Clinical validation of a capnodynamic method for measuring end-expiratory lung volume in critically ill patients.

RATIONALE: End-expiratory lung volume (EELV) is reduced in mechanically ventilated patients, especially in pathologic conditions. The resulting heterogeneous distribution of ventilation increases the risk for ventilation induced lung injury. Clinical measurement of EELV however, remains difficult. OBJECTIVE: Validation of a novel continuous capnodynamic method based on expired carbon dioxide (CO2) kinetics for measuring EELV in mechanically ventilated critically-ill patients. METHODS: Prospective study of mechanically ventilated patients scheduled for a diagnostic computed tomography exploration. Comparisons were made between absolute and corrected EELVCO2 values, the latter accounting for the amount of CO2 dissolved in lung tissue, with the reference EELV measured by computed tomography (EELVCT). Uncorrected and corrected EELVCO2 was compared with total CT volume (density compartments between - 1000 and 0 Hounsfield units (HU) and functional CT volume, including density compartments of - 1000 to - 200HU eliminating regions of increased shunt. We used comparative statistics including correlations and measurement of accuracy and precision by the Bland Altman method. MEASUREMENTS AND MAIN RESULTS: Of the 46 patients included in the final analysis, 25 had a diagnosis of ARDS (24 of which COVID-19). Both EELVCT and EELVCO2 were significantly reduced (39 and 40% respectively) when compared with theoretical values of functional residual capacity (p < 0.0001). Uncorrected EELVCO2 tended to overestimate EELVCT with a correlation r2 0.58; Bias - 285 and limits of agreement (LoA) (+ 513 to - 1083; 95% CI) ml. Agreement improved for the corrected EELVCO2 to a Bias of - 23 and LoA of (+ 763 to - 716; 95% CI) ml. The best agreement of the method was obtained by comparison of corrected EELVCO2 with functional EELVCT with a r2 of 0.59; Bias - 2.75 (+ 755 to - 761; 95% CI) ml. We did not observe major differences in the performance of the method between ARDS (most of them COVID related) and non-ARDS patients. CONCLUSION: In this first validation in critically ill patients, the capnodynamic method provided good estimates of both total and functional EELV. Bias improved after correcting EELVCO2 for extra-alveolar CO2 content when compared with CT estimated volume. If confirmed in further validations EELVCO2 may become an attractive monitoring option for continuously monitor EELV in critically ill mechanically ventilated patients. TRIAL REGISTRATION: clinicaltrials.gov (NCT04045262).

Utilization of abdominal radiography in the emergency department: Appropriateness, interpretation, radiation protection and costs.

INTRODUCTION: The use of abdominal radiography (AXR) apparently continues to be widespread despite its limited indications, the potential radiation and unnecessary costs associated. In addition, the interpretation and its report seem variable and not always performed by a radiologist. Our objective is to analyze the use, adequacy and usefulness of AXR in the emergency of a tertiary referral hospital. MATERIAL AND METHODS: We retrospectively reviewed all the AXR performed in January 2020 in the emergency of our centre, as well as the patient's demographics and medical records, technical quality of the radiographs, indications according to the SERAM (Spanish Society of Radiology) Appropriateness Guidelines, presence of a formal radiology report, and impact on the clinical management of the patient. Of all non-appropriated AXR we calculated the radiation received by the patients and its extra costs. RESULTS: In January 2020, 429 AXR (9.1% of all radiographies) were performed in the emergency of our centre. The most frequent indication was abdominal pain (40%, n = 176), followed by low back pain (21.4%, n = 92). 12.4% of AXR requested did not include any clinical information. Most of the AXR (79.6%) had sufficient technical quality. 61.3% (n = 263) of the AXR performed were not indicated, assuming an average unjustified radiation dose per patient of 0.50 ±â€¯0.33 mSv, and a total additional cost of 6575;. Only 6% of the inadequate AXRs led to a change in the clinical management of the patient, compared to 29% of the adequate AXR (p < 0.001). Only 3% of the AXR had a formal radiology report. CONCLUSIONS: AXR is still common in the emergency setting, although most of them might be inadequate according to the SERAM Appropriateness Guidelines. Its use should be optimized to avoid unnecessary radiation and costs. Radiologists must have a more active participation in the management of AXR.