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Diffusing capacity and spirometry following a 60-minute dive to 4.5 meters.

The purpose of this study was to assess the contribution of SCUBA to the pulmonary effects of diving to 4.5 meters depth in healthy subjects using a randomized crossover control condition. Ten healthy divers performed two 60-minute 'dives' using SCUBA in a swimming pool. The non-immersed 1 ATA SCUBA control exposure took place at ambient pressure in the laboratory. Thirty minutes prior to, and 30 and 90 minutes post-exposure, FVC (forced vital capacity), FEV1.0 (forced expired volume), peak expiratory flow rate (PEFR), diffusing capacity (DL(co)), heart rate (HR) and temperature were measured. No significant differences were noted in HR, temperature or spirometry between the two conditions. A significant reduction in diffusing capacity occurred at 30 and 90 minutes after the pool dive (9.3% and 15.1%, respectively, p < 0.05). There was no concordant change in DL(co) following the non-immersed 1 ATA SCUBA control. Thus, a pool dive to 4.5 meters for 60 minutes causes a decrease in DL(co), without a change in spirometry, while breathing from SCUBA equipment without immersion causes no significant change in lung function.

Adult↗
PubMed2004

Clinical significance of elevated diffusing capacity.

STUDY OBJECTIVE: Single-breath diffusing capacity of the lung for carbon monoxide (DLCO) is used as a pulmonary function test (PFT) to assess gas transfer in the lungs. The implications of a low DLCO are well-recognized, but the clinical significance of a high DLCO is not clear. The aim of this study was to identify the clinical correlates of a high DLCO. PATIENTS AND METHODS: We identified 245 patients with a high DLCO (ie, > 140% predicted) and a matched group of 245 patients with normal DLCO (ie, 85 to 115% predicted), who were selected from a laboratory database of 45,000 patients tested between January 1997 and December 1999. We compared the demographic features, clinical diagnoses, and PFT data between the two groups. SETTINGS: Large multispecialty group practice. RESULTS: The patients in the high DLCO group were heavier (mean [+/- SD] weight, 96.0 +/- 22.9 vs 85.0 +/- 21.3 kg, respectively; p < 0.001), had a higher mean body mass index (32.9 +/- 7.4 vs 29.4 +/- 6.4 kg/m(2), respectively; p < 0.001), larger body surface area (p < 0.001), and larger mean total lung capacity (p = 0.007) and alveolar volume (p < 0.001). The clinical diagnoses of obesity (p < 0.001) and asthma (p < 0.001) were more common among patients with high DLCO values. The majority of patients (62%) with a high DLCO had a diagnosis of obesity, asthma, or both. Polycythemia, hemoptysis, and left-to-right shunt were uncommon. CONCLUSION: A high DLCO on a PFT is most frequently associated with large lung volumes, obesity, and asthma. Other conditions are much less common. A clinical condition, which typically reduces DLCO, may deceptively normalize DLCO in such patients.

Adult↗
PubMed1998

Single breath diffusing capacity for carbon monoxide: effects of adjustment for inspired volume dead space, carbon dioxide, hemoglobin and carboxyhemoglobin.

In order to assess the additive effects of taking into account dead space volume (VD), carbon dioxide, hemoglobin (Hb) and carboxyhemoglobin on computation of single breath carbon monoxide diffusing capacity (DLCOsb), we sequentially applied all the corrections recommended by the 1987 American Thoracic Society (ATS) document on DLCOsb standardization. We used data from 739 men (333 nonsmokers and 406 current smokers) and 475 women (403 nonsmokers and 72 current smokers) who underwent measurement of DLCOsb in the decade 1985-1994 at the Lung Function Laboratory of our institute. With respect to the unadjusted DLCOsb value, significant small differences were found for all the corrected formulas, ranging from -0.18 to 1.48 ml/min/mm Hg in men and from -0.24 to 1.57 ml/min/mm Hg in women. After computing the percent change of DLCOsb [(unadjusted-adjusted value) x 100/unadjusted value], we observed that the correction for VD caused an underestimation of DLCOsb of about 5.8% in men and 7.7% in women. However, when all the corrections were considered, these figures decreased to about 0.9% in males and 2.9% in females. Regarding specifically the correction for Hb, the adjusted value was slightly lower in men, while it was some-what higher in women, with respect to the unadjusted DLCOsb. In conclusion, the corrections suggested by ATS in the computation of DLCOsb, when considered altogether, seem to account for a limited proportion of test variability in usual clinical conditions, especially in males.

Adolescent↗
PubMed1978

Collateral ventilation and the middle lobe syndrome.

The mechanics of collateral ventilation in the right middle lobe of 5 young, normal volunteers were studied using a bronchoscopic wedge technique, and the results were compared with those from an upper lobe of the same subjects. At functional residual capacity, the resistance to collateral ventilation in the right middle lobe was 4,042 +/- 559 cm H2O per liter per sec (mean +/- SE), whereas that of the upper lobes was 799 +/- 168 cm H2O per liter per sec. The time constant for collateral ventilation could not be measured in the right middle lobe of any of the subjects because it exceeded their breath-holding times of 6 to 16 sec. The time constant for collateral ventilation in the upper lobes was 4.5 +/- 1.0 sec. We concluded that collateral ventilation in the right middle lobe of young normal subjects is characterized by a high resistance and a long-time constant relative to the upper lobes. This is probably explained by a greater ratio of pleural surface to nonpleural surface in the right middle lobe as compared to the upper lobes. We suggest that ineffective collateral ventilation is a major factor in the pathophysiology of the Middle Lobe Syndrome.

Adult↗
PubMed1976

Pulmonary dysfunction in systemic lupus erythematosus without pulmonary symptoms.

Pulmonary function was measured in a group of 28 patients with systemic lupus erythematosus (SLE) who were free of pulmonary involvement at the time of the study. When compared with age and sex matched controls, the SLE patients had a pattern of restriction with reduced lung volumes and vital capacity. Diffusing capacity was reduced in proportion to the reduction in lung volume. This is felt to be most compatible with inapparent pleural thickening resulting in impaired lung expansion. There was no evidence of airway obstruction on maximal expiratory flow-volume curves. The effect of cigarette smoking in the SLE patients was a reduction in flows at low lung volumes, which was indistinguishable from the effects in the control smokers. Both SLE and control smokers had a significant reduction in DL/VA when compared with control nonsmokers. Pulmonary function was not influenced by the presence of renal disease.

Female↗
PubMed1994

Single breath diffusing capacity for carbon monoxide in stable asthma.

BACKGROUND: Single breath diffusing capacity for carbon monoxide (Dco) is commonly used as a simple method of assessing overall pulmonary gas exchange properties. Studies of Dco in bronchial asthma have yielded conflicting results. OBJECTIVE: To study Dco and to determine the factors influencing Dco in patients with asthma. METHODS: Dco was prospectively measured in 80 consecutive never-smoker patients with uncomplicated stable asthma. The topographic distribution of lung perfusion was determined in 10 asthmatics and 10 controls, with a 133Xe radionuclide scan. RESULTS: The mean (SD) value of Dco was increased to 117 (17) percent of predicted values; individual values were either within or above normal limits; diffusion was also elevated at 116 (19) percent after correction for alveolar volume (transfer coefficient, D/VA). The Dco was not correlated with atopic status, duration of asthma, or results of spirometric tests; there was a weak negative correlation between D/VA and FEV1 or residual volume. There was a better perfusion of the upper zones of the lungs in asthmatics as compared with controls. Among the asthmatics, there was a strong positive correlation between Dco and the apex to base perfusion ratio (r = 0.975). CONCLUSIONS: Dco is normal or high among never smoker patients with uncomplicated asthma; elevated Dco may be attributed to a better perfusion of the apices of teh lungs; the latter could result from two mutually nonexclusive mechanisms: an increase in pulmonary arterial pressure and/or a more negative pleural pressure generated during inspiration as a consequence of bronchial narrowing. The unexpected finding of high Dco should raise the possibility of bronchial asthma in patients with otherwise undiagnosed conditions.

Adult↗