Relationship between Chronic Dyspnea and Expiratory Flow-Limitation in COPD Patients

Our findings suggest that the expiratory flow limitation as measured by the negative expiratory pressure tecnique may be more useful in the evaluation of dyspnea in patients with COPD than spirometru measurement

A simple Method to Monitor Performance of Forced Vital Capacity

APPLICATION OF PULSES OF NEGATIVE PRESSURE PROVIDES A SIMPLE METHOD FOR ON-LINE RECOGNITION OF WHETHER AN FVC MANEUVERS IS PERFORMED WITH SUFFICIENT EFFORT TO ACHIEVE FLOW LIMITATIO

Low volume ventilation causes peripheral airway injury and increased airway resistance in normal rabbits

Abstract Lung mechanics and morphometry of 10 normal open-chest rabbits (group A), mechanically ventilated (MV) with physiological tidal volumes (8-12 ml/kg), at zero end-expiratory pressure (ZEEP), for 3-4 h, were compared with those of five rabbits (group B) after 3-4 h of MV with a positive end-expiratory pressure (PEEP) of 2.3 cmH(2)O. Relative to initial MV on PEEP, MV on ZEEP caused a progressive increase in quasi-static elastance (+36%) and airway (Rint; +71%) and viscoelastic resistance (+29%), with no change in the viscoelastic time constant. After restoration of PEEP, quasi-static elastance and viscoelastic resistance returned to control levels, whereas Rint remained elevated (+22%). On PEEP, MV had no effect on lung mechanics. Gas exchange on PEEP was equally preserved in groups A and B, and the lung wet-to-dry ratios were normal. Both groups had normal alveolar morphology, whereas only group A had injured respiratory and membranous bronchioles. In conclusion, prolonged MV on ZEEP induces histological evidence of peripheral airway injury with a concurrent increase in Rint, which persists after restoration of normal end-expiratory volumes. This is probably due to cyclic opening and closing of peripheral airways on ZEEP

Dependence of forced vital capacity manoeuvre on time course of preceding inspiration in patients with restrictive lung disease

In normal subjects and patients with airway obstruction, flows during a forced vital capacity (FVC) manoeuvre are higher after a fast inspiration without an end-inspiratory pause (manoeuvre 1) as compared to a slow inspiration with an end-expiratory pause of similar to 5 s (manoeuvre 2). In this study, we investigated the influence of these manoeuvres on maximal expiratory volume-time and flow-volume curves in patients with restrictive lung disease. Eleven patients with restrictive lung disease were studied. Their average (+/-sD) lung function test results were: FVC=55+/-12% predicted value, forced expiratory volume in one second (FEV1) 52+/-20% pred, FEV1/FVC 85+/-6%, total lung capacity 55+/-8% pred, and carbon monoxide transfer factor 47+/-18% pred. The patients performed the two FVC manoeuvres in random order. We compared the ensuing spirograms and maximal expiratory flow-volume curves from which peak expiratory flow, FEV1, FEV1/FVC, maximal mid-expiratory flow, and maximal flows were computed. All spirometric indices were significantly higher with manoeuvre 1 than 2. Maximal expiratory flows at the same lung volume were also significantly higher with manoeuvre 1 than 2, in all patients. Routine spirometric indices, obtained during a forced vital capacity manoeuvre depend on the time course of the preceding inspiration in patients with restrictive lung disease. Therefore, the forced vital capacity manoeuvre should be standardized if used in clinical, epidemiological and research studies