#pulmonary function

View On WordPress

Follow us on Linkedin @http://bit.ly/2c0W5l2

The patients had most of the features of the entity called idiopathic or primary pulmonary artery hypertension and fulfilled the accepted criteria for the diagnosis. Accordingly, in three patients, the lung biopsy or the necropsy specimens showed the arterial histopathologic spectrum described for IPAH. It has been previously stated that pulmonary mechanical function is close to normal in IPAH patients. However, using lung function tests that detect peripheral airways disease, this concept can no longer be supported. Our patients were nonsmokers, and no other cause of airway disease was identified. Therefore, the abnormalities seen were most likely related to IPAH. Normal forced exhaled flow rates may be preserved in the presence of significant peripheral airways obstruction. If tests to detect such peripheral airways abnormalities had not been performed, only three of our patients would have shown an increased airways resistance as measured by the observed MMEF and Raw values (cases 4,5, and 10). Also, such abnormalities could only explain the abnormal increase in RV documented in three of the seven patients.When MMEF values are adjusted for air density at high altitude, two additional patients showed an abnormality (case 1 and 6) that could explain the increase in RV. A measurement of FEF 75-85 percent lower than 75 percent of the predicted value is capable of identifying subjects with small airways disease. In the present study, this index was abnormal in eight patients, three of whom had a normal MMEF with an increased RV (case 1,3, and 6). With the indices derived from the flow-volume curves with air, it could only be possible to detect abnormalities in exhaled flow rates in four patients in whom the MMEF and FEF 75-85 percent were abnormal. Be protected from severe and unwanted ramifications with Birth Control Online - https://mybirthcontrolonline.com/birth-control-online-with-oral-contraceptives.html. The habitat of the studied population was 2,240 m and the predicted normal values used to detect airways obstruction were taken from sea level studies and also from the FEVj/FVC, MMEF, and FEF 75-85 percent reported at a higher altitude of 3,100 m. The latter data were considered because, although flow limitation may not be apparent in airways in which flow is turbulent, the diminished air density at a higher altitude could underestimate an abnormal resistance to air flow. Using flow-volume curves with He-Oj, an increased resistance to air flow in the peripheral airways was found in eight of the cases studied. On the other hand, the closing volume and the closing capacity were also abnormal in eight cases. As far as we know, there is no evidence that values obtained from the flow-volume curves with He-02 or from indices derived from the single breath nitrogen curves might be different at our altitude relative to those obtained at sea level. Flow rates may be reduced solely by loss of elasticity, and the airways themselves may appear structurally normal. None of the IPAH patients studied showed a loss of elasticity. In fact, in four, the elastic recoil was increased. The abnormal figures recorded for the MMEF curves, for the FEF 75-85 percent, for the Vmax 50 percent VC and Vmax 25 percent VC (with air), for the CV/VC, for the closing capacity in the absence of loss of elastic recoil, and in the presence of close to normal Raw measurements, represent abnormalities that reflect peripheral airways obstruction in the IPAH patients. An increase in flow at 50 percent of VC when breathing He-02 was observed in eight of the patients. This is independent of lung elastic recoil, and thus, may be more specific for detecting abnormality in peripheral airways. These findings in IPAH patients support the idea that the caliber of the small airways is reduced. This feature could explain the increase in RV observed in this entity. Our findings are also supported by the pathologic observations in the three cases studied that showed small airways disease. The observed changes in lung compliance and elastic recoil in IPAH cannot be attributed to a reduction in the number of air spaces (ie, pulmonary fibrosis). It is, however, possible that such changes might be the result of the pathologic changes present in the pulmonary vasculature. As has been proposed previously by our group, and by other investigators, it could be the result of perivascular and vascular thickening which may render the air-vessel space less distensible. Clearly, the real explanation for the observed changes in lung compliance and elastic recoil remain speculative. It has been observed that arterial oxygen saturation decreases with progression of the disease and that hypoxemia and/or widened P(A-a)Oa is caused mainly by V/0 inequality and low mixed venous oxygen content without evidence of a diffusion impairment. In some cases, it is also due to an intracardiac shunt secondary to a patent foramen ovale.The development of hypoxemia and the increased ratio of dead space to TV observed in some of our patients in the absence of evidence suggesting alveolar destruction, also suggest abnormalities of ventilation distribution. Also Vd/Vt changes could result from the vascular abnormality causing a decrease in perfusion with secondary increase in airways resistance to flow in nonperfused areas. The anatomic lesions of IPAH primarily cause a restriction of the pulmonary vascular bed that results in maldistribution of the pulmonary blood flow. On the other hand, as a result of abnormalities in the peripheral airways with secondary maldistribution of alveolar ventilation, a ventilation-blood flow imbalance ensues. The knowledge of the peripheral airways obstruction that occurs in IPAH patients could help to better understand the impairment in gas exchange when present in this entity. The results from this study indicate that in IPAH, besides the pulmonary microcirculation, the peripheral airways are affected. In considering the relation of vascular and airway disease, we cannot, however, distinguish between cause/effect or independent processes.