Surgical margins and survival after head and neck cancer surgery

BACKGROUND: Mixed results exist as to whether positive surgical margins impact survival. The aim of this study was to determine whether positive surgical margins are indeed associated with decreased survival in patients with primary head and neck cancer. METHODS: We conducted a retrospective cohort study of 261 cases diagnosed with cancer of the larynx or tongue between 1995 and 1999. Cases were followed through December 31, 2002. Survival curves by margin status were generated by Kaplan-Meier methods. Categorical data were evaluated with odds ratios (OR). RESULTS: All-cause mortality was markedly higher in cases with positive margins as compared with those with negative margins (54% versus 29%, P = 0.005). This pattern also appeared after adjusting for age and sex (OR = 2.97, 95% CI: 1.29 – 6.84). CONCLUSION: Our findings suggest that positive surgical margin status is associated with increased mortality. This association also generally persists after adjustment for tumor size, stage, and adjuvant therapy

Modelling Heart Rate Variability due to Respiration and Baroreflex

This chapter is devoted to the interactions of heart beat, respiration, and blood pressure oscillations. A nonlinear model is derived which describes the essential parts of the baroreceptor loop: blood pressure wave, baroreceptor activity, cardiorespiratory center, and regulation of heart rate and vascular resistance via the autonomic nerves. Special attention is devoted to the phase response properties of the cardiac pacemaker. The model covers heart rate regulation, respiratory sinus arrhythmia (RSA), and resonant interaction of respiration and blood pressure oscillations (Mayer waves). External stimulations can induce toroidal oscillations, resonances, perioddoubling, and chaotic behavior. 1. Introduction For some decades, it has been realized that the dynamics of living beings are more than homeostasis and the relaxation towards it. Very complex rhythms can occur, sometimes they are normal or even necessary, sometimes they are pathological or mortal. Dysfunctions originating from ..