C. Veriter

Effect of alveolar volume on the interpretation of single breath DlCO

Single-breath carbon monoxide diffusing capacity in the whole lung (DLCO) and per unit alveolar volume (DLCO/VA), as expressed in percentage of normal values, gave discordant results when VA of the patients was abnormal. It was hypothesized that normal reference values were inappropriate to interpret data collected in such patients. To substantiate this hypothesis, DLCO and DLCO/VA were measured in four groups: (1) normal volunteers in whom both indices were measured at five different VA; (2) patients with high VA; (3) emphysematous patients; and (4) patients with diffuse interstitial lung diseases (DILD). In normal subjects, DLCO increased and DLCO/VA decreased with VA. In patients with overinflated lungs, the percentage of DLCO was more increased than DLCO/VA. In the emphysematous patients, both indices were equally decreased. In patients with DILD, DLCO was significantly more decreased than DLCO/VA in those suffering from a restrictive pattern. Theoretical values were re-calculated taking into account their true VA and using the relationships observed between DLCO, DLCO/VA and VA. The divergences between DLCO and DLCO/VA were strongly minimized. Therefore, the authors suggest the need to correct theoretical formulas in the presence of a restrictive pattern.

A normal FEV1/VC ratio does not exclude airway obstruction

Background: A decreased forced expiratory volume in 1 s/vital capacity (FEV1/VC) ratio is the hallmark of the definition of airway obstruction. We recently suggested that a lung function pattern, we called small airways syndrome (SAOS), has a normal FEV1/VC and total lung capacity (TLC) and reflects obstruction of small airways. Objectives: To substantiate our hypothesis we measured and compared lung function tests including maximal expiratory flow rates (MEFR), sensitive indicators of airway obstruction, in SAOS subjects and in matched controls. Methods: We selected 12 subjects with the pattern of SAOS, but without chronic lung or heart disease (average age: 40.7 ± 7.8 years) and 36 age-matched subjects with normal lung function (42.8 ± 6.3 years). We measured static and dynamic lung volumes, MEFR and lung diffusing capacity (DLCO). Results: SAOS subjects were heavier smokers (p < 0.05) and body mass index was less than in control subjects (p < 0.01). Both FEV1/VC ratio and TLC were comparable in the two groups. However, FEV1, VC, DLCO, and MEFR were lower and residual volume (RV) and RV/TLC ratio were higher (p < 0.05) in the SAOS group than in the control one. Furthermore, the MEFR curve of the SAOS group was displaced to the left without any change in slope, suggesting premature airway closure. Conclusion: Our results suggest that a normal FEV1/VC ratio does not exclude airway obstruction. A decrease of FEV1, provided TLC is normal, reflects small airway obstruction.

Expiratory flow limitation during sleep in heavy snorers and obstructive sleep apnoea patients.

Inspiratory flow limitation (FL) during sleep has previously been reported both in obstructive sleep apnoea (OSA) patients and heavy snorers (HS). Recent results from this laboratory have shown the occurrence both of inspiratory and expiratory flow limitation during muscular relaxation in awake healthy subjects and OSA patients. In this study, we have investigated whether expiratory flow limitation occurs during sleep in heavy snorers and in patients with OSA. We studied four nonapnoeic, heavy snorers and five OSA patients. Airflow was measured with a pneumotachograph attached to a tight-fitting mask, and supraglottic pressure with a catheter placed at the supraglottic level. Scoring for flow limitation was achieved by visual inspection of 200 breaths recorded during sleep. About 20% of the respiratory cycles presented isolated inspiratory flow limitation. Approximately the same percentage was observed in heavy snorers and OSA patients. Isolated expiratory flow limitation was less frequently recorded. Coupled inspiratory and expiratory flow limitations were more numerous, especially in heavy snorers. We conclude that both in heavy snorers and obstructive sleep apnoea patients, inspiratory flow limitation is associated with expiratory flow limitation. This suggests that upper airway obstruction during sleep is both an inspiratory and expiratory event.

Effects of two inotropic drugs, dopamine and dobutamine, on pulmonary gas exchange in artificially ventilated patients.

AbstractThe inotropic agents, dopamine (DP) and dobutamine (DB), both decrease PaO2, probably by a resistribution of the

Pulmonary gas exchange in life-long nonsmoking patients with diabetes mellitus.

{{\dot VA} \mathord{\left/ {\vphantom {{\dot VA} {\dot Q}}} \right. \kern-\nulldelimiterspace} {\dot Q}}

Tracheal distensibility in cystic fibrosis

ratio. The aim of this study was to assess the effect of both drugs on the

Identification of smokers susceptible to development of chronic airflow limitation: a 13-year follow-up.

{{\dot VA} \mathord{\left/ {\vphantom {{\dot VA} {\dot Q}}} \right. \kern-\nulldelimiterspace} {\dot Q}}