 patients. During one-lung/differential lung ventilation, arterial blood samples for estimation of blood gases (ABG) were taken every 45-90 min or when clinically needed. The PCO(2), PO(2), and pH values displayed by the CIABG monitor were recorded prior to arterial blood sampling and were compared with the results of ABG analysis. The mean (bias) and the standard deviation (precision) of the differences were calculated from the data for each parameter. Ninety-four blood samples were obtained. The correlation between CIABG and ABG measurements was strong for each parameter: r = 0.83 (PCO(2)), 0.89 (PO(2)), 0.74 (pH). The bias +/- precision between the two methods was 0.4 +/- 3.0 mmHg for PCO(2), -6 +/- 47 mmHg for PO(2), -1.2 +/- 27.4% for PO(2) and -0.01 +/- 0.04 for pH. For PO(2) values <150 mmHg, the bias +/- precision was 1 +/- 28 mmHg. The agreement between CIABG and ABG measurements was better for PCO(2) and pH than for PO(2). The PO(2) value displayed on the CIABG monitor may not always be reliable during thoracic surgical procedures.

Continuous Intra-Arterial Blood Gas Monitoring During Oesophagectomy

Purpose: To evaluate the clinical usefulness of the continuous intra-arterial blood gas (ClABG) monitoring system, Paratrend 7 TM, during differential lung ventilation (DLV) in 12 patients undergoing oesophagectomy. Methods: Anaesthesia was induced with propofol and was maintained with isoflurane, oxygen and air, supplemented by an epidural infusion of mepivacaine. Arterial samples for estimation of blood gases (ABG) were taken just before and 5, 10, 20, 30, 60, and 90 rain after the pleura was opened. The pH, PO z, and PCO 2 values displayed by the CIABG monitor, which were recorded prior to the arterial blood sampling, were compared with the results of ABG analysis. R~sults: Eighty-four blood samples were obtained and the ranges for the measured variables were PCO 2 24.857.4 mmHg, PO 2 47-449 mmHg, and pH 7.30-7.49. The correlation between CIABG and ABG measurements was strong and significant (r values : PCO 2 0.80, PO 2 0.93, pH 0.94). The overall bias _+ precision between the two methods was PCO 2 0.9 _ 3. I mmHg, PO 2 -I _ 40 mmHg, %PO 2 0.8 _ 21.6 %, pH 0.00 _ 0.02. For PO 2 values < 150 mmHg, the biases _ precision were PO 2 -5 - 17 mmHg, %PO 2 -2. I +_ 20.7%. Conclusion: The agreement between CIABG and ABG measurements was better for PCO 2 and pH than for PO 2. Although the CIABG system is clinically useful for monitoring trends in blood gas changes, the accuracy of the PO 2 value may be unacceptable during DLV because the error is theoretically < 34 mmHg with 95% reliability in the clinically important rang e of PO 2, < 150 mmHg.

Substantial Changes in Arterial Blood Gases During Thoracoscopic Surgery Can Be Missed by Conventional Intermittent Laboratory Blood Gas Analyses

Substantial and clinically relevant changes in arterial blood gases are likely to occur during thoracoscopic surgery with one-lung ventilation (OLV). We hypothesized that they may be missed when using the conventional intermittent blood gas sampling practice. Therefore, during 30 thoracoscopic procedures with OLV, the sampling intervals between consecutive intermittent laboratory blood gas analyses (BGA) were evaluated with respect to changes of PaO2, PaCO2, and pHa ([H+]) using a continuous intraarterial blood gas monitoring system. Frequency and timing of BGA were based on the clinical judgment of 16 experienced anesthesiologists who were blinded to the continuously measured values. Extreme fluctuations of PaO2 (37-625 mm Hg), PaCO2 (27-56 mm Hg), and pHa (7.24-7.51) were observed by continuous blood gas monitoring. During 63% of all sampling intervals, PaO2 decreased >20% compared with the preceding BGA value, which remained undetected by intermittent analysis. In 10 patients with a continuously measured minimal PaO2 value <or=to60 mm Hg, the preceding BGA overestimated this minimal PaO2 by >47%. Correspondingly, PaCO2 increases of >10% were observed in 35% of all sampling intervals, and [H+] increases of >10% were observed in 24% of all sampling intervals. Because these blood gas changes were not reliably detected by using noninvasive monitoring and their magnitude is not predictable during OLV, intermittent BGA with short sampling intervals is warranted. In critical cases, continuous blood gas monitoring may be helpful. Implications: The magnitude of blood gas changes during thoracoscopic surgery with one-lung ventilation is not predictable and not reliably detected by noninvasive monitoring. Using a continuous intraarterial blood gas monitoring device, we demonstrated that intermittent laboratory blood gas analysis with short sampling intervals is warranted to detect arterial hypoxemia. (Anesth Analg 1998;87:647-53)

HOW OFTEN DO WE HAVE TO MONITOR ARTERIAL BLOOD GASES DURING THORACOSCOPIC SURGERY?

S248 Introduction: Intermittent arterial blood gas analysis (ABG) is currently the standard practice to monitor the significant changes in arterial blood gas parameters occurring during thoracoscopic surgery (TS) [1]. Noninvasive monitoring modalities such as pulse oximetry and capnometry were reported to have poor reliability when monitoring the blood gas parameters during one-lung ventilation (OLV) [2]. However, no guidelines concerning the sampling rate at which ABG should be performed during TS are available at the time. It was the aim of the study to determine the theoretical sampling frequency for ABG needed to detect the most substantial changes in arterial PO2 and PCO2 during TS. Methods: After approval by the Ethics Committee, 13 consenting patients (mean age 61 years; ASA physical status II-III) scheduled for elective thoracoscopic surgery were enrolled in the study. Arterial PO2 and PCO2 were continuously monitored during the 18 OLV intervals (oxygen fraction of 1.0, respiratory patterns adjusted to individual demands, short periods of two-lung ventilation (TLV) and apneic oxygen insufflation as needed) using the intraarterial blood gas monitoring system Paratrend 7 (PT7) (Biomedical Sensors Ltd, Pfizer Hospital Group, High Wycombe, UK). Data were recorded every 10 sec and processed by Fast Fourier Transform Analysis (FFTA) with a Hamming window [3]. Prior to FFTA a constant value of 60 mmHg for PO2 and 30 mmHg for PCO2 was subtracted from the original data (direct current offset). FFTA decomposes the original signal into a sum of sinusoids of different frequencies and amplitudes. The resulting spectral density function represents a measure of the contribution of each sinusoid to the original signal. 95% of the total spectral energy is accounted for by contributions at frequencies smaller than the cut-off frequency, fmax. The Nyquist frequency (2x fmax) was used to determine the theoretical maximum sampling interval that preserves most of the signal information (i.e. the true course of arterial PO2 and PCO2 during OLV). Results: The mean duration +/- SD of OLV was 50 +/- 41 (15-158) min. The mean minimum +/- SD (range) (min) and maximum +/- SD (range) (max) PT7 PO2 and PCO2 values were: PO2min 81 +/- 38 (30-180) mmHg, PO2max 328 +/- 150 (75-700) mmHg, PCO2min 42 +/- 9 (18-59) mmHg, PCO2max 54 +/- 10 (24-71) mmHg. Figure 1a shows a typical PO2 course (OLV with short periods of TLV) with its corresponding spectral density plot (Figure 2). The calculated mean sampling interval +/- SD (range) for PO2 was 5.7 +/- 2.7 (3-11) min and for PCO2 12.6 +/- 6.5 (5-22) min.Figure 1: a: PO2 during OLVFigure 2: (Figure 1)b: FFTA of PO2Discussion: FFTA generates objective data based on signal analysis providing us with the blood gas sampling interval needed to detect the most substantial changes. In contrast to current clinical practice (1 ABG per 20-30 minutes), our data indicate that for ASA II-III patients during TS a considerably higher sampling rate (1 ABG per 6 minutes) would be necessary. Since this may be impossible in routine clinical practice, the use of continuous intraarterial blood gas monitoring appears to be justified at least in critical cases.

Clinical evaluation of a new continuous intraarterial blood gas monitoring system in the intensive care setting

The present study was designed to evaluate a new continuous intraarterial blood gas monitoring system under routine clinical intensive care conditions. Nine mechanically ventilated adult patients were enrolled in this study. A multiparameter intravascular sensor was inserted into the radial or dorsalis pedis artery through a 20-gauge cannula in each patient. The accuracy of the sensor for pH, Pco2, and Po2 values was evaluated by comparing the data simultaneously obtained from the monitoring system and from conventional blood gas analysis. Measurements were performed for 3 days for each sensor. A total of 62 blood samples were obtained for comparison. The ranges of measured variables were: pH 7.185-7.602, Pco2, 28.8-68.5 mmHg, and Po2 45.2-542.4 mmHg. The overall bias ±precision values were 0.002±0.018 for pH units, 0.53±2.04mmHg for Pco2, and -1.62±20.00 mmHg for Po2. In clinically important ranges of Po2, less than 200 mmHg in particular, the bias and precision values were -2.25±6.48 mmHg in the range of less than 100mmHg, and 0.98±14.38 mmHg in the range of 100-200 mmHg. Variations of sensor accuracy as a function of elapsed time were within the clinically acceptable range throughout the study period. These findings suggest that this new device is sufficiently useful for routine clinical settings.

Clinical evaluation of a new continuous intraarterial blood gas monitoring system in the intensive care setting

Clinical evaluation of a new continuous intraarterial blood gas monitoring system in the intensive care setting

Long-term evaluation of a continuous intra-arterial blood gas monitoring system in patients with severe respiratory failure.

The purpose of this study was to evaluate the reliability and accuracy of a new continuous intra-arterial blood gas monitoring system (IABG; PB3300, Puritan Bennett) over a prolonged period of time (> 7 days). Prospective criterion standard study. Anesthesiological intensive care unit in a university hospital. 11 sensors were tested in 10 mechanically ventilated patients with severe respiratory failure. PO2, PCO2, and pH measured using IABG were compared to values obtained from 2 conventional blood gas analyzers. The quality of blood pressure tracings was assessed using a scoring system consisting of 5 grades. The median study period was 205h/sensor (range: 169-506h). 320 blood samples were obtained. The ranges of measured parameters were: PO2 = 46-433 mmHg, PCO2 = 25-79 mmHg, pH = 7.25-7.55. The mean (SD) differences for the whole study period were: -4.3 (11.9) mmHg for PO2, for the clinically important range (PO2 < 150 mmHg) -1.9 (5.4) mmHg, -2.8 (4.5) mmHg for PCO2, and -0.03 (0.04) for the pH value. The MD (SD) in relation to the sensor lifetime were for days 1-3: -1.1 (5.1) mmHg for PO2, -0.4 (3.9) mmHg for PCO2, and -0.01 (0.03) for the pH value; for days 4-6: -1.5 (6.0) mmHg for PO2, -3.3 (4.0) mmHg for PCO2, and -0.03 (0.03) for the pH value; for days 7-9: -2.5 (4.7) mmHg for PO2, -5.1 (4.6) mmHg for PCO2, and -0.04 (0.04) for the pH value; for days > 9: -4.9 (4.4) mmHg for PO2, -5.3 (4.1) mmHg for PCO2, and -0.05 (0.03) for the pH value. The IABG reliably measured blood gases and pH values with acceptable clinical performance based on the overall results. There was, however, a decline in the agreement of the sensors and conventional values with increasing sensor lifetime. The mean differences (bias) and the standard deviation of differences (precision) of PO2, PCO2 and the pH values were acceptable for clinical purposes up to day 6. The arterial blood pressure tracings and blood withdrawal were not adversely affected. No side effects due to the sensors occurred. In summary, a prolonged sensor use for a period of up to 6 days appears to be reasonable. This system offers on-line information on oxygenation, ventilation, and acid-base status and allows immediate detection of acute and potentially life-threatening events.

Clinical assessment of a continuous intraarterial blood gas monitoring system.

We evaluated the clinical performance of a continuous intraarterial blood gas monitoring (CIABG) system which includes a fluorometric intravascular sensor. Seventeen patients undergoing elective surgery were monitored perioperatively with the CIABG system (PB3300; Puritan Bennett, Carlsbad, CA). Conventional laboratory blood gas analyses (BGA) were performed simultaneously whenever indicated, and the values were compared with those obtained from the CIABG system. Monitoring time ranged from 24 to 72 hr. The biases (average error between PB3300 and BGA) of pH, PCO2 and PO2 were 0.003 pH unit, -2.8 mmHg, and 0.9 mmHg in the operating room (OR), and 0.005 pH unit, 3.9 mmHg, and 8.5 mmHg in the intensive care unit (ICU), respectively. The precision (standard deviation of the bias) of pH, PCO2 and PO2 were 0.030 pH unit, 2.1 mmHg, and 29.9 mmHg in the OR and 0.035 pH unit, 3.8 mmHg, and 14.7 mmHg in the ICU, respectively. Although the PB3300 system was clinically useful as a trend monitor, the system's precision and reliability were unacceptable for estimation of true blood gas values.

The PB3300 intraarterial blood gas monitoring system.

Continuous intraarterial blood gas (IABG) monitoring is in clinical use both in the operating room and intensive care unit. This technology uses miniature, optically-based sensors that can be placed into a patient's artery. The arterial blood gas values are transduced into an optical signal that is measured by a bedside monitor on which the values are displayed. In this paper, we describe the operating principles of the PB3300 Intra-Arterial Blood Gas Monitoring System (Puritan-Bennett Corporation, FOxS Division, Carlsbad, CA). Topics include the principles of fluorescent determinations of pH, PCO2, and PO2; the optical path of the PB3300; system calibration; dye layer geometry; and clinical operation. The accuracy, precision, and drift of the system measuring tonometered aqueous standards are reported. The following values were noted for eight sensors sending data to eight monitors: system bias and precisions of 0.00 +/- 0.02 pH at a pH of 7.40, -2.5 +/- 1.5 mm Hg PCO2 at a PCO2 of 40 mm Hg, and 3.3 +/- 1.3 mm Hg PO2 at a PO2 of 80 mm Hg.