Patterns of Correlation of Pulmonary Function Values Determined by Spirography and Body Plethysmography

Expiratory flow‐volume curves in mechanically ventilated patients with chronic obstructive pulmonary disease

“…Large increases from relatively high FEV 1 values have only minimal effect on effective time constant, whilst at lower values an inverse relationship is found. The apparent exponential behaviour is similar to earlier relationships found between FEV 1 and airways resistance from body plethysmography in spon-taneously breathing patients (16). In patients ventilated for respiratory causes other than COPD, low effective time constants were established.…”

“…In anesthetized humans and animals, a time constant (t) has been derived from the flow-volume relationship during spontaneous breathing. It is assumed that for this calculation the resistance of the total respiratory system (Rrs) and the compliance of the total respiratory system (Crs) behave linearly (16)(17)(18). The lung emptying was then assumed to follow an exponential equation V(t)ΩV(0)exp(ªt/t), with V(0) and V(t) the lung volume at the start (time tΩ0) and at t (timeΩt) seconds from the onset of expiration, respectively.…”

Pulmonary Emphysema and the Crossover Point

“…As a consequence the difference of these parameters for the two measuring techniques is higher in the pa tient group with emphysema (table III). Such differences are also found by other investigators and can be ascribed to inade quate mixing of helium during a rather short wash-in time [27][28][29][30][31].…”

Lung volume measurements

“…In fact, dilution methods do underestimate lung volume in moderate-to-severe airflow obstruction [2][3][4]. The more severe the airflow obstruction, the larger the underestimation [4].…”