On behalf of my colleagues, I would like to thank the reader for her interest and analysis of our research article titled "Presurgical Risk Factors for Late Extubation in Medicare Recipients After Cardiac Surgery." The focus of this research study was to use an existing clinical database to develop an explanatory model for prolonged mechanical ventilation based on selected presurgical patient characteristics. I would refer the reader to a revision of the ventilatory conceptual framework that illustrates but distinguishes the collective contribution of presurgical patient characteristics and intraoperative patient care factors on pulmonary outcome (Bezanson et al., 2001). Our conscious effort to focus on presurgical patient factors was based on the intent to examine presurgical characteristics amenable to nursing care as well as to understand the contribution of presurgical factors in explaining the pulmonary outcome of prolonged mechanical ventilation in older adults. Based on the explanatory model developed, the concordance statistic of 0.66 suggested that the model provided moderate discrimination between time to extubation groups. We concur that more explanatory power would be necessary for use in clinical practice. Guided by the ventilatory framework, we would anticipate that the inclusion of presurgical psychosocial factors as well as intraoperative and postoperative clinical practices in the context of patient responses would enhance the predictive power of a model for prolonged mechanical ventilation after cardiac surgery.

Based on the retrospective nature of this study, postoperative readiness for extubation was evaluated according to established clinical guidelines. Due to the use of databased information, documentation regarding patient variances or clinical decisions during the weaning process was not available. It was anticipated that the careful selection of subject inclusion criteria would render acceptable variability in the measurement of duration of mechanical ventilation.

Importantly, this study examined a methodological approach through the use of time-to-event analysis to: (a) evaluate the time point in which the probability for extubation markedly decreased; and (b) address the lack of consistency in defining prolonged mechanical ventilation after cardiac surgery in an exclusive sample of older adults. As discussed in the article, prior studies have defined prolonged mechanical ventilation from greater than 6 hours to 72 hours in combined adult and older adult samples with subjects as young as 20 years of age. This study addressed the need to develop a standard for defining prolonged mechanical ventilation and has provided a better understanding of the presurgical risk factors which contribute to prolonged mechanical ventilation in older adults after coronary artery bypass grafting surgery.

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