Table 4

Associations of respiratory symptoms with each of the cardiopulmonary exercise outputs and SHS exposure

Independent variablesDependent variables
Modified Borg Dyspnoea ScalemMRC Dyspnoea ScaleFAMRI SHS Questionnaire
Dyspnoea score ≥either leg fatigue or tiredness scoreHaving mMRC ≥1Having any respiratory symptoms
NOR ±SEM
(95% CI)
P valueNOR ±SEM
(95% CI)
P valueNOR ±SEM
(95% CI)
P value
Exercise capacity
 VO2Peak2361.284±0.543 (0.562 to 2.977)0.5542450.078±0.072 (0.011 to 0.438)0.0052450.475±0.204 (0.200 to 1.084)0.082
 WattPeak2361.003±0.004 (0.995 to 1.012)0.4722450.975±0.008 (0.958 to 0.991)0.0032450.998±0.004 (0.989 to 1.006)0.618
 WorkTotal2351.001±0.001 (0.999 to 1.002)0.3762390.996±0.002 (0.993 to 0.999)0.0142390.999±0.001 (0.998 to 1.001)0.289
Cardiovascular outputs
 Peaks
  O2-PulsePeak2360.992±0.066 (0.871 to 1.130)0.9052450.808±0.108 (0.614 to 1.039)0.1102450.929±0.061 (0.816 to 1.056)0.264
  HRPeak2361.008±0.008 (0.992 to 1.024)0.3372450.969±0.013 (0.943 to 0.995)0.0212450.990±0.008 (0.975 to 1.006)0.233
  SBPPeak2231.009±0.007 (0.994 to 1.023)0.2512261.015±0.013 (0.990 to 1.043)0.2442260.999±0.007 (0.984 to 1.013)0.851
  DBPPeak2231.030±0.015 (1.002 to 1.060)0.0392260.969±0.023 (0.925 to 1.015)0.1812260.987±0.014 (0.959 to 1.014)0.342
 Slopes
  O2-PulseSlope2350.266±0.348 (0.02 to 3.423)0.3112382.777±5.966 (0.040 to 198.051)0.6342380.140±0.185 (0.010 to 1.835)0.136
  HRSlope2351.159±0.16 (0.886 to 1.526)0.2842381.165±0.279 (0.725 to 1.865)0.5232381.111±0.155 (0.845 to 1.463)0.451
  SBPSlope2241.068±0.114 (0.867 to 1.32)0.5352271.714±0.354 (1.149 to 2.599)0.0092271.103±0.118 (0.894 to 1.364)0.360
  DBPSlope2241.433±0.294 (0.962 to 2.161)0.0792271.539±0.547 (0.761 to 3.092)0.2252271.245±0.253 (0.836 to 1.865)0.281
Pulmonary outputs
 RRPeak2300.995±0.016 (0.965 to 1.026)0.7512350.931±0.030 (0.872 to 0.988)0.0232350.966±0.016 (0.934 to 0.996)0.031
 VEPeak2361.002±0.010 (0.983 to 1.021)0.8542450.931±0.020 (0.891 to 0.968)<0.0012450.982±0.009 (0.964 to 1.001)0.060
 VTPeak2341.437±0.584 (0.651 to 3.225)0.3712390.887±0.585 (0.232 to 3.135)0.8552391.018±0.403 (0.466 to 2.219)0.964
 VO2AT1961.067±0.634 (0.331 to 3.439)0.9122020.027±0.033 (0.002 to 0.268)0.0032020.542±0.312 (0.172 to 1.667)0.287
 VE/VCO2Peak2360.953±0.038 (0.879 to 1.028)0.2212450.976±0.073 (0.836 to 1.118)0.7402450.939±0.038 (0.864 to 1.015)0.126
 RV/TLC2280.977±0.032 (0.915 to 1.042)0.4782351.102±0.061 (0.989 to 1.232)0.0792351.061±0.035 (0.996 to 1.134)0.069
 FRC/TLC2171.024±0.026 (0.974 to 1.078)0.3642201.136±0.052 (1.043 to 1.247)0.0042201.032±0.026 (0.983 to 1.085)0.212
SHS exposure
 Airline SHS exposure (years)2321.009±0.016 (0.978 to 1.042)0.5602410.982±0.026 (0.932 to 1.034)0.4962411.009±0.015 (0.979 to 1.040)0.556
 Childhood home SHS exposure (Y/N)2361.078±0.296 (0.628 to 1.85)0.7842451.660±0.777 (0.671 to 4.289)0.2792452.048±0.563 (1.201 to 3.530)0.009
 Adult home SHS exposure (Y/N)2361.156±0.379 (0.609 to 2.209)0.6572451.113±0.554 (0.401 to 2.882)0.8282452.048±0.660 (1.094 to 3.884)0.026
  • Associations of respiratory symptoms at rest (mMRC Dyspnoea Scale and FAMRI SHS Questionnaire) and during exercise (modified Borg Dyspnoea Scale) (dependent variables) with each of the cardiopulmonary exercise measures and SHS exposure (predictors) were assessed by univariate linear regression models with adjustment for age, sex, height, body mass index and corresponding baseline values (for slope predictors). Statistically significant values are shown in bold.

  • DBP, diastolic blood pressure; FRC, functional residual capacity; HR, heart rate; O2-PulsePeak, oxygen uptake per heartbeat at peak exercise; RRPeak, peak respiratory rate; RV, residual volume; SBP, systolic blood pressure; SHS, secondhand smoke; TLC, total lung capacity; VCO2Peak, peak carbon dioxide production; VEPeak, peak minute ventilation value; VO2AT, oxygen uptake at Anaerobic Threshold; VO2Peak, peak oxygen uptake; VTPeak, peak tidal volume.