Standardisation of the measurement of lung volumes

Breath-hold diving: respiratory function on the longer term

PURPOSE

Extensive breath-hold (BH) diving imposes high pulmonary stress by performing voluntary lung hyperinflation maneuvers (glossopharyngeal insufflation, GI), hyperinflating the lung up to 50% of total lung capacity. Breath-hold durations of up to 10 min without oxygen support may also presume cerebral alterations of respiratory drive. Little is known about the long-term effects of GI onto the pulmonary parenchyma and respiratory adaptation processes in this popular extreme sport.

METHODS

Lung function assessments and subsequent measures of pulmonary static compliance were obtained for 5 min after GI in 12 elite competitive breath-hold divers (BHD) with a mean apnea diving performance of 6.6 yr. Three-year follow-up measurements were performed in 4 BHD. Respiratory drive was assessed in steady-state measurements for 6% and 9% CO2 in ambient air.

RESULTS

Short-term pulmonary stress effects for static compliance during GI (13.75 L·kPa) could be confirmed in these 12 divers without exhibiting permanent changes to the lungs' distensibility (7.41 L·kPa) or lung function parameters as confirmed by the follow-up measurements and for 4 BHD after 3 yr (P>0.05). Respiratory drive was significantly reduced in these BHD revealing a characteristic breathing pattern with a significant increase in VE and mouth occlusion pressure (P0.1) between free breathing and 6% CO2, as well as between 6% CO2 and 9% CO2 (all P<0.001).

CONCLUSION

BH diving with performance of GI does not permanently alter pulmonary distensibility or impair ventilatory flows and volumes. A blunted response to elevated CO2 concentrations could be demonstrated, which was supportive of the hypothesis that CO2 tolerance is a training effect due to BH diving rather than being an inherited phenomenon.

Acute effects of indacaterol on lung hyperinflation in moderate COPD: a comparison with tiotropium

BACKGROUND

Evidence has been provided that high-dose indacaterol (300 μg) can reduce lung hyperinflation in moderate-to-severe chronic obstructive pulmonary disease (COPD).

AIM

To study whether low-dose indacaterol (150 μg) also reduces lung hyperinflation in comparison with the recommended dose of tiotropium (18 μg) in moderate COPD.

METHODS

This was a multicenter, randomized, blinded, 3-period cross-over, placebo-controlled study. Spirometry and lung volumes were measured before and 30, 60, 120, 180 and 240 min after the administration of single-doses of indacaterol, tiotropium, or placebo. The primary end-point was the change in peak inspiratory capacity (IC). The area under the 4-h curve (AUC(0-4)) for IC, 1-s forced expiratory volume (FEV(1)) and forced vital capacity (FVC) were secondary variables.

RESULTS

49 patients completed the study. On average, peak IC and AUC(0-4) for IC were significantly greater after indacaterol than placebo by 177 mL (p = 0.007) and 142 mL (p = 0.001), respectively. Differences in peak IC and AUC(0-4) for IC between tiotropium and placebo were 120 mL (p = 0.07) and 85 mL (p = 0.052), respectively. Differences between indacaterol and tiotropium were statistically insignificant. Peak IC increased by >20% in 12 patients with indacaterol and 9 with tiotropium (p = 0.001), and by >30% in 8 patients with indacaterol and 3 with tiotropium (p = 0.001). The effects of indacaterol and tiotropium on FEV(1) and FVC were statistically significant vs placebo.

CONCLUSIONS

Low-dose indacaterol has a bronchodilator effect that is similar to the recommended dose of tiotropium, but it is slightly superior in reducing lung hyperinflation.

TRIAL REGISTRATION

ClinicalTrials.gov number: NCT00999908.

Alveolarization continues during childhood and adolescence: new evidence from helium-3 magnetic resonance

RATIONALE

The current hypothesis that human pulmonary alveolarization is complete by 3 years is contradicted by new evidence of alveolarization throughout adolescence in mammals.

OBJECTIVES

We reexamined the current hypothesis using helium-3 ((3)He) magnetic resonance (MR) to assess alveolar size noninvasively between 7 and 21 years, during which lung volume nearly quadruples. If new alveolarization does not occur, alveolar size should increase to the same extent.

METHODS

Lung volumes were measured by spirometry and plethysmography in 109 healthy subjects aged 7-21 years. Using (3)HeMR we determined two independent measures of peripheral airspace dimensions: apparent diffusion coefficient (ADC) of (3)He at FRC (n = 109), and average diffusion distance of helium (X(rms)) by q-space analysis (n = 46). We compared the change in these parameters with lung growth against a model of lung expansion with no new alveolarization.

MEASUREMENTS AND MAIN RESULTS

ADC increased by 0.19% for every 1% increment in FRC (95% confidence interval [CI], 0.13-0.25), whereas the expected change in the absence of neoalveolarization is 0.41% (95% CI, 0.31-0.52). Similarly, increase of (X(rms)) with FRC was significantly less than the predicted increase in the absence of neoalveolarization. The number of alveoli is estimated to increase 1.94-fold (95% CI, 1.64-2.30) across the age range studied.

CONCLUSIONS

Our observations are best explained by postulating that the lungs grow partly by neoalveolarization throughout childhood and adolescence. This has important implications: developing lungs have the potential to recover from early life insults and respond to emerging alveolar therapies. Conversely, drugs, diseases, or environmental exposures could adversely affect alveolarization throughout childhood.

Predictors of fatigue severity in early systemic sclerosis: a prospective longitudinal study of the GENISOS cohort

Objectives

Longitudinal studies examining the baseline predictors of fatigue in SSc have not been reported. Our objectives were to examine the course of fatigue severity over time and to identify baseline clinical, demographic, and psychosocial predictors of sequentially obtained fatigue scores in early SSc. We also examined baseline predictors of change in fatigue severity over time.

Methods

We analyzed 1090 longitudinal Fatigue Severity Scale (FSS) scores belonging to 256 patients who were enrolled in the Genetics versus Environment in Scleroderma Outcomes Study (GENISOS). Predictive significance of baseline variables for sequentially obtained FSS scores was examined with generalized linear mixed models. Predictors of change in FSS over time were examined by adding an interaction term between the baseline variable and time-in-study to the model.

Results

The patients' mean age was 48.6 years, 47% were Caucasians, and 59% had diffuse cutaneous involvement. The mean disease duration at enrollment was 2.5 years. The FSS was obtained at enrollment and follow-up visits (mean follow-up time = 3.8 years). Average baseline FSS score was 4.7(±0.96). The FSS was relatively stable and did not show a consistent trend for change over time (p = 0.221). In a multivariable model of objective clinical variables, higher Medsger Gastrointestinal (p = 0.006) and Joint (p = 0.024) Severity Indices, and anti-U1-RNP antibodies (p = 0.024) were independent predictors of higher FSS. In the final model, ineffective coping skills captured by higher Illness Behavior Questionnaire scores (p<0.001), higher self-reported pain (p = 0.006), and higher Medsger Gastrointestinal Severity Index (p = 0.009) at enrollment were independent predictors of higher longitudinal FSS scores. Baseline DLco % predicted was the only independent variable that significantly predicted a change in FSS scores over time (p = 0.013), with lower DLco levels predicting an increase in FSS over time.

Conclusions

This study identified potentially modifiable clinical and psychological factors that predict longitudinal fatigue severity in early SSc.

A randomized crossover study to determine the effect of a 30° head-up versus a supine position on the functional residual capacity of term parturients

BACKGROUND

Airway management continues to pose challenges to the obstetric anesthesiologist. Functional residual capacity (FRC), which acts as an oxygen reservoir, is reduced from the second trimester onwards and is exacerbated in the supine position. Mechanisms to increase FRC may delay the onset of hypoxemia during periods of apnea. Values for changes in FRC in term parturients in semierect positions are unknown. We hypothesized that the FRC of healthy term parturients would increase significantly in the 30° head-up position in comparison with the supine position.

METHODS

Twenty-two healthy term parturients were recruited. Initial screening spirometry was performed to exclude undiagnosed respiratory disease. FRC was measured using the helium dilution technique in the supine, 30° head-up, and sitting erect positions. Subjects were randomized to sequence of position testing order. Noninvasive systolic blood pressure, heart rate, and oxygen saturation were measured twice in each testing position.

RESULTS

Results from 20 subjects were analyzed. The spirometry results for all subjects were within predicted normal reference intervals. FRC measurements differed significantly (P<0.001) among all positions. FRC increased by a mean of 188 mL (95% confidence interval 18 to 358 mL) from the supine to the 30° head-up position (P=0.03). There were no significant differences in vital signs among testing positions (P>0.16).

CONCLUSIONS

We have demonstrated that the FRC of healthy term parturients increases significantly in the 30° head-up position in comparison with supine.

Evolution of dyspnea during exercise in chronic obstructive pulmonary disease: impact of critical volume constraints

RATIONALE

Patients with chronic obstructive pulmonary disease (COPD) primarily describe their exertional dyspnea using descriptors alluding to increased effort or work of breathing and unsatisfied inspiration or inspiratory difficulty.

OBJECTIVES

The purpose of this study was to examine the impact of changes in dynamic respiratory mechanics during incremental (INCR) and high-intensity constant work-rate (CWR) cycle exercise on the evolution of dyspnea intensity and its major qualitative dimensions in patients with moderate-to-severe COPD.

METHODS

Sixteen subjects with COPD performed symptom-limited INCR and CWR cycle exercise tests. Measurements included dyspnea intensity and qualitative descriptors, breathing pattern, operating lung volumes, and esophageal pressure (Pes).

MEASUREMENTS AND MAIN RESULTS

During both exercise tests, there was an inflection in the relation between tidal volume (Vt) and ventilation. This inflection occurred significantly earlier in time during CWR versus INCR exercise but at a similar ventilation, Vt, and tidal Pes swing. Beyond this inflection, there was no further change in Vt despite a continued increase in ventilation and tidal Pes. During both tests, "work and effort" was the dominant dyspnea descriptor selected up to the inflection point, whereas after this point dyspnea intensity and the selection frequency of "unsatisfied inspiration" rose sharply.

CONCLUSIONS

Regardless of the exercise test protocol, the inflection (or plateau) in the Vt response marked the point where dyspnea intensity rose abruptly and there was a transition in the dominant qualitative descriptor choice from "work and effort" to "unsatisfied inspiration." Intensity and quality of dyspnea evolve separately and are strongly influenced by mechanical constraints on Vt expansion during exercise in COPD.

Impaired response to deep inspiration in obesity

Deep inspirations modulate airway caliber and airway closure and their effects are impaired in asthma. The association between asthma and obesity raises the question whether the deep inspiration (DI) effect is also impaired in the latter condition. We assessed the DI effects in obese and nonobese nonasthmatics. Thirty-six subjects (17 obese, 19 nonobese) underwent routine methacholine (Mch) challenge and 30 of them also had a modified bronchoprovocation in the absence of DIs. Lung function was monitored with spirometry and forced oscillation (FO) [resistance (R) at 5 Hz (R5), at 20 Hz (R20), R5-R20 and the integrated area of low-frequency reactance (AX)]. The response to Mch, assessed with area under the dose-response curves (AUC), was consistently greater in the routine challenge in the obese (mean ± SE, obese vs. nonobese AUC: R5: 15.7 ± 2.3 vs. 2.4 ± 2.0, P < 0.0005; R20: 5.6 ± 1.4 vs. 1.4 ± 1.2, P = 0.027; R5-R20: 10.2 ± 1.6 vs. 0.9 ± 0.1.4, P < 0.0005; AX: 115.6 ± 22.0 vs. 1.5 ± 18.9, P < 0.0005), but differences between groups in the modified challenge were smaller, indicating reduced DI effects in obesity. Given that DI has bronchodilatory and bronchoprotective effects, we further assessed these components separately. In the obese subjects, DI prior to Mch enhanced Mch-induced bronchoconstriction, but DI after Mch resulted in bronchodilation that was of similar magnitude as in the nonobese. We conclude that obesity is characterized by increased Mch responsiveness, predominantly of the small airways, due to a DI effect that renders the airways more sensitive to the stimulus.

Smoking, COPD, and 3-nitrotyrosine levels of plasma proteins

BACKGROUND

Nitric oxide is a physiological regulator of endothelial function and hemodynamics. Oxidized products of nitric oxide can form nitrotyrosine, which is a marker of nitrative stress. Cigarette smoking decreases exhaled nitric oxide, and the underlying mechanism may be important in the cardiovascular toxicity of smoking. Even so, it is unclear if this effect results from decreased nitric oxide production or increased oxidative degradation of nitric oxide to reactive nitrating species. These two processes would be expected to have opposite effects on nitrotyrosine levels, a marker of nitrative stress.

OBJECTIVE

In this study, we evaluated associations of cigarette smoking and chronic obstructive pulmonary disease (COPD) with nitrotyrosine modifications of specific plasma proteins to gain insight into the processes regulating nitrotyrosine formation.

METHODS

A custom antibody microarray platform was developed to analyze the levels of 3-nitrotyrosine modifications on 24 proteins in plasma. In a cross-sectional study, plasma samples from 458 individuals were analyzed.

RESULTS

Average nitrotyrosine levels in plasma proteins were consistently lower in smokers and former smokers than in never smokers but increased in smokers with COPD compared with smokers who had normal lung-function tests.

CONCLUSIONS

Smoking is associated with a broad decrease in 3-nitrotyrosine levels of plasma proteins, consistent with an inhibitory effect of cigarette smoke on endothelial nitric oxide production. In contrast, we observed higher nitrotyrosine levels in smokers with COPD than in smokers without COPD. This finding is consistent with increased nitration associated with inflammatory processes. This study provides insight into a mechanism through which smoking could induce endothelial dysfunction and increase the risk of cardiovascular disease.

The evolving spectrum of pulmonary disease in responders to the World Trade Center tragedy

On September 11, 2001, events at the World Trade Center (WTC) exposed residents ofNew York City to WTC dust and products of combustion and pyrolysis. The majority ofWTC-exposed fire department rescue workers experienced a substantial decline in airflowover the first 12 months post-9/11, in addition to the normal age-related declinethat affected all responders, followed by a persistent plateau in pulmonary function inthe 6 years thereafter. The spectrum of the resulting pulmonary diseases consists ofchronic inflammation, characterized by airflow obstruction, and expressing itself indifferent ways in large and small airways. These conditions include irritant-inducedasthma, non-specific chronic bronchitis, aggravated pre-existing obstructive lung disease(asthma or COPD), and bronchiolitis. Conditions concomitant with airwaysobstruction, particularly chronic rhinosinusitis and upper airway disease, and gastroesophagealreflux, have been prominent in this population. Less common have beenreports of sarcoidosis or interstitial pulmonary fibrosis. Pulmonary fibrosis and bronchiolitisare generally characterized by long latency, relatively slow progression, and asilent period with respect to pulmonary function during its evolution. For these reasons,the incidence of these outcomes may be underestimated and may increase overtime. The spectrum of chronic obstructive airways disease is broad in this populationand may importantly include involvement at the bronchiolar level, manifested as smallairways disease. Protocols that go beyond conventional screening pulmonary functiontesting and imaging may be necessary to identify these diseases in order to understandthe underlying pathologic processes so that treatment can be most effective.

The role of CT scanning in multidimensional phenotyping of COPD

BACKGROUND

COPD is a heterogeneous disease characterized by airflow obstruction and diagnosed by lung function. CT imaging is emerging as an important, noninvasive tool in phenotyping COPD. However, the use of CT imaging in defining the disease heterogeneity above lung function is not fully known.

METHODS

Seventy-five patients with COPD (58 men, 17 women) were studied with CT imaging and with measures of airway inflammation. Airway physiology and health status were also determined.

RESULTS

The presence of emphysema (EM), bronchiectasis (BE), and bronchial wall thickening (BWT) was found in 67%, 27%, and 27% of subjects, respectively. The presence of EM was associated with lower lung function (mean difference % FEV(1), -20%; 95% CI, -28 to -11; P < .001). There was no difference in airway inflammation, exacerbation frequency, or bacterial load in patients with EM alone or with BE and/or BWT ± EM. The diffusing capacity of the lung for carbon monoxide/alveolar volume ratio was the most sensitive and specific parameter in identifying EM (area under the receiver operator characteristic curve, 0.87; 95% CI, 0.79-0.96). Physiologic cluster analysis identified three clusters, two of which were EM predominant and the third characterized by a heterogeneous combination of EM and BE.

CONCLUSIONS

The application of CT imaging can be useful as a tool in the multidimensional approach to phenotyping patients with COPD.

Response patterns to bronchodilator and quantitative computed tomography in chronic obstructive pulmonary disease

BACKGROUND

Patients with chronic obstructive pulmonary disease (COPD) show different spirometric response patterns to bronchodilator, such that some patients show improvement principally in expiratory flow (forced expiratory volume in 1 s; FEV(1)), whereas others respond by improvement of lung volume (forced vital capacity; FVC). The mechanisms of these different response patterns to bronchodilator remain unclear. We investigated the associations between bronchodilator responsiveness and quantitative computed tomography (CT) indices in patients with COPD.

METHODS

Data on a total of 101 patients with stable COPD were retrospectively analysed. Volume and flow responses to bronchodilator were assessed by FVC and FEV(1) changes before and after inhalation of salbutamol (400 μg). Volumetric CT was performed to quantify emphysema, air trapping and large airway thickness. Emphysema was assessed by the volume fraction of the lung under -950 Hounsfield units (HU; V(950)) at full inspiration and air trapping by the ratio of mean lung density (MLD) at full expiration and inspiration. Airway wall thickness and wall area percentage (WA%; defined as wall area/[wall area + lumen area] × 100), were measured near the origin of right apical and left apico-posterior bronchus.

RESULTS

Among quantitative CT indices, the CT emphysema index (V(950 insp)) showed a significant negative correlation with postbronchodilator FEV(1) change (R = -0·213, P = 0·004), and the CT air-trapping index correlated positively with postbronchodilator FVC change(R = 0·286, P≤0·001). Multiple linear regression analysis showed that CT emphysema index had independent association with postbronchodilator FEV(1) change and CT air-trapping index with postbronchodilator FVC change.

CONCLUSION

The degrees of emphysema and air trapping may contribute to the different response patterns to bronchodilator in patients with COPD.

Manual hyperinflation partly prevents reductions of functional residual capacity in cardiac surgical patients--a randomized controlled trial

INTRODUCTION

Cardiac surgery is associated with post-operative reductions of functional residual capacity (FRC). Manual hyperinflation (MH) aims to prevent airway plugging, and as such could prevent the reduction of FRC after surgery. The main purpose of this study was to determine the effect of MH on post-operative FRC of cardiac surgical patients.

METHODS

This was a randomized controlled trial of patients after elective coronary artery bypass graft and/or valve surgery admitted to the intensive care unit (ICU) of a university hospital. Patients were randomly assigned to a "routine MH group" (MH was performed within 30 minutes after admission to the ICU and every 6 hours thereafter, and before tracheal extubation), or a "control group" (MH was performed only if perceptible (audible) sputum was present in the larger airways causing problems with mechanical ventilation, or if oxygen saturation (SpO2) dropped below 92%). The primary endpoint was the reduction of FRC from the day before cardiac surgery to one, three, and five days after tracheal extubation. Secondary endpoints were SpO2 (at similar time points) and chest radiograph abnormalities, including atelectasis (at three days after tracheal extubation).

RESULTS

A total of 100 patients were enrolled. Patients in the routine MH group showed a decrease of FRC on the first post-operative day to 71% of the pre-operative value, versus 57% in the control group (P = 0.002). Differences in FRC became less prominent over time; differences between the two study groups were no longer statistically significant at Day 5. There were no differences in SpO2 between the study groups. Chest radiographs showed more abnormalities (merely atelectasis) in the control group compared to patients in the routine MH group (P = 0.002).

CONCLUSIONS

MH partly prevents the reduction of FRC in the first post-operative days after cardiac surgery.

TRIAL REGISTRATION

Netherlands Trial Register (NTR): NTR1384. http://www.trialregister.nl.

The relationship between anthropometric measures, blood gases, and lung function in morbidly obese white subjects

Background

Obesity may cause adverse effects on the respiratory system. The main purpose of this study was to investigate how various measures of obesity are related to arterial blood gases and pulmonary function.

Methods

This is a cross-sectional study of consecutive morbidly obese patients with normal lung function. Blood gas samples were taken from the radial artery after 5 min of rest with subjects sitting upright. Lung function measurements included dynamic spirometry, static lung volumes, and gas diffusing capacity.

Results

The 149 patients (77% women) had a mean (SD) age of 43 years (11 years) and BMI of 45.0 kg/m² (6.3 kg/m²). The mean expiratory reserve volume (ERV) was less than half (49%) of predicted value, whilst most other lung function values were within predicted range. Forty-two patients had an abnormally low pO2 value (<10.7 kPa [80 mmHg]), while eight patients had a high pCO2 value (>6.0 kPa [45 mmHg]). All anthropometric measures correlated significantly with decreasing pO2 and increasing pCO2 (all P values < 0.05). BMI, neck circumference (NC), and waist circumference (WC) were negatively correlated with ERV (r = −0.25, −0.19, −0.21, respectively, all P values < 0.05). Multiple linear regression showed that BMI, WC, and NC were significantly associated with pO2 after adjustments for age, gender, and pack-years (all P values < 0.001). The models explained 34–36% of the variations in pO2. BMI, NC, and WC were also significantly associated with pCO2 (all P values < 0.05).There was no significant association between waist-to-hip ratio and blood gases (both P values > 0.27).

Conclusions

Both central and overall obesity were associated with unfavorable blood gases and low ERV.

Effect of indacaterol on dynamic lung hyperinflation and breathlessness in hyperinflated patients with COPD

Indacaterol is a novel, inhaled once-daily ultra long-acting β2-agonist for the treatment of COPD. This randomised, double-blind, placebo-controlled, two-period crossover study evaluated the effect of two-week treatment with indacaterol 300 μg on peak and isotime exercise inspiratory capacity (IC) in patients with COPD. Patients (40-80 years) with post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) < 70%, percent predicted FEV1 ≥ 40% and ≤ 80%, smoking history ≥ 20 pack-years and functional residual capacity > 120% of predicted normal were randomised to receive indacaterol 300 μg or placebo once-daily via a single-dose dry powder inhaler. Following 14 days of treatment, IC at peak and isotime during constant-load (80% of maximum workload) cycle ergometry was analysed using linear mixed-effects models. Safety and tolerability were also monitored. Twenty-seven patients (67% male; mean age, 61.3 years) were randomised; 24 completed the study. On Day 14, indacaterol showed statistically significant improvements over placebo in peak (317 mL [95% CI: 118-517]; p < 0.01) and isotime IC (268 mL [95% CI: 104-432]; p < 0.01). Statistically significant improvements were observed with indacaterol versus placebo on Day 14 for the following secondary endpoints: resting IC, trough FEV1, dyspnoea (BDI/TDI and Borg CR10 scale at isotime) and exercise endurance time. Indacaterol was well tolerated, with no serious adverse events or deaths. In conclusion, indacaterol 300 μg administered once-daily showed a clinically relevant increase in IC after 14 days of treatment, reflecting a reduction in dynamic hyperinflation.

Measurement of functional residual capacity by modified multiple breath nitrogen washout for spontaneously breathing and mechanically ventilated patients

BACKGROUND

There is a need for a bedside functional residual capacity (FRC) measurement method that performs well in intensive care patients during many modes of ventilation including controlled, assisted, spontaneous, and mixed. We developed a modified multiple breath nitrogen washout method for FRC measurement that relies on end-tidal gas fractions and alveolar tidal volume measurements as inputs but does not require the traditional measurements of volume of nitrogen or oxygen. Using end-tidal measurements, not volume, reduces errors from signal synchronization. This study was designed to assess the accuracy, precision, and repeatability of the proposed FRC system in subjects with variable ventilation patterns including some spontaneous effort.

METHODS

The accuracy and precision of measurements were assessed by comparing the novel N₂ washout FRC values to the gold standard, body plethysmography, in 20 spontaneously breathing volunteers. Repeatability was assessed by comparing subsequent measurements in 20 intensive care patients whose lungs were under controlled and assisted mechanical ventilation.

RESULTS

Compared with body plethysmography, the accuracy (mean bias) of the novel method was -0.004 litre and precision [1 standard deviation (sd)] was 0.209 litre [mean (sd)] [-0.1 (5.9)% of body plethysmography]. The difference between repeated measurements was 0.009 (0.15) litre [mean (sd)] [0.4 (6.4)%]. The coefficient of repeatability was 0.31 litre (12.7%).

CONCLUSIONS

The modified multiple breath nitrogen washout method for FRC measurement provides improved precision and equivalent accuracy and repeatability compared with existing methods during ventilation with variable ventilation patterns. Further study of the novel N₂ washout method is needed.

Chest wall kinematics and breathlessness during unsupported arm exercise in COPD patients

We hypothesised that chest wall displacement inappropriate to increased ventilation contributes to dyspnoea more than dynamic hyperinflation or dyssynchronous breathing during unsupported arm exercise (UAE) in COPD patients. We used optoelectronic plethysmography to evaluate operational volumes of chest wall compartments, the upper rib cage, lower rib cage and abdomen, at 80% of peak incremental exercise in 13 patients. The phase shift between the volumes of upper and lower rib cage (RC) was taken as an index of RC distortion. With UAE, no chest wall dynamic hyperinflation was found; sometimes the lower RC paradoxed inward while in other patients it was the upper RC. Phase shift did not correlate with dyspnoea (by Borg scale) at any time, and chest wall displacement was in proportion to increased ventilation. In conclusions neither chest wall dynamic hyperinflation nor dyssynchronous breathing per se were major contributors to dyspnoea. Unlike our prediction, chest wall expansion and ventilation were adequately coupled with each other.

Using spirometry to rule out restriction in patients with concomitant low forced vital capacity and obstructive pattern

Background:

Different formulas have been proposed to exclude restriction based on spirometry, however none of them have specifically tested the patients whose spirometry show both obstruction and a low forced vital capacity (FVC).

Study Objective:

The study was designed to create an algorithm that would better predict the absence of restriction in such patients.

Design:

Retrospective analysis of prospectively collected data.

Methods:

A cohort of consecutive adults that underwent complete pulmonary function testing from 2002-2004 was analyzed. The data was randomly split into two groups to allow for derivation and then validation of a predictive formula. Patients were randomly assigned into either a “derivation” or “validation” group. In the derivation group, stepwise logistic regression was used to determine a formula and optimal cut-off value for the variable with the best discriminative capacity. The formula was applied subsequently to the validation group to test the results and compared to previously published formula.

Results:

The study group contained 766 patients. We determined that the variable with the highest association with TLC was [(FEV₁/FVC) % predicted/FVC % predicted]. A value of ≥1.11 was found to be the maximal cutoff to predict the absence of restriction.

The formula was applied to a validation group (n=397) and performed better than prior published algorithm with a sensitivity, specificity, positive predictive value and negative predictive value of 95%, 44%, 22%, and 98%, respectively.

Conclusion:

Our formula performs superior to the previously published algorithms in patients with concomitant low FVC and obstruction to exclude restriction.

Airway dysfunction in nasal polyposis: a spectrum of asthmatic disease?

BACKGROUND

Chronic rhinosinusitis with nasal polyposis (CRSwNP) represents an interesting model to investigate the existence of a non-allergic unified airway. The factors associated with airway dysfunction in CRSwNP are not fully understood.

OBJECTIVE

To assess the impact of nasal disease on lower airway dysfunction in CRSwNP.

METHODS

Fifty-seven patients with CRSwNP underwent spirometry, nasal endoscopy, exhaled nitric oxide, methacholine bronchial challenge, blood sampling for total IgE, eosinophil count and radioallergosorbent testing (NCT00788749). Three phenotypic groups were identified: 'asthma group' (asthma diagnosis); 'inflammatory group' [no asthma diagnosis, but elevated fractionated exhaled nitric oxide (FE(NO)) and/or bronchial-hyperreactivity (BHR)]; and 'non-inflammatory group' (no asthma diagnosis, no BHR and normal FE(NO)). Group comparisons, univariate and multivariate analyses were performed to examine associations with airway dysfunction.

RESULTS

FEV(1) and FEF(25-75%) were reduced in asthma, but there was no difference between the non-asthmatic groups. Total IgE and eosinophils were elevated in asthma vs. the non-inflammatory group, but there was no difference for asthma vs. inflammatory groups. BHR was the only significant predictor of FEV(1) (P<0.001). For FEF(25-75), BHR and eosinophil count were independent predictors (P<0.001 and P=0.04). Nasal outcomes were not predictors of spirometry.

CONCLUSION AND CLINICAL RELEVANCE

In CRSwNP there is asymptomatic airway dysfunction suggestive of an asthmatic phenotype. Impairment of lung function is significantly associated with BHR and eosinophilia but not parameters of nasal disease suggesting that severity of airway dysfunction relates to the spectrum of asthma rather than rhinosinusitis. Lower airway dysfunction is common in CRSwNP but does not correlate to the severity of nasal disease. Signs and symptoms of asthma should be sought and treated in CRSwNP.

Clinical, radiological, and physiological differences between obliterative bronchiolitis and problematic severe asthma in adolescents and young adults: the early origins of the overlap syndrome?

PURPOSE

Few reports have compared chronic obstructive lung diseases (OLDs) starting in childhood.

AIMS

To describe functional, radiological, and biological features of obliterative bronchiolitis (OB) and further discriminate to problematic severe asthma (PSA) or to diagnose a group with overlapping features.

RESULTS

Patients with OB showed a greater degree of obstructive lung defect and higher hyperinflation (P < 0.001). The most frequent high-resolution computed tomography (HRCT) features (increased lung volume, inspiratory decreased attenuation, mosaic pattern, and expiratory air trapping) showed significantly greater scores in OB patients. Patients with PSA have shown a higher frequency of atopy (P < 0.05). ROC curve analysis demonstrated discriminative power for the LF variables, HRCT findings and for atopy between diagnoses. Further analysis released five final variables more accurate for the identification of a third diagnostic group (FVC%t, post-bronchodilator ΔFEV(1) in ml, HRCT mosaic pattern, SPT, and D. pteronyssinus-specific IgE).

CONCLUSIONS

We found that OB and PSA possess identifiable characteristic features but overlapping values may turn them undistinguishable.

Appropriate Pediatric Spirometry Reference Equations and Interpretation

Spirometry is an important tool in the diagnosis and management of pediatric pulmonary diseases. Reference equations enable the comparison of an individual's lung function to that of a healthy reference population of the same age, sex, height, and race/ethnicity. This comparison is important both in distinguishing health from disease and in monitoring the lung function of a growing child over time. A range of reference equations exist, and no single equation is ideal for all situations. However, there are important considerations to understand when choosing an equation. This article reviews how reference equations are created, how to use them to interpret lung function measurements, and how to choose appropriate reference equations, highlights current limitations, and suggests areas for future research and collaboration.

Pulmonary function in children and adolescents with postinfectious bronchiolitis obliterans

OBJECTIVE

To describe the pulmonary function in children and adolescents with postinfectious bronchiolitis obliterans (PIBO), as well as to evaluate potential risk factors for severe impairment of pulmonary function.

METHODS

The pulmonary function of 77 participants, aged 8-18 years, was assessed by spirometry and plethysmography. The following parameters were analyzed: FVC; FEV1; FEF25-75%; FEV1/FVC; RV; TLC; RV/TLC; intrathoracic gas volume; and specific airway resistance (sRaw). We used Poisson regression to investigate the following potential risk factors for severe impairment of pulmonary function: gender; age at first wheeze; age at diagnosis; family history of asthma; tobacco smoke exposure; length of hospital stay; and duration of mechanical ventilation.

RESULTS

The mean age was 13.5 years. There were pronounced decreases in FEV1 and FEF25-75%, as well as increases in RV and sRaw. These alterations are characteristic of obstructive airway disease. For the parameters that were the most affected, the mean values (percentage of predicted) were as follows: FEV1 = 45.9%; FEF25-75% = 21.5%; RV = 281.1%; RV/TLC = 236.2%; and sRaw = 665.3%. None of the potential risk factors studied showed a significant association with severely impaired pulmonary function.

CONCLUSIONS

The patients with PIBO had a common pattern of severe pulmonary function impairment, characterized by marked airway obstruction and pronounced increases in RV and sRaw. The combination of spirometric and plethysmographic measurements can be more useful for assessing functional damage, as well as in the follow-up of these patients, than are either of these techniques used in isolation. Known risk factors for respiratory diseases do not seem to be associated with severely impaired pulmonary function in PIBO.

Predicting reduced TLC in patients with low FVC and a normal or elevated FEV1/FVC ratio

OBJECTIVE

To use clinical and spirometry findings in order to distinguish between the restrictive and nonspecific patterns of pulmonary function test results in patients with low FVC and a normal or elevated FEV1/FVC ratio.

METHODS

We analyzed the pulmonary function test results of 211 adult patients submitted to spirometry and lung volume measurements. We used the clinical diagnosis at the time spirometry was ordered, together with various functional data, in order to distinguish between patients presenting with a "true" restrictive pattern (reduced TLC) and those presenting with a nonspecific pattern (normal TLC).

RESULTS

In the study sample, TLC was reduced in 144 cases and was within the normal range in 67. The most common causes of a nonspecific pattern were obstructive disorders, congestive heart failure, obesity, bronchiolitis, interstitial diseases, and neuromuscular disorders. In patients given a working diagnosis of pulmonary fibrosis, pleural disease, or chest wall disease, the positive predictive value (PPV) for restriction was >or= 90%. In males, an FVC <or= 60% of predicted had a PPV for restriction of 98.8%. In females, the restrictive pattern was found in 84.4% of those with an FVC <or= 50% of predicted. A difference of >or= 0% between the FEV1% and the FVC% had a PPV for restriction of 89.5%. After performing logistic regression, we developed a point scale for predicting the restrictive pattern.

CONCLUSIONS

In many patients with reduced FEV1, reduced FVC, and a normal FEV1/FVC ratio, the restrictive pattern can be identified with confidence through the use of an algorithm that takes the clinical diagnosis and certain spirometry measurements into account.

Autoimmune-featured interstitial lung disease: a distinct entity

BACKGROUND

Patients with interstitial lung disease (ILD) may have features of an autoimmune disorder that do not meet the diagnostic criteria for connective tissue diseases. We determined the prevalence and characteristics of autoimmune-featured ILD (AIF-ILD) and compared these with those of idiopathic pulmonary fibrosis (IPF) and known connective tissue disease-related ILD (CTD-ILD).

METHODS

Patients with ILD who did not meet the criteria for a connective tissue disease were defined as having AIF-ILD if they had a sign or symptom suggestive of a connective tissue disease and a serologic test reflective of an autoimmune process. Clinical characteristics, high-resolution CT images, and lung biopsy specimens were analyzed and compared with those of patients with IPF and CTD-ILD. Survival was evaluated using a Kaplan-Meier curve.

RESULTS

Two hundred subjects completed the questionnaire and serologic testing. AIF-ILD was identified in 32%, IPF in 29%, and CTD-ILD in 19%. Gender, age, and race differed among groups (P < .01). Sixty-two percent of patients with AIF-ILD had a typical usual interstitial pneumonia (UIP) pattern on CT images. In 31 patients with AIF-ILD, lung biopsy specimens showed UIP in 81% and nonspecific interstitial pneumonia in 6%. Patients with AIF-ILD and IPF had similar survival, worse than those with CTD-ILD (P < .01). Antinuclear antibody (ANA) titers ≥ 1:1280 were associated with improved survival in patients with AIF-ILD (P = .02).

CONCLUSIONS

Systematic evaluation of symptoms and serologic tests in ILD can identify AIF-ILD. A UIP pattern on CT images and histopathology is common in AIF-ILD. Although survival for patients with AIF-ILD is poor, ANA titers ≥ 1:1280 are associated with improved survival.

Evaluating nocturnal oxygen desaturation in COPD--revised

BACKGROUND

Although in patients with COPD, the approach to daytime hypoxemia using long-term oxygen therapy (LTOT) is established, the best approach to transient nocturnal desaturation varies among clinicians. An understanding of the prevalence of nocturnal desaturation in COPD, in the absence of other respiratory co-morbidities, is an important step towards its standardized management.

METHODS

We conducted a 5 site cross-sectional study of stable patients with COPD and mild-to-moderate daytime hypoxemia (PaO(2) 56-69 mmHg). Nocturnal saturation was monitored using home oximetry on 2 occasions over a 2-week period. Patients were classified in 3 categories: (A) no significant nocturnal desaturation; (B) significant nocturnal desaturation without evidence of sleep apnea; (C) significant nocturnal desaturation with evidence of sleep apnea.

RESULTS

In 128 patients (mean FEV(1): 37% predicted), we noted an excellent test-retest reliability between the 2 oximetries. Forty-nine patients (38%) were classified as nocturnal desaturators without evidence of sleep apnea, and 20 patients (16%) were classified as desaturators with evidence of sleep apnea. Nocturnal desaturation without sleep apnea could not be predicted by any patient characteristic or physiological measure.

CONCLUSIONS

A significant proportion (38%) of patients with moderate-to-severe COPD who do not qualify for home oxygen therapy based on their daytime PaO(2) have nocturnal oxygen desaturation without evidence of sleep apnea. Home oximetry is an effective practical method for screening this population.

Reference values for paediatric pulmonary function testing: The Utrecht dataset

BACKGROUND

Since populations evolve, measurement protocols and equipment improve and analysis techniques progress, there is an ongoing need to reassess reference data for pulmonary function tests. Furthermore, reference values for total lung capacity and carbon monoxide diffusion capacity are scarcely available in children. We aimed to provide updated reference equations for most commonly used pulmonary function indices in Caucasian children.

METHODS

In the 'Utrecht Pulmonary Function Reference Data Study' we collected data in Caucasian children aged 2-18 years. We analyzed them using the 'Generalized Additive Models for Location Scale and Shape' (GAMLSS) statistical method.

RESULTS

Measurements of interrupter resistance (R(int)) (n = 877), spirometry (n = 1042), body plethysmography (n = 723) and carbon monoxide diffusion/helium dilution (n = 543) were obtained in healthy children. Height (or the natural logarithm of height) and age (or the natural logarithm of age) were both significantly related to most outcome measures. Also sex was a significant determinant, except for RV, RV/TLC, FRC(pleth), Raw(0,5), Raw(tot), R(int) and FEF values. The application of previously published reference equations on the study population resulted in misinterpretation of pulmonary function.

CONCLUSION

These new paediatric reference equations provide accurate estimates of the range of normality for most commonly used pulmonary function indices, resulting in less underdiagnosis and overdiagnosis of pulmonary diseases.

Lung dysfunction of chronic smokers with no signs of COPD

Cigarette smoking causes airflow limitation with lung hyperinflation being the primary causes of COPD. Fifty chronic smokers (CSs) with no signs of GOLD-adjusted COPD with smoking habit at least ≥10 pack-years (p/yrs) were divided into CS-mild (n = 24) with smoking history from ≥10 to ≤20 p/yrs and CS-heavy groups (n = 26) with smoking history ≥21 p/yrs. Spirometry, plethysmography and diffusing capacity were measured and lung computed tomography (CT) was performed. Residual volume (RV) (L) and RV/TLC (total lung capacity) ratio were significantly increased in CS-heavy when compared to CS-mild (p = 0.001, p = 0.03). A significant reduction of forced expiratory volume in 1 second/forced vital capacity (FEV(1)/FVC) ratio and airway specific conductance was shown in CS-heavy (p = 0.02, p = 0.03). Lung emphysema signs at CTs were revealed in 17 CSs and ten of them had declined diffusing capacity below 70% of predicted. The percentage of emphysematous lesions inversely and significantly correlated with measured diffusing capacity (p = 0.0009, r = --0.72). Study groups' smoking intensity inversely correlated the declined airway specific conductance (p = 0.004, r = --0.39) and increase of the RV (L) (p = 0.0004, r = 0.46). Multiple regression analysis determined that smoking intensity regardless of the subjects' age was significant factor for decline of airway specific conductance and increase of RV (L). Here we conclude that lung function deviation and lung structural changes are present in CSs before the clinical signs of airway obstruction reveal. Body plethysmography and diffusing capacity measurement with routine spirometry can provide valuable information for detection of changes reflecting to the early onset of COPD in CSs.

Lung hyperinflation and its reversibility in patients with airway obstruction of varying severity

The natural history of lung hyperinflation in patients with airway obstruction is unknown. In particular, little information exists about the extent of air trapping and its reversibility to bronchodilator therapy in those with mild airway obstruction. We completed a retrospective analysis of data from individuals with airway obstruction who attended our pulmonary function laboratory and had plethysmographic lung volume measurements pre- and post-bronchodilator (salbutamol). COPD was likely the predominant diagnosis but patients with asthma may have been included. We studied 2,265 subjects (61% male), age 65 ± 9 years (mean ± SD) with a post-bronchodilator FEV(1)/FVC <0.70. We examined relationships between indices of airway obstruction and lung hyperinflation, and measured responses to bronchodilation across subgroups stratified by GOLD criteria. In GOLD stage I, vital capacity (VC) and inspiratory capacity (IC) were in the normal range; pre-bronchodilator residual volume (RV), functional residual capacity (FRC) and specific airway resistance were increased to 135%, 119% and 250% of predicted, respectively. For the group as a whole, RV and FRC increased exponentially as FEV(1) decreased, while VC and IC decreased linearly. Regardless of baseline FEV(1), the most consistent improvement following bronchodilation was RV reduction, in terms of magnitude and responder rate. In conclusion, increases (above normal) in airway resistance and plethysmographic lung volumes were found in those with only minor airway obstruction. Indices of lung hyperinflation increased exponentially as airway obstruction worsened. Those with the greatest resting lung hyperinflation showed the largest bronchodilator-induced volume deflation effects. Reduced air trapping was the predominant response to acute bronchodilation across severity subgroups.

Sex differences in exertional dyspnea in patients with mild COPD: physiological mechanisms

The purpose of this study was to evaluate the physiological basis for sex-differences in exercise-induced dyspnea in patients with mild COPD. We compared operating lung volumes, breathing pattern and dyspnea during incremental cycling in 32 men (FEV(1)=86±10% predicted) and women (FEV(1)=86±12% predicted) with mild COPD and 32 age-matched controls. There were no sex differences in dyspnea in the control group at any work-rate or ventilation (V(E)). Women with COPD had significantly greater dyspnea than men at 60 and 80 W. At 80 W, dyspnea ratings were 5.7±2.3 and 3.3±2.5 Borg units (P<0.05) and the V(E) to maximal ventilatory capacity ratio was 72% and 55% in women and men, respectively (P<0.05). Comparable increases in dynamic hyperinflation were seen in both male and female COPD groups at symptom limitation but women reached tidal volume constraints at a lower work rate and V(E) than men. Superimposing mild COPD on the normal aging effects had greater sensory consequences in women because of their naturally reduced ventilatory reserve.

Impaired lipid metabolism in idiopathic pulmonary alveolar proteinosis

BACKGROUND

It is well known that lipids abnormally accumulate in the alveoli during idiopathic pulmonary alveolar proteinosis (PAP). It is unclear, however, whether lipids also abnormally accumulate in serum. This study investigated the serum lipid panels in idiopathic PAP patients and explored the relationships between serum levels and the severity of idiopathic PAP.

METHODS AND RESULTS

Clinical data including the level of serum lipids were evaluated in 33 non-diabetic idiopathic PAP patients and 157 healthy volunteers. Serum levels of triglyceride were higher in PAP patients than in healthy subjects (median: 192.00 mg/dl (P25: 104.36, P75: 219.00) vs 119.56 mg/dl (P25: 78.81, P75: 193.03), P < 0.05), while high-density lipoprotein cholesterol (HDL-C) levels were lower in patients than in the control group (42.50 ± 10.30 vs 51.34 ± 12.06 mg/dl, P < 0.01). Forced expiratory volume in one second and forced vital capacity in hypertriglyceridemia patients were lower than those in patients with normal triglyceride. Serum LDL-C and HDL-C ratio correlated negatively with PaO2 (r = -0.403, P < 0.05) and positively with lactate dehydrogenase (r = 0.381, P < 0.05).

CONCLUSIONS

PAP associates with high triglyceride and low HDL levels in the serum, and these lipids provide potential intervention strategy for treatment.

Respiratory system impedance with impulse oscillometry in healthy and COPD subjects: ECLIPSE baseline results

RATIONALE

Current assessment of COPD relies extensively on the use of spirometry, an effort-dependent maneuver. Impulse oscillometry (IOS) is a non-volitional way to measure respiratory system mechanics, but its relationship to structural and functional measurements in large groups of patients with COPD is not clear.

OBJECTIVES

We evaluated the ability of IOS to detect and stage COPD severity in the prospective ECLIPSE cohort of COPD patients defined spirometrically, and contrasted with smoking and non-smoking healthy subjects. Additionally, we assessed whether IOS relates to extent of CT-defined emphysema.

METHODS

We measured lung impedance with IOS in healthy non-smokers (n = 233), healthy former smokers (n = 322) or patients with COPD (n = 2054) and related these parameters with spirometry and areas of low attenuation in lung CT.

MEASUREMENTS AND MAIN RESULTS

In healthy control subjects, IOS demonstrated good repeatability over 3 months. In the COPD group, respiratory system impedance was worse compared with controls as was frequency dependence of resistance, which related to GOLD stage. However, 29-86% of the COPD subjects had values that fell within the 90% confidence interval of several parameters of the healthy non-smokers. Although mean values for impedance parameters and CT indices worsened as GOLD severity increased, actual correlations between them were poor (r ≤ 0.16).

CONCLUSIONS

IOS can be reliably used in large cohorts of subjects to assess respiratory system impedance. Cross-sectional data suggest that it may have limited usefulness in evaluating the degree of pathologic disease, whereas its role in assessing disease progression in COPD currently remains undefined.

Gas exchanges and pulmonary vascular abnormalities at different stages of chronic liver disease

BACKGROUND

It is unclear whether and to which extent respiratory function abnormalities may complicate the earliest stages of chronic liver disease (CLD). Aim of this study was to compare pulmonary capillary volumes and gas exchange efficiency of CLD patients with and without cirrhosis.

METHODS

Sixty-seven participants (mean age 56.5 years; women 22.4%) were divided into three groups (matched by age, sex, smoking) according to the baseline CLD stage as follows: (a) healthy controls (Group A, n=20); (b) non-cirrhotic CLD patients (Group B; n=23); (c) cirrhotic CLD patients (Group C; n=24). All participants underwent clinical assessment, respiratory function tests, gas exchange estimation by the alveolar diffusion of carbon monoxide (TLCO) measurement and 6-min walking test. Groups were compared by chi-square and one-way anova tests.

RESULTS

Chronic liver disease patients had significantly lower levels of TLCO (Group B=17.7 ml/min mmHg, and Group C=14.2 ml/min mmHg) compared with healthy controls (Group A=24.4 ml/min mmHg). Consistent results were obtained when analyses were performed using TLCO expressed as percentage of the predicted value. TLCO adjusted for the alveolar volume was lower in cirrhotic patients compared with both controls and non-cirrhotic CLD patients (P<0.001 and P=0.035 respectively). Group C participants presented blood gas parameters tending to a compensated chronic respiratory alkalosis status compared with the other groups.

CONCLUSIONS

Pulmonary microvascular and gas exchange modifications are present at early stages of CLD. Future studies should be focused at evaluating the pathophysiological mechanisms underlying this relationship.

Cardiopulmonary response to exercise and cardiac assessment in patients with turner syndrome

Turner syndrome (TS) is a chromosomal disorder; however, little is known about the exercise tolerance of patients with this syndrome. The aim of the present study was to measure the maximal aerobic capacity and cardiac function using cardiopulmonary exercise testing and lung function tests and to evaluate the cardiac parameters using echocardiography in patients with TS and control subjects. A total of 50 women with TS (mean age 21.3 ± 8.5 years) and 56 age-matched controls (mean age 21.1 ± 3.7 years) were enrolled from the Pediatric Department of "Sapienza" University of Rome and underwent cardiopulmonary exercise testing, lung function testing, and echocardiography. The maximal oxygen uptake was lower in the patients with TS than in the controls (28.4 ± 4.0 vs 35.6 ± 6.2 ml/min/kg; p <0.0001). Also, the forced expiratory volume in 1 second, expressed as a percentage of the predicted value, was greater in the patients with TS than in the controls (116.2 ± 15.2% vs 102.8 ± 4.8%, p <0.0001). The patients with TS had a smaller left ventricle than did the controls. Tissue Doppler imaging revealed subclinical systolic and diastolic dysfunction in the left ventricle in those with TS but not in the controls. The left ventricular mass index was greater in the patients with TS than in the controls (38.6 ± 9.3 vs 27.2 ± 4.5 g/m(2.7), p <0.0001). In conclusion, the patients with TS had a lower maximal aerobic capacity and exercise tolerance than did the controls. The anatomic and functional cardiac aspects were peculiar to those with TS and might represent a specific cardiac phenotype.

Determinants of work disability in patients with systemic sclerosis: a longitudinal study of the GENISOS cohort

OBJECTIVES

To determine the prevalence, correlates, and predictors of work disability (WD) in the Genetics versus ENvironment In Scleroderma Outcome Study (GENISOS). We hypothesized that WD in systemic sclerosis (SSc) is a function of demographic, clinical, and psychosocial factors.

METHODS

Patients enrolled in the GENISOS cohort were subdivided in 3 groups: work disabled, working, and retired or homemakers. The latter group (n = 29) was excluded from further analysis. We used logistic regression analysis with a forward hierarchical variable selection strategy to investigate the independent correlates of WD at enrollment. Cox regression proportional Hazard's model with a similar variable selection strategy was utilized to determine the predictors of WD in those working at enrollment.

RESULTS

Overall, 284 patients with a mean age of 48.7 years and disease duration of 2.5 (±1.6) years were enrolled into the GENISOS cohort, consisting of 83.5% female, 46.8% white, 28.9% Hispanic, and 20.4% African American. Patients were longitudinally followed in 1438 study visits. At enrollment, 124 patients (43.7%) were work disabled, whereas 131 (46.1%) were working. Lower level of education (P < 0.001), higher Medsger Lung Severity Index (P = 0.012), higher Fatigue Severity Score (P = 0.008), and less social support (P < 0.001) correlated independently with WD. Of those working at baseline, 35 (26.7%) eventually developed WD. Non-white ethnicity (P = 0.038), lower DLCO % predicted value (P = 0.038), and higher Fatigue Severity Score (P = 0.009) at enrollment independently predicted WD on follow-up visits.

CONCLUSIONS

WD is a major problem among SSc patients and its prevalence is substantially higher than other rheumatic conditions. Demographic, clinical, and psychosocial factors correlate with WD cross-sectionally and predict WD longitudinally in these patients.

Comparison of per cent predicted and percentile values for pulmonary function test interpretation

BACKGROUND

Pulmonary function tests (PFTs) are commonly interpreted as a fraction of predicted normal values, with an abnormal test often defined as less than 80% or greater than 120% of the predicted value. However, recommendations of the American Thoracic Society/European Respiratory Society suggest using a percentile-based approach to define an abnormal test (less than the fifth or greater than the 95th percentiles).

OBJECTIVE

To compare PFT values obtained by the per cent predicted method with the percentile-based method for lung function parameters.

METHODS

Full PFTs performed between January 2000 and July 2004, at the Health Sciences Centre (Winnipeg, Manitoba) were analyzed. Using the Crapo and Gutierrez equations, per cent predicted and percentile values were calculated. An abnormal test was defined as less than 80% or greater than 120% of predicted (per cent predicted method) or as less than the fifth or greater than the 95th percentiles (percentile method). Using the percentile method as reference standard, the diagnostic test characteristics of the per cent predicted method were calculated.

RESULTS

The full PFTs of 2176 men and 1658 women were analyzed using the Crapo and Gutierrez equations. The mean (+/- SD) age of all subjects was 52+/-15 years. Per cent agreement between the two tests was more than 94% for all parameters except for reduced residual volume (88%). Per cent predicted methods had suboptimal sensitivity for abnormal total lung capacity (88% to 89%), increased residual volume (83% to 89%) and reduced diffusion capacity (89% with Crapo equations). Suboptimal specificity (83% to 86%) was observed for decreased residual volume.

CONCLUSION

The results of the per cent predicted and percentile-based approaches for PFT interpretation were similar for the majority of lung function parameters. These two methods can be used interchangeably for spirometry. However, caution may be warranted in relying solely on per cent predicted methods for assessing lung volume or diffusion capacity.

Grading the severity of obstruction in mixed obstructive-restrictive lung disease

BACKGROUND

The severity of obstructive pulmonary disease is determined by the FEV(1) % predicted based on the American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines. In patients with coexisting restrictive lung disease, the decrease in FEV(1) can overestimate the degree of obstruction. We hypothesize that adjusting the FEV(1) for the decrease in total lung capacity (TLC) results in a more appropriate grading of the severity of obstruction.

METHODS

We examined a large pulmonary function test database and identified patients with both restrictive (TLC < 80% predicted) and obstructive (FEV(1)/FVC < the lower limit of normal) lung disease. FEV(1) % predicted was adjusted for the degree of restriction by dividing it by TLC % predicted. We compared the distribution of severity grading between adjusted and unadjusted values according to ATS/ERS criteria and determined how the distribution of severity would change based on asthma and COPD guidelines.

RESULTS

We identified 199 patients with coexisting restrictive and obstructive lung disease. By ATS/ERS grading, the unadjusted data categorized 76% of patients as having severe or very severe obstruction and 11% as having mild or moderate obstruction. The adjusted data classified 33% with severe or very severe obstruction and 44% with mild or moderate obstruction. Of the corrected values, 83% resulted in a change to less severe obstruction by ATS/ERS guidelines, and 44% and 70% of patients, respectively, would be reclassified as having less severe obstruction by current asthma and COPD guidelines.

CONCLUSIONS

This method results in a more appropriate distribution of severity of obstruction, which should lead to more accurate treatment of obstruction in these patients.