Quality Fade in Medical Device Manufacturing: Thinness of Airway Breathing Circuit Plastic.

Mechanical respirators typically use a plastic circuit apparatus to pass gases from the ventilator to the patient. Structural integrity of these circuits is crucial for maintaining oxygenation. Anesthesiologists, respiratory therapists, and other critical care professionals rely on the circuit to be free of defects. The American Society for Testing and Materials maintains standards of medical devices and had a standard (titled Standard Specification for Anesthesia Breathing Tubes) that included circuits. This standard, which was last updated in 2008, has since been withdrawn. Lack of a defined standard can invite quality fade-the phenomenon whereby manufacturers deliberately but surreptitiously reduce material quality to widen profit margins. With plastics, this is often in the form of thinner material. A minimum thickness delineated in the breathing circuit standard would help ensure product quality, maintain tolerance to mechanical insults, and avert leaks. Our impression is that over the recent years, the plastic in many of the commercially available breathing circuits has gotten thinner. We experienced a circuit leak in the middle of a laminectomy due to compromised plastic tubing in a location that evaded the safety circuit leak check that is performed prior to surgery. This compromised ventilation and oxygenation in the middle of a surgery in which the patient is positioned prone and hence with a minimally accessible airway; it could have resulted in anoxic brain injury or death. The incident led us to reflect on the degree of thinness of the circuit's plastic.

Contrived Breathing Circuit Connection for Emergency Percutaneous Transtracheal Ventilation by Needle Cricothyrotomy in the Field.

Surgical airway approaches are, at times, last resort options in difficult airway management. In Special Operations these interventions confront distorted anatomy from combat trauma, extreme conditions, and may be performed by non-medically trained personnel. Under these circumstances, needle cricothyroidotomy using a large bore intravenous catheter can be considered. A small syringe connected to the needle can confirm transtracheal placement through air aspiration before passing the angiocatheter over the needle. Button activated retracting needles should be avoided for this when possible. We recommend a 3-mL Luer-lock syringe because a small syringe is better suited for generating pressure and once the catheter is in the trachea, this same syringe can be connected to bag valve ventilation by replacing its plunger with a connector from a 6.5-, 7-, or 7.5-mm endotracheal tube. Adding these small and light high-yield items to the Tactical Combat Casualty Care medic inventory should be considered in future revisions.

The carotid sinus acts as a mechanotransducer of shear oscillation rather than a baroreceptor.

The carotid sinus is a dilated area at the base of the internal carotid artery of humans and is located immediately superior to the bifurcation of the internal and external carotid arteries. It is widely accepted, in the fields of medicine and physiology, to function as a baroreceptor in its central control role. This paper presents a hypothesis challenging this paradigm - that the carotid sinus functions by detecting oscillations at the vessel wall which result from shear stress due to vortical flow. This is contrary to conventional thinking which presumes that the carotid sinus responds to blood pressure or wall pressure. Our hypothesis is based on anatomy, physiology and physical properties of fluid which make the sinus the area of highest vorticity. Utilizing magnetic resonance angiograms of undiseased carotid vessels, we computed the oscillatory shear index (OSI) via a computational fluid dynamics simulation of flow. This region of highest OSI coincides with the area where the nerve to the carotid sinus lies within the vessel wall. Accordingly, the hypothesis is that the carotid sinus acts as a mechanotransducer of wall shear stress oscillation and not as a baroreceptor.