Lung volumes identify an at-risk group in persons with prolonged secondhand tobacco smoke exposure but without overt airflow obstruction

Abstract

IntroductionExposure to secondhand smoke (SHS) is associated with occult obstructive lung disease as evident by abnormal airflow indices representing small airway disease despite having preserved spirometry (normal forced expiratory volume in 1 s-to-forced vital capacity ratio, FEV1/FVC). The significance of lung volumes that reflect air trapping in the presence of preserved spirometry is unclear.MethodsTo investigate whether lung volumes representing air trapping could determine susceptibility to respiratory morbidity in people with SHS exposure but without spirometric chronic obstructive pulmonary disease, we examined a cohort of 256 subjects with prolonged occupational SHS exposure and preserved spirometry. We elicited symptom prevalence by structured questionnaires, examined functional capacity (maximum oxygen uptake, VO2max) by exercise testing, and estimated associations of those outcomes with air trapping (plethysmography-measured residual volume-to-total lung capacity ratio, RV/TLC), and progressive air trapping with exertion (increase in fraction of tidal breathing that is flow limited on expiration during exercise (per cent of expiratory flow limitation, %EFL)).ResultsRV/TLC was within the predicted normal limits, but was highly variable spanning 22%±13% and 16%±8% across the increments of FEV1/FVC and FEV1, respectively. Respiratory complaints were prevalent (50.4%) with the most common symptom being ≥2 episodes of cough per year (44.5%). Higher RV/TLC was associated with higher OR of reporting respiratory symptoms (n=256; r2=0.03; p=0.011) and lower VO2max (n=179; r2=0.47; p=0.013), and %EFL was negatively associated with VO2max (n=32; r2=0.40; p=0.017).ConclusionsIn those at risk for obstruction due to SHS exposure but with preserved spirometry, higher RV/TLC identifies a subgroup with increased respiratory symptoms and lower exercise capacity.

The importance of CT quantitative evaluation of emphysema in lung cancer screening cohort with negative findings by visual evaluation

“…Secondhand smoke exposure was another important risk for COPD, and it has been reported that prolonged secondhand smoke exposure can cause increased lung volume without marked airflow limitation. In those at risk for obstruction because of secondhand smoke exposure but with preserved spirometry, higher RV/TLC can identify a subgroup with increased respiratory symptoms and lower exercise capacity . The TLV of the emphysema group was greater than that of the non‐emphysema group.…”

“…CT has been extensively validated as a tool for assessment of the presence, pattern and severity of emphysema . Quantitative CT is currently regarded as an important and complementary method to assess emphysema . However, the normal limit of the EI in the healthy non‐smokers varied from less than 1% to 6.8% in previous studies with different age ranges .…”

“…The proportion of smokers in men was significantly higher than that in women in this study ( P < 0.001). It has been reported that lung volumes could identify an at‐risk group in persons with prolonged secondhand tobacco smoke exposure but without overt airflow obstruction . Moreover, smoking duration alone provides stronger risk estimates of COPD than the composite index of pack‐years .…”

Remote exposure to secondhand tobacco smoke is associated with lower exercise capacity through effects on oxygen pulse, a proxy of cardiac stroke volume

“…In previous studies of never-smoking flight crew with history of remote but prolonged exposure to SHS in aircraft cabin, we examined the pulmonary health effects of long-term exposure to SHS and showed the association of those outcomes with the number of years during which the flight crew were exposed to SHS in aircraft cabin. [13][14][15] While this never-smoking SHSexposed cohort had no evidence of spirometric chronic obstructive pulmonary disease (COPD) (a All rights reserved. No reuse allowed without permission.…”

“…29.21258054 doi: medRxiv preprint preserved ratio of forced expiratory volume in second to forced vital capacity [FEV1/FVC]), they had abnormal lung function that were suggestive of presence of an occult early/mild obstructive lung disease. 15 In the current study, we wished to examine the cardiovascular health effects of remote but prolonged exposure to SHS in this never-smoking cohort with evidence of early obstructive lung disease. We hypothesized that prolonged exposure to SHS contributes to exercise limitation through its adverse cardiovascular health effects, in addition to its contribution through pulmonary mechanisms (air trapping).…”