Respiratory dead space measurements in a model lung and healthy human subjects according to the single breath method

Abstract

Observations on the dead space (Fowler's method) in a lung model were compared to observations on three human subjects. Corresponding to the theoretical gas front between dead space O2 and alveolar N2, a point in the model experiment was found dividing the S-shaped form of the N2 curve in a ratio of 2:3. The washout volume for the model dead space was about twice its volume. Similar findings were noted in the human subjects. Washout time did not influence the dead space values at flow rates of 5–37 l/min. In the human subjects the dead space values increased by 2.4–3.3 ml/100 ml of increasing end-inspiratory lung volume. The values for the dead space fell during an inspiratory pause even in the normal interval of quiet breathing. The accuracy of the method in tests on the model with a known dead space of 190 ml was 189 ± 1.4 ml with a standard deviation of ±7.0 ml. In human subjects the standard deviation was about 10%. Submitted on August 21, 1958

Ventilation.

“…Anatomical dead space can be measured by the Fowler method (Fowler, 1948), in which a single breath of oxygen is inhaled to total lung capacity and then exhaled through a nitrogen meter. The volume from TLC to a point mid-way up the steep initial rise of nitrogen concentration to the alveolar plateau (Figure 1) is the anatomical dead space (Birath, 1959 (Bates, Macklem & Christie, 1971). In normal subjects anatomical and physiological dead spaces are equal but in patients with lung disease physiological dead space is enlarged, which means that more of each breath is useless for the purpose of gas exchange.…”

Acromegalic pneumonomegaly: lung growth in the adult

“…However, VD in these four subjects was similar to values predicted on the basis of lung size. This implies that the lungs became larger as a result of lung growth since an increase in lung size due to diminished lung elasticity (22) or due to stretch of the lung, as illustrated by measurements of VD at different lung volumes (8,23), would be expected to result in smaller changes in VD. Tissue volume (VT) was elevated in the five male acromegal'cs where it was measured averaging almost twice the normal value.…”

Airway and Physiologic Dead Space in Patients with Obstructive Emphysema

“…1 and was described in detail in an earlier paper [4], The subject inspired from a spirometer with pure 0 2 and expired into another one with a small volume factor. The expired air was continu ously sucked through a N2 analyzer and recorded simultaneously with the volume.…”

“…The expired air was continu ously sucked through a N2 analyzer and recorded simultaneously with the volume. The standard deviation for this determination can be kept within 10%, if the dead space is of ordinary size [4].…”