Lack of agreement between tonometric and gastric juice partial carbon dioxide tension

Abstract

measurement should be interpreted with caution. of the upper layers of the gastric mucosa. are not interchangeable. The present study was approved by the local ethics committee, and informed consent was obtained from the next of kin of each patient. in both samples was measured using a blood gas analyzer (AVL 945; AVL List GMBH, Gratz, Austria). These measurements were taken at various time points in each patient, and under various haemodynamic and oxygen transport conditions, All measurements were performed with the patient fasted. Correlation between the two measurements was examined using the Bland-Altman technique. in saline solution was achieved by bubbling 5% carbon dioxide calibration gas. < 0.0001). In an effort to prevent the bias related to multiple measurements per patient, we performed Bland-Altman analysis with the first measurement of each patient. After this the results remained similar (bias 55 mmHg, 95% limits of agreement 216 mmHg). The AVL 945 blood gas analyzer showed a negative bias of 0.97 mmHg and a precision of 2.13 mmHg. This bias was considered negligible, so no further correction was made to saline tonometric values. values the differences widen, and data dispersion becomes even more marked. might reflect rapid changes in mucosal metabolism. Different equilibrium time could also account for data dispersion, but not for the positive bias for gastric juice. Rapid changes should occur in both directions. is equilibrated in human albumin solution 4.5%. and to estimate pHi. Simultaneously, mucosa pH was recorded with a microglass probe. They found a statistically significant correlation between both methods. However, data dispersion in the graph was considerable. performance of the AVL 945 in blood was good. It showed a negative bias less than 1 mmHg and a precision of about 2 mmHg. in gastric juice. . increased. ARDS, acute respiratory distress syndrome.

Introduction:

of the upper layers of the gastric mucosa.

are not interchangeable.

Patients and methods:

The present study was approved by the local ethics committee, and informed consent was obtained from the next of kin of each patient.

in both samples was measured using a blood gas analyzer (AVL 945; AVL List GMBH, Gratz, Austria). These measurements were taken at various time points in each patient, and under various haemodynamic and oxygen transport conditions, All measurements were performed with the patient fasted. Correlation between the two measurements was examined using the Bland-Altman technique.

in saline solution was achieved by bubbling 5% carbon dioxide calibration gas.

Results:

< 0.0001).

In an effort to prevent the bias related to multiple measurements per patient, we performed Bland-Altman analysis with the first measurement of each patient. After this the results remained similar (bias 55 mmHg, 95% limits of agreement 216 mmHg).

The AVL 945 blood gas analyzer showed a negative bias of 0.97 mmHg and a precision of 2.13 mmHg. This bias was considered negligible, so no further correction was made to saline tonometric values.

Discussion:

values the differences widen, and data dispersion becomes even more marked.

might reflect rapid changes in mucosal metabolism. Different equilibrium time could also account for data dispersion, but not for the positive bias for gastric juice. Rapid changes should occur in both directions.

is equilibrated in human albumin solution 4.5%.

and to estimate pHi. Simultaneously, mucosa pH was recorded with a microglass probe. They found a statistically significant correlation between both methods. However, data dispersion in the graph was considerable.

performance of the AVL 945 in blood was good. It showed a negative bias less than 1 mmHg and a precision of about 2 mmHg.

in gastric juice.

.

increased.

ARDS, acute respiratory distress syndrome.

Introduction

].

].

are not interchangeable.

Patients and methods

The present study was approved by the local ethics committee and informed consent was obtained from the next of kin of each patient.

].

. The latter was calculated from the carbon dioxide content of the calibration gas and from barometric pressure, according to gas laws. Measurements were repeated six times.

Results

< 0.0001).

was always higher and the 95% limits of agreement were clinically significant.

In an effort to prevent bias related to multiple measurements per patient we used another approach, taking into account the initial measurement of each patient. Despite this, results continued to be similar (bias 55 mmHg, 95% limits of agreement 216 mmHg).

The AVL 945 blood gas analyzer showed a negative bias of 0.97 mmHg and a precision of 2.13 mmHg. This was considered negligible, so no further correction was done to tonometric values.

Discussion

values, this difference widened, and data dispersion became even more marked.

may generate data on minute-to-minute changes in mucosal metabolism. This different equilibrium time could account for data dispersion. However, the positive bias for gastric juice is harder to interpret, because such rapid changes should appear in both directions.

].

solubility and its subsequent measurement. In this way, intersubject and intrasubject variation of gastric juice composition could also account for data dispersion. Therefore, analytic issues related to the various constituents of gastric juice could have added to the observed differences.

in gastric juice, which could produce marked differences in the results.

results. The performance of the AVL 945 was fairly good. It showed a minor negative bias of less than 1 mmHg and a precision of approximately 2 mmHg. Thus, it appears to be a suitable device for saline tonometry.

were quite different. We believe that this is the novel point in this study.

measurement in gastric juice should be considered with caution.

Keywords

• gastric tonometry
• intramucosal partial carbon dioxide tension
• intramucosal pH