Respiration; international review of thoracic diseases
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We have studied the role of 5-hydroxytryptamine (5-HT) in monocrotaline pulmonary hypertension and chronic hypoxic pulmonary hypertension in rats using p-chlorophenylalanine (PCPA) which inhibits 5-HT synthesis. We measured right ventricular mean systolic pressure (Prvs), right ventricular hypertrophy, medial thickness of muscular pulmonary arteries, and muscularization of pulmonary arterioles 17 days after a single dose of monocrotaline (60 mg/kg) and after 26 days of chronic hypobaric hypoxia (380 mm Hg). In monocrotaline pulmonary hypertension, pretreatment with PCPA (500 mg/kg) was associated with significant reductions (p less than 0.05) in Prvs (29%), right ventricular hypertrophy (33%), and medial thickness of muscular pulmonary arteries (14%). In chronic hypoxic pulmonary hypertension, pretreatment with PCPA was associated with significant reductions in Prvs (20%), right ventricular hypertrophy (28%), medial thickness of muscular pulmonary arteries (14%), and muscularization of pulmonary arterioles (47%). 5-HT may play a role in the development of monocrotaline pulmonary hypertension and chronic hypoxic pulmonary hypertension in rats.
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Comparative Study
Comparison of the effect of continuous positive airway pressure and blowing bottles on functional residual capacity after abdominal surgery.
In two groups of comparable patients undergoing elective abdominal surgery, functional residual capacity (FRC) was measured preoperatively and on the first 2 days after surgery. One group was treated by regular application of continuous positive airway pressure (CPAP), the other group by bottle blowing (BB). In both groups there was a significant reduction of FRC on the first postoperative day. ⋯ BB resulted in especially high expiratory and total resistive work. It is concluded that CPAP and BB increase temporarily the reduced FRC after abdominal surgery. CPAP was much better tolerated by the patients due to the lower resistive work of breathing.
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Comparative Study
Effects of end-expiratory lung volume on lung mechanics in normal and edematous lungs.
This study determined the effects of end-expiratory pressures (EEP) and alterations in end-expiratory lung volume (EELV) on lung compliance (CL) and pulmonary resistance to gas flow (RP) in 20 cats with normal and edematous lungs. EELV was varied using EEP ranging from -8 to +10 cm H2O. Negative EEP was used to decrease EELV of the healthy lung causing CL to decrease and RP to increase. ⋯ An EEP of 4 cm H2O returned EELV to normal FRC levels and produced maximum values for CL. Increases in EEP to 4 cm H2O also caused decreases in RP in the edematous lungs but further increase did not cause significant changes in RP. These results show that (1) relatively low levels of EEP returned EELV to normal FRC levels in alloxan-induced pulmonary edema, and (2) optimal lung mechanics were obtained when EELV was equal to or slightly above normal FRC values in both healthy and edematous lungs.
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In order to assess the effect of breathing pattern on measurements of dead space ventilation (VD/VT) during exercise, we studied 6 patients with the complaint of exertional dyspnea. They had essentially normal resting pulmonary function studies and the only abnormality noted during an initial exercise study was an elevated VD/VT associated with a rapid respiratory rate. ⋯ During the exercise study with coaching, the VD/VT response was normal. We conclude that breathing pattern during exercise influences VD/VT and that an increase in total minute ventilation which is accomplished by a preferential increase in respiratory rate may result in an abnormally high VD/VT.