Stable Small Animal Ventilation for Dynamic Lung Imaging to Support Computational Fluid Dynamics Models

Pulmonary computational fluid dynamics models require that three-dimensional images be acquired over multiple points in the dynamic breathing cycle without breath holds or changes in ventilatory mechanics. With small animals, these requirements can result in long imaging times (∼90 minutes), over which lung mechanics, such as compliance, may gradually change if not carefully monitored and controlled. These changes, caused by derecruitment of parenchymal tissue, are manifested as an upward drift in peak inspiratory pressure (PIP) or by changes in the pressure waveform and/or lung volume over the course of the experiment. We demonstrate highly repeatable mechanical ventilation in anesthetized rats over a long duration for dynamic lung x-ray computed tomography (CT) imaging. We describe significant updates to a basic commercial ventilator that was acquired for these experiments. Key to achieving consistent results was the implementation of periodic deep breaths, or sighs, of extended duration to maintain lung recruitment. In addition, continuous monitoring of breath-to-breath pressure and volume waveforms and long-term trends in PIP and flow provide diagnostics of changes in breathing mechanics

An Examination of Trinidadian Officer\u27s Behavioral Beliefs and Intent to Participate in an International Extension Experience

Participation in an international extension experience empowers extension professionals to meet the needs of diverse clientele in an increasingly global world. A survey of governmental extension workers in Trinidad was conducted to understand how their behavioral beliefs about an international extension experience influenced their intention to participate in such an experience. Behavioral beliefs can be positively or negatively modified based on an individual’s perceptions of the components (time, location, activities) of a specific international extension experience, so manipulating the components should cause corresponding changes in behavioral beliefs and ultimately intent to participate. This study found positive behavioral beliefs about international extension experience participation are held by Trinidadian extension officers. They are willing to travel to a wide variety of locations and are most interested in acquiring hands-on experience and working one-on-one with another extension professional. The most desirable locations and activities should be integrated into international extension experiences in order to positively influence behavioral beliefs, and thereby intent to participate. Future research is needed to more closely examine the impact of participation on extension officers in Trinidad

The Comprehensive Post-Acute Stroke Services (COMPASS) study: design and methods for a cluster-randomized pragmatic trial

Background: Patients discharged home after stroke face significant challenges managing residual neurological deficits, secondary prevention, and pre-existing chronic conditions. Post-discharge care is often fragmented leading to increased healthcare costs, readmissions, and sub-optimal utilization of rehabilitation and community services. The COMprehensive Post-Acute Stroke Services (COMPASS) Study is an ongoing cluster-randomized pragmatic trial to assess the effectiveness of a comprehensive, evidence-based, post-acute care model on patient-centered outcomes. Methods: Forty-one hospitals in North Carolina were randomized (as 40 units) to either implement the COMPASS care model or continue their usual care. The recruitment goal is 6000 patients (3000 per arm). Hospital staff ascertain and enroll patients discharged home with a clinical diagnosis of stroke or transient ischemic attack. Patients discharged from intervention hospitals receive 2-day telephone follow-up; a comprehensive clinic visit within 2 weeks that includes a neurological evaluation, assessments of social and functional determinants of health, and an individualized COMPASS Care PlanTM integrated with a community-specific resource database; and additional follow-up calls at 30 and 60 days post-stroke discharge. This model is consistent with the Centers for Medicare and Medicaid Services transitional care management services provided by physicians or advanced practice providers with support from a nurse to conduct patient assessments and coordinate follow-up services. Patients discharged from usual care hospitals represent the control group and receive the standard of care in place at that hospital. Patient-centered outcomes are collected from telephone surveys administered at 90 days. The primary endpoint is patient-reported functional status as measured by the Stroke Impact Scale 16. Secondary outcomes are: caregiver strain, all-cause readmissions, mortality, healthcare utilization, and medication adherence. The study engages patients, caregivers, and other stakeholders (including policymakers, advocacy groups, payers, and local community coalitions) to advise and support the design, implementation, and sustainability of the COMPASS care model. Discussion: Given the high societal and economic burden of stroke, identifying a care model to improve recovery, independence, and quality of life is critical for stroke survivors and their caregivers. The pragmatic trial design provides a real-world assessment of the COMPASS care model effectiveness and will facilitate rapid implementation into clinical practice if successful

Schematic diagram of the airflow paths of the ventilator (the box indicates the extent of the ventilator chassis).

<p>Two- or three-way solenoid valves control the airflow. “F” indicates the flow meter, or pneumotachograph, and “P” indicates the pressure transducer. A check valve, immediately upstream from the pneumotach, assures unidirectional flow. Vented air is passed through filters to remove isoflurane. The dashed lines indicate the flow path during sigh breaths, in which the low-pressure regulator is employed and the needle valve in the flow meter is bypassed to facilitate more rapid inflation.</p

Pressure and volume waveforms of a typical 4 sec sigh breath.

<p>The inhale duration is 2800 ms, and peak pressure is limited by the low-pressure regulator.</p

Three pressure waveforms and corresponding inspiratory flow volumes, taken from different points during an imaging experiment with a 306 g rat are shown.

<p>The “noise” at the tail end of the pressure traces is due to the beating heart. The strong similarity between waveforms demonstrates the consistency of lung mechanical properties over the course of the experiment.</p

Examples of transverse (top) and coronal (bottom) images of a 359g rat.

<p>The images were taken from four different points (out of 11 total) in the breathing cycle. Reconstructed resolution is 150 µm, isotropic.</p

The pressure waveform of a typical single breath with the trigger positions (grey bars) superimposed.

<p>The width of the bars represents the 16 ms duration of the x-ray exposure.</p

A sample segment of the long-term trend data of peak pressure and inhale volume.

<p>An arbitrary t = 0 starting point was chosen on the x-axis to illustrate the timing of the sigh-sigh interval. The red sections show the duration of the gate muting, when no imaging took place during the sigh and for five breaths following. The modulations on the pressure line are due to constructive/destructive interference with the heartbeat.</p