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PubMed2007

Diffusing capacity for nitric oxide: reference values and dependence on alveolar volume.

Nitric oxide (NO) has a much stronger affinity for hemoglobin than carbon monoxide (CO); therefore, the DL(NO) (diffusing capacity for NO) is less influenced by changes in capillary blood volume than the DL(CO) (diffusing capacity for CO), and represents the true membrane diffusing capacity. We measured the combined single breath DL(NO)/DL(CO) in 124 healthy subjects, and generated reference equations for the DL(NO) and K(NO). In a subset of 21 subjects the measurements were performed on different inspiratory levels. The reference equation for DL(NO) in females is 53.47*H(height)0.077*A(age)-48.28(RSD5.22) and for males 59.84*H-0.25*A-44.20(RSD6.39). Reference equations for K(NO) in females is -2.03*H-0.025*A+11.52(RSD0.48) and for males -0.15*H-0.045*A+9.47(RSD0.65). The K(CO) (DL(CO)/V(A)) increases when V(A) (alveolar volume) decreases, probably due to an increase of blood volume per unit lung volume. The DL(NO) was much stronger related to the V(A), the K(NO) was almost independent of V(A). Because of the relative independence of the K(NO) on V(A), the K(NO) appears to be a much better index for the diffusion capacity per unit lung volume (transfer coefficient) than the K(CO).

Adult↗
PubMed2002

Intrabreath diffusing capacity of the lung in healthy individuals at rest and during exercise.

BACKGROUND: Traditional approaches to measuring the diffusing capacity of the lung for carbon monoxide (DLCO) treat the lung as a single, well-mixed compartment and produce a single value for DLCO to represent an average diffusing capacity of the lung (DL). Because DL distribution in the lung is inhomogeneous, and changes in the DL in diseased lungs may be regional, measuring regional DL, especially during exercise, may be more sensitive in detecting pulmonary vascular diseases. OBJECTIVES: To characterize regional changes in DL in healthy individuals from rest to exercise, and to provide normal references for future studies in pulmonary vascular disorders. METHODS: We reanalyzed DLCO and phase III CH(4) slopes that were obtained during a slow, single exhalation at rest and during exercise in our extended database of 105 healthy individuals. DLCO profiles between 20% and 80% of exhaled vital capacity (VC) (ie, the intrabreath DLCO) were analyzed by calculating the average DLCO measured at midlung volume (ie, 30 to 45% of exhaled VC [DLCOMLV]) and by fitting the whole curve with a third-order polynomial equation. RESULTS: DLCO decreased nonlinearly by approximately 30%, from 20 to 80% of exhaled VC at rest. DLCO during exercise was greater than that at rest, and the increase was similar at all lung volumes. The CH(4) slopes at rest and during exercise were similar. Prediction equations based on regressions on age, sex, and height were computed for resting and exercise DLCOMLV and the phase III CH(4) slope (an index of ventilation distribution). CONCLUSIONS: Capillary recruitment/dilation during exercise in healthy individuals is a uniform process throughout the lungs. Our analyses provide a database for a noninvasive method that can incorporate exercise to evaluate the volume-dependent distribution of DLCO in lung diseases.

Adult↗
PubMed2006

Effect of lung resection on exercise capacity and on carbon monoxide diffusing capacity during exercise.

OBJECTIVE: To evaluate the effect of lung resection on lung function and exercise capacity values, including diffusion capacity of the lung for carbon monoxide (Dlco), during exercise, and to determine whether postoperative lung function, including exercise capacity and Dlco during exercise, could be predicted from preoperative lung function and the number of functional segments resected. DESIGN: Prospective study. SETTING: Clinical pulmonary function laboratory in a university teaching hospital. PATIENTS: Twenty-eight patients undergoing lung resection at Vancouver General Hospital from October 1998 to May 1999, were studied preoperatively and 1-year postoperatively. INTERVENTIONS: We determined FEV(1) and FVC, and maximal oxygen uptake (Vo(2)max) and maximal workload (Wmax) achieved during incremental exercise testing. We used the three-equation modification of the single-breath Dlco technique to determine Dlco at rest (RDlco) and during steady-state exercise at 70% of Wmax, and the increase in Dlco from rest to exercise (ie, the mean increase in Dlco percent predicted at 70% of Wmax from resting Dlco percent predicted [(70%-R)Dlco]). We calculated the predicted postoperative (PPO) values for all the above parameters using the preoperative test data and the extent of functioning bronchopulmonary segments resected, and compared the results with the actual 1-year postoperative results. RESULTS: Following lung resection, there was a significant reduction in FEV(1), FVC, and Dlco with decreases of 12%, 13%, and 22% predicted, respectively. There were also significant decreases in Vo(2)max per kilogram of 2.1 mL/min/kg (8% of predicted Vo(2)max) and in Wmax of 12 W (7% of predicted Wmax). However, (70%-R)Dlco did not significantly decrease after lobectomy but decreased after pneumonectomy. The calculated PPO values significantly underestimated postoperative values after pneumonectomy but were acceptable for lobectomy. CONCLUSIONS: Exercise tests may be better indicators of functional capacity after lung resection than measurements of FEV(1) and FVC or RDlco. PPO results calculated by estimating the functional contribution of the resected segments, are comparable with those obtained using ventilation-perfusion lung scanning and significantly underestimate postoperative lung function after pneumonectomy, but are acceptable for lobectomy.

Aged↗
PubMed1996

Terpene exposure and respiratory effects among sawmill workers.

OBJECTIVES: This study was performed to evaluate exposure to terpenes in sawmills and to study the acute effects on lung function and the respiratory tract of exposed laborers. METHODS: The relationships between personal exposure to sawing fumes, assessed by air sampling, and terpene metabolites in urine were studied. The association between exposure to terpenes and acute effects on lung function was studied for 48 workers. The reactivity to methacholine within the study population was investigated. Variation in acute subjective respiratory symptoms during a workshift was evaluated by interviewing the employees before and after work, following a standardized questionnaire. RESULTS: Personal exposure to terpenes in the sawmills was 11-158 mg. m-3. The correlation (correlation coefficient = 0.84) between exposure to alpha-pinene and the concentration of verbenols (metabolites from alpha-pinene) in urine was good. No acute effects on forced vital capacity or forced expiratory volume during 1 s were detected. A decrease in carbon monoxide lung diffusing capacity after a workshift was detected. Workers with > or = 5 years of sawmill employment showed a higher reactivity to methacholine than those with < 5 years. Eye irritation increased during a workday. CONCLUSIONS: Personal exposure to monoterpenes during a workshift sometimes exceeds the present Swedish limit value. The results show that verbenols in urine can be used as a biological exposure index of sawing fumes. Exposure in sawmills can cause an acute decrease in diffusing capacity. Workers with < or = 5 years of employment showed increased bronchial reactivity.

Acute Disease↗
PubMed2003

Red blood cell orientation in pulmonary capillaries and its effect on gas diffusion.

When alveoli are inflated, the stretched alveolar walls draw their capillaries into oval cross sections. This causes the disk-shaped red blood cells to be oriented near alveolar gas, thereby minimizing diffusion distance. We tested these ideas by measuring red blood cell orientation in histological slides from rapidly frozen rat lungs. High lung inflation did cause the capillaries to have oval cross sections, which constrained the red blood cells within them to flow with their broad sides facing alveolar gas. Low lung inflation stretched alveolar walls less and allowed the capillaries to assume a circular cross section. The circular luminal profile permitted the red blood cells to have their edges facing alveolar gas, which increased the diffusion distance. Using a finite-element method to calculate the diffusing capacity of red blood cells in the broad-side and edge-on orientations, we found that edge-on red blood cells had a 40% lower diffusing capacity. This suggests that, when capillary cross sections become circular, whether through low-alveolar volume or through increased microvascular pressure, the red blood cells are likely to be less favorably oriented for gas exchange.

Animals↗
PubMed1985

Carbon monoxide diffusing capacity: a reliable indicator of bleomycin-induced pulmonary toxicity.

Seventy-seven untreated patients with germ-cell tumors, of whom 20 had no pulmonary involvement, no clinical or radiological evidence of pulmonary disease, received 6 courses of cisplatin, vinblastine and bleomycin. Pulmonary function tests were performed before, every 3 weeks during treatment, and once a month from then on. The carbon monoxide diffusion capacity tests were normalized with respect to the actual hemoglobin concentration. During treatment a nonsignificant decrease (P greater than 0.05) was seen in the flow volume relationships, but as it was reversible it was attributed to the strenuous treatment. In contrast a significant decrease of 35% (P less than 0.01) in the corrected carbon monoxide diffusion capacity was seen in 15 of 18 evaluable patients with neither clinical nor radiological signs of pulmonary toxicity. The decrease was correlated to the increasing dose of bleomycin (r = 0.63).

Adolescent↗
PubMed2000

Thickness of the air-blood tissue barrier in infants.

The harmonic mean barrier thickness of the alveolar air-blood tissue barrier was measured in nine SIDS cases, six cases of unnatural death (three with asphyxiation, three without asphyxiation) and six cases showing interstitial pneumonia (IP, three cases with lymphomonocyte infiltration of alveolar walls, three cases with peribronchiolar infiltration). Approximately 550-600 measurements were carried out in each case using micrographs with a final magnification of 11,000. The Th values ranged between 0.37 micron and 0.39 micron in the SIDS group, in deaths due to asphyxiation and IP with a peribronchiolar type of infiltration, were lowest in the unnatural deaths without asphyxiation (0.32 micron) and highest in cases showing IP with alveoloseptal infiltration (0.44 micron). The differences between the groups were significant (H-test, Hcor = 5.927). Compared to "normal" unnatural deaths (Th = 0.32 micron), cases with interstitial cell infiltration of the alveolar septa showed a nearly 40% increase of the barrier thickness which indicates a corresponding decrease of the diffusion capacity. A decreased diffusion capacity can cause hypoxemia which could be an additional trigger mechanism in the death process.

Age Factors↗
PubMed1985

Respiration and lung function in the mouse, Mus musculus (with a note on mass exponents and respiratory variables).

Ventilatory ability, the diffusing capacity of the lung and oxygen uptake have been investigated in mice of different sizes. Breathing frequency decreased with body weight although minute ventilation (V) increased (V alpha W 1.725). Weight-specific diffusing capacity for carbon monoxide showed little variation with size. Oxygen consumption (VO2) rose with weight according to VO2 alpha W0.41. In older, larger mice this resulted in increased ventilatory requirements (V/VO2).

Animals↗
PubMed1983

CO2 diffusing capacity in isolated dog lung lobes and the role of carbonic anhydrase.

CO2 diffusing capacities (DmCO2) were measured at 22 degrees C on 12 isolated perfused dog lung lobes before and after inhibition of lung tissue carbonic anhydrase (CA) by acetazolamide (Diamox). The hypothesis is that CA in the alveolar-capillary tissue enhances overall transport of CO2 by converting CO2 to HCO-3 within aqueous portions of the tissue. HCO-3 diffuses simultaneously with molecular CO2, increasing the overall CO2 flux, and then converts back to molecular CO2 at the end of the aqueous pathway. To ensure at least partial diffusion limitation, lobes were perfused with phosphate buffer at high pH (7.7) and high flow rates. Plant CA (which is not inhibited significantly by Diamox) was added to the perfusate to provide rapid uptake of CO2 via conversion to HCO-3. After Diamox, DCO2 decreased 39.6%, indicating that CA does increase CO2 transport through lung tissue. Surprisingly, DCO2 exceeds CO diffusing capacity by only 9.3 +/- 2.1 times (without Diamox inhibition) rather than by the factor of 24 predicted by Graham's law on the basis of solubilities and molecular weights of the gases.

Acetazolamide↗
PubMed1991

Lung volume, diffusing capacity, chest roentgenogram and dyspnea index in interstitial lung disease.

To investigate the physiologic impairment and the role played by pulmonary function tests in interstitial lung disease (ILD), we performed spirometry tests and tested the single-breath carbon monoxide diffusing capacity of 27 patients with diffuse interstitial pulmonary fibrosis (DIPF) and 35 patients with collagen vascular disease (CVD). All of the patients showed irregular linear opacities on their chest X-ray films. Corresponding chest roentgenograms for each patient were evaluated according to the International Labour Organization (ILO) classification. A modified Baseline Dyspnea Index (BDI), which incorporate a patient's physical activity into the recording, was used to quantitate dyspnea. Patients with DIPF demonstrated a comparable reduction in both lung volumes and diffusing capacity. In contrast, patients with CVD had a greater reduction in diffusing capacity than in forced vital capacity (FVC) and total lung capacity (TLC). There were no significant correlations between the type of linear opacities and the severity of the pulmonary function abnormalities, or between the opacities and the dyspnea in either disease group. The profusion of pulmonary infiltrates also did not affect the lung function except for diffusing capacity in patients with DIPF. However, there was a significant loss of FVC, TLC, forced expiratory volume in one second (FEV1) and diffusing capacity with increasing levels of dyspnea. We conclude that pulmonary function parameters may not be equally affected in DIPF and CVD. Approaches using the ILO classification for analysis of chest roentgenograms provide limited information regarding the functional status of patients. Pulmonary functions are significantly related to the extent of a patient's physical activity, if the severity of dyspnea is evaluated carefully using a quantifiable system.

Adult↗
PubMed2001

Single-breath carbon monoxide diffusing capacity.

Measurement of DL(CO) remains a clinically useful way to assess transfer of gases across the lung. It is important, however, to be vigilant in controlling the sources of variation and to be aware of those that remain when interpreting the measured values.

Breath Tests↗
PubMed1981

Quantitative analysis of the respiratory system of the house sparrow, budgerigar and violet-eared hummingbird.

In the house sparrow, the budgerigar and the violet-eared hummingbird the volumes of the lungs and air sacs are estimated from silicone casts. The quantitative composition of the lungs and of their compartments are measured on lung slices, the relative volumes of the parabronchi on histological sections, and the volume composition of the blood-air capillary network of the parabronchi on electron micrographs. On electron micrographs the exchange surface and the thickness of the air-blood diffusion barrier are also measured. From these data the morphological membrane diffusion capacity is calculated and related to several organ weights. The volume of the lungs and air sacs makes up 14-22% of the total body volume, the lungs only 2.3-2.9%. The exchange surface varies from 61 cm2/g (budgerigar) over 70 cm2/g (house sparrow) to 99 cm2/g (violet-eared hummingbird). The very thin barrier in these small birds results in a membrane diffusion capacity of 0.122 in budgerigars up to 0.271 ml O2/mm Hg . min . g in violet-eared hummingbirds. The various parameters are compared with those of corresponding mammals, and the quantitative advantages of the avian respiratory system are discussed.

Animals↗
PubMed1978

[Comparative study of a vagolytic and a beta 2 sympathomimetic drug on the respiratory function of the asthmatic patient].

The authors compared the effects of a synthetic vagolytic drug, the SCH 1000, and a beta2 sympathicomimetic one (Fenoterol) in two groups of control children (n = 11) and two groups of asthmatic children (n = 23). They studied the following parameters, flow volumes curves, steady state lung diffusing capacity and the blood gases. No difference of efficiency was found between the two types of bronchodilators although the graphic modification of flow volumes curves was different after Fenoterol and after SCH 1000. The modifications consisted in a great improvement in instantaneous flow, a decrease in diffusion capacity and an increase of the Pa O2 significant in the group of asthmatic children after Fenoterol.

Adolescent↗
PubMed1989

Body weight in chronic obstructive pulmonary disease. The National Institutes of Health Intermittent Positive-Pressure Breathing Trial.

This study reviews the relationship between body weight, pulmonary function, and survival in the recent clinical trial of intermittent positive pressure breathing (IPPB). We related body weight, expressed as a percent of the ideal (%IBW), to the numerous other features of the disease recorded in this data set. Body weight was directly related to FEV1 (p = 0.0001), so that all subsequent analyses of body weight had to first consider FEV1. Mortality appeared to be influenced by body weight independent of FEV1. In patients with %FEV1 less than 35, mortality increased with decreasing body weight (p = 0.093), and this relationship was stronger in patients with %FEV1 35 to 47 (p = 0.048) and even stronger in patients with %FEV1 greater than 47 (p = 0.007). After adjusting for FEV1, body weight was a powerful positive correlate with exercise capacity (p = 0.0001). Body weight was also inversely related to %TLC (p = 0.0408) after adjusting for FEV1. Body weight was a powerful predictor of diffusing capacity (p = 0.0001) in patients with the same FEV1. These results support the hypothesis that factors related to nutritional status are an independent influence on the course of COPD.

Adult↗
PubMed1981

Improved accuracy and precision of single-breath CO diffusing capacity measurements.

Using three conventional methods and a new method we measured the single-breath diffusing capacity for carbon monoxide [DLCO(SB)] in a group of normal subjects. Whereas the conventional methods calculated DLCO(SB) from a single equation valid only for breath holding, the new method used three equations, one for each phase of the single-breath maneuver, i.e., inhalation, breath holding, and exhalation. We found that while the conventional methods of calculating DLCO(SB) were greatly affected by variations in the way in which the single-breath maneuver was performed and/or the way in which the alveolar gas sample was collected, these variations had little effect on the calculations of DLCO(SB) using the new method. These results were in close agreement with results from a computerized mathematical lung model in which the diffusing capacity did not change with lung volume. We concluded that the new method significantly improves the accuracy and precision of DLCO(SB) measurements while reducing the effects of maneuver variability. For these reasons comparisons of DLCO(SB) values between patients and normal subjects or between two groups with different pulmonary function may be more valid using the new method than using conventional methods.

Adult↗
PubMed1983

Comparison of total lung diffusion capacity and the membrane component of diffusion capacity as determined by physiologic and morphometric techniques.

Morphometric estimates of diffusion capacity have traditionally been calculated for oxygen (DLO2) while physiologic techniques have been used to determine diffusion capacity for carbon monoxide (DLCO). Morphometric estimates of DLCO and Dm were determined for carbon monoxide so that the results can be directly compared to those obtained using physiologic techniques. Multiple gas rebreathing techniques were used to measure total lung diffusion capacity (DLCO), membrane component of diffusion capacity (Dm) and pulmonary capillary blood volume (Vc) in five anesthetized dogs. After the rebreathing measurements were made, the lungs were inflation fixed with glutaraldehyde and subjected to morphometric analysis. The morphometric estimate of diffusion capacity was three times higher than the physiologic estimate. The major components of diffusion capacity, Dm and theta Vc were found to be of approximately equal size when measured physiologically (Dm = 34 and theta Vc = 27 ml X min-1 X mm Hg-1). In contrast, the morphometric estimate of Dm was about six times higher than the morphometric estimate of theta Vc. The widely different ratios of the two major subcomponents of the total lung diffusion capacity as measured by these two different techniques suggest that the same lung function is not being accurately measured by at least one of these two techniques. Differences in results for DLCO cannot be explained by differences in the physiologic state of the animal at the time the measurement was made. Morphometric analysis predicts that Vc is the major term affecting the value of DLCO whereas the physiologic techniques predict that both Dm and Vc contribute substantially to the value of DLCO.

Animals↗
PubMed1981

Pulmonary oxygen transport during activity in lizards.

Oxygen consumption (MO2), effective alveolar ventilation (Veff), arterial and alveolar PO2 (PaO2, PAO2) and the alveolar-arterial PO2 difference [(A--a)PO2] were determined in the lizards Varanus exanthematicus and Iguana iguana at rest and during treadmill exercise at 35 degrees C. In both species, Veff increased more rapidly than MO2 giving rise to an increased PAO2. In contrast, PaO2 remained unchanged through the highest levels of MO2 attained. As a result, the (A--a)PO2 increased with increasing MO2. We suggest that the observed increase in (A--a)PO2 may be due to a rather low pulmonary oxygen diffusing capacity (DLO2) and limited capacity to increase DLO2 during exercise. Arterial desaturation was prevented by a compensatory hyperventilation, thus enhancing the gradient for alveolar-capillary gas exchange. These results indicate that both lizard species increase pulmonary oxygen transport sufficiently so that it is not a limiting factor to aerobic scope under the conditions of this study.

Animals↗
PubMed1982

[Respiratory function study on insulin-dependant diabetics (author's transl)].

A present report on insulin dependant diabetics described changes in ventilatory mechanics and a decrease of pulmonary volumes; other studies ended up with different results, i.e. an absence of any spirographic change: the current study agrees with the latter findings. Yet, we noticed an alteration in the CO transfer of the lungs at the alveolar-capillary membrane level which appeared to be due to a reduced pulmonary capillary volume. The duration of the disease and the possible appearance of characteristic complications of diabetes did not seem to have any influence on the functional parameters measured. On the other hand, a broncho-pulmonary disorder independant of diabetes but associated with certain ailments (chronic bronchitis, sequelae of tuberculosis, ... tobacco smoking, etc.) led, as one might have foreseen, to functional ventilatory disturbances. A histological and haematological study would be a logical sequel to our study to clarify the mechanism of the diminished pulmonary transfer capacity.

Adolescent↗