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PubMed1979

Interrelationships between neutrophil elastase, serum alpha, -antitrypsin, lung function and chest radiography in patients with chronic airflow obstruction.

We assayed protease and elastase activity of lysosomal granules of purified neutrophil suspensions in 58 patients with chronic irreversible airflow obstruction and compared them to 26 healthy control subjects. Denatured hemoglobin and tritiated elastin were used as substrates for protease and elastase assays. Forty-two patients had M antitrypsin phemotype, five had MS, and 11 had Z variant (five were homozygotes and six were heterozygotes). We did not find significant differences in mean lysosomal elastase or protease activity between patients with normal antitrypsin and control subjects; however, a few patients had concentrations of neutrophil elastase that exceeded the range among control subjects. There was no significant correlation between neutrophil protease or elastase activity and age, smoking, degree of airway obstruction, diffusing capacity, lung elastic recoil, or radiologic presence of emphysema in patients with M and MS antitrypsin. In patients with Z variant antitrypsin, protease and elastase concentrations per unit of lysosomal protein were not significantly different from those in control subjects or M patients; however, both elastase and protease content per 108 neurtophils was significantly higher in homozygous and heterozygous Z patients as compared to normalsubjects and M patients, which suggest an increase in the neutrophil content of protease and elastase in patients with Z antitrypsin deficiency. These results suggest that hte concentrations of protease and elastase in neutrophils do not appear to interact as additive risk factors in the pulmonary impairment of most patients with chronic airflow obstruction, but may be of importance as risk factors in patients with Z or MZ phenotype and in a few patients with M phenotype.

Forced Expiratory Volume↗
PubMed1997

Determination of production of nitric oxide by lower airways of humans--theory.

Exercise and inflammatory lung disorders such as asthma and acute lung injury increase exhaled nitric oxide (NO). This finding is interpreted as a rise in production of NO by the lungs (VNO) but fails to take into account the diffusing capacity for NO (DNO) that carries NO into the pulmonary capillary blood. We have derived equations to measure VNO from the following rates, which determine NO tension in the lungs (PL) at any moment from 1) production (VNO); 2) diffusion, where DNO(PL) = rate of removal by lung capillary blood; and 3) ventilation, where V A(PL)/(PB - 47) = the rate of NO removal by alveolar ventilation (V A) and PB is barometric pressure. During open-circuit breathing when PL is not in equilibrium, d/dt PL[V(L)/ (PB - 47)] (where V(L) is volume of NO in the lower airways) = VNO - DNO(PL) - V A(PL)/(PB - 47). When PL reaches a steady state so that d/dt = 0 and V A is eliminated by rebreathing or breath holding, then PL = VNO/DNO. PL can be interpreted as NO production per unit of DNO. This equation predicts that diseases that diminish DNO but do not alter VNO will increase expired NO levels. These equations permit precise measurements of VNO that can be applied to determining factors controlling NO production by the lungs.

Air Pressure↗
PubMed2001

Static lung compliance as an index of early pulmonary disease in systemic sclerosis.

Pulmonary function abnormalities constitute the most important cause of morbidity and mortality in patients with systemic sclerosis (SSc). A restrictive ventilatory defect with a reduction in pulmonary carbon monoxide diffusion capacity (DLCO) is the commonest finding. Static lung compliance (Cst) is perhaps the most sensitive parameter for the detection of abnormal pulmonary mechanics. We compared the results of Cst and DLCO in patients with SSc and normal spirometry to identify early pulmonary disease. Sixteen of 50 patients had normal spirometry, eight of whom had abnormal Cst. Four of them also had a reduced DLCO. Two patients had abnormal DLCO but their Cst was normal. One of them had pulmonary hypertension on echocardiography. We conclude that Cst was helpful in diagnosing early pulmonary abnormality in 50% of patients with normal spirometry. Among these patients Cst was a better index of abnormality than DLCO.

Adult↗
PubMed2003

Silicosis in 76 men: qualitative and quantitative CT evaluation--clinical-radiologic correlation study.

PURPOSE: To use qualitative and quantitative computed tomography (CT) to test the hypothesis that impaired lung function with silicosis is due to progressive massive fibrosis (PMF) and associated emphysema. MATERIALS AND METHODS: Seventy-six men with silicosis underwent volumetric and thin-section CT of the thorax. Lung function, Borg scale dyspnea grade, silica exposure duration, and cigarette consumption were determined. Nodular profusion (NP) at chest radiography was graded according to the International Labor Organization radiographic classification system; NP and PMF at CT were visually graded by using five-point (ie, grades 0-4) and four-point (grades 0-3) scales, respectively. Emphysema and NP, which together are defined as the NP index, were quantified by using attenuation threshold values of less than -950 HU and greater than -100 HU, respectively. Mean lung attenuation was also determined. Relationships among the CT, chest radiographic, and clinical parameters were analyzed by using Spearman correlation. RESULTS: NP at chest radiography correlated (r > 0.50) with all CT parameters of nodularity. CT PMF had the highest correlation with emphysema (r = 0.58, P <.001). NP at chest radiography and all CT parameters were inversely related to lung function. At multiple regression analysis, PMF and emphysema index (both at CT) were significant determinants of forced expiratory volume in 1 second (FEV1) (P =.006 and.03, respectively) and FEV1 to forced vital capacity (FVC) ratio (P =.007 and.02, respectively). Mean lung attenuation remained related to FVC (P =.03), diffusing capacity of lung for carbon monoxide (P =.04), and Borg scale grade (P =.01). Cigarette consumption and silica exposure duration had no independent effects on lung function. CONCLUSION: Qualitative and quantitative CT parameters can be used as indirect measures of functional impairment in silicosis. PMF and emphysema are independently related to airflow obstruction, whereas mean lung attenuation is related to clinical dyspnea and reduced lung volume.

Adult↗
PubMed1989

[Replacement of helium by argon in the measurement of the carbon monoxide diffusing capacity of the lung].

Carbon monoxide diffusing capacity of the lung (DLco) of 118 normal subjects and 48 patients was measured by using three different gas mixtures respectively: (1) 10% He, 0.3% CO, 21% O2 and the remainder N2; (2) 10% Ar, 0.3% CO, 21% O2 and the remainder N2; (3) 10% He, 10% Ar, 0.3% CO, 21% O2 and the remainder N2. The results were extremely close with each other, value was 0.99 (P less than 0.0005). These results indicate for the first time that the much cheaper and easy-available gas-argon can be used instead of the very expensive helium for measurement of DLco.

Adult↗
PubMed1988

Lung function in silica-exposed workers. A relationship to disease severity assessed by CT scan.

To investigate the relationship of lung function, airflow limitation, and lung injury in silica-exposed workers, we analyzed the clinical, functional, and radiologic data of 94 long-term workers exposed in the granite industry or in foundries. The subjects were divided into four subsets based on chest roentgenogram and CT scan of the thorax: group 1 consisted of 21 subjects with category 0 chest roentgenogram and category 0 CT scan; group 2, 28 subjects with category E 1 on both chest roentgenogram and CT scan; group 3, 18 subjects with category E 1 on chest roentgenogram but with coalescence or conglomeration or both seen only on CT scan; and group 4, 27 subjects with category E 1 and coalescence or conglomeration or both on roentgenogram and CT scan. The groups did not differ in terms of age, height, cigarette smoking, or years of exposure. Lung volumes were significantly reduced only in group 4 (p less than 0.05). Lung compliance, diffusion capacity, and the rest-exercise P(A-a)O2 gradient were reduced in groups 3 and 4 (p less than 0.05). Expiratory flow rates were significantly reduced in groups 2, 3, and 4, with the lowest values in group 4. The expiratory flow rates in group 3 were significantly lower in group 3 than in group 2. These results support the concept that airflow in silica-exposed workers is significantly reduced when the disease is detectable on simple chest roentgenogram; coalescence or conglomeration or both on chest roentgenogram or CT scan is associated with significant loss of lung volumes, gas exchange function, and increased airflow obstruction.

Humans↗
PubMed2006

Bronchoscopic lung volume reduction for end-stage emphysema: report on the first 98 patients.

OBJECTIVES: To report the first multicenter experience on the treatment of end-stage emphysema using an endobronchial valve (EBV) [Emphasys EBV; Emphasys Medical; Redwood City, CA]. DESIGN: Retrospective analysis from prospective multicenter registry. PATIENTS AND INTERVENTIONS: This is a study of the use of EBVs in the treatment of end-stage emphysema at nine centers in seven countries. Ninety-eight patients with mean FEV(1) of 0.9 +/- 0.3 L (30.1 +/- 10.7% of predicted) [+/- SD] and residual volume (RV) of 5.1 +/- 1.3 L (244.3 +/- 0.3% of predicted) were treated over a period of 20 months. Spirometry, plethysmography, and diffusing capacity of the lung for carbon monoxide (Dlco) and exercise tolerance testing were performed at 30 days and 90 days after the procedure. RESULTS: RV decreased by 4.9 +/- 17.4% (p = 0.025), FEV(1) increased by 10.7 +/- 26.2% (p = 0.007), FVC increased by 9.0 +/- 23.9% (p = 0.024), and 6-min walk distance increased by 23.0 + 55.3% (p = 0.001). There was a trend toward improvement in Dlco, but this did not reach statistical significance (17.2 +/- 52.0%, p = 0.063). Patients treated unilaterally showed a trend toward greater improvement than those treated bilaterally. A similar trend toward improvement was observed in patients who had one entire lobe treated compared to those with just one or two bronchopulmonary segments treated. Eight patients (8.2%) had serious complications in the first 90 days, including one death (1.0%). CONCLUSION: This multicenter analysis confirms that improvement in pulmonary function and exercise tolerance can be achieved in emphysematous patients using EBVs. Future efforts should be directed to determining how to select those patients who would benefit most from this procedure and the best endobronchial treatment strategy.

Aged↗
PubMed2000

Performance level and cardiopulmonary responses during a cycle-run trial.

To determine the effect of triathlete performance level on the cardiorespiratory responses elicited by the cycle-run succession, eight regionally and nationally-ranked (Competitive) and five internationally-ranked (Elite) male triathletes underwent four successive laboratory trials: 1) an incremental treadmill test, 2) an incremental cycle test, 3) 30 min of cycling followed by 20 min of running (C-R), and 4) a 20-min control run (R) at the same speed as the run in C-R. Before and 10 min after the third and fourth trials the triathletes underwent lung function testing: spirometry and diffusing capacity testing for carbon monoxide (DL(CO)). During the C-R trial blood samples were drawn to measure venous lactate concentration. During all trials ventilatory data were collected every minute using an automated breath-by-breath system. The results showed that 1) the oxygen uptake (VO2) of post-cycling running versus running alone was similar for both groups; 2) the ventilatory responses (VE, VE/VO2, VE/VC02 and f) of C-R running versus R were significantly higher (P < 0.005) for the Competitive group; and 3) a significant decrease (P< 0.05) in DL(CO) was also noted after the C-R trial in the Competitive group but not in the Elite group. We concluded that 1) the ventilatory responses during a run subsequent to cycling may be related to the triathlete performance level, and 2) the C-R trial induced specific alterations in pulmonary function that may be associated with respiratory muscle alteration and exercise-induced hypoxemia in the Competitive triathletes.

Adult↗
PubMed1997

Patients with emphysema: quantitative CT analysis before and after lung volume reduction surgery. Work in progress.

PURPOSE: To quantitatively assess the morphologic changes in the lungs after lung volume reduction surgery and determine whether changes at quantitative computed tomography (CT) reflect changes in lung function. MATERIALS AND METHODS: In 10 patients, chest CT images were obtained at full inspiration and expiration before and after surgery. A semiautomated segmentation method was developed to isolate the lung regions and calculate the lung volumes and frequency distribution of attenuation values. The changes in lung volume and attenuation after surgery were compared with clinical findings, and an exploratory evaluation of outcome predictors was conducted. RESULTS: Semiautomated segmentation and quantitative analysis compared favorably with manual techniques, and there was good correlation between the emphysema indexes and percentage predicted forced expiratory volume in 1 second, forced expiratory volume in 1 second/forced vital capacity, and diffusing capacity. The emphysema index decreased from 60% to 38% at inspiration and from 60% to 27% at expiration after surgery. The average CT lung volume decreased from 7.5 to 5.6 L at inspiration (25%) and from 6.4 to 3.8 L (41%) at expiration after surgery and correlated well with measurements at plethysmography. CONCLUSION: Substantial decreases in the lung volumes and emphysema index, increased airflow, possible reexpansion of some remaining lung, and the relation between preoperative quantitative CT indexes and clinical outcome suggest a multifactorial mechanism for improvement seen after surgery.

Adult↗
PubMed1989

The National Institutes of Health Intermittent Positive-Pressure Breathing Trial: pathology studies. IV. The Destructive index.

A Destructive Index (DI) was recently devised by Saetta and coworkers (7), and their data suggest that the DI may be a better assessment of emphysema than the traditional indexes. We have applied the DI as well as conventional assessments of emphysema-panel grading (emphysema score), mean linear intercept (Lm), and internal surface area at a volume of 5 L (ISA5) - to the lungs of patients in the National Institutes of Health Intermittent Positive Pressure Breathing Trial, which admitted patients with moderate to severe chronic airflow obstruction. In the 41 patients with satisfactory morphologic material who died and were autopsied, the DI was significantly correlated with emphysema score (p less than 0.001), Lm (p less than 0.001), and ISA5 (p less than 0.001). There was a rapid increase in the DI between emphysema scores of 30 and 60; when the DI reached a score of about 90, it did not increase much further. A wide spread of the DI from 23.7 to 86.5 was present in lungs with a Lm of less than 0.55 mm. The DI was well related to the diffusing capacity for carbon monoxide (DLCO) (p less than 0.001) and %TLC (p less than 0.01), but not to %FEV1, slope of phase III (phase III), nor recoil pressure at 90% of TLC (P90). The correlations between emphysema score and either DLCO or %TLC were about the same as for the DI. Also, correlations were significant for %FEV1, phase III, and P90. Lesions of bronchioles had no correlation with the DI. We therefore conclude that the DI is related to conventional assessments of emphysema, but beyond an emphysema score of 55 or a Lm of 0.55 mm, it does not discriminate emphysema severity.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1998

Serial lung function and elastic recoil 2 years after lung volume reduction surgery for emphysema.

STUDY OBJECTIVE: To evaluate serial lung function studies, including elastic recoil, in patients with severe emphysema who undergo lung volume reduction surgery (LVRS). To determine mechanism(s) responsible for changes in airflow limitation. METHODS: We studied 12 (10 male) patients aged 68+/-9 years (mean+/-SD) 6 to 12 months prior to and at 6-month intervals for 2 years after thoracoscopic bilateral LVRS for emphysema. RESULTS: At 2 years post-LVRS, relief of dyspnea remained improved in 10 of 12 patients, and partial or full-time oxygen dependency was eliminated in 2 of 7 patients. There was significant reduction in total lung capacity (TLC) compared with pre-LVRS baseline, 7.8+/-0.6 L (mean+/-SEM) (133+/-5% predicted) vs 8.6+/-0.6 L (144+/-5% predicted) (p=0.003); functional residual capacity, 5.6+/-0.5 L (157+/-9% predicted) vs 6.7+/-0.5 L (185+/-10% predicted) (p=0.001); and residual volume, 4.9+/-0.5 L (210+/-16% predicted) vs 6.0+/-0.5 L (260+/-13% predicted) (p=0.000). Increases were noted in FEV1, 0.88+/-0.08 L (37+/-6% predicted) vs 0.72+/-0.05 L (29+/-3% predicted) (p=0.02); diffusing capacity, 8.5+/-1.0 mL/min/mm Hg (43+/-3% predicted) vs 4.2+/-0.7 mL/min/mm Hg (18+/-3% predicted) (p=0.001); static lung elastic recoil pressure at TLC (Pstat), 13.7+/-0.5 cm H2O vs 11.3+/-0.6 cm H2O (p=0.008); and maximum oxygen consumption, 8.7+/-0.8 mL/min/kg vs 6.9+/-1.5 mL/min/kg (p=0.03). Increase in FEV1 correlated with the increase in TLC Pstat/TLC (r=0.75, p=0.03), but not with any baseline parameter. CONCLUSION: Two years post-LVRS, there is variable clinical and physiologic improvement that does not correlate with any baseline parameter. Increased lung elastic recoil appears to be the primary mechanism for improved airflow limitation.

Aged↗
PubMed1984

Exercise alveolar-arterial oxygen pressure difference in interstitial lung disease.

Abnormality of gas exchange is best evaluated by the exercise alveolar-arterial oxygen pressure difference, P(A-a)O2. We studied the P(A-a)O2 in 168 patients with sarcoidosis, desquamative interstitial pneumonia (DIP), usual interstitial pneumonia (UIP), berylliosis, and asbestosis who were seen for clinical and disability consultations. The increase of P(A-a)O2 with exercise was greatest in UIP (mean 16 mm Hg), least in sarcoidosis (mean 1 mm Hg), and intermediate in DIP, berylliosis, and asbestosis (means 9, 9, and 7 mm Hg, respectively). The increase was best predicted by the single breath diffusing capacity (Dsb), and it occurred in patients with sarcoidosis and DIP if the Dsb was less than 50 percent predicted and in patients with the other diseases if the Dsb was less than 70 percent predicted. However, the magnitude of the increase could not be predicted from resting tests, even when multilinear regression equations were used. We conclude that for clinical evaluation of patients with interstitial lung disease, the exercise test with arterial blood gas measurement adds important information if the Dsb is less than 70 percent predicted. For disability evaluation, the invasive exercise study may be helpful when there is a wide discrepancy between clinical findings and resting physiologic studies.

Adult↗
PubMed1983

Climbing Mt. Everest without oxygen: an analysis of maximal exercise during extreme hypoxia.

Climbers have reached the summit of Mt. Everest without supplementary oxygen in spite of measurements at lower altitudes which suggest that this is impossible. In the present study, data obtained on the American Medical Research Expedition to Everest were used to analyze the oxygen transport system during maximal exercise at the highest point on earth. Barometric pressure was 253 Torr, giving an inspired PO2 of only 43 Torr, alveolar PCO2 was 7.5 Torr, hemoglobin 18.4 g/dl, P50 at pH 7.4 was 29.6 Torr, and base excess -7.2 mEq/L. Values for cardiac output and diffusing capacity were based on measurements previously made at an altitude of 5800 m. The analysis showed it is possible to account for a VO2 max of over 1 L/min while keeping the PO2 of mixed venous blood above 15 Torr. Differences between the present study and previous predictions of a lower VO2 max are explained. These differences include higher values of barometric pressure, ventilation and base excess than expected. The analysis shows that any rise in P50 caused by increased 2,3-diphosphoglycerate is a liability. While it is just possible for man to reach the summit of Everest without supplementary oxygen, this can only be done at the expense of extreme hyperventilation and respiratory alkalosis, and even then the arterial PO2 is less than 30 Torr.

Acid-Base Equilibrium↗
PubMed2003

Severe gastroesophageal reflux is associated with reduced carbon monoxide diffusing capacity.

OBJECTIVE: To assess whether severe gastroesophageal reflux (GER) is associated with abnormalities in lung function including measures of lung volume and gas diffusion. METHODS: Data from 147 patients with obesity (body mass index [BMI] range, 31.7 to 70 kg/m(2)) who presented for obesity surgery was analyzed retrospectively. A questionnaire was completed preoperatively that included a history of GER, frequency and severity of symptoms, investigations, and medications used. A history of lung disease, sleep-disordered breathing, and smoking also was obtained. A physician who was blinded to lung function graded GER severity prospectively by the results of pH monitoring and/or gastroscopy, and medication use. Spirometry, lung volumes, and gas transfer were measured preoperatively. RESULTS: Patients with severe GER had reduced levels of the diffusing capacity of the lung for carbon monoxide (DLCO) [21.1 mL/min/mm Hg; 95% confidence interval (CI), 18.9 to 23.2], as measured by CO transfer, compared with those patients without GER (26.3 mL/min/mm Hg; 95% CI, 24.4 to 28.2; p = 0.001). This remained significant after adjusting for age, gender, BMI, and smoking history. Gas transfer corrected for lung volume also was reduced in the group with severe GER (4.6 mL/min/mm Hg per L; 95% CI, 4.3 to 4.9) compared to the group without GER (5.3 mL/min/mm Hg per L; 95% CI, 5.1 to 5.5; p = 0.001). There was no significant difference in other measures of lung function. CONCLUSIONS: Severe GER is associated with an impairment of gas exchange. This may be due to microaspiration of gastric acid or fluid into the airways.

Adult↗
PubMed1989

Pulmonary function in long-term survivors of thoracoplasty.

Pulmonary function was assessed in 15 patients who had undergone thoracoplasty (TPL) approximately 30 years previously. Relation was noted to extent of TPL performed, side of TPL, age at TPL, and degree of secondary scoliosis. Test results showed mixed restrictive and obstructive defects. Although extent of TPL did not correlate with current lung function values, the restrictive defect was probably caused by a mixture of (a) compression of lung by TPL and (b) fibrosis from old pulmonary tuberculosis. The obstructive defect might have been due to the TPL procedure itself or to chronic bronchitis related to (a) previous pulmonary TB or (b) cigarette smoking, since 14 subjects were former or current smokers. That Dsb was relatively preserved suggests that pulmonary hypertension as a late sequela of TPL may be reactive (secondary to hypoxemia and respiratory acidemia) rather than obliterative.

Female↗
PubMed2001

Respiratory muscle strength, lung function, and dyspnea in patients with sarcoidosis.

BACKGROUND: Sarcoidosis is a systemic granulomatous disorder that is estimated to involve the skeletal muscles in up to 50% of patients. There is little information on the relationship among respiratory muscle strength, lung volumes, and the degree of dyspnea in patients with sarcoidosis. DESIGN AND PATIENTS: Lung function and maximal respiratory muscle force generation were measured in 36 patients with sarcoidosis (24 patients with pulmonary parenchymal infiltration) and 25 control subjects free of cardiorespiratory disease. Dyspnea in the sarcoidosis patients was quantitated by a score based on an activity tolerance assessment scale (ranging from rest to climbing hills or stairs). SETTING: Outpatient clinics of two teaching hospitals. RESULTS: Mean FVC, maximal voluntary ventilation, total lung capacity (TLC), functional residual capacity, residual volume (RV), and diffusing capacity of the lung for carbon monoxide (DLCO) were all at least 16% less than corresponding control values (in all cases, p < 0.001), while maximal inspiratory mouth pressure (PImax) and maximal expiratory mouth pressure (PEmax) were 37% and 39% less, respectively, than control values (both at p < 0.0001). PImax and PEmax declined with increasing dyspnea in a more graded, steady manner than did spirometric and DLCO values. For all measurements, however, the lowest mean values were found in patients with the most severe level of dyspnea. Strong inverse relationships were observed between PEmax and PImax with dyspnea level (p < 0.0001 and p < 0.01, respectively). Both PImax and PEmax correlated best with absolute values of FVC, while only PEmax correlated with RV (absolute and percent predicted) and percent predicted values of TLC. CONCLUSIONS: Maximal respiratory pressures correlate more closely with dyspnea level than lung volumes and DLCO. Since dyspnea is the most common presentation in early to moderately advanced sarcoidosis, respiratory pressures may be a more reliable index of functional work capacity and reflection of activities of daily living than standard tests of lung function.

Adult↗
PubMed2000

Unsuspected pseudophysiologic emphysema in chronic persistent asthma.

The current literature emphasizes the role of airway remodeling in chronic persistent asthma and its putative effect on causing fixed expiratory airflow limitation. We studied 18 adults with chronic persistent asthma; 12 men, six women, age 59 +/- 15 yr (mean +/- SD) with fixed expiratory airflow obstruction. We measured lung elastic recoil and examined the mechanism of expiratory airflow limitation. Diaphragmatic strength was also measured in six asthmatics, using both sniff and partially occluded airway technique. All 18 asthmatics had markedly abnormal maximal expiratory flow-volume curves at both high and low lung volumes. Hyperinflation was present at residual volume (RV), FRC, and TLC in all subjects. Diffusing capacity was normal or elevated and lung computed tomography (CT) was normal in all 18 asthmatic subjects. There was a significant loss of lung elastic recoil in three of four asthmatics age 30 to 49, all five age 51 to 60 yr, and seven of nine age 61 to 82 yr. Maximal expiratory airflow limitation in only four elderly asthmatics and only at low lung volumes was due completely to loss of lung elastic recoil. In the others, we estimate the reduction in lung elastic recoil was responsible for 35% reduction in maximal expiratory airflow at 80% of TLC, and 55% at 70% of TLC. Despite hyperinflation, transdiaphragmatic pressures and strength were normal. The mechanisms responsible for loss of lung elastic recoil remain elusive. The high incidence of loss of lung elastic recoil in chronic persistent asthma was unexpected, and its contribution to abnormal lung function needs to be emphasized.

Adult↗
PubMed2001

A single-breath technique with variable flow rate to characterize nitric oxide exchange dynamics in the lungs.

Current techniques to estimate nitric oxide (NO) production and elimination in the lungs are inherently nonspecific or are cumbersome to perform (multiple-breathing maneuvers). We present a new technique capable of estimating key flow-independent parameters characteristic of NO exchange in the lungs: 1) the steady-state alveolar concentration (C(alv,ss)), 2) the maximum flux of NO from the airways (J(NO,max)), and 3) the diffusing capacity of NO in the airways (D(NO,air)). Importantly, the parameters were estimated from a single experimental single-exhalation maneuver that consisted of a preexpiratory breath hold, followed by an exhalation in which the flow rate progressively decreased. The mean values for J(NO,max), D(NO,air), and C(alv,ss) do not depend on breath-hold time and range from 280-600 pl/s, 3.7-7.1 pl. s(-1). parts per billion (ppb)(-1), and 0.73-2.2 ppb, respectively, in two healthy human subjects. A priori estimates of the parameter confidence intervals demonstrate that a breath hold no longer than 20 s may be adequate and that J(NO,max) can be estimated with the smallest uncertainty and D(NO,air) with the largest, which is consistent with theoretical predictions. We conclude that our new technique can be used to characterize flow-independent NO exchange parameters from a single experimental single-exhalation breathing maneuver.

Adult↗