Smith Jean

Regional distribution of acoustic-based lung vibration as a function of mechanical ventilation mode

IntroductionThere are several ventilator modes that are used for maintenance mechanical ventilation but no conclusive evidence that one mode of ventilation is better than another. Vibration response imaging is a novel bedside imaging technique that displays vibration energy of lung sounds generated during the respiratory cycle as a real-time structural and functional image of the respiration process. In this study, we objectively evaluated the differences in regional lung vibration during different modes of mechanical ventilation by means of this new technology.MethodsVibration response imaging was performed on 38 patients on assist volume control, assist pressure control, and pressure support modes of mechanical ventilation with constant tidal volumes. Images and vibration intensities of three lung regions at maximal inspiration were analyzed.ResultsThere was a significant increase in overall geographical area (p < 0.001) and vibration intensity (p < 0.02) in pressure control and pressure support (greatest in pressure support), compared to volume control, when each patient served as his or her own control while targeting the same tidal volume in each mode. This increase in geographical area and vibration intensity occurred primarily in the lower lung regions. The relative percentage increases were 28.5% from volume control to pressure support and 18.8% from volume control to pressure control (p < 0.05). Concomitantly, the areas of the image in the middle lung regions decreased by 3.6% from volume control to pressure support and by 3.7% from volume control to pressure control (p < 0.05). In addition, analysis of regional vibration intensity showed a 35.5% relative percentage increase in the lower region with pressure support versus volume control (p < 0.05).ConclusionPressure support and (to a lesser extent) pressure control modes cause a shift of vibration toward lower lung regions compared to volume control when tidal volumes are held constant. Better patient synchronization with the ventilator, greater downward movement of the diaphragm, and decelerating flow waveform are potential physiologic explanations for the redistribution of vibration energy to lower lung regions in pressure-targeted modes of mechanical ventilation.

Lung Sound Analysis in the Diagnosis of Obstructive Airway Disease

Background: Dyspnea is prevalent and has a broad differential diagnosis. Difficulty in determining the correct etiology can delay proper treatment. Non-invasively obtained acoustic signals may offer benefit in identifying patients with dyspnea due to obstructive airway disease (OAD). Objectives: The aim of this pilot study was to determine whether patients with acute dyspnea due to OAD had distinguishing features when studied with a computerized acoustic-based imaging technique. Methods: Respiratory sounds from patients with dyspnea due to OAD (n = 32) and those with dyspnea not due to OAD (n = 39) were studied and compared with normal controls (n = 16). Results: In patients without OAD and in controls, the ratios of peak inspiratory to peak expiratory vibration energy values (peak I/E vibration ratio) were remarkably similar, 6.3 ± 5.1 and 5.6 ± 4, respectively. For the OAD patients, the peak I/E vibration ratio was significantly lower at 1.3 ± 0.04 (p < 0.01). In the patients without OAD and the controls, the ratios of inspiratory time to expiratory time (I/E time ratio) were again similar, 1.0 ± 0.1 and 0.99 ± 0.11, respectively. For the OAD patients, the I/E time ratio was significantly lower at 0.72 ± 0.19 (p < 0.01). Conclusions: This modality was useful in identifying patients whose dyspnea was due to OAD. The ability to objectively and non-invasively measure these differences may prove clinically useful in distinguishing the operant physiology in patients presenting with acute dyspnea.

Respiratory sound energy and its distribution patterns following clinical improvement of congestive heart failure: a pilot study

BackgroundAlthough congestive heart failure (CHF) patients typically present with abnormal auscultatory findings on lung examination, respiratory sounds are not normally subjected to additional analysis. The aim of this pilot study was to examine respiratory sound patterns of CHF patients using acoustic-based imaging technology. Lung vibration energy was examined during acute exacerbation and after clinical improvement.MethodsRespiratory sounds throughout the respiratory cycle were captured using an acoustic-based imaging technique. Twenty-three consecutive CHF patients were imaged at the time of presentation to the emergency department and after clinical improvement. Digital images were created (a larger image represents more homogeneously distributed vibration energy of respiratory sound). Geographical area of the images and respiratory sound patterns were quantitatively analyzed. Data from the CHF patients were also compared to healthy volunteers.ResultsThe median (interquartile range) geographical areas of the vibration energy image of acute CHF patients without and with radiographically evident pulmonary edema were 66.9 (9.0) and 64.1(9.0) kilo-pixels, respectively (p < 0.05). After clinical improvement, the geographical area of the vibration energy image of CHF patients without and with radiographically evident pulmonary edema were increased by 18 ± 15% (p < 0.05) and 25 ± 16% (p < 0.05), respectively.ConclusionsWith clinical improvement of acute CHF exacerbations, there was more homogenous distribution of lung vibration energy, as demonstrated by the increased geographical area of the vibration energy image.

Image-based monitoring of one-lung ventilation.

Background and objectives: With the increasing demand for one‐lung ventilation in both thoracic surgery and other procedures, identifying the correct placement becomes increasingly important. Currently, endobronchial intubation is suspected based on a combination of auscultation and physiological findings. We investigated the ability of the visual display of airflow‐induced vibrations to detect single‐lung ventilation with a double‐lumen endotracheal tube. Methods: Double‐lumen tubes were placed prior to surgery. Tracheal and endobronchial lumens were alternately clamped to produce unilateral lung ventilation of right and left lung. Vibration response imaging, which detects vibrations transmitted to the surface of the thorax, was performed during both right‐ and left‐lung ventilation. Geographical area of vibration response image as well as amount and distribution of lung sounds were assessed. Results: During single‐lung ventilation, the image and video obtained from the vibration response imaging identifies the ventilated lung with a larger and darker image on the ventilated side. During single‐lung ventilation, 87.2 ± 5.7% of the measured vibrations was detected over the ventilated lung and 12.8 ± 5.7% over the non‐ventilated lung (P < 0.0001). It was also noted that during single‐lung ventilation, the vibration distribution in the non‐ventilated lung had a majority of vibration detected by the medial sensors closest to the midline (P < 0.05) as opposed to the midclavicular sensors when the lung is ventilated. Conclusions: During single‐lung ventilation, vibration response imaging clearly showed increased vibration in the lung that is being ventilated. Distribution of residual vibration differed in the non‐ventilated lung in a manner that suggests transmission of vibrations across the mediastinum from the ventilated lung. The lung image and video obtained from vibration response imaging may provide useful and immediate information to help one‐lung ventilation assessment.

Asynchrony Between Left and Right Lungs in Acute Asthma

Background: Asthma is a disease of air flow obstruction. Transmitted sounds can be analyzed in detail and may shed light upon the physiology of asthma and how it changes over time. The goals of this study were to use a computerized analytic acoustic tool to evaluate respiratory sound patterns in asthmatic patients during acute attacks and after clinical improvement and to compare asthmatic profiles with those of normal individuals. Methods: Respiratory sound analysis throughout the respiratory cycle was performed on 22 symptomatic asthma patients at the time of presentation to the emergency department (ED) and after clinical improvement. Fifteen healthy volunteers were analyzed as a control group. Vibrations patterns were plotted. Right and left lungs were analyzed separately. Results: Asthmatic attacks were found to be correlated with asynchrony between lungs. In normal subjects, the inspiratory and expiratory vibration energy peaks (VEPs) occurred almost simultaneously in both lungs; the time interval between right and left expiratory VEPs was 0.006 ± 0.012 seconds. In symptomatic asthmatic patients on admission, the time interval between right and left expiratory VEPs was 0.14 ± 0.09 seconds and after clinical improvement the interval decreased to 0.04 ± 0.04 seconds. Compared to healthy volunteers, asynchrony between two lungs was increased in asthmatics (p < 0.05). The asynchrony was significantly reduced after clinical improvement (p < 0.05). Conclusions: Respiratory sound analysis demonstrated significant asynchrony between right and left lungs in asthma exacerbations, a finding which, to our knowledge, has never been reported to date. The asynchrony is significantly reduced with clinical improvement following treatment.

Case report: vibration response imaging findings following inadvertent esophageal intubation.

Purpose: We describe the effect that inadvertent esophageal intubation has on the images and on the vibration distribution of vibration response imaging (VRI).Clinical features: Vibration response imaging (VRI) is a novel, non-invasive, computer-based technology that measures vibration energy of lung sounds during respiration and displays regional intensity, in both visual and graphic format. Vibration response images, obtained prior to tracheal intubation (spontaneous breathing) and during endotracheal ventilation using a controlled mode, resulted in evenly distributed vibrations throughout the patient’s lungs. During inadvertent esophageal ventilation, however, the majority of vibrations were detected in the upper regions of the image, compared to those of the lower (60%vs 8%, respectively). During spontaneous breathing and endotracheal ventilation, the midclavicular column of sensors, located over the centre of each lung, detected more vibrations compared to either the medial or the axillary column of sensors. During inadvertent esophageal ventilation, more vibrations were detected by the medial column of sensors (nearest to the midline/esophagus); and fewer were detected by the sensors that were positioned more laterally.Conclusion: This report illustrates the potential for a visual image of distribution of lung vibration energy to differentiate endotracheal intubation from inadvertent esophageal intubation.RésuméObjectif: Nous décrivons l’effet qu’une intubation oesophagienne involontaire a eu sur les images et sur la distribution des vibrations de l’imagerie par réponse vibratoire (VRI — vibration response imaging).Éléments cliniques: L’imagerie par réponse vibratoire (VRI) est une nouvelle technologie informatique non invasive qui mesure l’énergie de vibration des sons pulmonaires pendant la respiration et affiche l’intensité régionale en format visuel et graphique. Les images de réponse vibratoire obtenues avant l’intubation trachéale (respiration spontanée) et pendant la ventilation endotrachéale à l’aide d’un mode contrôlé ont eu pour résultat des vibrations uniformément distribuées dans l’ensemble des poumons du patient. Cependant, pendant la ventilation oesophagienne involontaire, la majorité des vibrations ont été détectées dans la région supérieure de l’image, par rapport à celle de la région inférieure (60 % vs 8 %, respectivement). Durant la respiration spontanée et la respiration endotrachéale, la colonne de détecteurs médio-claviculaires situés au dessus du centre de chaque poumon a détecté davantage de vibrations que les colonnes de détecteurs médianes et axillaires. Pendant une ventilation oesophagienne involontaire, davantage de vibrations ont été détectées par la colonne médiane de détecteurs (la plus proche de la ligne médiane / œsophage) ; moins de vibrations ont été détectées par ceux situés davantage sur les côtés.Conclusion: Ce compte-rendu démontre le potentiel qu’une image visuelle de la distribution de l’énergie de vibration pulmonaire pourrait avoir pour distinguer l’intubation endotrachéale d’une intubation oesophagienne involontaire.

Assessment of Asymmetric Lung Disease in Intensive Care Unit Patients Using Vibration Response Imaging

BACKGROUND: Vibration response imaging (VRI) is a computer-based technology that creates a visual dynamic two-dimensional image of distribution of vibration within the lung during the respiratory process. The acoustic signals, recorded from 36 posteriorly positioned surface skin sensors, are transferred to a hardware board where several stages of filtering are applied to select a specific frequency band. The filtered output signal frequencies are presented as a gray-scale coded dynamic image, consisting of a series of 0.17 s frames, and as a table featuring the percentage contribution of each lung to the total vibration signal. METHODS: We describe the VRI technology in detail and examine images obtained from consecutive intensive care unit (ICU) patients with one diseased lung on chest radiograph. ICU patients with normal chest radiographs are presented as controls. Analysis of the image was performed by comparing the weighted pixel count analysis from both lungs. In this method, the pixels in the image were assigned values based on their grayscale color with the darker pixels assigned higher values. RESULTS: In patients with normal chest radiographs, the right and left lungs developed similarly in dynamic VRI images, and the percent lung vibrations from both sides were comparable (53% ± 12% and 47% ± 12%, respectively). In ICU patients with asymmetric lung disease, however, the percent lung vibrations from the diseased and nondiseased lungs were 27% ± 23% and 73% ± 23%, respectively (P < 0.001). In patients with asymmetric lung disease (one lung has moderate to severe disease and the other appears normal or close to normal as per chest radiograph), the diseased lung usually appeared in VRI as irregular, smaller, and lighter in color (reduced vibration signal) when compared to the nonaffected lung. The weighted pixel count from diseased and nondiseased lungs were 33% ± 21% and 67% ± 21%, respectively (P < 0.003). CONCLUSION: The VRI technology may provide a radiation-free method for identifying and tracking of asymmetric lung parenchymal processes.

Tyrosine Sulfation of Arylsulfatase A and Its Peptide

Purified human liver arylsulfatase A (ASA) as well as an ASA peptide (residues 28-39) were sulfated by tyrosyl protein sulfotransferase in vitro. The media, but not the cell lysate, of normal human fibroblasts contained a tyrosine sulfated protein (pI = 4.5-5.5). This protein was not present in either media or cell lysate of human fibroblasts lacking ASA protein. These results suggest that tyrosine sulfation facilitates secretion of ASA and that this may have pathophysiological consequences.