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At least 199 records · Page 11Linked to original sources
PubMed2005

Evaluation of capnography using a genetic algorithm to predict PaCO2.

INTRODUCTION: Noninvasive estimates of Paco(2) are usually done by measuring exhaled carbon dioxide at end-expiration (Petco(2)). While commonly used in studies involving healthy patients, it is less useful in sicker patients. Conditions that affect the terminal dead space and hence the accuracy of Petco(2) as a surrogate for Paco(2) may also affect other components of the capnogram. A genetic algorithm is a computer technique for discovering relationships between variables. The purpose of this study was to use a genetic algorithm to improve the precision of Paco(2) prediction in comparison to Petco(2). METHODS: Inspiratory and expiratory volumes were measured and analyzed by the computerized capnogram. Data were recorded for 2 min. Within 5 min of recording the capnograms, arterial blood gases were obtained. After excluding artifact and incomplete capnograms, five of the remaining breaths from each patient were selected. A genetic algorithm, constructed in postfix notation, consisted of 1,000 chromosomes with genes randomly selected from the 11 capnographic data fields and mathematical operators. The algorithm was constructed on 400 breaths from 83 randomly selected patients (construction group) and tested on 160 breaths from the remaining 32 patients (test group). RESULTS: For the construction group, the bias and precision between Petco(2) and Paco(2) were 4.3 +/- 4.9 mm Hg (mean +/- SD). For the 160 breaths in the test group, Petco(2) predicted Paco(2) with bias and precision of 2.9 +/- 4.2 mm Hg. The best chromosome found by the genetic algorithm was (10 x 5 + 5 x 5 x 5)/(10 x 10) x Petco(2) - (5 x 5 x 10 + 5 x 5)/(10 x 10) x int time + 2 x 2 x 2 x 2 + (2 x 2)/10, which reduces to 0.65 x Petco(2) - 2.75 x int time + 16.4. This produced a bias and precision of 0.9 +/- 4.1 mm Hg in the construction group and 0 +/- 3.7 mm Hg in the test group (p < 0.01). CONCLUSIONS: In this study of nonintubated emergency department patients, a genetic algorithm produced an improvement in bias and precision of Paco(2) prediction.

Adult↗
PubMed1999

The influence of breathing system filters on paediatric capnography.

Breathing system filters are in common use during paediatric anaesthesia. Expired gas sampling from the patient side of these filters may contaminate and saturate the sampling line, while sampling from the machine side may cause underestimation of end-tidal carbon dioxide (PECO 2). The aim of this investigation was to elucidate the degree of underestimation of PECO 2 induced by sampling from the machine side of a breathing system filter. Ten spontaneously breathing children and ten children receiving mechanical ventilation under general anaesthesia were studied. PECO 2 was higher at the patient side of the filter in both ventilated and spontaneously breathing groups (P<0.002 for each). The bias in measuring at the machine side of the filter was significantly greater in the spontaneously breathing children as compared with the mechanically ventilated children (-1.8 vs -0.7 kPa; P<0.004).

Anesthesia, General↗
PubMed2000

Capnography in EMS.

Explore the source record for details and available documents.

Allied Health Personnel↗
PubMed2001

Comparison between the cuffed oropharyngeal airway and the laryngeal mask with respect to breathing pattern and capnography.

This study evaluates spontaneous breathing and CO2-monitoring under sevoflurane anesthesia with a cuffed oropharyngeal (COPA) or laryngeal mask (LMA) as airway. Forty patients (ASA I-II) scheduled for varicose vein surgery were given 2 mg.kg-1 propofol for insertion of a COPA or a LMA. Anesthesia was maintained with sevoflurane at 2.5 vol% in 40/60% O2/N2O, while the patients breathed spontaneously. Arterial and end-tidal CO2 partial pressures (PaCO2, PE'CO2), respiratory rate (RR), tidal volume (VT) and expired minute volume (EMV) were recorded at different times before and during the procedure. The dead space (VD) was calculated from the modified Bohr equation. The PaCO2 and the PE'CO2 were generally lower in the LMA group as compared to the COPA group during most of the procedure. EMV was also higher in the LMA group as compared to the COPA group. This difference becomes statistically significant 5 min. before the end of surgery (6.22 +/- 0.34 vs. 5.23 +/- 0.39 L.min-1). RR was consistently higher in the LMA group, while VT and VD were similar. Correlation of PE'CO2 and PaCO2 was 0.87 when measured in the COPA group and 0.88 in the LMA group. The prediction of PaCO2 by PE'CO2 was more sensitive in the LMA group as compared to the COPA group. We conclude that spontaneous breathing is better with the LMA.

Anesthesia, Inhalation↗
PubMedDate not supplied

The use of capnography in the air medical environment.

We can count on two things when we receive a call as part of an air medical transport team--the patient is in critical condition, and time is of the essence. Whether the patient has experienced trauma from a motor vehicle crash, has fallen, or has suffered an insult as a consequence of poor health, our technique, skill, and judgment are tested constantly. Fortunately, we have equipment at our disposal to make our job easier. One of the more difficult aspects and responsibilities of air medical transport teams is placement of an endotracheal tube (ET). Along with the techniques used for successful endotracheal intubation (ETI), available technology can maximize patients' ventilatory status using an instrument that detects expired carbon dioxide (CO(2)) levels.

Air Ambulances↗