Lung ultrasound allows the diagnosis of weaning-induced pulmonary oedema.

RATIONALE: Detecting weaning-induced pulmonary oedema (WIPO) is important because its treatment might prompt extubation. For this purpose, lung ultrasound might be an attractive tool, since it demonstrates pulmonary oedema through the appearance of B-lines. OBJECTIVES: To test the ideal profile (increase in the number of B-lines) for diagnosing WIPO. METHODS: Before and at the end of 62 spontaneous breathing trials (SBT) performed in 42 patients, we prospectively assessed lung ultrasound on four anterior chest wall points. B-lines were counted before and at the end of SBT. We looked for the threshold of B-line increase (Delta-B-lines) that provided the best diagnostic accuracy, compared to the reference diagnosis of WIPO established by experts blinded to lung ultrasound. RESULTS: SBT failed in 33 cases. WIPO occurred in 17 cases and all failed. The best diagnostic accuracy was reached with a Delta-B-lines ≥ 6. Among WIPO, the number of B-lines increased by ≥ 6 in 15 cases (including 13 cases with an increase of ≥ 8 B-lines). Among the 16 cases with SBT failure but without WIPO, the Delta-B-lines was ≥ 6 in two cases. Among the 33 cases with SBT failure, this profile diagnosed WIPO with a sensitivity of 88% (64-98) and a specificity of 88% (62-98) [area under the receiver operating characteristic curve 0.91 (0.75-0.98)]. Among the 29 cases with SBT success, a Delta-B-lines ≥ 6 occurred in two cases. CONCLUSIONS: This study suggests that a Delta-B-lines ≥ 6 on four anterior points allows the diagnosis of WIPO with the best accuracy. This should be confirmed in larger populations.

A-lines and B-lines: lung ultrasound as a bedside tool for predicting pulmonary artery occlusion pressure in the critically ill.

BACKGROUND: The risk of pulmonary edema is the main limiting factor in fluid therapy in the critically ill. Interstitial edema is a subclinical step that precedes alveolar edema. This study assesses a bedside tool for detecting interstitial edema, lung ultrasound. The A-line is a horizontal artifact indicating a normal lung surface. The B-line is a kind of comet-tail artifact indicating subpleural interstitial edema. The relationship between anterior interstitial edema detected by lung ultrasound and the pulmonary artery occlusion pressure (PAOP) value was investigated. METHOD: We performed a prospective study in medicosurgical ICUs of university-affiliated teaching hospitals. We enrolled 102 consecutive mechanically ventilated patients who all underwent pulmonary artery catheterization. We defined A-predominance as a majority of anterior A-lines and B-predominance as a majority of anterior B-lines. These patterns were correlated with PAOP. RESULTS: For diagnosing PAOP

The dynamic air bronchogram. A lung ultrasound sign of alveolar consolidation ruling out atelectasis.

BACKGROUND: The objective of this study was to identify the relationship between a dynamic lung artifact, the dynamic air bronchogram, within alveolar consolidation and the diagnosis of pneumonia vs resorptive atelectasis. METHODS: This prospective study was undertaken within the medical ICU of a university-affiliated teaching hospital. The sample comprised 52 patients with proven pneumonia (pneumonia group) and 16 patients with proven resorptive atelectasis (atelectasis group). All patients had alveolar consolidation with air bronchograms on lung ultrasound, were mechanically ventilated, and received fibroscopy and bacteriological tests. The air bronchogram dynamic was analyzed within the ultrasound area of consolidation. RESULTS: The air bronchograms in the pneumonia group yielded the dynamic air bronchogram in 32 patients and a static air bronchogram in 20. In the atelectasis group, air bronchograms yielded a dynamic air bronchogram in 1 out of 16 patients. With regard to pneumonia vs resorptive atelectasis in patients with ultrasound-visible alveolar consolidation with air bronchograms, the dynamic air bronchogram had a specificity of 94% and a positive predictive value of 97%. The sensitivity was 61%, and the negative predictive value 43%. CONCLUSIONS: In patients with alveolar consolidation displaying air bronchograms on an ultrasound, the dynamic air bronchogram indicated pneumonia, distinguishing it from resorptive atelectasis. Static air bronchograms were seen in most resorptive atelectases and one third of cases of pneumonia. This finding increases the understanding of the pathophysiology of lung diseases within the clinical context and decreases the need for fibroscopy in practice.

Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol.

BACKGROUND: This study assesses the potential of lung ultrasonography to diagnose acute respiratory failure. METHODS: This observational study was conducted in university-affiliated teaching-hospital ICUs. We performed ultrasonography on consecutive patients admitted to the ICU with acute respiratory failure, comparing lung ultrasonography results on initial presentation with the final diagnosis by the ICU team. Uncertain diagnoses and rare causes (frequency<2%) were excluded. We included 260 dyspneic patients with a definite diagnosis. Three items were assessed: artifacts (horizontal A lines or vertical B lines indicating interstitial syndrome), lung sliding, and alveolar consolidation and/or pleural effusion. Combined with venous analysis, these items were grouped to assess ultrasound profiles. RESULTS: Predominant A lines plus lung sliding indicated asthma (n=34) or COPD (n=49) with 89% sensitivity and 97% specificity. Multiple anterior diffuse B lines with lung sliding indicated pulmonary edema (n=64) with 97% sensitivity and 95% specificity. A normal anterior profile plus deep venous thrombosis indicated pulmonary embolism (n=21) with 81% sensitivity and 99% specificity. Anterior absent lung sliding plus A lines plus lung point indicated pneumothorax (n=9) with 81% sensitivity and 100% specificity. Anterior alveolar consolidations, anterior diffuse B lines with abolished lung sliding, anterior asymmetric interstitial patterns, posterior consolidations or effusions without anterior diffuse B lines indicated pneumonia (n=83) with 89% sensitivity and 94% specificity. The use of these profiles would have provided correct diagnoses in 90.5% of cases. CONCLUSIONS: Lung ultrasound can help the clinician make a rapid diagnosis in patients with acute respiratory failure, thus meeting the priority objective of saving time.

Ultrasound diagnosis of occult pneumothorax.

OBJECTIVES: Pneumothorax can be missed by bedside radiography, and computed tomography is the current alternative. We asked whether lung ultrasound could be of any help in this situation. DESIGN: Retrospective study. SETTING: The medical intensive care unit of a university-affiliated teaching hospital. PATIENTS: All patients admitted to the intensive care unit are routinely scanned with whole-body ultrasound (including screening for pneumothorax) and chest radiography. The study population included 200 consecutive undifferentiated intensive care unit patients who received a chest computed tomography scan in addition to ultrasound and chest radiograph. Forty-seven consecutive cases of radioccult pneumothorax were compared with 310 consecutive hemithoraces free from pneumothorax in the intensive care unit. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Three signs were investigated at the anterolateral chest wall in supine patients: lung sliding, the A line sign, and the lung point. A total of 357 hemithoraces were analyzed in this study, 47 with occult pneumothorax and 310 controls. Four of the 47 cases of pneumothorax were excluded from the final analysis (parietal emphysema) as well as eight of the 310 controls (large dressings), leaving a final study population of 345 hemithoraces in 197 patients. Feasibility was 98%. Ultrasound scans in all 43 examinable patients with pneumothorax showed absent lung sliding, 41 of 43 patients had the A line sign, and 34 exhibited a lung point. Among 302 analyzable controls, 65 had absent lung sliding, 16 of them showed an A line sign, and none showed a lung point. For the diagnosis of occult pneumothorax, the abolition of lung sliding alone had a sensitivity of 100% and a specificity of 78%. Absent lung sliding plus the A line sign had a sensitivity of 95% and a specificity of 94%. The lung point had a sensitivity of 79% and a specificity of 100%. CONCLUSIONS: For the diagnosis of occult pneumothorax, ultrasound can decrease the need for computed tomography.

Ultrasound diagnosis of alveolar consolidation in the critically ill.

OBJECTIVE: Alveolar consolidation is a basic concern in critically ill patients. Radiography is not a precise tool, and referral to CT raises problems (transport, irradiation). The aim of this study was to assess the utility of ultrasound in the diagnosis of alveolar consolidation. DESIGN: Prospective clinical study. SETTING: The medical ICU of a university-affiliated teaching hospital. PATIENTS: A total of 65 cases of alveolar consolidation proven on CT were compared to 53 CT controls. MEASUREMENTS: Alveolar consolidation was defined as a tissue-like pattern visible at the chest wall, arising from the pleural line and devoid of centrifugal inspiratory dynamics. RESULTS: Feasibility was 99%. In 65 cases of alveolar consolidation, ultrasound was positive in 59 and negative in 6. In 52 analyzable controls, ultrasound was negative in 51 and positive in 1. Sensitivity of ultrasound was 90% and specificity 98%. A concordance test showed a Kappa coefficient of 0.89. Among 62 posterior locations on CT, ultrasound showed posterior consolidation patterns in 56 cases and was negative in 6. Ultrasound showed anterior involvement in all 3 cases of whole lung consolidation. CONCLUSIONS: Ultrasound provides a reliable non-invasive, bedside method for accurate detection and location of alveolar consolidation in critically ill patients.

The "lung pulse": an early ultrasound sign of complete atelectasis.

OBJECTIVE: Complete atelectasis can be immediately generated by selective intubation. A dynamic lung ultrasound sign can be described as the association of absent lung sliding with the perception of heart activity at the pleural line, a sign which was called "lung pulse." We examined whether this sign be used promptly to confirm complete atelectasis due to selective intubation. DESIGN AND SETTING: Prospective study in the medical intensive care unit of a university-affiliated teaching hospital. PATIENTS: Consecutive patients with no history of respiratory disorders and needing intubation were enrolled. Fifteen patients with selective intubation of the right lung were compared with 30 patients with nonselective intubation and 15 healthy volunteers. INTERVENTIONS: The "lung pulse" was sought at the left anterolateral chest wall in intubated patients. Healthy subjects were studied during breathing and apnea. RESULTS: A left "lung pulse" was immediately present in 14 of 15 patients with right selective intubation, and absent, with normal lung sliding, in all 30 correctly intubated patients and in all 15 healthy subjects during breathing. All healthy subjects exhibited a "lung pulse" in apnea. The "lung pulse" had a sensitivity of 93% and a specificity of 100% for the diagnosis of complete atelectasis following selective intubation in patients without previous respiratory disorders. CONCLUSIONS: The "lung pulse" is a sign of complete atelectasis which is observable immediately before radiological changes. Its absence which is correlated with the absence of selective intubation and of conserved lung inflation can eliminate the need for confirmation radiography.