Informative value of simple multibreath nitrogen washout measurements for clinical and research purposes

Some simple multibreath nitrogen washout indexes quantifying inspired gas distribution and ventilatory efficiency were obtained in a group of patients with mild to advanced chronic obstructive pulmonary disease (COPD) and studied in their relationships with routine pulmonary function tests. The indexes (lung clearance index (LCI), mixing ratio (MR) and data obtained by graphic analysis of the washout curve) were correlated with spirometric, pulmonary mechanics and arterial blood gas measurements, but only 8-38% of the interindividual variation in these indexes was explained by the above routine tests. An additional 5-13% of the variation was explained by the washout tidal volume (VT); this finding may reflect changes in gas distribution with VT and/or the influence of the dead space on ventilatory efficiency. Our data indicate that, in patients with COPD, nitrogen washout indexes tend to change in parallel with routine pulmonary function tests, reflecting the severity of the disease; these indexes also contain specific information (in addition to that provided by routine physiologic tests), presumably related to the distribution and efficiency of ventilation. Nitrogen washout measurements may thus represent a helpful adjunct to routine pulmonary function testing; LCI and MR appear to be particularly convenient for practical purposes because of their simplicity, and an informative content comparable with that of more complex indexes.     

Comparison of lung volume measurements by single breath helium and multiple breath nitrogen equilibration methods in normal subjects and COPD patients

The validity of the single breath helium dilution method for accurate measurement of the total lung capacity (TLC) was investigated. Comparison was made with the multiple breath nitrogen equilibration technique in 22 normal subjects and 37 patients with chronic obstructive pulmonary disease (COPD). The single breath method underestimated the TLC in all the normal individuals and 33 of 37 patients with COPD. Possible explanations for the falsely low lung volumes include uneven distribution of inspired air due to closing volumes and induced bronchoconstriction.     

无创正压呼吸机辅助治疗慢性阻塞性肺疾病合并呼吸衰竭的疗效观察

目的探讨（鼻）面罩多功能双水平无创正压通气辅助治疗慢性阻塞性肺疾病合并呼吸衰竭的作用。方法40例慢性阻塞性肺疾病急性加重期合并呼衰患者,分为常规治疗组及应用双水平无创正压呼吸机辅助通气治疗组,记录通气各组治疗前后血气及心率（HR）变化。结果经双水平无创正压呼吸机辅助通气治疗组的临床症状改善和血气分析指标恢复正常,与常规治疗的对照组比较差异有统计学意义（P〈0．01）。同时治疗组间差异均有统计学意义（P〈0．05）。结论应用多功能双水平无创呼吸机辅助通气治疗慢性阻塞性肺疾病合并呼吸衰竭效果肯定,可明显提高患者血气的PH值及PaO2,同时可降低PaCO2,使患者通气功能和缺氧体征得到明显的改善。     

Effect of varying the pressurisation rate during noninvasive pressure support ventilation.

The aim of the study was to assess the effects of varying the pressurisation rate during noninvasive pressure support ventilation on patients' breathing pattern, inspiratory effort, arterial blood gases, tolerance to ventilation and amount of air leakage. A total of 15 chronic obstructive pulmonary disease patients recovering from an acute episode of hypercapnic acute respiratory failure were studied during four randomised trials with different levels of pressurisation rate. No significant changes were observed in breathing pattern and arterial blood gases between the different runs. The pressure time product of the diaphragm, an estimate of its metabolic consumption, was significantly lower with all pressurisation rates than with spontaneous breathing, but was significantly lowest with the fastest rate. However, air leak, assessed by the ratio between expired and inspired tidal volumes, increased and the patients' tolerance of ventilation, measured using a standardised scale, was significantly poorer with the fastest pressurisation rate. In chronic obstructive pulmonary disease patients recovering from an episode of acute hypercapnic respiratory failure and ventilated with noninvasive pressure support ventilation, different pressurisation rates resulted in different reductions in the pressure time product of the diaphragm; this reduction was greater with the fastest rate, but was accompanied by significant air leaks and poor tolerance.     

Regional ventilation-perfusion relationships.

Regional ventilation-perfusion ratios have been determined in 12 healthy subjects, 16 patients with pulmonary embolism, and 22 patients with chronic obstructive lung disease. The ventilation-perfusion ratios were determined from xenon-133 ventilation studies and 99-tc-m-labeled particle perfusion scans, using either the fractional exchange of air or the relative distribution of tidal volume per unit volume as the numerator of the ratio. A comparison of these two methods showed comparable distributions of regional ventilation-perfusion relationships in the healthy subjects and patients with pulmonary embolism. However, in the patients with chronic obstructive pulmonary disease, the fractional exchange method clearly separated this group of patients from the others.     

Captopril effects on pulmonary and systemic hemodynamics in chronic cor pulmonale

A placebo-controlled single-blind study on acute effects of captopril on hypoxic pulmonary hypertension was performed in 15 patients with severe chronic obstructive lung disease recovering from right heart failure. Ten patients received active drug (25 mg captopril orally), five patients received placebo and served as control subjects. Before drug administration, there was no difference in lung function data and pulmonary hemodynamics between patients in both groups. Captopril produced highly significant fall in systemic arterial pressure. No change in breathing frequency, minute ventilation, and pulmonary gas exchange was observed. There was no significant change in studied variables after placebo. The presented data suggest that captopril does not decrease pulmonary vascular resistance in patients with hypoxic pulmonary hypertension. A fall in pulmonary wedge pressure reflects a decrease in left ventricular afterload.     

Right and left ventricular dysfunction in patients with chronic obstructive lung disease: Assessment by first-pass radionuclide angiography

To evaluate the relationship between right and left ventricular function in patients with obstructive lung disease, we studied 10 normal subjects (group 1) and 37 patients with chronic obstructive pulmonary disease by first pass radionuclide angiography. These 37 patients were divided into three groups: nine with mild chronic obstructive pulmonary disease (group 2), 20 with severe chronic obstructive pulmonary disease (group 3) and eight with severe chronic obstructive pulmonary disease and primary left ventricular disease (group 4). In each subject right ventricular ejection fraction (RVEF), left ventricular ejection fraction (LVEF) and ejection fraction during first third of systole (first third LVEF) were calculated. LVEF RVEF First-Third LVEF Group 1 0.60 ± 0.05 0.52 ± 0.03 0.29 ± 0.04 Group 2 0.61 ± 0.08 0.52 ± 0.03 0.29 ± 0.02 Group 3 0.58 ± 0.09 0.46 ± 0.091 0.24 ± 0.061 Group 4 0.51 ± 0.061 0.44 ± 0.091 0.20 ± 0.031 1 p < 0.05 versus 1. All subjects in group 2 had normal left ventricular and right ventricular function. In group 3,11 of 10 (55 per cent) had a low RVEF and three of 20 (15 per cent) a low LVEF. However eight of 20 in this group (40 per cent) had a depressed first-third LVEF. The correlation between decline in RVEF and first-third LVEF was good r = 0.73. We conclude that (1) certain indices of early systolic left ventricular ejection are abnormal in many patients with chronic obstructive pulmonary disease and correlate with the decline in right ventricular function; (2) this is not seen in patients with mild chronic obstructive pulmonary disease and is worse in patients with underlying left-sided heart disease.     

Hemodynamic compromise associated with air trapping following coronary artery bypass surgery

Cardiovascular collapse due to pulmonary hyperinflation was noted in a patient with chronic obstructive pulmonary disease following median sternotomy for cardiac surgery. Treatment included bronchodilator therapy to reduce airway obstruction, limitation of minute ventilation, and increasing time available for exhalation. High inspiratory flow rates and expiratory retard may be beneficial.     

Hemodynamic effects of ibopamine on the pulmonary circulation and right ventricular performance in patients with chronic obstructive pulmonary disease.

We have studied the effects of ibopamine, an oral dopamine derivative, on pulmonary hemodynamics and blood gas values when given as a single oral dose (100 mg) to patients with severe hypoxic chronic obstructive pulmonary disease. A small but significant increase in mean pulmonary arterial pressure from 29 +/- 8 to 32 +/- 7 mm Hg (p < 0.01) was noted 30 min after ibopamine was given associated with a small increase in cardiac index. No other consistent hemodynamic changes were observed, and no alteration in blood gas values or oxygen saturation occurred. These results do not indicate a role for ibopamine in the treatment of patients with hypoxic chronic obstructive pulmonary disease and pulmonary hypertension, but, in addition, do not indicate any major deleterious effects of ibopamine on pulmonary hemodynamics or blood gas values in such patients.     

Phlebotomy improves pulmonary gas exchange in chronic mountain polycythemia

There is not unanimous agreement in the literature regarding the effects of bleeding on pulmonary gas exchange in polycythemic patients. Spirometry, alveolar arterial O2 and CO2 tension differences, PaO2 breathing 100% oxygen and carbon monoxide-diffusing capacity were measured before and after 1 week of chronic phlebotomy in 4 chronic mountain polycythemic patients. Studies were carried out at 3,700 m above sea level (PB = 491 mm Hg). Before phlebotomy, 2 patients showed abnormal spirometry and gas exchange. Only 1 patient had high PaCO2 and all of them showed low values of PaO2 breathing oxygen. Phlebotomy improved both spirometry and gas exchange. Improvement in arterial oxygen saturation and PaO2 could not be attributed to changes in alveolar ventilation, but rather to better distribution of VA/Qc ratios since physiological dead space decreased. Our results are similar to those reported in polycythemia vera patients. A significant correlation between the changes in PaO2 with phlebotomy and the control PaO2 have been found from 45 polycythemic patients with chronic obstructive pulmonary disease collected from the literature. It is concluded that excessive polycythemia worsened hypoxemia and that phlebotomy improved gas exchange.     

Ventilatory and cerebrovascular responses in normocapnic and hypercapnic COPD patients.

This study investigated the hypothesis that hypercapnia in some chronic obstructive pulmonary disease (COPD) patients may be related to a high cerebrovascular response to carbon dioxide (CO2). The relationship between responses of ventilation and of cerebral blood volume (CBV) to acute changes in carbon dioxide tension in arterial blood (Pa,CO2) was measured in 17 chronic hypercapnic (Pa,CO2 >6.0 kPa) and 16 normocapnic (Pa,CO2 < or = 6.0 kPa) COPD patients, who were matched for degree of airway obstruction (forced expiratory volume in one second 27% predicted). Results were compared with 15 age-matched healthy subjects. CBV was measured using near infrared spectroscopy during normo- and hypercapnia and related to inspired minute ventilation (V'I) and mouth occlusion pressure (P0.1). Hypercapnia (end-tidal pressure of carbon dioxide (deltaPET,CO2) > 1 kPa) was induced by giving adequate amounts of CO2 in the inspired air. During normocapnia, CBV (mL x 100 g(-1)) was 2.41+/- 0.66 and 2.90 +/- 0.60 (mean +/- SD) in the normocapnic and chronic hypercapnic patients, respectively, which was significantly lower compared to healthy subjects (3.53 +/- 0.77). All slopes of CO2 responsiveness (deltaCBV/deltaPa,CO2, deltaV'I/deltaPa,CO2, deltaP0.1/deltaPa,CO2) were significantly lower in both COPD groups relative to healthy subjects, but were not significantly different between the COPD groups. A poor but positive correlation between ventilatory and cerebrovascular CO2 responsiveness (deltaCBV/deltaPa,CO2 and deltaV'I/deltaPa,CO2) was found in COPD patients and healthy subjects. The findings do not support the hypothesis of abnormal cerebrovascular responses to carbon dioxide in hypercapnic chronic obstructive pulmonary disease patients.     

无创通气治疗慢性阻塞性肺疾病呼吸衰竭的研究进展

慢性阻塞性肺疾病（COPD）常并发呼吸衰竭,机械通气是重要治疗措施,其中无创通气（NIV）是临床上常用治疗方法。NIV治疗COPD急性加重期急性呼吸衰竭可以改善患者的呼吸功能、动脉血氧饱和度和降低通气插管率。NIV治疗COPD稳定期慢性呼吸衰竭也能改善动脉血氧饱和度、生活质量和运动耐力。严重酸中毒、高血糖和患者病情严重等是预测NIV治疗失败因素。该文对NIV治疗COPD急性加重期和稳定期、NIV参数设置、影响NIV疗效因素方面进行了综述。     

99mTc-DTPA aerosol deposition and clearance in COPD, interstitial disease, and smokers

The application of 99mTc-DTPA radioaerosols to a variety of clinical disorders is described. With the development of simple equipment that can deliver very small droplets, this approach has become increasingly popular for measurements of the distribution of ventilation in patients with obstructive lung disease and suspected pulmonary embolism. In addition, by determining the rate at which the radionuclide is cleared from the lung, information has been obtained concerning the permeability of the pulmonary epithelium to extracellular indicators. Accelerated clearance rates have been found in patients with a variety of chronic interstitial lung diseases indicating that epithelial permeability is increased. Accelerated clearance rates have also been found with acute inflammation of the lung such as the adult respiratory distress syndrome and pneumocystis pneumonia. Furthermore, rapidly reversible increases in 99mTc-DTPA clearance occur in smokers and may be related to the inflammatory changes that contribute to the development of emphysema.     

Simultaneous magnetic resonance imaging of ventilation distribution and gas uptake in the human lung using hyperpolarized xenon-129

Despite a myriad of technical advances in medical imaging, as well as the growing need to address the global impact of pulmonary diseases, such as asthma and chronic obstructive pulmonary disease, on health and quality of life, it remains challenging to obtain in vivo regional depiction and quantification of the most basic physiological functions of the lung-gas delivery to the airspaces and gas uptake by the lung parenchyma and blood-in a manner suitable for routine application in humans. We report a method based on MRI of hyperpolarized xenon-129 that permits simultaneous observation of the 3D distributions of ventilation (gas delivery) and gas uptake, as well as quantification of regional gas uptake based on the associated ventilation. Subjects with lung disease showed variations in gas uptake that differed from those in ventilation in many regions, suggesting that gas uptake as measured by this technique reflects such features as underlying pathological alterations of lung tissue or of local blood flow. Furthermore, the ratio of the signal associated with gas uptake to that associated with ventilation was substantially altered in subjects with lung disease compared with healthy subjects. This MRI-based method provides a way to quantify relationships among gas delivery, exchange, and transport, and appears to have significant potential to provide more insight into lung disease.     

无创正压通气治疗慢性阻塞性肺病伴呼吸衰竭患者48例疗效观察

目的研究无创正压通气（NIPPV）治疗慢性阻塞性肺病急性加重期并发Ⅱ型呼吸衰竭的临床效果。方法选择2008年6月～2009年12月我院48例NIPPV治疗慢性阻塞性肺病急性加重期（AECOPD）并发Ⅱ型呼吸衰蝎患者的血气指标变化（pH值、PaO2和PaCO2）,住院病程,气管插管率,并同2007年6月～2008年12月未使用NIPPV治疗的36例COPD相似病例进行比较分析。结果 NIPPV治疗组48例患者前后24h血气指标明显改善,住院病程缩短,气管插管率明显降低,同非NIPPV治疗的对照组比较差异有显著性（P〈0.05）。结论NIPPV是治疗AECOPD并发Ⅱ型呼吸衰竭的一种有效方法,早期应用可阻止病情进一步发展,缩短病程,降低气管插管率。     

Lung function tests in connective tissue diseases associated with Raynaud's phenomenon

13 patients with various connective tissue diseases associated with Raynaud's phenomenon were studied with pulmonary physiologic techniques to see the alterations of lung functions and also whether spasm of pulmonary circulation occurs in these patients. We found that an increase in the dead space ventilation was common and associated with normal tidal volume. We interpreted this finding as evidence of redistribution of blood flow in the lung by spasm of blood vessels going to well-ventilated lung units generating a high dead space ventilation. We also found commonly that the distribution of inspired air in the lung was uneven, the diffusing capacity was reduced and the dynamic compliance decreased with increasing frequency of breathing suggestive of disease in small airways. The restrictive defect, the obstructive defect, the reduction of lung compliance and the arterial hypoxemia were relatively uncommon and probably occurred when the diseases were more advanced.     

布地奈德混悬液吸人治疗慢性阻塞性肺疾病急性加重期的临床观察

目的 探讨雾化吸入布地奈德混悬液治疗慢性阻塞性肺疾病（COPD）急性加重期患者的疗效。方法 40例COPD急性加重期患者随机分成治疗组和对照组各20例，分别给予布地奈德混悬液及全身性应用糖皮质激素。观察2组治疗前后呼吸困难、肺功能、动脉血气变化及副作用的情况。结果 治疗组和对照组治疗前后的呼吸困难、肺功能、动脉血气变化均差异无显著性，雾化吸入布地奈德混悬液治疗组的副作用明显少于全身应用糖皮质激素的对照组。结论 雾化吸入布地奈德混悬液是治疗COPD急性加重期患者安全有效的方法，值得推广。     

无创通气在COPD合并呼吸衰竭治疗中的应用

目的探讨双水平正压无创通气在COPD合并呼吸衰竭中的治疗作用。方法64例COPD合并呼吸衰竭患者随机分为B iPAP呼吸机无创通气组32例与常规治疗对照组32例,监测其治疗前、治疗后2、12、72 h血气变化,观察临床情况的变化及并发症的发生,对结果进行对比分析。结果无创通气组的pH、PaO2、PaCO2等指标明显改善(P<0.0 1,P<0.05)。结论无创双水平正压通气能明显改善COPD并呼吸衰竭患者的低氧血症及高碳酸血症,其疗效优于常规治疗方法。     

Right ventricular dysfunction and the exercise limitation of chronic obstructive pulmonary disease

This study examined right ventricular function during exercise in patients with chronic obstructive pulmonary disease to answer the following questions: Is there a significant correlation between oxygen consumption at maximal exercise and exercise right ventricular ejection fraction? Does the right ventricular ejection fraction response to exercise correlate with exercise changes in pulmonary artery pressure, total pulmonary resistance or pulmonary vascular resistance? Which combinations of cardiac, ventilatory and blood gas variables are the best predictors of oxygen consumption at maximal exercise? Twenty-six patients with stable chronic obstructive pulmonary disease performed symptom-limited supine bicycle exercise with simultaneous hemodynamic and radionuclide ventriculographic measurements. The oxygen consumption at maximal exercise correlated with the exercise right ventricular ejection fraction (n = 21, r = 0.66; p less than 0.005), exercise stroke volume (r = 0.68; p less than 0.001), exercise cardiac output (r = 0.77; p less than 0.00005) and exercise ventilation (r = 0.85; p less than 0.00001). The change in right ventricular ejection fraction from rest to exercise correlated inversely with the change from rest to exercise in total pulmonary resistance (r = -0.51; p less than 0.05) but not with the change in mean pulmonary pressure (r = -0.37) or in pulmonary vascular resistance (r = 0.09). Multivariate analysis showed that the variables giving the highest combined correlation with oxygen consumption were ventilation and right ventricular ejection fraction (r = 0.95, adjusted r2 = 0.88). These results suggest that exercise oxygen consumption of patients with chronic obstructive pulmonary disease is related to right ventricular systolic function, exercise right ventricular dysfunction is related, in part, to abnormal exercise total pulmonary resistance, and exercise limitation in chronic obstructive pulmonary disease occurs as a result of the dynamic interaction between disordered right heart function and ventilation.     

Central respiratory drive in acute respiratory failure of patients with chronic obstructive pulmonary disease

Control of breathing was studied in patients with chronic obstructive pulmonary disease, both in the chronic state and during acute respiratory failure. The results were compared to those in a group of age-matched normal subjects. In patients breathing air, minute ventilation was not different during acute and chronic states, and was similar to that in normal subjects. The pattern of breathing, however, was different: acutely ill patients took shorter and smaller breaths, with a breathing frequency higher than that of normal subjects. The pattern of the chronic group was intermediate between that of acutely ill patients and that of normal subjects. Mouth occlusion pressure, an index of neuromuscular respiratory drive, was 5 times greater in acutely ill patients than in normal subjects. Administration of O2 at a flow of 5 L/min caused a small (14%), bus significant, decrease in minute ventilation due to decreased respiratory frequency. The tidal volume did not change, so the decrease in minute ventilation was the result of decreased inspiratory flow. This was associated with a decreased mouth occlusion pressure that was still 3 times greater than that of normal subjects. The increase in arterial PCO2, observed after administration of O2 was not correlated with the decrease in ventilation, indicating that other factors must be responsible for the increase in arterial PCO2. We concluded that (1) despite the poor mechanical advantage of the respiratory muscles in acute respiratory failure, the increased drive to breathe results in high mouth occlusion pressure and inspiratory flow, and (2) the increase in arterial PCO2, observed during administration of O2 is not related solely to changes in respiratory drive.