Clinical validation of the Air-Test for the non-invasive detection of perioperative atelectasis in children.

BACKGROUND: The incidence of anesthesia-induced atelectasis in children is high and closely related to episodes of hypoxemia. The Air-Test is a simple maneuver to detect lung collapse. By a step-reduction in FiO2 to 0.21, a fall in pulse-oximetry hemoglobin saturation <97% unmasks the presence of collapse-related shunt in healthy lungs. The aim of this study was to validate the Air-Test as a diagnostic tool to detect perioperative atelectasis in children using lung ultrasound as a reference. METHODS: We first assessed the Air-Test in a retrospective cohort of 88 anesthetized children (Retrospective study) followed by a prospective study performed in 72 children (45 postconceptional weeks to 16 years old) using a similar protocol (Validation study). We analyzed the performance of the Air-Test to detect atelectasis by an operating characteristic curve (ROC) analysis, using lung ultrasound consolidation score as reference. RESULTS: Preoperative SpO2 was normal in both studies (retrospective 98.7±0.6%, validation 99.0±0.9%). The Air-Test, with a SpO2 cut point <97%, resulted positive in 67 patients in the retrospective study (SpO2 93.3±2.1%) and in 59 in the validation study (SpO2 94.9±1.8%); both P<0.0001. In the validation study, the Air-Test showed a sensitivity of 0.91 (95% CI 0.85-0.92), specificity of 1.00 (95% CI 0.84-1) and an area under the curve (AUC) of 0.98 (95% CI 0.97-1.00). AUC between both studies was similar (P=0.16). CONCLUSIONS: The Air-Test is a noninvasive and accurate method to detect atelectasis in healthy anesthetized children. It can be used as a screening tool to individualize patients that can benefit from lung recruitment maneuvers.

The agreement chart as an alternative to the receiver-operating characteristic curve for diagnostic tests.

OBJECTIVE: For diagnostic tests, the most common graphical representation of the information is the receiver-operating characteristic (ROC) curve. The "agreement chart" displays the information of two observers independently classifying the same n items into the same k categories, and can be used if one considers one of the "observers" as the diagnostic test and the other as the known outcome. This study compares the two charts and their ability to visually portray the various relevant summary statistics that assess how good a diagnostic test may be, such as sensitivity, specificity, predictive values, and likelihood ratios. STUDY DESIGN AND SETTING: The geometric relationships displayed in the charts are first described. The relationship between the two graphical representations and various summary statistics is illustrated using data from three common epidemiologically relevant health issues: coronary heart disease, screening for breast cancer, and screening for tuberculosis. RESULTS: Whereas the ROC curve incorporates information on sensitivity and specificity, the agreement chart includes information on the positive and negative predictive values of the diagnostic test. CONCLUSION: The agreement chart should be considered as an alternative visual representation to the ROC for diagnostic tests.

Utility of base deficit, lactic acid, microalbuminuria, and C-reactive protein in the early detection of complications in the immediate postoperative evolution.

OBJECTIVE: To determine the utility of biochemical parameters such as lactic acid (LA), C-reactive protein (CRP), microalbuminuria (MAU), and base deficit (BD) as early markers of complications in the immediate postoperative evolution of elective open gastrointestinal surgeries. DESIGN AND METHODS: Sixty-two patients subject to elective open gastrointestinal surgery were evaluated during a period of 22 months. RESULTS: From the initial 62 patients, 2 were excluded, 29 (48.3%) evolved without complications, and 31 (51.6%) with complications. It was observed that the most significant areas under the ROC curve corresponded to BD in the preoperative period, LA on the first day, and CRP from the second to the seventh day after surgery. MAU was not a discriminating parameter since it did not reach a significant area under the curve (AUC) at any time. CONCLUSIONS: The biochemical markers that best relate to the presence of complications are BD in the preoperative period, LA on the first day, and CRP from the second to the seventh day after surgery.