Standardisation of the measurement of lung volumes

Accurate characterization of extravascular lung water in acute respiratory distress syndrome

OBJECTIVES

Measurements of extravascular lung water (EVLW) correlate to the degree of pulmonary edema and have substantial prognostic information in critically ill patients. Prior studies using single indicator thermodilution have reported that 21% to 35% of patients with clinical acute respiratory distress syndrome (ARDS) have normal EVLW (<10 mL/kg). Given that lung size is independent of actual body weight, we sought to determine whether indexing EVLW to predicted or adjusted body weight affects the frequency of increased EVLW in patients with ARDS.

DESIGN

Prospective, observational cohort study.

SETTING

Medical and surgical intensive care units at two academic hospitals.

PATIENTS

Thirty patients within 72 hrs of meeting American-European Consensus Conference definition of ARDS and 14 severe sepsis patients without ARDS.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

EVLW was measured for 7 days by PiCCO transpulmonary thermodilution; 225 measurements of EVLW indexed to actual body weight (ActBW) were compared with EVLW indexed to predicted body weight (PBW) and adjusted body weight (AdjBW). Mean EVLW indexed to ActBW was 12.7 mg/kg for ARDS patients and 7.8 mg/kg for non-ARDS sepsis patients (p < .0001). In all patients, EVLW increased an average of 1.1 +/- 2.1 mL/kg when indexed to AdjBW and 2.0 +/- 4.1 mL/kg when indexed to PBW. Indexing EVLW to PBW or AdjBW increased the proportion of ARDS patients with elevated EVLW (each p < .05) without increasing the frequency of elevated EVLW in non-ARDS patients. EVLW indexed to PBW had a stronger correlation to Lung Injury Score (r2 = .39 vs. r2 = .17) and PaO2/FiO2 ratio (r2 = .25 vs. r2 = .10) than did EVLW indexed to ActBW.

CONCLUSIONS

Indexing EVLW to PBW or AdjBW reduces the number of ARDS patients with normal EVLW and correlates better to Lung Injury Score and oxygenation than using ActBW. Studies are needed to confirm the presumed superiority of this method for diagnosing ARDS and to determine the clinical treatment implications.

Evaluation of structure-function relationships in asthma using multidetector CT and hyperpolarized He-3 MRI

RATIONALE AND OBJECTIVES

Although multiple detector computed tomography (MDCT) and hyperpolarized gas magnetic resonance imaging (HP MRI) have demonstrated ability to detect structural and ventilation abnormalities in asthma, few studies have sought to exploit or cross-validate the regional information provided by these techniques. The purpose of this work is to assess regional disease in asthma by evaluating the association of sites of ventilation defect on HP MRI with other regional markers of airway disease, including air trapping on MDCT and inflammatory markers on bronchoscopy.

MATERIALS AND METHODS

Both HP MRI using helium-3 and MDCT were acquired in the same patients. Supervised segmentation of the lung lobes on MRI and MDCT facilitated regional comparisons of ventilation abnormalities in the lung parenchyma. The percentage of spatial overlap was evaluated between regions of ventilation defect on HP MRI and hyperlucency on MDCT to determine associations between obstruction and likely regions of gas trapping. Similarly, lung lobes with high defect volume were compared to lobes with low defect volume for differences in inflammatory cell number and percentage using bronchoscopic assessment.

RESULTS

There was significant overlap between sites of ventilation defect on HP MRI and hyperlucency on MDCT suggesting that sites of airway obstruction and air trapping are associated in asthma. The percent (r=0.68; P= .0039) and absolute (r=0.61; P= .0125) number of neutrophils on bronchoalveolar lavage for the sampled lung lobe also directly correlated with increased defect volume.

CONCLUSIONS

These results show promise for using image guidance to assess specific regions of ventilation defect or air trapping in heterogeneous obstructive lung diseases such as asthma.

Sex differences in the perceived intensity of breathlessness during exercise with advancing age

The prevalence of activity-related breathlessness increases with age, particularly in women, but the specific underlying mechanisms have not been studied. This novel cross-sectional study was undertaken to examine the effects of age and sex, and their interaction, on the perceptual and ventilatory responses to incremental treadmill exercise in 73 healthy participants (age range 40–80 yr old) with normal pulmonary function. Age-related changes at a standardized oxygen uptake (V̇o2) during exercise included significant increases in breathlessness ratings (Borg scale), ventilation (V̇e), ventilatory equivalent for carbon dioxide, and the ratio of tidal volume (Vt) to dynamic inspiratory capacity (IC) (all P < 0.05). These changes were quantitatively similar in women ( n = 39) and in men ( n = 34). For the group as a whole, exertional breathlessness ratings increased as resting static inspiratory muscle strength diminished ( P = 0.05), as exercise ventilation increased relative to capacity ( P = 0.013) and as the Vt/IC ratio increased ( P = 0.003) during exercise. Older women (60–80 yr old, n = 23) reported greater ( P < 0.05) intensity of exertional breathlessness at a standardized V̇o2 and V̇e than age-matched men ( n = 16), despite similar age-related changes in ventilatory demand and dynamic ventilatory mechanics. These increases in breathlessness ratings in older women disappeared when sex differences in baseline maximal ventilatory capacity were accounted for. In conclusion, although increased exertional breathlessness with advancing age is multifactorial, contributory factors included higher ventilatory requirements during exercise, progressive inspiratory muscle weakness, and restrictive mechanical constraints on Vt expansion related to reduced IC. The sensory consequences of this age-related respiratory impairment were more pronounced in women, who, by nature, have relatively reduced maximal ventilatory reserve.

Use of the 15-steps climbing exercise oximetry test in patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is often associated with exercise-induced hypoxemia. Although maximal oxygen consumption (VO2(max)) is considered the gold-standard index of functional capacity in IPF, its measurement requires sophisticated equipment and trained personnel. The aim of the present study was to investigate the value of the simple 15-steps climbing exercise oximetry test in patients with IPF. The 15-steps climbing test was administered to 51 patients with IPF. Pulmonary function tests (PFTs), cardiopulmonary exercise test (CPET), and the 6-min walk distance (6MWD) test were performed in the same session. Oxygen saturation in the 15-steps climbing test was measured by continuous oximetry, and quantified oxygen desaturation was determined by calculating the area under the curve of oxygen saturation from the beginning of exercise through the lowest desaturation point until recovery to baseline ("desaturation area"). There was a statistically significant correlation between all parameters of the 15-steps climbing test and both VO2(max)) on the CPET (lowest saturation, p=0.002, r=0.43; saturation difference, p=0.02, r=-0.33; recovery time, p=0.02, r=-0.32; and desaturation area, p=0.005, r=-0.39), and carbon dioxide diffusion in the lungs (DLCO) on the PFTs (lowest saturation, p=0.0001, r=0.52; saturation difference, p=0.0002, r=-0.50; recovery time, p=0.0001, r=-0.53; and desaturation area, p=0.0001, r=-0.53). On stepwise linear regression analysis, independent significant predictors of VO2(max) were lowest saturation on the 15-steps test and the 6MWD. We concluded that the 15-steps oximetry test is a simple and accurate bedside tool for the evaluation of functional capacity in patients with IPF.

Soluble triggering receptor expressed on myeloid cells 1 is released in patients with stable chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is increasingly recognized as a systemic disease that is associated with increased serum levels of markers of systemic inflammation. The triggering receptor expressed on myeloid cells 1 (TREM-1) is a recently identified activating receptor on neutrophils, monocytes, and macrophage subsets. TREM-1 expression is upregulated by microbial products such as the toll-like receptor ligand lipoteichoic acid of Gram-positive or lipopolysaccharides of Gram-negative bacteria. In the present study, sera from 12 COPD patients (GOLD stages I-IV, FEV1 51 +/- 6%) and 10 healthy individuals were retrospectively analyzed for soluble TREM-1 (sTREM-1) using a newly developed ELISA. In healthy subjects, sTREM-1 levels were low (median 0.25 ng/mL, range 0-5.9 ng/mL). In contrast, levels of sTREM-1 in sera of COPD patients were significantly increased (median 11.68 ng/mL, range 6.2-41.9 ng/mL, P<.05). Furthermore, serum levels of sTREM-1 showed a significant negative correlation with lung function impairment. In summary, serum concentrations of sTREM-1 are increased in patients with COPD. Prospective studies are warranted to evaluate the relevance of sTREM-1 as a potential marker of the disease in patients with COPD.

The forgotten message from gold: FVC is a primary clinical outcome measure of bronchodilator reversibility in COPD

BACKGROUND

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) recommends the use of forced expiratory volume in 1s (FEV(1)) to assess airways reversibility. The American Thoracic Society (ATS) and the European Respiratory Society (ERS) recommend FEV(1) and/or forced vital capacity (FVC). This study assessed whether FVC detects reversibility in more chronic obstructive pulmonary disease (COPD) patients than FEV(1) after acute short-acting bronchodilator inhalation.

METHODS

Plethysmographic data of 168 consecutive stable male COPD patients who underwent reversibility testing were analyzed.

RESULTS

Seventy-seven patients showed a clinically significant increase in FVC, whereas only 49 patients showed a clinically significant increase in FEV(1). Thus, FVC detected reversibility in 57% more patients than FEV(1). Of the 90 patients showing clinically significant reversibility, FEV(1) did not detect 41 patients that FVC detected, indicating a 45% difference.

CONCLUSION

FEV(1) underestimates acute bronchodilation effects. FVC should thus be a primary clinical outcome measure of bronchodilator reversibility in COPD, as it detects reversibility in more patients. This message, forgotten by GOLD, should be promoted in future consensus statements.

The uses of helium and xenon in current clinical practice

The noble gases have always been an enigma. Discovered late in the history of chemistry and in seemingly small quantities in our atmosphere, they are some of the most unreactive elements known. However, despite being extremely inert, the noble gases (helium, neon, argon, krypton, xenon and radon) have found diverse and ever expanding applications in medicine. Of all of them, the gases that have found the greatest number of uses in the field of anaesthesia and related specialties are helium and xenon. This review focuses on the history of the discovery of both gases, their unique physicochemical properties and describes their uses in clinical practice with particular emphasis on those applicable to anaesthesia.

Comparative efficacy of two doses of nebulized colistimethate in the eradication of Pseudomonas aeruginosa in children with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) affects the respiratory and digestive systems. It evolves toward deterioration of pulmonary function through colonization with Pseudomonas aeruginosa. There is no consensus with respect to its eradication. Nebulized colistimethate is used for eradication treatment, but the optimal dose and duration is yet to be determined.

OBJECTIVES

To compare the efficacy of two doses of nebulized colistimethate (30 mg versus 75 mg twice daily) for the eradication of P aeruginosa in children with CF and intermittent colonization.

METHODS

A cohort study with both historical (30 mg) and prospective (75 mg) arms was conducted from 1999 to 2003. Medical records were used to collect data.

RESULTS

Eighty-one patients were recruited in the retrospective group, for a total of 111 treatment courses. Twenty patients were recruited in the prospective group, for a total of 20 events. There was no statistically significant difference in the rate of eradication of P aeruginosa at days 28 and 90, neither when comparing the doses of colistimethate nor duration of treatment. There was a statistically significant difference (P=0.004) between days 1 and 90 in all analyzed subgroups (regardless of dose or duration of treatment) for forced vital capacity only. In the group of patients in whom eradication was achieved at day 28 (after receiving a three-week treatment course of colistimethate), 50% of patients developed a new infection 5.75 months later, on average, regardless of the dose administered. In the group of patients who achieved eradication at day 90 (after receiving a 15-week treatment course of colistimethate), 50% of the 14 patients developed a new infection after an average period of 7.3 months (P=0.28).

CONCLUSIONS

There is no difference in the efficacy between a 30 mg dose and a 75 mg dose of colistimethate for P aeruginosa eradication in children with CF and intermittent colonization.

[Which definition to use when defining reversibility of airway obstruction?]

INTRODUCTION

There is no clear consensus about what constitutes reversibility of airway obstruction. European Respiratory Society (ERS): Increase in FEV1 and/or FVC>12% of their theoretical value and>0.2l. British Thoracic Society: FEV1>15% of initial value and FEV1>0.2l. Global Initiative for Chronic Obstructive Lung Disease: Increase in FEV1>12% and>0.2l. Australia and New Zealand Thoracic Society: Increase in FEV1 >15%. American Thoracic Society/ERS: Increase in FEV1>12% and>0.2l or increase in FVC>12% and 0.2l. Our principal objective was to determine the percentage of patients with COPD (n=62) who were significant responders to the reversibility test according to the 5 recommendations.

METHODS

Plethysmography was performed before and 15 minutes after inhalation of 400 micrograms of a short acting bronchodilator (BD). COPD is defined as a FEV1/FVC post BD<0.7.

RESULTS

The percentage of responders varied from 24% to 50% depending on the recommendations used.

CONCLUSION

Reversibility of airway obstruction is recommendation dependent.

Effects of a program of hospital-supervised chest physical therapy on lung function tests in children with chronic respiratory disease: 1-year follow-up

To investigate whether a hospital-supervised program of chest physical therapy improves lung function in children with chronic pulmonary diseases, twenty-four children (4 with Kartagener?s syndrome, 12 with common variable immunodeficiency, and 8 with primary ciliary dyskinesia) average age 11.2 +/- 3.2 years, were randomly assigned to a one-month hospital-supervised program of chest physical therapy (13 patients) or to a control group (11 patients) that continued unsupervised chest physical therapy at home. Lung function was assessed before the program, and one and 12 months after. At the one-month assessment, thoracic gas volume was significantly lower in the supervised group than in the controls. At the one-year assessment, forced expiratory volume in one second was significantly higher in the supervised group than in controls. A supervised program of chest physical therapy significantly improved lung function in children with chronic pulmonary diseases.

Dynamic hyperinflation with bronchoconstriction: differences between obese and nonobese women with asthma

RATIONALE

Symptoms and respiratory function tests may be difficult to assess and interpret in obese patients with asthma, particularly if the asthma is severe. It is unclear whether the dynamic changes that occur during bronchoconstriction differ between obese versus nonobese patients with asthma.

OBJECTIVES

To explore whether the changes in airway caliber and lung volumes that occur with acute bronchoconstriction are different in obese and nonobese patients with asthma and whether any differences contribute to the quality and intensity of symptoms.

METHODS

Thirty female patients with asthma were studied. Spirometry, lung volume measurements, and dyspnea scores were obtained before and immediately after bronchoconstriction induced by methacholine, aiming to provoke a reduction in FEV1 of 30%.

MEASUREMENTS AND MAIN RESULTS

Body mass index was independently associated with changes in lung volume after adjustment for baseline airway caliber and hyperresponsiveness. Increases in functional residual capacity and decreases in inspiratory capacity were significantly greater in obese participants (P < 0.001 and P = 0.003, respectively).

CONCLUSIONS

Changes in respiratory function, notably dynamic hyperinflation, are greater in obese individuals with bronchoconstriction. This may potentially alter the perception and assessment of asthma severity in obese patients with asthma.

Acute effects of sildenafil on exercise pulmonary hemodynamics and capacity in patients with COPD

BACKGROUND

We investigated in chronic obstructive pulmonary disease (COPD) patients whether a single dose of sildenafil can attenuate the exercise-induced increase in pulmonary artery pressure, thereby allowing augmentation of stroke volume (SV), and improving maximal exercise capacity.

METHODS

Eighteen COPD patients (GOLD II-IV) underwent right heart catheterization at rest and submaximal exercise. Mean pulmonary artery pressure (mPpa) and cardiac output (CO) were assessed. Resting and exercise measurements were repeated 60 min after oral intake of 50mg sildenafil. Also, on different days, patients performed two maximal exercise tests (CPET) randomly, 1h after placebo and after 50mg sildenafil.

RESULTS

Five COPD patients had pulmonary hypertension (PH) at rest (mPpa >25 mmHg) and six developed PH during exercise (mPpa >30 mmHg). In all patients, mPpa increased from rest to submaximal exercise (23+/-10-35+/-14 mmHg). After sildenafil mPpa at rest was 20+/-10 mmHg, in exercise mPpa was increased less to 30+/-14 mmHg (p<0.01). The reduced augmentation in mPpa was not accompanied by an increased SV and CO. In COPD patients with PH the percentage increase in mPpa to submaximal exercise was 68% before, and 51% after oral intake of sildenafil (p=0.07). In COPD without PH, these values were 46% and 41% (ns), respectively. Maximal exercise capacity and CPET characteristics were unchanged after sildenafil.

CONCLUSION

Regardless of mPpa at rest, sildenafil attenuates the increase in mPpa during submaximal exercise in COPD. This attenuated increase is neither accompanied by enhanced SV and CO, nor by improved maximal exercise capacity.

Lung function made easy: assessing lung size

Spirometry is available in most GP surgeries and provides an invaluable tool for assessing respiratory function in chronic obstructive pulmonary disease (COPD) and asthma. Spirometry alone may not provide the clinician with an accurate assessment of lung disease as it misses two important measurements of lung volume. By measuring Residual Volume (RV) and Total Lung Capacity (TLC) it is possible to determine true restrictive or hyperinflated disease processes. Helium dilution, body plethysmography and nitrogen washout are three different methods which may be used to measure lung volume. These tests are normally only provided in the acute setting. Comparing values of RV and TLC to predicted values makes it possible to grade the severity of disease far more accurately than spirometry. Four case studies of asthma, obesity, COPD and pulmonary fibrosis clearly demonstrate anomalies that may arise when interpreting lung disease from spirometry compared to the interpretation made with additional lung volume data.

Monitoring recovery from diaphragm paralysis with ultrasound

BACKGROUND

Diaphragmatic paralysis is an uncommon, yet underdiagnosed cause of dyspnea. Data regarding the time course and potential for recovery has come from a few small case series. The methods that have been traditionally employed to diagnose diaphragmatic weakness or paralysis are either invasive or limited in sensitivity and specificity. A new technique utilizing two-dimensional, B-mode ultrasound (US) measurements of diaphragm muscle thickening during inspiration (Deltatdi%) has been validated in the diagnosis of diaphragm paralysis (DP). The purpose of this study was to assess whether serial US evaluation might be utilized to monitor the potential recovery of diaphragm function.

METHODS

Twenty-one consecutive patients with clinically suspected DP were referred to the pulmonary physiology laboratory. Sixteen patients were found to have DP by US (unilateral, 10 patients; bilateral, 6 patients). Subjects were followed up for up to 60 months. On initial and subsequent visits, Deltatdi% was measured by US. Additional measurements included upright and supine vital capacity (VC), maximal inspiratory pressure (Pimax), and maximal expiratory pressure.

RESULTS

Eleven of 16 patients functionally recovered from DP. The mean (+/- SD) recovery time was 14.9 +/- 6.1 months. No diaphragm thickening was noted in those patients who did not recover. Positive correlations were found between improvement in Deltatdi% and interval changes in VC, Pimax, and end-expiratory measurements of diaphragm thickness.

CONCLUSIONS

US may be used to assess for potential functional recovery from diaphragm weakness or DP. As in previous series, recovery occurs in a substantial number of individuals, but recovery time may be prolonged.

Identification of a predominant COPD phenotype in clinical practice

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation caused by small airways increased resistance and/or terminal airspaces emphysematous destruction. Spirometric detection of not fully reversible airflow limitation unifies under the acronym COPD, a spectrum of heterogeneous conditions, whose clinical presentations may be substantially different. In a cross-sectional study we aimed to ascertain whether COPD phenotypes reflecting different mechanisms of airflow limitation could be clinically identified.

METHODS

Multidimensional scaling was used to visualize as a single point in a two-dimension space the multidimensional variables derived from each of 322 COPD patients (derivation set) by clinical, functional, and chest radiographic evaluation. Cluster analysis assigned then a cluster membership to each patient data point. Finally, using cluster membership as dependent variable and all data acquired as independent variables, we developed multivariate models to prospectively classify another group of 93 COPD patients (validation set) in whom high-resolution computerized tomography (HRCT) density parameters were measured.

RESULTS

A multivariate model based on nine variables acquired from the derivation set by history (sputum characteristics), physical examination (adventitious sounds, hyperresonance), FEV1/VC, and chest radiography (increased vascular markings, bronchial wall thickening, increased lung volume, reduced lung density) partitioned the validation set into two groups whose clinical, functional, chest radiographic, and HRCT characteristics corresponded to either an airways obstructive or a parenchymal destructive COPD phenotype.

CONCLUSION

Patients with COPD can be assigned a clinical phenotype reflecting the prevalent mechanism of airflow limitation. The standardized identification of the predominant phenotype may permit to clinically characterize COPD beyond its unifying spirometric definition.

Mechanisms of dyspnea during cycle exercise in symptomatic patients with GOLD stage I chronic obstructive pulmonary disease

RATIONALE

Smokers with a relatively preserved FEV(1) may experience dyspnea and activity limitation but little is known about underlying mechanisms.

OBJECTIVES

To examine ventilatory constraints during exercise in symptomatic smokers with GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage I chronic obstructive lung disease (COPD) so as to uncover potential mechanisms of dyspnea and exercise curtailment.

METHODS

We compared resting pulmonary function and ventilatory responses (breathing pattern, operating lung volumes, pulmonary gas exchange) with incremental cycle exercise as well as Borg scale ratings of dyspnea intensity in 21 patients (post-bronchodilator FEV(1), 91 +/- 7% predicted, and FEV(1)/FVC, 60 +/- 6%; mean +/- SD) with significant breathlessness and 21 healthy age- and sex-matched control subjects with normal spirometry.

MEASUREMENTS AND MAIN RESULTS

In patients with COPD compared with control subjects, peak oxygen consumption and power output were significantly reduced by more than 20% and dyspnea ratings were higher for a given work rate and ventilation (P < 0.05). Compared with the control group, the COPD group had evidence of extensive small airway dysfunction with increased ventilatory requirements during exercise, likely on the basis of greater ventilation/perfusion abnormalities. Changes in end-expiratory lung volume during exercise were greater in COPD than in health (0.54 +/- 0.34 vs. 0.06 +/- 0.32 L, respectively; P < 0.05) and breathing pattern was correspondingly more shallow and rapid. Across groups, dyspnea intensity increased as ventilation expressed as a percentage of capacity increased (P < 0.0005) and as inspiratory reserve volume decreased (P < 0.0005).

CONCLUSIONS

Exertional dyspnea in symptomatic patients with mild COPD is associated with the combined deleterious effects of higher ventilatory demand and abnormal dynamic ventilatory mechanics, both of which are potentially amenable to treatment.

Lung function in adults with stable but severe asthma: air trapping and incomplete reversal of obstruction with bronchodilation

Five to ten percent of asthma cases are poorly controlled chronically and refractory to treatment, and these severe cases account for disproportionate asthma-associated morbidity, mortality, and health care utilization. While persons with severe asthma tend to have more airway obstruction, it is not known whether they represent the severe tail of a unimodal asthma population, or a severe asthma phenotype. We hypothesized that severe asthma has a characteristic physiology of airway obstruction, and we evaluated spirometry, lung volumes, and reversibility during a stable interval in 287 severe and 382 nonsevere asthma subjects from the National Heart, Lung, and Blood Institute Severe Asthma Research Program. We partitioned airway obstruction into components of air trapping [indicated by forced vital capacity (FVC)] and airflow limitation [indicated by forced expiratory volume in 1 s (FEV(1))/FVC]. Severe asthma had prominent air trapping, evident as reduced FVC over the entire range of FEV(1)/FVC. This pattern was confirmed with measures of residual lung volume/total lung capacity (TLC) in a subgroup. In contrast, nonsevere asthma did not exhibit prominent air trapping, even at FEV(1)/FVC <75% predicted. Air trapping also was associated with increases in TLC and functional reserve capacity. After maximal bronchodilation, FEV(1) reversed similarly from baseline in severe and nonsevere asthma, but the severe asthma classification was an independent predictor of residual reduction in FEV(1) after maximal bronchodilation. An increase in FVC accounted for most of the reversal of FEV(1) when baseline FEV(1) was <60% predicted. We conclude that air trapping is a characteristic feature of the severe asthma population, suggesting that there is a pathological process associated with severe asthma that makes airways more vulnerable to this component.

Air travel hypoxemia vs. the hypoxia inhalation test in passengers with COPD

BACKGROUND

Limited data are available comparing air travel with the hypoxia inhalation test (HIT) in passengers with COPD. The aim of this study was to assess the predictive capability of the HIT to in-flight hypoxemia in passengers with COPD.

METHODS

Thirteen passengers (seven female passengers) with COPD (mean [+/- SD], FEV(1)/FVC ratio, 44 +/- 17%) volunteered for this study. Respiratory function tests were performed preflight. Pulse oximetry, cabin pressure, and dyspnea were recorded in flight. The HIT and a 6-min walk test were performed postflight. The in-flight oxygenation response was compared to the HIT results and respiratory function parameters.

RESULTS

All subjects flew without the use of oxygen, and no adverse events were recorded in-flight (mean cabin altitude, 2,165 m; altitude range, 1,892 to 2,365 m). Air travel caused significant desaturation (mean preflight oxygen saturation, 95 +/- 1%; mean in-flight oxygen saturation, 86 +/- 4%), which was worsened by activity (nadir pulse oximetric saturation [Spo(2)], 78 +/- 6%). The HIT caused mean desaturation that was comparable to that of air travel (84 +/- 4%). The mean in-flight partial pressure of inspired oxygen (Pio(2)) was higher than the HIT Pio(2) (113 +/- 3 mm Hg vs 107 +/- 1 mm Hg, respectively; p < 0.001). The HIT Spo(2) showed the strongest correlation with in-flight Spo(2) (r = 0.84; p < 0.001).

CONCLUSION

Significant in-flight desaturation can be expected in passengers with COPD. The HIT results compared favorably with the air travel data, with differences explainable by Pio(2) and physical activity. The HIT is the best widely available laboratory test to predict in-flight hypoxemia.

Comparison of High-Frequency Chest Wall Oscillation With Differing Waveforms for Airway Clearance in Cystic Fibrosis

BACKGROUND

High-frequency chest wall oscillation (HFCWO) is commonly used by cystic fibrosis (CF) patients for airway clearance. The primary objective of this study was to determine whether the use of a newer HFCWO device that generates oscillations with a triangular waveform results in greater sputum production than a commonly used device that generates oscillations with a sine waveform.

METHODS

This was a controlled, randomized, double-blind, crossover study. Fifteen clinically stable, adult CF patients participated. Patients performed airway clearance with each device once and at matched oscillation frequencies and pressures. All sputum produced during each session was collected. Patients completed pulmonary function tests before and after each session, and rated the comfort of the two devices.

RESULTS

Mean sputum wet and dry weight produced during sine waveform and triangular waveform HFCWO sessions did not differ (p = 0.11 and p = 0.2, respectively). Mean changes in FEV(1) and FVC following HFCWO therapy were also comparable (p = 0.21 and p = 0.56, respectively). However, there was a significant reduction in air trapping by residual volume/total lung capacity ratio following triangular waveform HFCWO (p = 0.01). In addition, in vitro cough transportability was 10.6% greater following therapy with the triangular waveform device (p = 0.05). Patients perceived the two devices as equally comfortable (p = 0.8).

CONCLUSIONS

Single-session sputum production is comparable with sine and triangular waveform HFCWO devices. Longer term comparisons are needed to determine whether sustained use of the devices results in clinically important differences in outcomes.

Impact of the new ATS/ERS pulmonary function test interpretation guidelines

RATIONALE

In November 2005, the American Thoracic and European Respiratory Societies jointly published a statement proposing a new interpretation scheme for pulmonary function tests. The practical effect of adoption of these new guidelines has not yet been studied. The purpose of the current study was to address the effects of the new interpretation strategy on the relative distribution of obstructive and restrictive diagnoses in patients evaluated at a single academic medical center laboratory.

PATIENTS/METHODS

Pulmonary functions tests from 319 patients were analyzed according to four different interpretation schemes. The number of patients classified according to each as obstructed, restricted, neither, or both were compared, and factors associated with a change in classification using the different approaches were examined.

RESULTS

Although similar proportions of patients were identified as restricted using either the "GOLD" scheme (23%) or new approaches (22%), significantly more (P<0.005) were defined as obstructed using the newly proposed scheme (44% versus 33%). Additionally, 36% of subjects defined as obstructed using either the traditional or new schemes were classified differently (i.e., either "gained" or "lost" the diagnosis of obstruction) using the new approach. Women were significantly more likely than men to have a change in classification.

CONCLUSIONS

The new interpretation scheme leads to a diagnosis of obstruction in a greater proportion of patients undergoing pulmonary function testing. The clinical significance of this finding has not yet been validated, and its economic impact remains to be assessed.

Pulmonary function testing in New Zealand: the use and importance of reference ranges

BACKGROUND AND OBJECTIVES

The diagnosis, assessment and management of a wide range of respiratory diseases rely on accurate interpretation of lung function tests through the use of reference equations to generate predicted values. This paper ascertains the suitability of reference equations currently used in New Zealand through comparison with newly derived equations from the Wellington Respiratory Survey, and discusses the relevance of the findings to the Asia Pacific region.

METHODS

A survey of lung function testing facilities determined the reference equations in common usage. Pulmonary function test results from healthy, lifelong non-smoking subjects (n = 180) were expressed as percentage predicted values, with comparisons made between the currently used and Wellington Respiratory Survey reference equations. Differences in disease severity classification in subjects with COPD (n = 46) and asthma (n = 61) were determined, using the different reference equations.

RESULTS

Currently used equations significantly underpredict measured values for FEV(1), PEF, TLC and RV by up to 20%. Severity classification of COPD and asthma based on per cent predicted FEV(1) was substantially altered by the choice of reference equation.

CONCLUSION

Many reference equations in current usage in New Zealand are no longer suitable for use. The applicability of reference equations used in other populations and countries within the Asia Pacific region requires further investigation. We recommend that up-to-date reference equations are derived and implemented if those currently used are shown to be unsatisfactory.

Variations in physician interpretation of overnight pulse oximetry monitoring

BACKGROUND

Overnight pulse oximetry is commonly used for hypoxemia evaluation in patients with COPD and sleep-disordered breathing. There is little information regarding its impact on physician decision making, and therefore an important measure of its clinical utility is untested and unknown. The aim of this study was to describe physician interpretation, use, and opinions regarding overnight pulse oximetry.

METHODS

Forty-one pulmonary physicians and fellows participated in structured interviews consisting of three oximetry record interpretations, oral responses to a standard question set, and a questionnaire. Qualitative data were analyzed using an open coding process. Quantitative data were assessed for distributions.

RESULTS

Four measures were consistently used by the majority of physicians in record interpretation: background information, arterial oxygen saturation measured by pulse oximetry (Spo(2)) waveform and pattern, and time spent with Spo(2) < 90%. An additional 10 measures were consistently used by 5 to 46% of physicians. No interpretation generated a recommendation with > 60% consensus. There was a wide range of opinions on important matters related to this test, including test utility, indications, variables considered most important for interpretation, and criteria for nocturnal oxygen prescription. Forty-one physicians provided 35 different opinions on when nocturnal supplemental oxygen should be initiated.

CONCLUSIONS

The variation in physician interpretation, use, and opinions regarding overnight pulse oximetry calls into question its clinical utility and underscores a need for standardization of presentation, training, and interpretation.

Induced sputum as a tool for early detection of airway inflammation in connective diseases-related lung involvement

BACKGROUND

Induced sputum (IS) sampling is a safe and validated approach to study bronchial inflammation in chronic obstructive lung diseases. Although promising results have also been reported in various diffuse interstitial lung disorders, the potential use of IS in the assessment of connective tissue diseases (CTD)-related lung involvement has not yet been investigated.

AIM OF THE STUDY

To evaluate the clinical usefulness of IS in the early management of patients suffering from rheumatoid arthritis (RA) and systemic sclerosis (SSc) at the onset of respiratory symptoms.

PATIENTS AND METHODS

The study population included 19 patients (RA=12; SSc=7) and 14 age- and sex-matched healthy volunteers. Lung function testing, high resolution computed tomography (HRCT) of the thorax and IS collection were performed in all cases. Broncho-alveolar lavage (BAL) was obtained in selected patients.

RESULTS

IS samples from patients contained a significantly higher percentage of neutrophils and a lower percentage of macrophages compared to healthy subjects (p=0.002 and 0.001, respectively), while the total cell number showed no differences. In addition, sputa yielded both higher cell counts and higher neutrophils than BAL samples (p=0.02 in all instances). No correlations were found between IS findings and lung function parameters, HRCT and BAL findings.

CONCLUSIONS

This is the first study investigating the inflammatory cell pattern in IS from CTD patients with early clinical evidence of lung involvement. Future studies are needed to determine whether the assessment of airway inflammation adds significant information that may result in a relevant improvement of disease management.

Spirometer calibration checks: is 3.5% good enough?

BACKGROUND

Current standards for spirometry require daily calibration checks to come within 3.5% of the inserted volume but do not require evaluation of trends over time. We examined the current guidelines and candidate quality control rules to determine the best method for identifying spirometers with suboptimal performance.

METHODS

Daily calibration checks on seven volume spirometers recorded over 4 to 11 years were reviewed. Current guidelines and candidate quality control rules were applied to determine how well each detected suboptimal spirometer performance.

RESULTS

Overall, 98% of 7,497 calibration checks were within 3.5%. However, based on visual inspection of calibration check data plots, spirometers 3 and 5 demonstrated systematic sources of error, drift, and bias. The +/- 3.5% criteria did not identify these spirometers. The application of +/- 2% criteria identified these spirometers (9% out-of control values in spirometers 3 and 5 vs < 5% in other spirometers). A rule stipulating out-of-control conditions when four consecutive checks exceeded 1% deviation identified suboptimal spirometers (14% and 20% out-of-control values) but maintained low error detection rates in other spirometers (< or = 2%). Other candidate rules were less effective or required longer times to error detection.

CONCLUSIONS

The current recommendation that calibration checks come within +/- 3.5% of the inserted volume did not detect subtle errors. Alternative candidate rules were more effective in detecting errors and maintained low overall error-detection rates. Our findings emphasize the need for laboratories to systematically review calibration checks over time and suggest that more stringent guidelines for calibration checks may be warranted for volume spirometers. Although our general approach may also be appropriate for flow-type spirometers, the details are likely to differ since flow-type spirometers are a much more varied category of equipment.

[Which definition to use when defining airflow obstruction?]

INTRODUCTION

There is no clear consensus as to what constitutes an obstructive ventilatory defect (OVD). According to the American Thoracic Society and European Respiratory Society, it is defined as being when the ratio of the forced expiratory volume (FEV1) and the slow expiratory vital capacity (VC) is below the lower limit of normal (LLN). According to the Global initiative for chronic Obstructive Lung Disease and the British Thoracic Society, it is an FEV1/forced expiratory vital capacity (FVC)<0.70 and an FEV1<80%. In addition, in daily practice, the OVD is diagnosed by a "Fixed ratio" FEV1/FVC<0.70 or<LLN. The aim of this study is to determine, according to the different recommendations, the percentage of subjects having an OVD among them addressed for suspicion of chronic obstructive pulmonary disease.

METHODS

A medical questionnaire was administered and anthropometric data were collected. The expiratory flows and pulmonary volumes were measured by a body plethysmograph.

RESULTS

121 (81%) subjects among the 150 examined were included. The percentage of subjects having an OVD was 56.1% (FEV1/VC<LLN), 54.1% (FEV1/FVC<0.70), 48.7% (FEV1/FVC<0.70 and FEV1<80%), and 47.8% (FEV1/FVC<LLN).

CONCLUSION

The prevalence of obstructive ventilatory defect in a population depends on the definition chosen.

Ventilatory and perceptual responses to cycle exercise in obese women

The main purpose of this study was to examine the relative contribution of respiratory mechanical factors and the increased metabolic cost of locomotion to exertional breathlessness in obese women. We examined the relationship of intensity of breathlessness to ventilation (V̇e) when exertional oxygen uptake (V̇o2) of obesity was minimized by cycle exercise. Eighteen middle-aged (54 ± 8 yr, mean ± SD) obese [body mass index (BMI) 40.2 ± 7.8 kg/m2] and 13 age-matched normal-weight (BMI 23.3 ± 1.7 kg/m2) women were studied. Breathlessness at higher submaximal cycle work rates was significantly increased (by ≥1 Borg unit) in obese compared with normal-weight women, in association with a 35–45% increase in V̇e and a higher metabolic cost of exercise. Obese women demonstrated greater resting expiratory flow limitation, reduced resting end-expiratory lung volume (EELV)(by 20%), and progressive increases in dynamic EELV during exercise: peak inspiratory capacity (IC) decreased by 16% (0.39 liter) of the resting value. V̇e/V̇o2 slopes were unchanged in obesity. Breathlessness ratings at any given V̇e or V̇o2 were not increased in obesity, suggesting that respiratory mechanical factors were not contributory. Our results indicate that in obese women, recruitment of resting IC and dynamic increases in EELV with exercise served to optimize operating lung volumes and to attenuate expiratory flow limitation so as to accommodate the increased ventilatory demand without increased breathlessness.

Do supervised weekly exercise programs maintain functional exercise capacity and quality of life, twelve months after pulmonary rehabilitation in COPD?

BACKGROUND

Pulmonary rehabilitation programs have been shown to increase functional exercise capacity and quality of life in COPD patients. However, following the completion of pulmonary rehabilitation the benefits begin to decline unless the program is of longer duration or ongoing maintenance exercise is followed. Therefore, the aim of this study is to determine if supervised, weekly, hospital-based exercise compared to home exercise will maintain the benefits gained from an eight-week pulmonary rehabilitation program in COPD subjects to twelve months.

METHODS

Following completion of an eight-week pulmonary rehabilitation program, COPD subjects will be recruited and randomised (using concealed allocation in numbered envelopes) into either the maintenance exercise group (supervised, weekly, hospital-based exercise) or the control group (unsupervised home exercise) and followed for twelve months. Measurements will be taken at baseline (post an eight-week pulmonary rehabilitation program), three, six and twelve months. The exercise measurements will include two six-minute walk tests, two incremental shuttle walk tests, and two endurance shuttle walk tests. Oxygen saturation, heart rate and dyspnoea will be monitored during all these tests. Quality of life will be measured using the St George's Respiratory Questionnaire and the Hospital Anxiety and Depression Scale. Participants will be excluded if they require supplemental oxygen or have neurological or musculoskeletal co-morbidities that will prevent them from exercising independently.

DISCUSSION

Pulmonary rehabilitation plays an important part in the management of COPD and the results from this study will help determine if supervised, weekly, hospital-based exercise can successfully maintain functional exercise capacity and quality of life following an eight-week pulmonary rehabilitation program in COPD subjects in Australia.

Reliability and validity of the lung volume measurement made by the BOD POD body composition system

The BOD POD Body Composition System uses air-displacement plethysmography to measure body volume. To correct the body volume measurement for the subject's lung volume, the BOD POD utilizes pulmonary plethysmography to measure functional residual capacity (FRC) at mid-exhalation as that is the subject's lung volume during the body volume measurement. Normally, FRC is measured at end-exhalation. The BOD POD FRC measurement can be corrected to an end-exhalation volume by subtracting approximately one-half of the measured tidal volume. Our purpose was to determine the reliability and validity of the BOD POD FRC measurement at end-exhalation. Ninety-two healthy adults (half female) underwent duplicate FRC measurements by the BOD POD and one FRC measurement by a traditional gas dilution technique. The latter method was used as the reference method for the validity component of the study. The order of the FRC measurements by the two methods was randomized. The test-retest correlation coefficients for the duplicate BOD POD FRC measurements for the male and female subjects were 0.966 and 0.948, respectively. The mean differences between the BOD POD FRC trial #1 measurement and gas dilution FRC measurement for the male and female subjects were -32 and -23 ml, respectively. Neither difference was statistically significant. The correlation coefficients for these two measurements in the male and female subjects were 0.925 and 0.917, respectively. Based on these results, we conclude that the BOD POD FRC measurement in healthy males and females is both reliable and valid.

Comparison of Total-Breath and Single-Breath Diffusing Capacity in Healthy Volunteers and COPD Patients

BACKGROUND

The measurement of single-breath diffusing capacity (Dlco(SB)) assumes that diffusing capacity per liter of alveolar volume (Dlco/VA) determined in a 750-mL gas sample represents the diffusing capacity (Dlco) of the entire lung. Fast-responding gas analyzers provide the opportunity to verify this assumption because of the possibility to measure CO and CH(4) fractions continuously throughout the entire expiration. Continuous gas sampling provides more information per measurement, but this information cannot be expressed in the traditional parameters. Our goals were to find new parameters to express the extra information of the continuous gas sampling, and to compare these new parameters with the traditional parameters.

METHODS

We compared a new method to determine Dlco with the traditional method in 62 healthy volunteers and 26 COPD patients. Traditionally, Dlco(SB) is determined by multiplying Dlco/VA with alveolar volume, both calculated from gas concentrations in a 750-mL gas sample. The new method calculates total-breath Dlco (Dlco(TB)) by integration of Dlco/VA against exhaled volume.

RESULTS

In healthy volunteers, Dlco/VA shows a slight upward slope during exhalation, while in COPD patients Dlco/VA shows a horizontal line. Total-breath total lung capacity (TLC) is larger than single-breath TLC both in healthy volunteers and in COPD patients, leading to a Dlco(TB) that is significantly larger than Dlco(SB) in both groups (p < 0.001).

CONCLUSION

The assumption that a 750-mL gas sample represents the entire lung seems to be correct for Dlco/VA but not for the CH(4) fraction in case of ventilation inhomogeneity.

Standardizing lung function laboratories for multicenter trials

Multi-center studies provide advantages in clinical research but differences between centers can introduce bias. Three specialist pediatric respiratory laboratories standardized their methodology and examined differences between centers. The specific aims were to (i) assess the variability of measurements on adults within and between centers and (ii) to exchange and cross-analyze data from children to assess the extent of agreement between centers. Each laboratory used identical equipment and software. Inter-laboratory visits were used to (i) standardize protocols for data collection and analysis and (ii) make spirometric and plethysmographic measurements on participating staff at each location. Staff also had repeat measurements in their home laboratories. Measurements from children in each laboratory were exchanged on disk, cross-analyzed, and data compared by ANOVA. There were no significant within-subject, between-center differences in FVC, FEV1, FEF50, FRCpleth, or VC. There was a slight trend for TLC and RV (P=0.07) to be higher at one center. The 95% limits of agreement within and between centers were similar for all parameters. There were no differences between centers in cross-analyzed data from 10 children. By standardizing hardware, software, and protocol, potential inter-laboratory differences can be minimized. We recommend that this approach be adopted prior to multi-center studies.

Simvastatin does not exhibit therapeutic anti-inflammatory effects in asthma

BACKGROUND

Statins lower cholesterol and also exhibit anti-inflammatory properties. In vitro and animal studies have suggested they may be useful for the treatment of a number of inflammatory conditions.

OBJECTIVE

To evaluate the in vivo therapeutic potential of simvastatin as an anti-inflammatory agent in patients with asthma.

METHODS

Potential signal from treatment effect was optimized by withdrawing all anti-inflammatory treatment for the duration of the study. Participants received 1 month of daily simvastatin and 1 month of daily placebo in a randomized, double-blind crossover trial. A total of 16 patients completed per protocol. Asthmatic inflammation was evaluated by measuring exhaled tidal nitric oxide, alveolar nitric oxide, sputum and peripheral eosinophil count, methacholine hyperresponsiveness, salivary eosinophilic cationic protein, and C-reactive protein. Measurements of dynamic and static lung volumes and of cholesterol were also made.

RESULTS

After initial withdrawal of usual asthma medication, there was a 1.43 geometric mean fold increase (ie, 43% difference) in fraction of exhaled nitric oxide (95% CI, 1.15 to 1.78; P = .004). Compared with placebo, simvastatin led to a 0.86 geometric mean fold decrease (95% CI, 0.7 to 1.04; P = .15) in exhaled nitric oxide (ie, a 14% difference), and a -0.18 doubling dilution shift (95% CI, -1.90 to 1.55; P = 1.0) in methacholine hyperresponsiveness. There were no significant differences in other inflammatory outcomes, lung volumes, or airway resistance between simvastatin and placebo. Treatment with simvastatin led to a significant reduction (P < .005) of total and low-density lipoprotein cholesterol.

CONCLUSION

There is no evidence to suggest simvastatin has anti-inflammatory activity in patients with asthma.

CLINICAL IMPLICATIONS

Simvastatin is not useful for the treatment of asthma.

Longitudinal changes in hyperinflation parameters and exercise capacity after giant bullous emphysema surgery

OBJECTIVE

Although resection of giant bullae for the purpose of improving the function of underlying compressed lung is an accepted form of surgery for emphysema, there is only limited information regarding long-term improvement in dynamic hyperinflation and exercise tolerance. Our major goal was to investigate the effects of lung resection for giant bullae on pulmonary function, dynamic hyperinflation, and exercise capacity in patients with chronic obstructive pulmonary disease characterized by emphysema.

METHODS

Pulmonary function and exercise testing were assessed prospectively before and 3, 6, 12, 24, and 48 months after surgery in 12 patients who had chronic obstructive pulmonary disease with emphysema who underwent lung resection of giant bullae.

RESULTS

Forced expiratory volume, diffusing capacity for carbon monoxide, arterial partial pressure of oxygen, and exercise capacity were significantly increased after resection of surgical bullae. Dynamic hyperinflation, as assessed by reduction in inspiratory capacity and dyspnea Borg scale, were significantly decreased during exercise. Improvement in baseline and exercise functional capacity slightly decreased over time, remaining, however, far above the value before surgery.

CONCLUSION

Altogether, these findings suggest that surgery for resection of giant bullae is an effective procedure for improving airflow, limiting gas exchange, and limiting exercise dynamic hyperinflation over time.

Mechanical response to methacholine and deep inspiration in supine men

The effects of supine posture on airway responses to inhaled methacholine and deep inspiration (DI) were studied in seven male volunteers. On a control day, subjects were in a seated position during both methacholine inhalation and lung function measurements. On a second occasion, the whole procedure was repeated with the subjects lying supine for the entire duration of the study. On a third occasion, methacholine was inhaled from the seated position and measurements were taken in a supine position. Finally, on a fourth occasion, methacholine was inhaled from the supine position and measurements were taken in the seated position. Going from sitting to supine position, the functional residual capacity decreased by approximately 1 liter in all subjects. When lung function measurements (pulmonary resistance, dynamic elastance, residual volume, and maximal flows) were taken in supine position, the response to methacholine was greater than at control, and this was associated with a greater dyspnea and a faster recovery of dynamic elastance after DI. By contrast, when methacholine was inhaled in supine position but measurements were taken in sitting position, the response to methacholine was similar to control day. These findings document the potential of the decrease in the operational lung volumes in eliciting or sustaining airflow obstruction in nocturnal asthma. It is speculated that the exaggerated response to methacholine in the supine posture may variably contribute to airway smooth muscle adaptation to short length, airway wall edema, and faster airway renarrowing after a large inflation.