Standardisation of the measurement of lung volumes

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.