Journal of clinical monitoring and computing
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J Clin Monit Comput · Jan 2000
ReviewAssessment and monitoring of flow limitation and other parameters from flow/volume loops.
Flow/volume (F/V) spirometry is routinely used for assessing the type and severity of lung disease. Forced vital capacity (FVC) and timed vital capacity (FEV1) provide the best estimates of airflow obstruction in patients with asthma, chronic obstructive pulmonary disease (COPD) and emphysema. Computerized spirometers are now available for early home recognition of asthma exacerbation in high risk patients with severe persistent disease, and for recognition of either infection or rejection in lung transplant patients. ⋯ Finally, the mechanism of ventilatory constraint can be identified with the use of exercise tidal volume F/V loops referenced to maximum F/V loops and static lung volumes. Patients with severe COPD show inspiratory F/V loops approaching 95% of total lung capacity, and flow limitation over the entire expiratory F/V curve during light levels of exercise. Surprisingly, patients with a history of congestive heart failure may lower lung volume towards residual volume during exercise, thereby reducing airway diameter and inducing expiratory flow limitation.
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J Clin Monit Comput · Jan 2000
ReviewAtelectasis formation during anesthesia: causes and measures to prevent it.
Pulmonary gas exchange is regularly impaired during general anaesthesia with mechanical ventilation. This results in decreased oxygenation of blood. A major cause is collapse of lung tissue (atelectasis), which can be demonstrated by computed tomography but not by conventional chest x-ray. ⋯ In summary, atelectasis is present in most humans during anaesthesia and is a major cause of impaired oxygenation. Avoiding high fractions of oxygen in inspired gas during induction and maintenance of anaesthesia may prevent formation of atelectasis. Finally, intermittent "vital capacity"-manoeuvres together with PEEP reduces the amount of atelectasis and pulmonary shunt.
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Inhaled nitric oxide is a ubiquitous molecule which is produced endogenously and is also found in air pollution and in cigarette smoke. After describing the chemistry of NO, we review its history from the first description in 1980 to the current clinical indications. ⋯ Possible drug interactions are listed. Inhaled nitric oxide is here to stay, and future studies will provide more information on its therapeutic dose, duration and potential toxicity.
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Identification of humoral markers of acute lung injury may lead to insights into pathologic mechanisms. In addition, specific markers may be useful for predicting development of acute respiratory distress syndrome (ARDS) or for assessing prognosis. Ultimately, studies of lung injury markers may help define interventions that prevent or moderate ARDS. ⋯ Surfactant apoproteins may be important markers of injury or for prognosis. Levels of surfactant apoprotein A (SP-A) fall 50-75% in patients with severe lung injury compared to normal patients. Serum levels of SP-A in patients dying of acute respiratory distress syndrome are double serum levels of survivors.
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Noninvasive ventilation refers to any form of ventilatory support applied without the use of an endotracheal tube. It offers the potential to provide primary treatment for acute respiratory failure while avoiding complications associated with mechanical ventilation with endotracheal intubation. Noninvasive ventilation has been most commonly studied in hypercapnic respiratory failure. ⋯ Patient selection is clearly the most important issue in considering noninvasive ventilation for acute respiratory failure. Unfortunately, patients who benefit from noninvasive ventilation represent only a minority of the total group with any one disease, and thus it is difficult to make broad conclusions concerning applicability of this treatment modality. Future studies are needed to focus on determining the specific patient populations who will benefit the most, evaluating the optimal ventilatory mode and mask for providing noninvasive ventilation, and clarifying its impact on clinical outcomes.