Does a surgical helmet provide protection against aerosol transmitted disease?

Background and purpose - The COVID-19 pandemic caused by infection with SARS-CoV-2 has led to a global shortage of personal protective equipment (PPE). Various alternatives to ordinary PPE have been suggested to reduce transmission, which is primarily through droplets and aerosols. For many years orthopedic surgeons have been using surgical helmets as personal protection against blood-borne pathogens during arthroplasty surgery. We have investigated the possibility of using the Stryker Flyte surgical helmet as a respiratory protective device against airborne- and droplet-transmitted disease, since the helmet shares many features with powered air-purifying respirators. Materials and methods - Using an aerosol particle generator, we determined the filtration capacity of the Stryker Flyte helmet by placing particle counters measuring the concentrations of 0.3, 0.5, and 5 µm particles inside and outside of the helmet. Results - We found that the helmet has insufficient capacity for filtrating aerosol particles, and, for 0.3 µm sized particles, we even recorded an accumulation of particles inside the helmet. Interpretation - We conclude that the Stryker Flyte surgical helmet should not be used as a respiratory protective device when there is a risk for exposure to aerosol containing SARS-CoV-2, the virus causing COVID-19, in accordance with the recommendation from the manufacture

Cross-Table Lateral Radiographs Accurately Predict Displacement in Valgus-Impacted Femoral Neck Fractures

Background: Femoral neck fractures are classified as nondisplaced (Garden types I and II) or displaced (Garden types III and IV) on the basis of anteroposterior radiographs. Cross-table lateral radiographs are important in the assessment of Garden type-I and II fractures as posterior tilt of the femoral head may influence treatment results. A posterior tilt of >20° has been associated with an increased risk of treatment failure after internal fixation, although the precision of these measurements has not been validated. Therefore, the purpose of the present study was to compare cross-table lateral radiographs with 3-dimensional computed tomographic (3D-CT) reconstructions of Garden type-I and II femoral neck fractures. Methods: Twenty-three patients presenting with Garden type-I and II femoral neck fractures that were verified on anteroposterior radiographs underwent CT scanning immediately after radiographic examination. 3D models of the fractured and uninjured femora were reconstructed from the CT images, and displacement of the 3D models was determined by superimposing the fractured and uninjured femora. We defined a coordinate system with its origin at the center of the uninjured femoral head with the x axis oriented medially; the y axis, posteriorly; and the z axis, cranially. Correlations between lateral radiographs and 3D models were assessed with the Spearman rank coefficient, mean difference, and limits of agreement. Results: Posterior tilt of the femoral head on lateral radiographs was strongly correlated with displacement of the femoral head along the y axis of the 3D models, with a correlation coefficient of 0.86 (p < 0.001). Correlations between the findings on lateral radiographs and displacements along the x or z axis were weak, with coefficients of −0.30 (p = 0.18) and 0.21 (p = 0.34), respectively. The mean difference between displacement on lateral radiographs and displacement along the y axis of the 3D models was smaller, and demonstrated a smaller limits-of-agreement interval, compared with the x or z axis. Conclusions: Our results demonstrated a strong correlation between posterior displacement of the femoral head on lateral radiographs and displacement along the y axis in 3D models of Garden type-I and II femoral neck fractures. This finding indicates that lateral radiographs provide an accurate assessment of posterior tilt

Surgical helmets can be converted into efficient disinfectable powered air-purifying respirators

Background Filtering facepiece respirators often fail to provide sufficient protection due to a poor fit. Powered air-purifying respirators (PAPRs) are not designed for healthcare personnel, and are challenging to disinfect. Surgical helmets (SH) are available in many United States hospitals but do not provide respiratory protection. Several modifications to SH have been suggested, but none are sufficiently compliant with safety and efficiency standards. The purpose of this investigation was the development of a filter adaptor, which converts SHs into efficient, safe, and disinfectable PAPRs. Methods Four critical features were investigated close to regulatory requirements: total inward leakage of particles, CO2 concentrations, intra-helmet differential pressure, and automated disinfection. Results The average total inward leakage in the 2 independent tests were 0.005% and 0.01%. CO2 concentrations were lower than in the original SH. The modification generates a positive differential pressure. The filter's performance was not compromised after 50 cycles in a sterilization machine. Discussion The modified SH provides several hundred times better protection than FFP-3 masks. Conclusions Surgical helmets can be modified into safe, efficient, and disinfectable PAPRs, suitable for HCP and the operating room in particular. They can play a role in the preparedness for upcoming events requiring efficient respiratory protection