Plethysmographic Loops : a Window on the Lung Pathophysiology of COPD Patients

Plethysmographic alveolar pressure-flow (Palv\u2013F) loops contain potentially relevant information about the pathophysiology of chronic obstructive pulmonary disease (COPD), but no quantitative analysis of these loops during spontaneous breathing has ever been performed. The area of the loop\u2019s inspiratory (Ains) and expiratory portion (Aexp), and the difference between the end-expiratory and end-inspiratory alveolar pressure (\u394Palv) were measured in 20 young, 20 elderly healthy subjects, and 130 stable COPD patients. Ains and \u394Palv increased by 55 and 78% from young to elderly subjects, and by 107 and 122% from elderly subjects to COPD patients, reflecting changes in mechanical heterogeneity, lung-units recruitment/derecruitment, and possibly air trapping occurring with aging and/or obstructive disease. Aexp increased by 38% from young to elderly subjects, and by 198% from elderly subjects to COPD patients, consistent with the additional contribution of tidal expiratory flow-limitation, which occurs only in COPD patients and affects Aexp only. In COPD patients, Aexp and \u394Palv showed a significant negative correlation with VC, FEV1, IC, and a significant positive correlation with RV/TLC. The results suggest that the analysis of plethysmographic Palv\u2013F loops provides an insight of the pathophysiological factors, especially tidal expiratory flow-limitation, that affect lung function in COPD patients

Normal cervical changes in parous women during the second half of pregnancy - a prospective, longitudinal ultrasound study

OBJECTIVE: To determine what constitutes normal cervical changes during the second half of pregnancy in parous women delivering at term. DESIGN: The study comprises 21 healthy, pregnant parous women who all gave birth at term. They were examined with transvaginal ultrasound every two weeks from 24 gestational weeks until delivery. Cervical length and width were measured. The inner cervical os was assessed as being closed or open, the length and width of any opening were measured, and dynamic cervical changes (i.e. opening and closing of the inner cervical os during examination) were noted. RESULTS: Median cervical length was 41 mm (range 26-55) at the first examination and 29 mm (range 8-56) at the last examination. The corresponding figures for cervical width were 38 mm (range 29-47) and 46 mm (range 38-64). Cervical length decreased in 18 women but remained unchanged in three. Three patterns of change in cervical length were observed: in 12 women there was a steady, continuous decrease in cervical length (median decrease rate 1.1 mm/week, range 0.6-2.4); in four women the decrease rate accelerated towards the end of pregnancy, the median decrease rate after the change being 3.0 mm/week (range 1.5-4.8); and in two women there was a sudden drop in cervical length at term. Cervical width increased in 16 women but remained unchanged in five. Two patterns of change in cervical width were seen: 14 women manifested a steady continuous increase in cervical width (median 0.8 mm/week, range 0.4-1.8); in two women the increase rate accelerated from around 34 gestational weeks, the increase rate after the change being 4.1 and 5.9 mm/week, respectively. Opening of the internal cervical os was observed at least once in 11 (52%) women and was seen as early as at 24 and 25 gestational weeks in two women. The opening was always V-shaped (median length 6 mm, range 4-17; median width 7 mm, range 3-20). Dynamic changes of the internal cervical os were seen in three women (14%) at 25, 30 and 41 gestational weeks, respectively. CONCLUSION: The cervix of parous women decreases in length and increases in width from midpregnancy to term, but the pattern of change varies between individuals. Knowledge of the different patterns of normal change forms the basis of transvaginal ultrasound studies of pathological cervical changes during pregnancy

Plethysmographic measurement of intrinsic PEEP in stable COPD patients at rest

Background: In stable chronic obstructive pulmonary disease (COPD), intrinsic positive end-expiratory pressure (PEEPi) due to tidal expiratory flow-limitation (FL) is responsible for the increase in work of breathing and for adverse haemodynamic effects. PEEPi during spontaneous breathing can be only measured invasively with the esophageal balloon technique (ES). Aims: To obtain a non-invasive estimation of PEEPi in stable COPD patients using a commercially available plethysmograph (PEEPipl) and to compare it with existing data on PEEPi obtained with ES (PEEPies) [Haluszka, J. et al. Am Rev Respir Dis 1990; 141:1194-97;Dal Vecchio, L. et al. Eur Respir J 1990; 3:74-80]. Methods: Stable mild to very severe COPD patients performed body-plethysmography before and after bronchodilation (BD) according to current guidelines. PEEPipl was calculated by converting into alveolar pressure the shift volume measured at the end of a spontaneous tidal expiration. FL was assessed with the negative expiratory pressure method. Results: 62 COPD patients were enrolled (mean\ub1SD 72\ub17 years; 40 males). At baseline patients with FL (N=35) exhibited a higher PEEPipl than those with no FL (0.8\ub10.4 vs 0.3\ub10.2 cmH2O, P<0.01). After BD PEEPipl decreased (P=0.01) similarly in both groups (-12% vs -15%). As previously documented for PEEPies, PEEPipl was correlated with FEV1 (R=-0.597), vital capacity (R=-0.541), inspiratory capacity (R=-0.521) and residual volume (R=0.489), all P<0.01. However, PEEPipl and changes post-BD were lower than previously reported for PEEPies (2.4\ub11.5 cmH2O and -60%). Conclusions: Although further implementations are necessary, the non invasive assessment of PEEPi by means of plethismography appears achievable