General Reviews

Dynamic hyperinflation - the main mechanism of decreased exercise tolerance in patients with COPD

Dynamic hyperinflation - the main mechanism of decreased exercise tolerance in patients with COPD. Decreased exercise tolerance in patients with COPD is the result of involvement in variable proportion of three mechanisms: ventilatory limitation, muscle dysfunction and cardio-vascular involvement (inadequate intake of oxygen at tissue level). Ventilatory limitation is caused by the combination of increased demand and decreased ventilatory capacity. Increased ventilatory demand is the result of exercise worsening of ventilation-perfusion imbalance, and decreased ventilatory capacity is the result of decreased elastic recoil and dynamic obstruction. The consequence is the expiratory flow limitation, leading to inefficient expiratory muscle activity and dynamic hyperinflation. Dynamic hyperinflation is a result of structural abnormalities in COPD producing mechanical disorders that limit ventilation. Dynamic hyperinflation has some beneficial effects by facilitating maximal exhalation. Negative effects of hyperinflation are: (1) decreased tidal volume ability to grow properly at exercise, which causes mechanical ventilator limitation; (2) decreased functional capacity of inspiratory muscles (by increasing elastic load with respiratory muscle fatigue and increase work of breathing); (3) exercise hypoxemia and carbon dioxide retention; (4) impairment of cardiac function during exercise by decreasing venous return and cardiac output. Evaluation of pulmonary hyperinflation is a useful tool for better characterizing the effects of disease and for monitoring the response of therapeutic interventions on exercise tolerance of patients with COPD.

Keywords: COPD, pulmonary hyperinflation

Article

Devices used in non-invasive ventilation for obstructive sleep apnea associating COPD and/or morbid obesity

Devices used in non-invasive ventilation for obstructive sleep apnea associating COPD and/or morbid obesity. Obstructive Sleep Apnea (OSA), COPD and morbid obesity are three medical conditions with increasing prevalence, and their association is not rare in clinical practice. Whereas CPAP remains the gold standard therapy of severe symptomatic OSA, non-invasive ventilation, often requiring additional oxygen therapy, could be necessary to achieve a satisfactory arterial oxyhaemoglobin saturation and carbon dioxide level, and is used on a long term basis for patients with OSA and COPD/morbid obesity. Thus, non-invasive ventilation is intended to increase the minute ventilation, and the devices used could achieve this either by providing a targeted volume as a result of a pressure (barometric devices), or an actual volume (volumetric devices). In this paper are described the basic mechanisms, operating principle, the advantages and limitations of the most used devices for this kind of patients, in ambulatory settings.

Keywords: non invasive ventilation, sleep apnea syndrome, obesity, COPD

Article

A case of cardiac hydatidosis: role for transesophageal echocardiography in evaluating bilateral pulmonary nodules

Echinococcusis is a zoonotic disease, which is endemic in sheep-raising areas such as Iran. Cardiac involvement of the hydatidosis is rare and mostly asymptomatic, but it could lead to lethal complications. Thus, early diagnosis with accurate treatment would be life-saving. Here we report a 17-year-old female with nonspecific pulmonary presentations and a positive history of pulmonary hydatid cysts. Transesophageal echocardiography showed multiple cardiac hydatid cysts in the right ventricle. Patient underwent the bypass surgery to remove cardiac cysts. Postoperatively patient was on Albendazole and Praziquantel for two years. In a two-year-follow up, the patient had no complications.

Keywords: cardiac surgery, hydatid cyst, transesophageal echocardiography, pulmonary nodule

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