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PubMed2003

Measurement variability in single-breath diffusing capacity of the lung.

STUDY OBJECTIVES: The single-breath diffusing capacity of the lung (DLCO) is a commonly performed pulmonary function test. The current American Thoracic Society (ATS) recommendations for reproducibility of DLCO measurements suggest that two measurements for the DLCO agree within 10% or 3 mL/min/mm Hg of the average value. The European Respiratory Society (ERS) recommends that two measurements should agree within 10%. The objectives of the present study were to examine whether the current reproducibility criteria were met in a general pulmonary function laboratory and to determine whether alternative criteria might be appropriate. DESIGN: Cross-sectional study. SETTING: University-based pulmonary function laboratory. PATIENTS OR PARTICIPANTS: Patients referred for spirometry, helium lung volumes, and DLCO measurement. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: In a sample of 6,193 patients referred for clinical testing, 98.3% had two DLCO values that fulfilled the current ATS criteria for reproducibility. The coefficient of variation (CV) and the percentage difference between two repeat measurements were inversely associated with the baseline DLCO and the FEV(1). As the baseline DLCO (percentage of predicted) or FEV(1) (percentage of predicted) decreased, there was an increase in the CV and the percentage difference. In contrast, the absolute difference between repeat measurements was relatively stable irrespective of the baseline DLCO or FEV(1) values. Other patient factors, such as gender and race, were not associated with measurement variability. Using an absolute difference of 2 to 2.5 mL/min/mm Hg between two DLCO measurements as alternative criteria for reproducibility, 91.5% and 95.8% of the patient sample fulfilled these criteria, respectively. CONCLUSIONS: Reproducibility of the DLCO measurement is generally much better than current standards allow. Future standards should consider an absolute difference rather than a percentage difference criterion for DLCO reproducibility.

Adult↗
PubMed2005

Idiopathic pulmonary fibrosis in patients younger than 50 years.

OBJECTIVE: To assess clinical, radiological, histopathologic, and prognostic differences in younger patients with idiopathic pulmonary fibrosis (IPF). PATIENTS AND METHODS: This study consisted of patients younger than 50 years with IPF who were seen at the Mayo Clinic in Rochester, Minn, from January 1, 1994, to December 31, 2000. Clinical, radiological, and histopathologic data were abstracted from clinical records. Total lung capacity using plethysmography, vital capacity, diffusing capacity for carbon monoxide using the single-breath method, and alveolar volume using single-breath neon wash-in were measured. RESULTS: Our study population was composed of 16 men and 6 women with a median age of 45 years (range, 28-49 years). Median survival was 2.1 years, with 1- and 2-year survival rates of 68% and 53%, respectively. Of the 22 patients, 2 were current smokers, 14 were former smokers, and 6 had never smoked. Three patients had familial pulmonary fibrosis, 21 had bibasilar inspiratory crackles, and 10 had digital clubbing. Median total lung capacity was 56.2%, vital capacity was 51.0%, diffusing capacity was 45.5%, and alveolar volume was 65.0%. CONCLUSION: Although previous studies have suggested that younger age is a favorable prognostic factor in patients with IPF, we found that younger patients have the same poor prognosis as do older patients with this disorder. We observed no distinguishing differences in the clinical, radiological, and histopathologic features compared with those in older patients in whom the disorder is more common. Lung transplantation should be considered early in the treatment of younger patients with IPF.

Adult↗
PubMed1996

Pulmonary function in children treated for rhabdomyosarcoma.

Chemotherapy, radiation therapy, and surgical intervention have markedly improved the survival of patients treated for rhabdomyosarcoma. Unfortunately, the therapy may have deleterious effects on the lung. Pulmonary functions tests were obtained from 17 patients treated for rhabdomyosarcoma because of our concern regarding potential pulmonary dysfunction in this group of patients who had received bleomycin, which is known to be associated with lung injury. Mean age at the time of the diagnosis of rhabdomyosarcoma was 10.1 (+/- 7.2) years (range 0.01-23.5 years). The mean age at the time of pulmonary function testing was 17.0 (+/- 7.5) years (range 5.8-34.0 years). Study patients reportedly had no pulmonary symptoms. Approximately 87% of study patients had a restrictive ventilatory impairment on pulmonary function testing as measured by total lung capacity (TLC) values less than the lower limit of normal. Approximately 70% of study patients had carbon monoxide diffusing capacity (DLCO) values less than the lower limit of normal. There were no significant differences in pulmonary function parameters when male study patients were compared to female study patients. There was a statistically significant lower forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) ratio (P=0.03) and percent predicted forced expiratory flow at 25-75% of the FVC (FEF25-75; P=0.03) in the group of patients diagnosed with rhabdomyosarcoma over 8 years of age as compared to those individuals diagnosed under 8 years of age. In addition, there were no statistically significant differences in pulmonary function when the variables of sex and age at diagnosis (as outlined above) were studied in combination. In summary, we identified a high incidence of restrictive ventilatory abnormalities in a group of individuals (predominantly children) treated for rhabdomyosarcoma as well as a significantly lower FEV1/FVC ratio and percent predicted FEF25-75 in the group of patients diagnosed with the neoplasm over 8 years of age. Individuals caring for such patients are encouraged to obtain pre- and sequential posttreatment pulmonary function tests.

Adolescent↗
PubMed1994

Cardiopulmonary adaptations to pneumonectomy in dogs. IV. Membrane diffusing capacity and capillary blood volume.

Lung diffusing capacity for carbon monoxide (DLco) and its components, membrane diffusing capacity (Dmco) and capillary blood volume (Vc), as well as pulmonary blood flow (Qc), were measured at rest at several lung volumes and during treadmill exercise by a rebreathing technique in four adult dogs after right pneumonectomy (R-PNX) and in six matched control dogs (Sham) 6-12 mo after surgery. In both groups, lung inflation at rest was associated with a small increase in DLco and Dmco but not in Vc. After R-PNX, total DLco was lower by 30% at peak exercise compared with control values. When compared with DLco in a normal left lung, DLco in the remaining lung continued to increase along the normal relationship with respect to Qc up to a cardiac output equivalent to 34 l/min through both lungs of the Sham dog. There was no evidence of an upper limit of DLco being reached. The augmentation of DLco from rest to exercise was associated with corresponding increases in Dmco and Vc; after R-PNX, both Dmco and Vc continued to increase with respect to Qc along similar relationships as in control dogs without reaching an upper limit, suggesting a much larger alveolar-capillary reserve for gas exchange by diffusion than previously recognized. At higher levels of blood flow through the remaining lung, DLco was greater in adult dogs after R-PNX than after left pneumonectomy (Carlin et al. J. Appl. Physiol. 70: 135-142, 1991), suggesting that additional sources of compensation, e.g., lung growth, exist after removal of > 50% of lung.

Animals↗
PubMed2004

[Continuous ambulatory peritoneal dialysis and respiratory pulmonary functions].

Acidobasic balance and respiratory pulmonary functions were examined in 15 patients with chronic renal insufficiency during continuous ambulatory peritoneal dialysis (CAPD) using a dialysis solution containing 1.5% or 2.5% of glucose. Patients did not suffer from any pulmonary disease nor ischemic heart disease. Biochemical indicators of acidobasic balance were in reference range or on its lower margin. Respiratory pulmonary functions were in tolerance except maximum expiratory flow volume at 50% and 25% of vital capacity (MEF50 and MEF25) and except diffusion lung capacity (DLCO) which were decreased. Decrease of maximum expiratory flow could be caused by a loss of elasticity of pulmonary parenchyma and by a beginning increased resistance in peripheral pulmonary ways. Decreased DLCO was identified in majority of patients and was caused by anaemia and a minimal interstitial pulmonary edema. Use of a single peritoneal dialysis with dialysis solutions of various glucose concentrations did not have any significant effect on acidobasic balance markers nor pulmonary respiratory functions.

Acid-Base Equilibrium↗
PubMed1988

Diffusing capacity predicts morbidity and mortality after pulmonary resection.

Patients who are considered for major pulmonary resection are normally evaluated by spirometry and clinical assessment. Despite this, the morbidity and mortality rates are high after these operations. We retrospectively reviewed results of lung resection performed during a period of 7.5 years in 237 patients to identify other important predictors of morbidity and mortality. There were 144 male and 93 female patients with a mean age of 59.4 +/- 11.4 years. The indication for operation was lung cancer in 199 (76 stage I, 34 stage II, 89 stage IIIA-B), benign disease in 34, and metastatic disease from other primary tumors in four. Lobectomy or bilobectomy was performed in 164 patients and pneumonectomy in 73. Data on 38 preoperative and operative risk factors were correlated with information on 24 postoperative events grouped into four major categories: death, pulmonary complications, cardiovascular complications, and other problems. Logistic regression analysis and chi 2 analysis were used to identify the relationship of the preoperative risk factors to the grouped postoperative complications. The diffusing capacity of the lung for carbon monoxide was the most important predictor of mortality (p less 0.01) and was the sole predictor of postoperative pulmonary complications (p less than 0.005). This diffusing capacity can reveal the existence of emphysematous changes in the lung, even when spirometric values are acceptable, and it usually should be a part of the evaluation of patients being considered for pulmonary resection.

Adolescent↗
PubMed1982

Effect of nitroglycerin on DL of normal subjects at rest and during exercise.

By use of the single-breath diffusing capacity for carbon monoxide (DL) as an index of the pulmonary capillary filling, the effects of 3 mg sublingual nitroglycerin (NTG) were studied in eight healthy subjects at rest and during exercise. At rest, NTG induced a significant and persistent decrease of DL when subjects were sitting or supine (60 min of observation) and also when they were in the lateral decubitus or supine with legs up position (30 min of observation). Subjects in the supine positions showed more pronounced percentage decreases in DL than when sitting. In the sitting position 1 mg NTG also induces a decrease of DL. During a moderate upright cycloergometer exercise, NTG also induces a significant decrease of DL; the decrease is smaller and of shorter duration (less than 15 min) than at rest, but it reappears as soon as the exercise is stopped. The decrease of DL may be attributed to an outward shift of blood from the thorax to the periphery or to a redistribution of lung perfusion consequent to changes in pulmonary vascular pressures.

Adult↗
PubMed1982

Diffusion at high altitude.

The problems posed by exercise at high altitude for oxygen diffusion across the blood-gas barrier have been recognized since the early part of this century. But the successful ascent of Mt. Everest (altitude 8848 m) by two climbers without supplementary oxygen in 1978 focused attention on this issue. We have therefore carried out a theoretical study of gas exchange under these conditions of extreme hypoxia. Calculations of oxygenation along the pulmonary capillaries show that, even at rest, there is an alveolar-end capillary PO2 of about 6 torr caused by diffusion limitation, and this widens rapidly on mild exercise. As the oxygen uptake is increased, the PO2 of mixed venous blood falls to very low values. If we assume a minimal value of 15 torr, a maximal oxygen uptake on the summit of less than 700 ml/min is predicted. VO2max is extremely sensitive to barometric pressure, and to a lesser extent to lung diffusing capacity.

Altitude↗