Journal of applied physiology
-
We examined the stability of acute lobar hypoxic pulmonary vasoconstriction. In 12 mongrel dogs the left lower lobe (LLL) was selectively ventilated with a constant minute molume with nitrogen and the electromagnetically measured fraction of the cardiac output perfusing the LLL and the LLL end-tidal CO2 concentration were observed for 1 h. ⋯ We conclude that if minute ventilation of a hypoxic area of lung is kept constant, then decreased regional blood flow decreases regional alveolar PCO2. As a consequence of these two opposing influences, blood flow to an acutely hypoxic area will be oscillatory.
-
We have conducted two experimental series in the chicken in order to study CO2 exchange in the parabronchial lungs of birds. In the first series, the animals were artifically ventilated and end-expired PCO2, PE'CO2, was measured and compared with mixed venous PCO2, PVCO2. On the average, PECO2 exceeded PVCO2 by 2.8 Torr. ⋯ Only if O2 uptake continued, we observed a positive gas-to-mixed venous blood PCO2 difference. The results suggest that positive gas-blood PCO2 differences both during rebreathing and steady-state ventilation are brought about by the Haldane effect. Model calculations show that in the homogeneous avian lung, unlike in the alveolar lung, the Haldane effect can produce positive (PE'-PV)CO2 differences during steady-state breathing due to the peculiarities of the crosscurrent arrangement and parabronchial ventilation and blood perfusion.
-
The elastic behavior of postmortem human lungs has been studied in an effort to differentiate the effects of normal aging from those of mild emphysema. Static pressure-volume (P-V) curves were measured in 50 lungs obtained from men 15-85 yr of age, including 12 lungs with mild-to-moderate emphysema. The emphysema was quantitatively assessed by gross and microscopic methods. ⋯ Further decreases in alpha1 are found in most emphysematous lungs. Alpha1 is more than 2 SEE below the age-predicted mean in five of nine lungs with minimal emphysema (1-10% by point count) and more than 5 SEE below the mean in the three more severely affected lungs. There is a close correlation (R = +0.90) between alpha1 and the alveolar surface-to-volume ratio in both normal and emphysematous lungs.
-
Two healthy males relaxing supine on a ballistobed were mechanically ventilated at positive end-expiratory pressures (PEEP) from 0 to 19 cmH2O. Pressures at the airway opening, middle esophagus, and stomach were monitored, together with tidal volume (VT) and ballistobed displacement. ⋯ The combined effective elastance of abdomen and diaphragm (E'ab+di) first decreased and then increased again. The abdomen-diaphragm contribution to VT during mechanical ventilation was approximately half that of spontaneous breathing.
-
By use of the method of Konno and Mead and the respiratory magnetometer, the partition of respired gas volumes into rib cage and diaphragm-abdomen components was accomplished in 81 normal subjects including 32 young and middle-aged men, 29 young and middle-aged women, and 20 elderly men. Studied were isovolume maneuvers and the relaxation configuration over the inspiratory capacity range, quiet tidal breathing, increased amplitudes of slow breathing, rapid inspirations and expirations, and both quiet and forceful phonation. ⋯ Rapid respiratory maneuvers were accomplished mostly through rib cage displacement suggesting that rib cage muscles are capable of more rapid action than diaphragm and abdominal muscles. Data from deep breathing and rapid maneuvers supported the view that abdominal and rib cage muscles often act to optimize the mechanical (length-tension) advantage of the diaphragm.