Transfer coefficient of the lung for carbon monoxide and the accessible alveolar volume: clinically useful if used wisely

Abnormal Exertional Breathlessness on Cardiopulmonary Cycle Exercise Testing in Relation to Self-Reported and Physiologic Responses in Chronic Airflow Limitation

BACKGROUND

Exertional breathlessness is a cardinal symptom of cardiorespiratory disease.

RESEARCH QUESTION

How does breathlessness abnormality, graded using normative reference equations during cardiopulmonary exercise testing (CPET), relate to self-reported and physiologic responses in people with chronic airflow limitation (CAL)?

STUDY DESIGN AND METHODS

An analysis was done of people aged ≥ 40 years with CAL undergoing CPET in the Canadian Cohort Obstructive Lung Disease study. Breathlessness intensity ratings (Borg CR10 scale [0-10 category-ratio scale for breathlessness intensity rating]) were evaluated in relation to power output, rate of oxygen uptake, and minute ventilation at peak exercise, using normative reference equations as follows: (1) probability of breathlessness normality (probability of having an equal or greater Borg CR10 rating among healthy people; lower probability reflecting more severe breathlessness) and (2) presence of abnormal breathlessness (rating above the upper limit of normal). Associations with relevant participant-reported and physiologic outcomes were evaluated.

RESULTS

We included 330 participants (44% women): mean ± SD age, 64 ± 10 years (range, 40-89 years); FEV1/FVC, 57.3% ± 8.2%; FEV1, 75.6% ± 17.9% predicted. Abnormally low exercise capacity (peak rate of oxygen uptake < lower limit of normal) was present in 26%. Relative to peak power output, rate of oxygen uptake, and minute ventilation, abnormally high breathlessness was present in 26%, 25%, and 18% of participants. For all equations, abnormally high exertional breathlessness was associated with worse lung function, exercise capacity, self-reported symptom burden, physical activity, and health-related quality of life; and greater physiologic abnormalities during CPET.

INTERPRETATION

Abnormal breathlessness graded using CPET normative reference equations was associated with worse clinical, physiological, and functional outcomes in people with CAL, supporting construct validity of abnormal exertional breathlessness.

Ventilation Heterogeneity in Asthma and COPD: The Value of the Poorly Communicating Fraction as the Ratio of Total Lung Capacity to Alveolar Volume

BACKGROUND

The ventilation heterogeneity (VH) is reliably assessed by the multiple-breath nitrogen washout (MBNW), which provides indices of conductive (Scond) and acinar (Sacin) VH as well as the lung clearance index (LCI), an index of global VH. VH can be alternatively measured by the poorly communicating fraction (PCF), that is, the ratio of total lung capacity by body plethysmography to alveolar volume from the single-breath lung diffusing capacity measurement.

OBJECTIVES

Our objective was to assess VH by PCF and MBNW in patients with asthma and with COPD and to compare PCF and MBNW parameters in both patient groups.

METHOD

We studied 35 asthmatic patients and 45 patients with COPD. Each patient performed spirometry, body plethysmography, diffusing capacity, and MBNW test.

RESULTS

Compared to COPD patients, asthmatics showed a significantly lesser degree of airflow obstruction and lung hyperinflation. In asthmatic patients, both PCF and LCI and Sacin values were significantly lower than the corresponding ones of COPD patients. In addition, in both patient groups, PCF showed a positive correlation with LCI (p < 0.05) and Sacin (p < 0.05), but not with Scond. Lastly, COPD patients with PCF >30% were highly likely to have a value ≥2 of the mMRC dyspnea scale.

CONCLUSIONS

These results showed that PCF, a readily measure derived from routine pulmonary function testing, can provide a comprehensive measure of both global and acinar VH in asthma and in COPD patients and can be considered as a comparable tool to the well-established MBNW technique.

Lung Function Testing in Chronic Obstructive Pulmonary Disease

Lung function testing has undisputed value in the comprehensive assessment and individualized management of chronic obstructive pulmonary disease, a pathologic condition in which a functional abnormality, poorly reversible expiratory airway obstruction, is at the core of its definition. After an overview of the physiologic underpinnings of the disease, the authors outline the role of lung function testing in this disease, including diagnosis, assessment of severity, and indication for and responses to pharmacologic and nonpharmacologic interventions. They discuss the current controversies surrounding test interpretation with these purposes in mind and provide balanced recommendations to optimize their usefulness in different clinical scenarios.

Too much or too little medicine? Overdiagnosis, underdiagnosis, overtreatment and undertreatment in respiratory diseases

At a time when technical possibilities for medical investigations are plentiful and ever expanding, there is growing awareness that more is not always better and that “too much medicine” may be harmful. In recent years, the global Choosing Wisely educational campaign has aimed to bring attention to unnecessary healthcare. Unnecessary healthcare includes overtesting, overdiagnosis and overtreatment [1]. The March issue of Breathe aims to challenge us to rethink our clinical practice, to reflect on the evidence, and to identify potential cognitive biases that might influence us to provide “too much” or “too little” medicine [2].

The March issue of Breathe focuses on overdiagnosis, underdiagnosis, overtreatment and undertreatment in respiratory diseaseshttp://ow.ly/63OW30ntCeu