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Biomedical subjects

P Szidon

Publications and source records attributed to P Szidon.

12 recordsLinked to original sources
PubMed1999

Loss of pulmonary function gains after lung volume reduction surgery.

Lung volume reduction surgery (LVRS) has been demonstrated to improve lung function, exercise tolerance and quality of life. However, the duration of improvement is unknown. While the maximal duration of improvement cannot be determined at this time due to an inadequate period of follow-up, we have observed in some patients significant and relatively rapid declines in gains following LVRS. We describe 6 patients who increased FEV1 by at least 10% of the predicted value after LVRS and subsequently experienced rapid loss of the increment in FEV1 (mean loss 79%, 95% CI 58-100%) over a period ranging from 14 to 20 months following surgery.

Aged↗
PubMed1999

Comparison of hallway and treadmill six-minute walk tests.

The 6-min walk test (SMWT) performed in the hallway (HW) is used as a clinical indicator of functional capacity in patients with lung disease. A 6-min walk test utilizing a treadmill (TM) is easier to perform and allows easier patient monitoring. Therefore, we formulated a standardized TM SMWT protocol and compared the results with those of a HW SMWT. All patients were enrolled in a pulmonary rehabilitation program. Patients with current infection, recent change in inhaled medications or oral steroid use, and significant cardiovascular disease were excluded. Each subject performed three HW SMWTs and three TM SMWTs assigned randomly on subsequent days. There was a 30-min rest between each walk and at least a 48-h rest between each test day. All patients completed both HW and TM SMWT within 7 d. Supplemental oxygen was utilized or increased if the saturation fell below 88%. The best of the three tests was used for data analysis. Twenty-one subjects completed the protocol. The mean age was 65 +/- 10.9 yr (range, 35 to 79 yr). Ten subjects were receiving supplemental oxygen. The mean FEV(1) was 1.07 +/- 0.53 L. The mean HW SMWT distance was 1,228 +/- 255 ft (range, 612 to 1,679 ft) and the mean TM SMWT distance was 1,060 +/- 389 ft (range, 475 to 1,819 ft), which were statistically different (p = 0.01). The mean difference was 168 +/- 280 ft (range, -326 to 743 ft). Oxygen saturation and supplemental oxygen requirements did not differ significantly. The intra-test variability of the three HW SMWTs was similar to the three TM SMWTs and no significant difference in the coefficient of variation was found. A standardized TM SMWT is feasible and allows easier patient monitoring, but there is a statistically significant difference between the HW and TM SMWT distance and therefore they are not interchangeable. However, the intratest reproducibility of the TM and HW SMWTs are similar when three walks are performed in a single test session. The role of the TM SMWT in pulmonary rehabilitation requires further exploration.

Adult↗
PubMed1993

Respiratory dyskinesia presenting as acute respiratory distress.

Incapacitating respiratory distress was the presenting manifestation of a choreiform movement disorder. Because the patient also had asthma, respiratory distress was at first mistakenly attributed to this condition. Despite vigorous asthma management, there was no improvement. However, once the neurologic condition was recognized, use of specific therapy (haloperidol and reserpine) resulted in rapid and sustained remission of respiratory symptoms.

Adult↗
PubMed1991

Variability of the respiratory gas exchange ratio during arterial puncture.

The value of R, the respiratory gas exchange ratio, was determined in 70 unselected outpatients while undergoing arterial blood sampling as part of routine pulmonary function testing. We wished to determine whether acute changes in alveolar ventilation occurring during blood drawing were of sufficient magnitude to cause a significant error in the calculation of alveolar PO2 if the value of 0.80 for R was assumed. In the majority of subjects, R ranged from 0.70 to 0.90. In approximately 25% of the cases, the assumption of the value of 0.80 for R would have led to an error equal to or greater than 10 mm Hg in the estimation of the alveolar-arterial PO2 difference.

Adult↗
PubMed1986

Reversible respiratory muscle weakness in hypothyroidism.

Physiological studies performed 1 week after initiation of thyroid replacement showed persistence of significant respiratory muscle weakness in a patient presenting with hypothyroidism and hypercapnia. Repeat studies 12 months later demonstrated return of respiratory muscle strength to normal. Earlier reports on respiratory failure in hypothyroidism had postulated a critical role for respiratory muscle weakness in the genesis of hypercapnia. Since hypercapnia was rapidly reversed despite the persistence of severe respiratory muscle weakness, this explanation may not be always correct. It appears than in our patient thyroid replacement had its primary effect on the respiratory control system.

Aged↗
PubMed1985

The value of gallium-67 scanning in pulmonary tuberculosis.

We studied 59 patients presumed to have pulmonary tuberculosis to determine whether gallium-67 citrate scintigraphy could improve diagnostic accuracy and help clinical decision making for empiric treatment pending culture results. The sensitivity of 67Ga scintigraphy was 95% and the specificity 27%. Our positive predictive value of 69% does not contribute substantially to increase the prior probability of diagnosis in settings similar to ours. The existence of a false negative rate essentially precludes the use of the scan to rule out active disease. The use of the scan for clinical decisions in pulmonary tuberculosis is not recommended.

Evaluation Studies as Topic↗
PubMed1983

Effect of hypoxia on the conversion of angiotensin I to II in cultured porcine pulmonary endothelial cells.

Earlier studies by other investigators have shown that acute exposure of cultured endothelial cells to hypoxic atmospheres inhibits the activity of the angiotensin converting enzyme in situ, resulting in severe but reversible depression of the rate of degradation of bradykinin. We exposed primary cultures of endothelial cells from the pulmonary artery of the pig to a range of hypoxic gas mixtures and measured the activity of the angiotensin converting enzyme in situ using angiotensin I as substrate. Each cell flask was exposed in random sequence to both hypoxic gas mixtures (PO2 29-69 torr) and room air for 40 min in Dulbecco's medium containing angiotensin I at concentrations of 1000 (N = 7), 500 (N = 8) or 100 ng/ml (N = 4). Angiotensin I disappearance rates and angiotensin II generation rates were linear. Recovery of immunoreactive peptide as either angiotensin I or II following 40 min of incubation was 86 +/- 17% (S.D.). The rate of increase in angiotensin II concentration in surface medium in room air experiments was 91 +/- 51 (S.D.) ng x ml-1 x hr-1. During hypoxia it was 85 +/- 42 ng x ml-1 x hr-1. The difference in rates was not significant by paired t analysis. The results of this study are consistent with earlier observations by the authors which suggest that hypoxia-induced depression of angiotensin I conversion in vivo is due to hemodynamic phenomena. Further studies are needed to clarify the role of cellular mechanisms in hypoxia-induced depression of angiotensin metabolism.

Angiotensin I↗
PubMed1982

Effect of hypoxia on the conversion of angiotensin I to II in the isolated perfused rat lung.

Acute hypoxia in the intact animal and in cultured endothelial cells has been shown to be associated with a decrease in conversion of angiotensin I (AI) to angiotensin II (AII). Alterations in capillary surface and in contact time resulting from hemodynamic changes have been shown to influence the rate of pulmonary AI conversion. The dependency of AI conversion on hemodynamics complicates the interpretation of experiments showing changes in AI conversion in intact animals. We studied the effect of acute hypoxia on AI conversion in the isolated rat lung perfused at constant flow without recirculation of perfusate. Three levels of oxygenation were produced by ventilating lungs and equilibrating perfusate with a range of hypoxic gas mixtures. AI (1 microgram) was injected into the pulmonary artery, and the effluent was collected for measurement of AI and AII. Instead of the expected hypoxic inhibition, percent conversion of AI to AII increased slightly but significantly from 69.3 +/- 3.1 (mean +/- S.E.M.) at normal oxygenation to 74.4 +/- 3.0 at moderate hypoxia (P less than 0.005, paired t) and to 73.5 +/- 3.9 at severe hypoxia (P less than 0.01, paired t). Decreasing mean transit time of substrate through the lung (by increasing perfusate flow rate from 5 to 20 ml/min) resulted in a significant decrease in conversion of AI from 88.7 +/- 2.9 to 73.4 +/- 2.1% (P less than 0.001, paired t). These data confirm the effect of contact time on the rate of AI conversion in the lungs. The isolated rat lung preparation does not exhibit the phenomenon of hypoxia-induced inhibition of AI conversion. The authors speculate that hypoxia-induced inhibition of AI conversion in vivo may be secondary to the effects of hypoxia on hemodynamics.

Angiotensin I↗
PubMed1981

Decreased serum angiotensin converting enzyme in adult respiratory distress syndrome associated with sepsis: a preliminary report.

Serum angiotensin converting enzyme (ACE) levels were obtained in 24 control patients who were critically ill, in 11 patients with cardiogenic pulmonary edema, in 8 patients with status postcardiopulmonary bypass, and in 12 patients with adult respiratory distress syndrome (ARDS). Mean values in cardiogenic pulmonary edema (24.3 +/- 3.9 SD) in cardiopulmonary bypass (19.5 +/- 3.1) and in patients with ARDS and no sepsis (n = 7, 19.0 +/- 5.5) were not significantly different from controls (20.7 +/- 2.8). In contrast, patients with ARDS and sepsis had markedly decreased serum ACE levels which fell outside of control range (n = 5, 8.6 +/- 2.3). The authors speculate that decreased ACE levels in the combination of sepsis and ARDS are due to the presence of circulating inhibitors of ACE. The finding of decreased serum ACE can be of potential clinical usefulness by raising the possibility of sepsis as the etiology of ARDS before results of blood cultures are available.

Adult↗
PubMed1980

Effect of acute hypoxia on the pulmonary conversion of angiotensin I to angiotensin II in dogs.

We studied the effect of acute hypoxia on pulmonary conversion of angiotensin I to II in anesthetized dogs. When arterial PO2 was decreased from 86 +/- 14 (SD) to 33 +/- 8 mm Hg without changing pH or PCO2, the single passage conversion of intravenous boluses of radiolabeled angiotensin I in tracer doses fell significantly (P less than 0.005) from 72 +/- 4 to 67 +/- 6%. The effect of comparable levels of hypoxemia on the conversion of continuous intravenous infusions of pharmacological doses (1000 times physiological) of angiotensin I was greater: from 55 +/- 14 to 33 +/- 13% (P less than 0.025). There was prompt return of percent conversion ratios to control levels when hypoxemia was reversed. We conclude that acute hypoxia is associated with a reversible decrease in pulmonary angiotensin converting enzyme availability.

Acute Disease↗