The relation of the intrapleural pressure to the mechanics of the circulation

Experiments have been carried out on the dog showing the effects of increased and decreased intrapleural pressure upon the heart, blood pressure, and pulmonic and peripheral circulation.It has been demonstrated that rendering the intrapleural pressure more negative produces dilatation of the heart, a diminished rate of flow through the pulmonary circuit with a relative anoxemia, a slow pulse, an increased blood pressure, fall of venous pressure, and rise in body temperature.Rendering the intrapleural pressure less negative, i.e., more nearly atmospheric, results in a fall of blood pressure, rise of venous pressure, increased pulse rate, relatively small heart, a lowered body temperature, and an increased rate of flow through the pulmonary circuit with increased oxygenation.An instrument has been devised for recording graphically changes in venous pressure.     

Estimation of the false-negative rate in newborn screening for congenital adrenal hyperplasia

OBJECTIVE: Newborn screening based on measurement of 17alpha-hydroxyprogesterone (17-OHP) in a dried blood spot on filter paper is an effective tool for early diagnosis of congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. Its most important rationale is prevention of a life-threatening salt-wasting (SW) crisis; in moderate forms of CAH, early diagnosis and treatment may prevent permanent negative effects of androgen overproduction. Our target was to analyse if all CAH patients who had been identified clinically before puberty would have been detected by the newborn screening. METHODS: Newborn screening cards of 110 CAH patients born between 1988 and 2000 in five Middle-European countries and diagnosed prior to puberty (77 SW and 33 moderate) and cards from 920 random, healthy newborn controls were analysed. CAH screening had not yet been introduced during this time. The diagnosis was based on clinical and laboratory signs and, in most cases, on CYP21 gene mutation analysis. All 17-OHP measurements in dried blood spots were carried out using a time-resolved fluoroimmunoassay kit. RESULTS: In the newborn screening blood spots, the median of 17-OHP levels was 561 nmol/l (range 91-1404 nmol/l) in subjects with the SW form and 40 nmol/l (4-247 nmol/l) in the moderate form. All 77 SW patients would have been detected by newborn screening using the recommended cut-off limits (30 nmol/l). However, 10 of 33 patients with moderate CAH would have been missed. 17-OHP levels of all controls were below the cut-off. CONCLUSION: Newborn screening is efficient for diagnosing the SW form of CAH, but is inappropriate for identifying all patients with a moderate form of CAH. It appears that the false-negative rate is at least one-third in children with the moderate form of CAH.     

Estimation of pulmonary artery pressure from pulmonary vein wedge pressure

Correlations between pulmonary artery and pulmonary vein wedge pressures were investigated in 13 patients with atrial septal defect and 1 patient with Tetralogy of Fallot. Pulmonary vein wedge pressure wave form resembled that of pulmonary artery pressure, and the former lagged behind the latter by 70 to 110 msec (mean 88 ± 14) as observed by the fluid-filled catheter system. Diastolic pulmonary artery and diastolic pulmonary vein wedge pressures were nearly identical. Although systolic and mean pulmonary artery pressures correlated well with respective pulmonary vein wedge pressures, there were discrepancies when systolic and mean pulmonary artery pressure exceeded 35 and 20 mm Hg, respectively. However, systolic and mean pulmonary artery pressures could be estimated by adding the difference between the diastolic pulmonary vein wedge pressure and the mean left atrial pressure to corresponding systolic or mean pulmonary artery pressure. In conclusion, pulmonary artery pressures can be estimated by measuring pulmonary vein wedge pressures and the mean left atrial pressure.     

Surgical management of intrapleural infections

Most patients with empyema require surgical intervention. Selection of therapy is based on the patient's overall condition, on the cause of the empyema, and on the stage of empyema progression. Parapneumonic effusions in the exudative or early fibrinopurulent stage may be responsive to tube thoracostomy and may not require further intervention in 65% of patients. More complicated parapneumonic effusions require thoracoscopic or open thoracotomy for debridement or decortication and are successfully managed in over 95% of patients. Empyemas that develop postoperatively are more challenging to diagnose and treat. Open thoracotomy is usually necessary unless patients are too ill to tolerate major surgery, in which case simple open drainage is an alternative. Closure of any bronchopleural fistula is necessary before an empyema can be eradicated. In patients with empyema associated with an extrapulmonary infectious process, control of the primary source of infection is required before definitive therapy of the empyema is undertaken. The overall success rate of therapy for empyema is greater than 90% and the associated mortality rate is about 8%.     

Use of intrapleural streptokinase in the treatment of thoracic empyema

The incidence of pleural effusions in bacterial pneumonia may exceed 40%, a factor that may be related to increased morbidity and mortality. Options in the treatment of complicated pleural effusions or empyema, when unresponsive to closed tube drainage, include repositioning of the indwelling tube thoracostomy or insertion of additional chest tubes, instillation of intrapleural streptokinase, and surgical intervention. The authors describe the course of three patients wherein the use of intrapleural streptokinase was efficacious in effecting prompt drainage of previously inadequately evacuated empyema, thus eliminating the necessity for further invasive intervention.     

Estimation of the peak-to-peak pressure gradient in aortic stenosis by Doppler echocardiography

The present study was designed to develop a new Doppler method to estimate noninvasively the peak-to-peak pressure gradient in patients with aortic stenosis. It was carried out in two steps. In the first study, left heart catheterization data were analysed in 58 patients with aortic stenosis. The peak pressure gradient correlated highly with (r = 0.98) but overestimated significantly the peak-to-peak pressure gradient. The averaged pressure gradient (average of the peak gradient and the gradient at the peak aortic pressure) was found to approximate closely the peak-to-peak pressure gradient (r = 0.99) with a good separation between significant and insignificant aortic stenosis. The ratio of the left ventricular ejection time over the aortic pressure descending time was studied and the beginning of the late one-third systole was chosen as the point for determining the late systolic gradient by the Doppler technique. In the second study, Doppler echocardiography and cardiac catheterization were performed in 35 patients with aortic stenosis. The Doppler-determined peak pressure gradient correlated highly with catheterization-measured peak pressure gradient (r = 0.95) but overestimated significantly the peak-to-peak pressure gradient. The Doppler-determined averaged pressure gradient (average of the peak and the late systolic gradients) estimated accurately the peak-to-peak gradient (r = 0.97) with a good separation between significant and insignificant aortic stenosis. These results demonstrate the limitations of the peak pressure gradient measurement and the reliability of the Doppler-determined averaged pressure gradient for estimation of the peak-to-peak pressure gradient.     

Doppler echocardiographic measurement of pulmonary artery pressure from ductal Doppler velocities in the newborn

The ductal flow velocities in 37 newborns (group 1: persistent pulmonary hypertension [n = 16], transient tachypnea [n = 3], other [n = 2]; group 2: respiratory distress syndrome [n = 16]) were prospectively evaluated by Doppler ultrasound for the purpose of deriving systolic pulmonary artery pressures. Maximal tricuspid regurgitant Doppler velocity in 21 of these patients was used to validate the pulmonary artery pressures derived from ductal flow velocities. There was a significant linear correlation between tricuspid regurgitant Doppler velocity and pulmonary artery systolic pressure derived from ductal Doppler velocities in patients with unidirectional (pure left to right or pure right to left) ductal shunting (p less than 0.001, r = 0.95, SEE 8) and in those with bidirectional shunting (p less than 0.001, r = 0.95, SEE 4.5). Systolic pulmonary artery pressure in group 1 (67 +/- 13 mm Hg) was significantly higher than that in group 2 (39 +/- 10 mm Hg) (p less than 0.001). In those with bidirectional shunting, duration of right to left shunting less than 60% of systole was found when pulmonary artery pressure was systemic or less, whereas duration greater than or equal to 60% was associated with suprasystemic pulmonary artery pressures. Serial changes in pulmonary artery systolic pressure, reflected by changes in ductal Doppler velocities, correlated with clinical status in persistent pulmonary hypertension of the newborn. Persistently suprasystemic pulmonary artery pressure was associated with death in five group 1 patients. It is concluded that ductal Doppler velocities can be reliably utilized to monitor the course of pulmonary artery systolic pressures in newborns.     

Kinetics of the intrapleural distribution of a radioactive bolus

Through the use of a gamma-camera placed horizontally over the chest of 5 supine, anesthetized and spontaneously breathing dogs we studied the kinetics of the intrapleural spreading of 1 ml saline containing 2 mg of 99mTc labelled albumin (250 microCi/kg) injected at various points on the costal side. From the postinjection sequence of gamma-camera images, we defined, along the intrapleural spreading pathways, some regions of interest (ROI) displaying a preferential label accumulation. In all the animals the ROI roughly corresponded to the apical, mediastinal and latero-diaphragmatic regions. The kinetics of the intrapleural label distribution, estimated from the time course of the activity under the ROI, displayed an initial rapid phase, lasting a few minutes, followed by a marked slowing down of the exchange processes. At 30 min regional counts reached an apparent steady state, the activity values greatly varying (even by 10 fold) among the animals, for the ROI corresponding to the same anatomical region, independently on the site of injection. The mathematical modelling of the regional activity curves required the assumption of a progressive decrease in the exchange coefficients to account for a marked slowing down of the exchange processes with increasing time.     

胸膜腔内注入纤溶剂治疗渗出性胸膜炎的研究进展

纤维蛋白溶解剂胸膜腔注入辅助治疗渗出性胸膜炎在临床上较大规模应用已有20年历史,最近5年之前的主要文献均肯定了其疗效,认为其可以促进引流,减少外科手术十预率,缩短住院时间及降低费用,但2005年英国牛津的一个迄今最大规模的胸膜腔注入链激酶治疗感染性胸水的前瞻性双盲对照试验则否定了这一结论,目前这一疗法的临床前景仍有待明确.一些新型纤溶剂及辅助引流胸水药物的研究已取得一些进展,但仍未见应用于人体,需要试验来验证其治疗作用.我国的研究应用主要是用尿激酶治疗结核性胸水.但只局限于临床指标的观察,尚缺乏检测应用尿激酶后胸水纤维蛋白、流变性等性状指标改变的实验数据支持研究结果.