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At least 1,261 records · Page 70Linked to original sources
PubMed1993

The assessment of respiratory function in a patient with dyspnoea and severe hypoxaemia.

In the investigation of dyspnoea and severe hypoxaemia the clinical relevance of multiple diagnostic techniques was studied. The patient was sequentially studied utilizing several techniques. The degree of lung impairment by spirometry, diffusing capacity for carbon monoxide, haemodynamics, pulmonary gas exchange, ventilation-perfusion relationships assessed by the multiple inert gases elimination techniques, ventilation and perfusion lung scans, gallium 67 scintigraphy, bronchoalveolar lavage and high resolution computerized tomography, twice over a period of 12 months during recovery under treatment. A marked impairment of pulmonary gas exchange was first explained by diffusion impairment and ventilation-perfusion mismatch. The multiple inert gas elimination technique allowed determination of the cause of hypoxaemia by ventilation-perfusion inequality. A pathological correlate of the ventilation-perfusion inequality was the appearance of honeycomb lungs detected by high resolution computed tomograph and active alveolitis by bronchoalveolar lavage. All results were consistent with a diagnosis of fibrosing alveolitis. The patient was evaluated again during treatment. Some functional improvement occurred despite persistence of the same pathological findings. In conclusion, this study demonstrates the value of information derived from different tests. Physiological correlations complemented by pathological observations expand understanding of the pathogenesis of disease. These procedures contribute to understanding mechanisms responsible for functional impairment.

Bronchoalveolar Lavage Fluid↗
PubMed1991

Effect of varying alveolar oxygen partial pressure on diffusing capacity for nitric oxide and carbon monoxide, membrane diffusing capacity and lung capillary blood volume.

1. To examine the effect of varying oxygen partial pressure (PAO2) on nitric oxide (DLNO) and carbon monoxide (DLCO) diffusing capacity (transfer factor), 10 subjects performed combined DLCO/DLNO measurements with the inspired mixture made up with three different oxygen concentrations (25%, 18% and 15%) to give PAO2 values of 12-20 kPa. 2. A novel method is described for calculating membrane diffusing capacity (DM) and pulmonary capillary volume (Qc) from DLNO and DLCO. 3. The mean DMCO was 52.89 mmol min-1 kPa-1 and Qc was 0.056 litre. Reducing PAO2 from 20 to 12 kPa resulted in an increase in DLCO = -0.124 (O2%) + 11.67 (P less than 0.001) and a fall in DLNO = 0.538 (O2%) + 32.01 (P less than 0.001) and a fall in DLNO/DLCO = 0.107 (O2%) + 2.52 (P less than 0.001). DM (P = 0.59) and Qc (P = 0.64) also tended to fall with falling PAO2. 4. It appears more likely that the minor reduction in DLNO that we have observed with falling PAO2 is due to diffusion rather than reaction limitation.

Blood Volume↗
PubMed1998

Dobutamine-induced changes in pulmonary artery pressure in patients with congestive heart failure and their relation to abnormalities of lung diffusing capacity.

Short-term infusion of dobutamine may determine a mild, statistically significant increase in pulmonary artery pressure from baseline in 30% of patients with moderate to severe heart failure despite systemic effects (changes in cardiac index and systemic vascular resistance) similar to those observed in patients showing a large reduction in right heart pressures. The increase in pulmonary artery pressure observed seems to be associated with a lower pulmonary diffusing capacity, probably reflecting a reduction in recruitment and distension capacity of pulmonary circulation.

Adult↗
PubMed1988

Alveolar-capillary block in patients with AIDS and Pneumocystis carinii pneumonia.

To determine the value of subdividing diffusing capacity for carbon monoxide (DL) in diagnosing and monitoring the course of Pneumocystis carinii pneumonia (PCP), we measured DL, membrane diffusing capacity (DM), and pulmonary capillary blood volume (VC) in 20 control subjects, 20 patients with a low DL (less than 75% predicted) and newly diagnosed PCP, and 16 patients with a low DL in most of whom PCP had been suspected and excluded. Ten patients with PCP were restudied approximately 60 days after treatment. When clinically indicated, lung biopsies were obtained for histologic examination. Compared with mean values in control subjects (DL = 92%, DM = 101%, and VC = 35 ml/m2), all values were decreased (p less than 0.01) in patients with PCP (DL = 58%, DM = 33%, and VC = 26 ml/m2) and in those without PCP (DL = 61%, DM = 56%, and VC = 22 ml/m2). Values of DM were significantly less (p less than 0.05) in patients with, than in those without, PCP. Analysis of lung biopsies by light and electron microscopy showed overlapping morphologic abnormalities in the 2 groups of patients. In the 10 patients with PCP restudied after successful treatment, the mean DL increased from 60 to 80% (p less than 0.0005), the DM increased from 35 to 108% (p less than 0.006), and the VC did not change. These results suggest that in contrast to most disorders in which DL is decreased, PCP causes reversible alveolar-capillary block.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Diffusion-perfusion inhomogeneity and alveolar-arterial O2 diffusion limitation: theory.

Unequal distribution of pulmonary O2 diffusing capacity (D) to pulmonary blood flow (Q) (D/Q heterogeneity) leads to decreased alveolar O2 exchange efficacy. It is shown on simple models that the effect increases with increasing amount of inequality and with increasing value of the equilibration index, D/(Q beta) (beta, increment in blood O2 content per partial pressure increment). This inhomogeneity effect, if not taken into account, leads to spurious increases of D in hypoxia and with elevated O2 uptake.

Animals↗
PubMed1992

Pulmonary responses to lower body negative pressure and fluid loading during head-down tilt bedrest.

Exposure to microgravity redistributes body fluids with important secondary effects on cardiovascular function. We tested the hypothesis that the fluid shifts also affect pulmonary gas exchange. Microgravity was simulated in six male volunteers by a 10-day period of bedrest at 6 degrees head-down tilt (HDT). Lower body negative pressure (LBNP) and intravenous saline loading superimposed acute changes in fluid distribution on the prolonged effects of HDT. HDT produced relative dehydration and hypovolemia with decreased pulmonary blood flow and diffusing capacity. Before bedrest, pulmonary blood flow decreased by 24% during LBNP and diffusing capacity by 7%, while functional residual capacity increased by 14% (p less than 0.05). Intravenous saline loading caused a 24% increase in pulmonary blood-flow (p less than 0.05). Functional residual capacity decreased by 10% and diffusing capacity by 6% (p less than 0.05). Lung tissue volume did not change significantly. Head-down tilt had only minor effects on the responses to LBNP and saline loading. We conclude that LBNP and intravenous saline loading produce major changes in pulmonary blood-flow and minor effects on pulmonary gas exchange, and that the response to acute changes in fluid distribution is not significantly altered during simulated microgravity.

Adult↗
PubMed1977

Rebreathing pulmonary capillary and tissue volume in normals after saline infusion.

A rebreathing technique was utilized to assess changes in diffusing capacity (DCO), pulmonary capillary blood volume (Vc), pulmonary parenchymal tissue volume (Vt), and cardiac output (Qc), after infusion of 2 liters of 0.9% saline intravenously in 13-25 min in five healthy subjects. Blood hemoglobin concentration decreased an average of 17%. Vc increased strikingly in all five subjects. No significant changes in Vt, or in Vt per unit lung volume were observed. Radiographic evidence of interstitial pulmonary edema was present in four of the five subjects. Radiographic total lung capacity was reduced significantly in four of the five subjects. Significant reductions in forced vital capacity (FVC), forced expiratory volume in 1.0 and 3.0 s, and mean forced expiratory flow during the middle half of the FVC occurred in three of the five subjects. No dyspnea, cough, or physical examination abnormalities of lungs or heart occurred. This noninvasive, ventilation-limited, rebreathing technique appears capable of detecting early changes in pulmonary congestion, at a time when definitive radiographic changes and changes in the physical examination are absent. It appears capable of detecting the increase in Vc associated with hypervolemia in man.

Adult↗
PubMed1979

Role of single-breath carbon monoxide-diffusing capacity in monitoring the pulmonary effects of bleomycin in germ cell tumor patients.

Serial pulmonary function tests including single-breath carbon monoxide-diffusing capacity (DLCO), forced vital capacity (FVC), and forced expiratory volume in 1 sec were performed in a relatively homogeneous group of male patients with germ cell tumors treated with vinblastine, bleomycin, and cis-diamminedichloroplatinum. Of the pulmonary function tests used, the DLCO was shown to be the most sensitive indicator of subclinical bleomycin pulmonary effects. Decreases in DLCO were both total dose and schedule dependent. Patients receiving their total dose of bleomycin at a rate of 25 +/- 2 (S.D.) units/week developed a linear decrease in DLCO with increasing total doses of bleomycin. Changes in FVC did not correlate with bleomycin total dose. Although both the mean DLCO and FVC decreased after completion of bleomycin therapy, the mean FVC returned to base-line levels rapidly, whereas the decrease in mean DLCO was persistent for several months. When routine volumetric tests (FVC and forced expiratory volume in 1 sec) and DLCO are used in a systematic manner, DLCO is the most sensitive indicator of the subclinical pulmonary effects of bleomycin in germ cell tumor patients treated with vinblastine, bleomycin, and cis-diamminedichloroplatinum.

Adult↗
PubMed2000

Relationship between impaired pulmonary diffusion and cardiopulmonary exercise capacity after heart transplantation.

STUDY OBJECTIVES: Diffusion impairment and reduced performance in cardiopulmonary exercise testing (CPX) have been found in patients after heart transplantation. The pathogenesis of these abnormalities is unclear. In particular, the contribution of pulmonary interstitial changes has not yet been verified. DESIGN: We analyzed pulmonary function tests, high-resolution CT (HRCT), echocardiography, left heart catheterization, and CPX in transplanted patients. PATIENTS: Forty long-term survivors were studied at a median of 47 months (range, 12 to 89 months) after heart transplantation. RESULTS: Diffusion was impaired in 40% (transfer factor for carbon monoxide) or 82.5% (carbon monoxide transfer coefficient) of the patients. Diffusion impairment was caused by a decreased diffusing capacity of the alveolar capillary membrane in 89% and/or by a decreased blood volume of the alveolar capillaries in 46% of cases. In five patients (12.5%), CT revealed interstitial lung changes. These patients did not have different values of diffusion capacity. Maximal oxygen uptake and ventilatory efficiency during exercise (minute ventilation/carbon dioxide output slope) were impaired in 92% and 46% of the cases, respectively. CONCLUSIONS: Our data show that the diffusion abnormalities are caused by an impaired diffusion status of the alveolar capillary membrane. Interstitial changes detectable in HRCT were found not to be involved in this process. The reduced performance in CPX in our long-term survivors is caused by pulmonary perfusion abnormalities and low tidal volume, which is due to the deconditioning of respiratory muscle, rather than by interstitial changes or diffusion abnormalities.

Adult↗
PubMed1996

Early and late morbidity in patients undergoing pulmonary resection with low diffusion capacity.

BACKGROUND: We sought to determine whether low diffusion capacity of the lung to carbon monoxide (DLCO) is a predictor of high postoperative mortality and morbidity after major pulmonary resection and whether major pulmonary resection in patients with low DLCO results in substantial long-term morbidity. METHODS: Sixty-two major pulmonary resections were performed in 61 patients with low DLCO (DLCO < or = 60% predicted for pneumonectomy or bilobectomy; < or = 50% predicted for lobectomy). Contemporaneously, 262 other patients underwent 263 major pulmonary resections (group II). Long-term morbidity was assessed in subsets of patients with low (n = 24) and high (n = 22; DLCO > 60% predicted) DLCO. RESULTS: The hospital mortality rates were equivalent (4.8% low DLCO versus 4.9% group II), whereas respiratory complications were more frequent in patients with low DLCO (18% versus 9.5%; p = 0.05). In the subgroup analyses, patients with low DLCO had more hospitalizations for respiratory compromise and worse median dyspnea scores. Analysis of patients with substantial dyspnea revealed an association with extended pulmonary resection and postoperative radiation therapy in patients with low DLCO. CONCLUSIONS: Patients with low DLCO underwent major pulmonary resection with a low mortality rate and an acceptable, but increased, respiratory complication rate. Long-term respiratory morbidity was increased in patients with low DLCO; however, the extent of pulmonary resection and the use of postoperative radiation therapy may have contributed to the development of dyspnea in these patients.

Aged↗
PubMed1975

Lung volumes, mechanics, and single-breath diffusing capacity in anesthetized cats.

We measured lung weight, lung volumes, pulmonary mechanics, and carbon monoxide transfer (DLCO, single-breath method) in healthy cats (3.3 +/- 0.4 kg) that were anesthetized, paralyzed, and mechanically ventilated through a tracheal cannula. Compared with Stahl's predicted values which were based on regression analyses of data collected from several species, our cats had larger and more compliant lungs in relation to body weight, higher DLCO per unit body weight, and similar DLCO/TLC (size independent constant). Compared with Robinson et al.'s values derived entirely from studies on dogs, our cats had significantly smaller lung volumes and DLCO per unit body weight, DLCO/TLC and similar ratios of CL/FRC. Several factors appear to contribute to the functional variations among mammalian species: differences in the relation of lung to body weight, differences in the relation of chest wall compliance to lung compliance, and differences in the fundamental structure and design of the respiratory systems. Differences in methodology are acknowledged to be an additional factor.

Anesthesia↗