Reliability and limits of transport-ventilators to safely ventilate severe patients in special surge situations.

BACKGROUND: Intensive Care Units (ICU) have sometimes been overwhelmed by the surge of COVID-19 patients. Extending ICU capacity can be limited by the lack of air and oxygen pressure sources available. Transport ventilators requiring only one O2 source may be used in such places. OBJECTIVE: To evaluate the performances of four transport ventilators and an ICU ventilator in simulated severe respiratory conditions. MATERIALS AND METHODS: Two pneumatic transport ventilators, (Oxylog 3000, Draeger; Osiris 3, Air Liquide Medical Systems), two turbine transport ventilators (Elisee 350, ResMed; Monnal T60, Air Liquide Medical Systems) and an ICU ventilator (Engström Carestation-GE Healthcare) were evaluated on a Michigan test lung. We tested each ventilator with different set volumes (Vtset = 350, 450, 550 ml) and compliances (20 or 50 ml/cmH2O) and a resistance of 15 cmH2O/l/s based on values described in COVID-19 Acute Respiratory Distress Syndrome. Volume error (percentage of Vtset) with P0.1 of 4 cmH2O and trigger delay during assist-control ventilation simulating spontaneous breathing activity with P0.1 of 4 cmH2O and 8 cmH2O were measured. RESULTS: Grouping all conditions, the volume error was 2.9 ± 2.2% for Engström Carestation; 3.6 ± 3.9% for Osiris 3; 2.5 ± 2.1% for Oxylog 3000; 5.4 ± 2.7% for Monnal T60 and 8.8 ± 4.8% for Elisee 350. Grouping all conditions (P0.1 of 4 cmH2O and 8 cmH2O), trigger delay was 50 ± 11 ms, 71 ± 8 ms, 132 ± 22 ms, 60 ± 12 and 67 ± 6 ms for Engström Carestation, Osiris 3, Oxylog 3000, Monnal T60 and Elisee 350, respectively. CONCLUSIONS: In surge situations such as COVID-19 pandemic, transport ventilators may be used to accurately control delivered volumes in locations, where only oxygen pressure supply is available. Performances regarding triggering function are acceptable for three out of the four transport ventilators tested.

Comparison of Whole-Blood Metal Ion Levels Among Four Types of Large-Head, Metal-on-Metal Total Hip Arthroplasty Implants: A Concise Follow-up, at Five Years, of a Previous Report.

Few studies of total hip arthroplasty (THA) implants with a large-diameter femoral head and metal-on-metal design have directly compared the progression of metal ion levels over time and the relationship to complications. As we previously reported, 144 patients received one of four types of large-diameter-head, metal-on-metal THA designs (Durom, Birmingham, ASR XL, or Magnum implants). Cobalt, chromium, and titanium ion levels were measured over five years. We compared ion levels and clinical results over time. The Durom group showed the highest levels of cobalt (p ≤ 0.002) and titanium ions (p ≤ 0.03). Both the Durom and Birmingham groups demonstrated significant ongoing cobalt increases up to five years. Eight patients (seven with a Durom implant and one with a Birmingham implant) developed adverse local tissue reaction. Six Durom implants and one Birmingham implant required revision, with one pseudotumor under surveillance at the time of the most recent follow-up. We found that ion generation and related complications varied among designs. More concerning was that, for some designs, ion levels continued to increase. Coupling a cobalt-chromium adapter sleeve to an unmodified titanium femoral trunnion along with a large metal-on-metal bearing may explain the poor performances of two of the designs in the current study.

Comparison of whole-blood metal ion levels in four types of metal-on-metal large-diameter femoral head total hip arthroplasty: the potential influence of the adapter sleeve.

BACKGROUND: Metal-on-metal bearings, as used in total hip arthroplasty prostheses that have a large-diameter femoral head, were proposed as an option for treating young and active patients with degenerative hip disorders. Despite the theoretical improved performance of large metal articulations with regard to wear, metal ion levels produced by total hip arthroplasty prostheses in which a large-diameter femoral head is used have not been thoroughly evaluated. METHODS: From 173 eligible patients, 144 patients were allocated to undergo a unilateral total hip arthroplasty with use of metal-on-metal components and a large-diameter femoral head. The purpose of this study was to compare the amount of metal ion release (chromium, cobalt, and titanium) from four different types of prostheses from four different implant manufacturers (Biomet, DePuy, Smith & Nephew, and Zimmer). RESULTS: For cobalt ion levels, a significant difference was found between the different types of total hip arthroplasty prostheses with a large-diameter femoral head at three, six, twelve, and twenty-four months, but only in male patients or patients with a femoral head size of 50 mm or greater. The highest mean cobalt levels at all follow-up periods were observed with the Zimmer implant and the lowest with the Biomet implant. Titanium ion levels were highest in the Zimmer group at all follow-up periods, whereas no difference between groups was found for chromium. At the most recent follow-up, one hip was revised after the development of an adverse local tissue reaction. Of concern was the observation at the time of revision surgery of black metallic deposits inside the adapter sleeve and on the prosthetic femoral neck. CONCLUSIONS: This investigation revealed that metal ion release differs greatly between various total hip arthroplasty implants with a large-diameter femoral head. The sources of metal ion production are numerous, but it is hypothesized that wear and corrosion at the junction between the adapter sleeve and the femoral stem in some patients may be responsible for the elevated cobalt ion levels that were found in the Zimmer group. On the other hand, an adapter sleeve made of titanium, such as the one used with the Biomet large-diameter-head total hip arthroplasty, is an unlikely contributor to the release of cobalt ions. Current technology or design of some total hip arthroplasty systems that make use of a large-diameter femoral head may not yet allow the use of modular large heads with a metal-on-metal articulation, especially in young, active male patients whose activities generate high loads at the hip joint. Further research is needed to better understand the favorable design characteristics of modular junctions in metal-on-metal total hip arthroplasty implants that make use of large-diameter femoral heads.