Measurement of transfer factor during constant exhalation

2017 ERS/ATS standards for single-breath carbon monoxide uptake in the lung

This document provides an update to the European Respiratory Society (ERS)/American Thoracic Society (ATS) technical standards for single-breath carbon monoxide uptake in the lung that was last updated in 2005. Although both D_LCO (diffusing capacity) and T_LCO (transfer factor) are valid terms to describe the uptake of carbon monoxide in the lung, the term D_LCO is used in this document. A joint taskforce appointed by the ERS and ATS reviewed the recent literature on the measurement of D_LCO and surveyed the current technical capabilities of instrumentation being manufactured around the world. The recommendations in this document represent the consensus of the taskforce members in regard to the evidence available for various aspects of D_LCO measurement. Furthermore, it reflects the expert opinion of the taskforce members on areas in which peer-reviewed evidence was either not available or was incomplete. The major changes in these technical standards relate to D_LCO measurement with systems using rapidly responding gas analysers for carbon monoxide and the tracer gas, which are now the most common type of D_LCO instrumentation being manufactured. Technical improvements and the increased capability afforded by these new systems permit enhanced measurement of D_LCO and the opportunity to include other optional measures of lung function.

Clinical applications of lung function tests: a revisit

The development and clinical application of lung function tests have a long history, and the various components of lung function tests provide very important tools for the clinical evaluation of respiratory health and disease. Spirometry, measurement of the diffusion factor, bronchial provocation tests and forced oscillation techniques have found diverse clinical applications in the diagnosis and monitoring of respiratory diseases, such as chronic obstructive pulmonary disease, interstitial lung diseases and asthma. However, there are some practical issues to be resolved, including the establishment of reference values for individual test parameters and the roles of these tests in preoperative risk assessment and pulmonary rehabilitation. Novel measurements, including negative expiratory pressure, the fraction of exhaled nitric oxide and analysis of exhaled breath condensate, may provide new insights into physiological abnormalities or airway inflammation in respiratory diseases, but their clinical applications need to be further evaluated. The clinical application of lung function tests continues to face challenges, which may be overcome by further improvement of conventional techniques for lung function testing and further specification of new testing techniques.

Reduced exercise tolerance and pulmonary capillary recruitment with remote secondhand smoke exposure

Rationale

Flight attendants who worked on commercial aircraft before the smoking ban in flights (pre-ban FAs) were exposed to high levels of secondhand smoke (SHS). We previously showed never-smoking pre-ban FAs to have reduced diffusing capacity (Dco) at rest.

Methods

To determine whether pre-ban FAs increase their Dco and pulmonary blood flow () during exercise, we administered a symptom-limited supine-posture progressively increasing cycle exercise test to determine the maximum work (watts) and oxygen uptake () achieved by FAs. After 30 min rest, we then measured Dco and at 20, 40, 60, and 80 percent of maximum observed work.

Results

The FAs with abnormal resting Dco achieved a lower level of maximum predicted work and compared to those with normal resting Dco (mean±SEM; 88.7±2.9 vs. 102.5±3.1%predicted ; p = 0.001). Exercise limitation was associated with the FAs' FEV₁ (r = 0.33; p = 0.003). The Dco increased less with exercise in those with abnormal resting Dco (mean±SEM: 1.36±0.16 vs. 1.90±0.16 ml/min/mmHg per 20% increase in predicted watts; p = 0.020), and amongst all FAs, the increase with exercise seemed to be incrementally lower in those with lower resting Dco. Exercise-induced increase in was not different in the two groups. However, the FAs with abnormal resting Dco had less augmentation of their Dco with increase in during exercise (mean±SEM: 0.93±0.06 vs. 1.47±0.09 ml/min/mmHg per L/min; p<0.0001). The Dco during exercise was inversely associated with years of exposure to SHS in those FAs with ≥10 years of pre-ban experience (r = −0.32; p = 0.032).

Conclusions

This cohort of never-smoking FAs with SHS exposure showed exercise limitation based on their resting Dco. Those with lower resting Dco had reduced pulmonary capillary recruitment. Exposure to SHS in the aircraft cabin seemed to be a predictor for lower Dco during exercise.

High-altitude exposure of three weeks duration increases lung diffusing capacity in humans

Background: high-altitude adaptation leads to progressive increase in arterial PaO2. In addition to increased ventilation, better arterial oxygenation may reflect improvements in lung gas exchange. Previous investigations reveal alterations at the alveolar-capillary barrier indicative of decreased resistance to gas exchange with prolonged hypoxia adaptation, but how quickly this occurs is unknown. Carbon monoxide lung diffusing capacity and its major determinants, hemoglobin, alveolar volume, pulmonary capillary blood volume, and alveolar-capillary membrane diffusion, have never been examined with early high-altitude adaptation. Methods and Results: lung diffusion was measured in 33 healthy lowlanders at sea level (Milan, Italy) and at Mount Everest South Base Camp (5,400 m) after a 9-day trek and 2-wk residence at 5,400 m. Measurements were adjusted for hemoglobin and inspired oxygen. Subjects with mountain sickness were excluded. After 2 wk at 5,400 m, hemoglobin oxygen saturation increased from 77.2 ± 6.0 to 85.3 ± 3.6%. Compared with sea level, there were increases in hemoglobin, lung diffusing capacity, membrane diffusion, and alveolar volume from 14.2 ± 1.2 to 17.2 ± 1.8 g/dl ( P < 0.01), from 23.6 ± 4.4 to 25.1 ± 5.3 ml·min−1·mmHg−1 ( P < 0.0303), 63 ± 34 to 102 ± 65 ml·min−1·mmHg−1 ( P < 0.01), and 5.6 ± 1.0 to 6.3 ± 1.1 liters ( P < 0.01), respectively. Pulmonary capillary blood volume was unchanged. Membrane diffusion normalized for alveolar volume was 10.9 ± 5.2 at sea level rising to 16.0 ± 9.2 ml·min−1·mmHg−1·l−1 ( P < 0.01) at 5,400 m. Conclusions: at high altitude, lung diffusing capacity improves with acclimatization due to increases of hemoglobin, alveolar volume, and membrane diffusion. Reduction in alveolar-capillary barrier resistance is possibly mediated by an increase of sympathetic tone and can develop in 3 wk.

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.

Advantages of the Intrabreath Technique as a Measure of Lung Function Before and After Heart Transplantation *

BACKGROUND

Pulmonary function testing is an integral part of evaluating patients who are being considered for cardiac transplantation. The accurate measurement of diffusing capacity (DLCO) and alveolar volume (VA) is dependent on a 10-s breath-holding maneuver that may be difficult for patients with congestive heart failure to perform. The intrabreath (IB) technique is not dependent on a breath-holding maneuver and may provide more accurate pulmonary function testing results in chronically debilitated patients.

METHODS

Seventy-five patients performed maneuvers with IB and single-breath (SB) techniques during evaluation for heart transplantation and at 3 and 12 months following transplantation. The DLCO, VA, and total lung capacity (TLC) were compared using Pearson correlation coefficients, a Student t test, and intercorrelation coefficients.

RESULTS

The DLCO and VA, when determined with the IB technique, had excellent correlations to the SB technique over all ranges of DLCO values. VA values that were determined by the IB technique were greater than those determined by the SB technique and more closely approximated the TLC values. The satisfactory correlation between the two techniques was maintained when DLCO was corrected for VA. However, due to the lower values for VA as determined by the SB method, the corrected measurements were consistently higher for the SB technique.

CONCLUSION

Pulmonary function can be measured accurately in a population of patients with long-standing congestive heart failure, both before and after cardiac transplantation, using the IB technique. Furthermore, the IB technique may provide a more accurate measurement of VA.

Intrabreath diffusing capacity of the lung in healthy individuals at rest and during exercise

BACKGROUND

Traditional approaches to measuring the diffusing capacity of the lung for carbon monoxide (DLCO) treat the lung as a single, well-mixed compartment and produce a single value for DLCO to represent an average diffusing capacity of the lung (DL). Because DL distribution in the lung is inhomogeneous, and changes in the DL in diseased lungs may be regional, measuring regional DL, especially during exercise, may be more sensitive in detecting pulmonary vascular diseases.

OBJECTIVES

To characterize regional changes in DL in healthy individuals from rest to exercise, and to provide normal references for future studies in pulmonary vascular disorders.

METHODS

We reanalyzed DLCO and phase III CH(4) slopes that were obtained during a slow, single exhalation at rest and during exercise in our extended database of 105 healthy individuals. DLCO profiles between 20% and 80% of exhaled vital capacity (VC) (ie, the intrabreath DLCO) were analyzed by calculating the average DLCO measured at midlung volume (ie, 30 to 45% of exhaled VC [DLCOMLV]) and by fitting the whole curve with a third-order polynomial equation.

RESULTS

DLCO decreased nonlinearly by approximately 30%, from 20 to 80% of exhaled VC at rest. DLCO during exercise was greater than that at rest, and the increase was similar at all lung volumes. The CH(4) slopes at rest and during exercise were similar. Prediction equations based on regressions on age, sex, and height were computed for resting and exercise DLCOMLV and the phase III CH(4) slope (an index of ventilation distribution).

CONCLUSIONS

Capillary recruitment/dilation during exercise in healthy individuals is a uniform process throughout the lungs. Our analyses provide a database for a noninvasive method that can incorporate exercise to evaluate the volume-dependent distribution of DLCO in lung diseases.

Noninvasive measurement of cardiac output by an acetylene uptake technique and simultaneous comparison with thermodilution in ICU patients

A simple, accurate, and noninvasive method of cardiac output measurement can be an extremely useful tool for the clinician and researcher. This study used the acetylene gas uptake technique to measure the absorption of acetylene into the pulmonary circulation during a constant exhalation, which is proportional to the pulmonary capillary blood flow and to the cardiac output, assuming no anatomic shunts. We compared cardiac output measured simultaneously by this and by the standard thermodilution (TD) technique in 21 patients in the ICU with a variety of medical and surgical conditions and a wide range of cardiac outputs. We also compared the two techniques in 19 ambulatory patients with a 2-h interval between the invasive and noninvasive test to assess variability over time. The two tests had an excellent correlation when done simultaneously with a correlation coefficient of 0.89 (p < 0.001). With a 2-h interval between the two tests, the correlation coefficient was 0.66 (p = 0.0018). Nine patients in the simultaneous group had cardiomyopathy. When they were excluded, the correlation coefficient increased to 0.96. Most of these patients had documented tricuspid regurgitation (TR), which may underlie the greater difference between acetylene uptake and TD values, with consistently higher TD values in these patients. This study confirms the correlation between the acetylene uptake and the standard invasive TD techniques in sick patients with various medical and surgical conditions and a wide range of cardiac outputs. Furthermore, we believe this would be a more accurate method for measuring cardiac output in patients with cardiomyopathy and TR because it is based only on pulmonary capillary blood flow.

Almost simultaneous measurement of cardiovascular and gas exchange variables during maximal exercise

We measured gas exchange variables such as oxygen uptake, carbon dioxide output, and lung diffusing capacity using noninvasive techniques almost simultaneous with assessment of cardiovascular variables such as pulmonary blood flow at several levels of treadmill exercise up to and including maximal capacity. We utilized a single breath exhalation technique for measurement of diffusing capacity and cardiac output and breath by breath methodology for evaluating oxygen uptake. The equipment required for these measurements--rapid gas analyzers, oximeters, on-line computation, and pneumatic valves--are well within the capabilities of many exercise laboratories and are not difficult to use with subjects even at the heaviest levels of exercise. The results agreed well with values reported in the literature. From these entirely noninvasive measures, we calculated mixed venous oxygen saturation and maximal tissue oxygen diffusing capacity.

Comparison of the single breath with the intrabreath method for the measurement of the carbon monoxide transfer factor in subjects with and without airways obstruction

BACKGROUND

Measurement of the carbon monoxide transfer factor (TLCO) has traditionally been performed using the single breath method but recently the intrabreath method has been developed. The aim of this study was to compare the two methods in the clinical evaluation of patients with obstructive and non-obstructive pulmonary disorders.

METHODS

Measurements of TLCO with the intrabreath method were carried out on a study sample composed of 50 patients with non-obstructive disorders and 50 with airways obstruction (FEV1/FVC < 70%) either before or after a single breath measurement of the TLCO had been performed. The method involves the continuous analysis of a single slow expirate using a computerised rapid multigas infrared analyser. TLCO, alveolar volume (VA), TLCO/VA, and inspired vital capacity (IVC) values were obtained for both groups by both methods.

RESULTS

When measured with the intrabreath method the group with airways obstruction showed lower TLCO and TLCO/VA values than the non-obstructive group. VA was higher in both patient groups when measured with the intrabreath technique. The same test also showed higher TLCO values with the intrabreath method in the group with non-obstructive disorders and lower TLCO/VA values with the intrabreath method in those with airways obstruction. The corresponding parameters obtained by the two methods correlated closely, with no correlation between the magnitude of the differences with the magnitude of the readings. An index of gas mixing indicated a better distribution of the inspired air for the intrabreath method than for the single breath method. The VA values obtained with the intrabreath method showed a closer agreement to the actual total lung capacities measured by body plethysmography.

CONCLUSION

The intrabreath method of determining TLCO is comparable to the traditional single breath method. Measurement of alveolar volume by the intrabreath method approximates more closely to total lung capacity, even in subjects with airways obstruction.