Effects of respiratory gas composition on transthoracic impedance

The transthoracic current generated during defibrillation comprises a cardiac and extracardiac component. Changes in impedance of transthoracic pathways will alter the transmyocardial current and may thus affect the outcome from defibrillation. The lungs comprise a large component of extracardiac tissue but the effects of different respiratory gases on transthoracic impedance has not been documented. We therefore measured transthoracic impedance (TTI) using different respiratory gas mixtures. TTI across self-adhesive defibrillation pads placed in the antero-apical position was measured at end-expiration using a 30 kHz low amplitude AC current. Ten healthy subjects aged 22-34 years (eight male) were studied whilst breathing alternate mixtures of air, 100% oxygen. 70% helium in 30% oxygen, and 70% nitrous oxide in 30% oxygen administered in a random sequence. There was no significant difference in TTI between any of the four respiratory gases. Therefore transthoracic current during defibrillation is unlikely to be affected by different respiratory gases. This is the first study to document that these respiratory gases do not change the impedance of transthoracic pathways

Supplementary Material for: Association of Self-Reported Frailty with Falls and Fractures among Patients New to Dialysis

<b><i>Background:</i></b> Although frailty has been linked to higher risk of falls and fracture in the general population, only few studies have examined the extent to which frailty is associated with these outcomes among patients with end-stage renal disease, who are at particularly high risk for these events. <b><i>Methods:</i></b> A total of 1,646 patients who were beginning maintenance hemodialysis in 297 dialysis units throughout the United States from September 2005 to June 2007 were enrolled in the Comprehensive Dialysis Study, and 1,053 Medicare beneficiaries were included in this study. Self-reported frailty was defined by the patients endorsing 2 or more of the following: poor physical functioning, exhaustion or low physical activity. Falls and fractures requiring medical attention were identified through Medicare claims data. We examined the association between frailty and the time to first fall or fracture using the Fine-Gray modification of Cox proportional hazards regression, adjusted for demographics, Quételet's body mass index, diabetes mellitus, heart failure and atherosclerosis. <b><i>Results:</i></b> Seventy-seven percent of patients were frail by self-report. The median length of follow-up was 2.5 (1.0-3.9) years. Crude rates of first medically urgent falls or fractures were 66 and 126 per 1,000 person-years in non-frail and self-reported frail participants, respectively. After accounting for demographic factors, comorbidities and the competing risk of death, self-reported frailty was associated with a higher risk of falls or fractures requiring medical attention (hazards ratio 1.60, 95% CI 1.16-2.20). <b><i>Conclusion:</i></b> Participants reporting frailty experienced nearly twice the risk of medically urgent falls or fractures compared to those who did not report frailty