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.

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.

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.

The "lung point": an ultrasound sign specific to pneumothorax

OBJECTIVE

We studied an ultrasound sign, the fleeting appearance of a lung pattern (lung sliding or pathologic comet-tail artifacts) replacing a pneumothorax pattern (absent lung sliding plus exclusive horizontal lines) in a particular location of the chest wall. This sign was called the "lung point".

DESIGN

Prospective study.

SETTING

The medical ICU of a university-affiliated teaching hospital.

PATIENTS

The "lung point" was sought in 66 consecutive cases of proven pneumothorax analyzable using ultrasound--including 8 radio-occult cases diagnosed by means of CT and in 233 consecutive hemithoraces studied by CT and free of pneumothorax-- including 17 cases where pneumothorax was suspected.

RESULTS

The "lung point" was observed in 44 of 66 cases of pneumothorax (including 6 of 8 radio-occult cases) and in no case in the control group. The location of this sign roughly correlated with the radiological size of the pneumothorax. The "lung point" therefore had an overall sensitivity of 66 % (75 % in the case of radio-occult pneumothorax alone) and a specificity of 100%.

CONCLUSION

The presence of a "lung point" allows positive diagnosis of pneumothorax at the bedside using ultrasound.

Feasibility and safety of ultrasound-aided thoracentesis in mechanically ventilated patients

OBJECTIVE

Thoracentesis in a ventilated patient is rarely performed because of the risk of pneumothorax. We have evaluated the safety of this procedure when aided by ultrasound.

DESIGN

Prospective study.

SETTING

Medical intensive care unit, university-affiliated hospital.

PATIENTS

45 procedures were performed in 40 consecutive patients with ultrasound signs of pleural effusion, all mechanically ventilated.

INTERVENTIONS

Pleural effusion was defined on ultrasound as a collection of fluid between parietal and visceral pleura leading to variations in interpleural distance during breathing. When the interpleural distance was >/= 15 mm and visible over three intercostal spaces, a needle (16 or 21 G) was inserted after ultrasound localization in a patient in either dorsal or lateral decubitus.

RESULTS

No complication occurred in the 45 thoracenteses. Fluid was obtained in 44 of 45 procedures, thus confirming the diagnosis of pleural effusion. The procedure was immediate (less than 10 s) in 40 of 45 cases. It was easy (i. e., keeping the patient supine) in 22 of 45 procedures. In 44 cases where fluid was obtained, only 27 bedside radiographs revealed signs of effusion, whereas 17 showed absence of a visible effusion. Ultrasound thus appeared more efficient than bedside X-ray in detecting pleural effusion.

CONCLUSIONS

If basic rules are followed, ultrasound localization makes thoracentesis a safe, easy and simple procedure in patients on mechanical ventilation.

The comet-tail artifact: an ultrasound sign ruling out pneumothorax

OBJECTIVE

Ultrasound artifacts arising from the lung-wall interface are either vertical (comet-tail artifacts) or horizontal. The significance of these artifacts for the diagnosis of pneumothorax was assessed.

DESIGN

Prospective clinical study.

SETTING

The medical ICU of a university-affiliated teaching hospital.

PATIENTS

We compared 41 complete pneumothoraces with 146 hemithoraces in 73 critically ill patients in which computed tomography showed absence of pneumothorax.

MEASUREMENTS

The anterior chest wall was investigated in supine patients using a portable device. The test was defined as positive for complete pneumothorax when only horizontal artifacts were visible, and negative when artifacts arising from the pleural line and spreading up to the edge of the screen (referred to as "comet-tail artifacts") were present.

RESULTS

The feasibility was 98%. Ultrasound showed exclusive horizontal artifacts in all 41 analyzable cases of complete pneumothorax. In the pneumothorax-free group, "comet-tail artifacts" were present in 87 cases and exclusive horizontal artifacts in 56. Ultrasound as well as computed tomography showed anterior consolidation or anterior pleural effusion in three cases. Horizontal artifacts had a sensitivity and a negative predictive value of 100% and a specificity of 60% for the diagnosis of pneumothorax. Horizontal artifacts and absent lung sliding, when combined, had a sensitivity and a negative predictive value of 100% and a specificity of 96.5%.

CONCLUSIONS

Ultrasound detection of the "comet-tail artifact" at the anterior chest wall allows complete pneumothorax to be discounted.

A lung ultrasound sign allowing bedside distinction between pulmonary edema and COPD: the comet-tail artifact

OBJECTIVE

Acute cardiogenic pulmonary edema and exacerbation of chronic obstructive pulmonary disease (COPD) can have a similar clinical presentation, and X-ray examination does not always solve the problem of differential diagnosis. The potential of lung ultrasound to distinguish these two disorders was assessed.

DESIGN

Prospective clinical study.

SETTING

The medical ICU of a university-affiliated teaching hospital.

PATIENTS

We investigated 66 consecutive dyspneic patients: 40 with pulmonary edema and 26 with COPD. In addition, 80 patients without clinical and radiologic respiratory disorders were studied.

MEASUREMENTS

The sign studied was the comet-tail artifact arising from the lung wall interface, multiple and bilaterally disseminated to the anterolateral chest wall.

RESULTS

The feasibility was 100%. The length of the examination was always under 1 min. The described pattern was present in all 40 patients with pulmonary edema. It was absent in 24 of 26 cases of COPD as well as in 79 of 80 patients without respiratory disorders. The sign studied had a sensitivity of 100% and a specificity of 92% in the diagnosis of pulmonary edema when compared with COPD.

CONCLUSIONS

With a described pattern present in 100% of the cases of pulmonary edema and absent in 92% of the cases of COPD and in 98.75% of the normal lungs, ultrasound detection of the comet-tail artifact arising from the lung-wall interface may help distinguish pulmonary edema from COPD.

The "sinusogram", a real-time ultrasound sign of maxillary sinusitis

OBJECTIVE

To describe a real-time ultrasound sign, the visualization of the cavity and the walls of the maxillary sinus ("sinusogram"), and to assess its correlation with total opacity of the sinus.

DESIGN

Prospective clinical study.

SETTING

The medical ICU of a university-affiliated hospital.

PATIENTS

The significance of this sign was assessed in 50 critically ill supine patients (100 maxillary sinuses) who underwent paranasal CT.

MEASUREMENTS AND RESULTS

The "sinusogram" was defined as complete when the internal, external and posterior walls were frankly visible, and incomplete in the case of partial visualization of the walls. The "sinusogram" was present in all 21 cases of total opacity, in 2 of 12 cases of air-fluid level, in 8 of 14 cases of mucosal thickening, in one giant polyp, and in none of 52 normal sinuses. The "sinusogram" was complete in 10 of 21 cases of total opacity. It was incomplete in 11 of 21 cases of total opacity and in all 8 cases of mucosal thickening with positive ultrasound. For the diagnosis of radiologic maxillary sinusitis (total opacity or air-fluid level within the maxillary cavity), the sensitivity was 67 % and the specificity 87 %. For the diagnosis of total opacity (versus absence of total opacity, which includes fluid level), the sensitivity was 100% and the specificity 86%. When the "sinusogram" was complete, the specificity was 100% for the diagnosis of total opacity.

CONCLUSIONS

Ultrasound may be proposed in first-line diagnosis of radiologic maxillary sinusitis.