Right Ventricular "Bubble Time" to Identify Patients With Right Ventricular Dysfunction.

STUDY OBJECTIVE: We propose a novel method of evaluating right ventricular (RV) dysfunction in the emergency department (ED) using RV "bubble time"-the duration of time bubbles from a saline solution flush are visualized in the RV on echocardiography. The objective was to identify the optimal cutoff value for RV bubble time that differentiates patients with RV dysfunction and report on its diagnostic test characteristics. METHODS: This prospective diagnostic accuracy study enrolled a convenience sample of hemodynamically stable patients in the ED. A sonographer administered a 10-mL saline solution flush into the patient's intravenous catheter, performed a bedside echocardiogram, and measured RV bubble time. Subsequently, the patient underwent a comprehensive cardiologist-interpreted echocardiogram within 36 hours, which served as the gold standard. Patients with RV strain or enlargement of the latter found on an echocardiogram were considered to have RV dysfunction. Bubble time was evaluated by a second provider, blinded to the initial results, who reviewed the ultrasound clips. The primary outcome measure was the optimal cutoff value of RV bubble time that identifies patients with and without RV dysfunction. RESULTS: Of 196 patients, median age was 67 year, and half were women, with 69 (35.2%) having RV dysfunction. Median RV bubble time among patients with RV dysfunction was 62 seconds (interquartile range [IQR]: 52, 93) compared with 21 seconds (IQR: 12, 32) among patients without (P<.0001). The optimal cutoff value of RV bubble time for identifying patients with RV dysfunction was 40 or more seconds, with a sensitivity of 0.97 (95% CI 0.93 to 1.00) and specificity of 0.87 (95% CI 0.82 to 0.93). CONCLUSION: In patients in the ED, an RV bubble time of 40 or more seconds had high sensitivity in identifying patients with RV dysfunction, whereas an RV bubble time of less than 40 seconds had good specificity in identifying patients without RV dysfunction. These findings warrant further investigation in undifferentiated patient populations and by emergency physicians without advanced ultrasound training.

Using Ultrasound to Determine Optimal Location for Needle Decompression of Tension Pneumothorax: A Pilot Study.

BACKGROUND: Chest injury can result in life-threatening complications like tension pneumothorax, in which rapid deterioration can occur without decompression. Traditionally, the second intercostal space (ICS) along the mid-clavicular line is taught as the site for decompression. However, this has been questioned due to high rates of treatment failure. The fifth ICS on the mid-axillary line (MAL) is hypothesized to have a shorter distance from skin to pleura based on recent studies. OBJECTIVE: The purpose of this study was to use point-of-care ultrasound (POCUS) to compare chest wall thickness at these two locations. The primary objective was to evaluate the distance from skin to pleura line at the second ICS along the mid-clavicular line and the fifth ICS along the MAL. Secondarily, we aimed to evaluate inter-rater reliability of the two assessments. METHODS: This was a single-center, observational, pilot study. POCUS was performed using a linear transducer. Measurements of skin to pleura line were obtained at the right second ICS and fifth ICS. These measurements were then repeated by a blinded second ultrasonographer. Intraclass correlations (ICCs) for each measurement site were calculated to determine the inter-rater reliability. RESULTS: Ninety-three percent of volunteers had a smaller chest wall distance at the fifth ICS-MAL. The median distance at the second and fifth ICS was 2.28 cm and 1.80 cm. The ICC for second ICS was 0.75 (95% CI 0.54-0.87), and 0.90 for the fifth ICS (95% CI 0.81-0.95), both indicating good reliability. CONCLUSIONS: The data support that patients have a smaller chest wall distance at the fifth ICS vs. the second ICS. We support performing needle decompression at the fifth ICS and believe POCUS can be used to determine the optimal location for decompression.

Femoral artery Doppler ultrasound is more accurate than manual palpation for pulse detection in cardiac arrest.

OBJECTIVES: Our primary objective was to assess the accuracy of Doppler ultrasound versus manual palpation in detecting any pulse with an arterial line waveform in cardiac arrest. Secondarily, we sought to determine whether peak systolic velocity (PSV) on Doppler ultrasound could detect a pulse with a systolic blood pressure (SBP) ≥ 60 mmHg. METHODS: We conducted a prospective, cross-sectional, diagnostic accuracy study on a convenience sample of adult, Emergency Department (ED) cardiac arrest patients. All patients had a femoral arterial line. During a pulse check, manual pulse detection, PSV and Doppler ultrasound clips, and SBP were recorded. A receiver operator characteristic curve analysis was performed to determine the optimal cut-off of PSV associated with a SBP ≥ 60 mmHg. Accuracy of manual palpation and Doppler ultrasound for detection of any pulse and SBP ≥ 60 mmHg were compared with McNemar's test. RESULTS: 54 patients and 213 pulse checks were analysed. Doppler ultrasound demonstrated higher accuracy than manual palpation (95.3% vs. 54.0%; p < 0.001) for detection of any pulse. Correlation between PSV and SBP was strong (Spearman correlation coefficient = 0.89; p < 0.001). The optimal cut-off value of PSV associated with a SBP ≥ 60 mmHg was 20 cm/s (area under the curve = 0.975). To detect SBP ≥ 60 mmHg, accuracy of a PSV ≥ 20 cm/s was higher than manual palpation (91.4% vs. 66.2%; p < 0.001). CONCLUSIONS: Among ED cardiac arrest patients, femoral artery Doppler ultrasound was more accurate than manual palpation for detecting any pulse. When using a PSV ≥ 20 cm/s, Doppler ultrasound was also more accurate for detecting a SBP ≥ 60 mmHg.

Analysis of Pseudomonas aeruginosa biofilm membrane vesicles supports multiple mechanisms of biogenesis.

Outer Membrane Vesicles (OMVs) are ubiquitous in bacterial environments and enable interactions within and between species. OMVs are observed in lab-grown and environmental biofilms, but our understanding of their function comes primarily from planktonic studies. Planktonic OMVs assist in toxin delivery, cell-cell communication, horizontal gene transfer, small RNA trafficking, and immune system evasion. Previous studies reported differences in size and proteomic cargo between planktonic and agar plate biofilm OMVs, suggesting possible differences in function between OMV types. In Pseudomonas aeruginosa interstitial biofilms, extracellular vesicles were reported to arise through cell lysis, in contrast to planktonic OMV biogenesis that involves the Pseudomonas Quinolone Signal (PQS) without appreciable autolysis. Differences in biogenesis mechanism could provide a rationale for observed differences in OMV characteristics between systems. Using nanoparticle tracking, we found that P. aeruginosa PAO1 planktonic and biofilm OMVs had similar characteristics. However, P. aeruginosa PA14 OMVs were smaller, with planktonic OMVs also being smaller than their biofilm counterparts. Large differences in Staphylococcus killing ability were measured between OMVs from different strains, and a smaller within-strain difference was recorded between PA14 planktonic and biofilm OMVs. Across all conditions, the predatory ability of OMVs negatively correlated with their size. To address biogenesis mechanism, we analyzed vesicles from wild type and pqsA mutant biofilms. This showed that PQS is required for physiological-scale production of biofilm OMVs, and time-course analysis confirmed that PQS production precedes OMV production as it does in planktonic cultures. However, a small sub-population of vesicles was detected in pqsA mutant biofilms whose size distribution more resembled sonicated cell debris than wild type OMVs. These results support the idea that, while a small and unique population of vesicles in P. aeruginosa biofilms may result from cell lysis, the PQS-induced mechanism is required to generate the majority of OMVs produced by wild type communities.