Lack of effect of an in-line filter on cardiopulmonary exercise testing variables in healthy subjects

PURPOSE

Pathogen transmission during cardio-pulmonary exercise testing (CPET) is caused by carrier aerosols generated during respiration.

METHODS

Ten healthy volunteers (age range: 34 ± 15; 4 females) were recruited to see if the physiological reactions to ramp-incremental CPET on a cycle ergometer were affected using an in-line filter placed between the mouthpiece and the flow sensor. The tests were in random order with or without an in-line bacterial/viral spirometer filter. The work rate aligned, time interpolated 10 s bin data were compared throughout the exercise period.

RESULTS

From rest to peak exercise, filter use increased only minute ventilation ([Formula: see text]E) (Δ[Formula: see text]E = 1.56 ± 0.70 L/min, P < 0.001) and tidal volume (VT) (ΔVT = 0.10 ± 0.11 L, P = 0.014). Over the entire test, the slope of the residuals for [Formula: see text]CO2 was positive (0.035 ± 0.041 (ΔL/L), P = 0.027). During a ramp-incremental CPET in healthy subjects, an in-line filter increased [Formula: see text]E and VT but not metabolic rate.

CONCLUSION

In conclusion, using an in-line filter is feasible, does not affect appreciably the physiological variables, and may mitigate risk of aerosol dispersion during CPET.

Dynamic airway function during exercise in COPD assessed via impulse oscillometry before and after inhaled bronchodilators

Assessing airway function during exercise provides useful information regarding mechanical properties of the airways and the extent of ventilatory limitation in COPD. The primary aim of this study was to use impulse oscillometry (IOS) to assess dynamic changes in airway impedance across a range of exercise intensities in patients with GOLD 1-4, before and after albuterol administration. A secondary aim was to assess the reproducibility of IOS measures during exercise. Fifteen patients with COPD (8 males/7 females; age = 66 ± 8 yr; prebronchodilator FEV₁ = 54.3 ± 23.6%Pred) performed incremental cycle ergometry before and 90 min after inhaled albuterol. Pulmonary ventilation and gas exchange were measured continuously, and IOS-derived indices of airway impedance were measured every 2 min immediately preceding inspiratory capacity maneuvers. Test-retest reproducibility of exercise IOS was assessed as mean difference between replicate tests in five healthy subjects (3 males/2 females). At rest and during incremental exercise, albuterol significantly increased airway reactance (X₅) and decreased airway resistance (R₅, R₅-R₂₀), impedance (Z₅), and end-expiratory lung volume (60% ± 12% vs. 58% ± 12% TLC, main effect P = 0.003). At peak exercise, there were moderate-to-strong associations between IOS variables and IC, and between IOS variables and concavity in the expiratory limb of the spontaneous flow-volume curve. Exercise IOS exhibited moderate reproducibility in healthy subjects which was strongest with R₅ (mean diff. = -0.01 ± 0.05 kPa/L/s; ICC = 0.68), R₅-R₂₀ (mean diff. = -0.004 ± 0.028 kPa/L/s; ICC = 0.65), and Z₅ (mean diff. = -0.006 ± 0.021 kPa/L/s; ICC = 0.69). In patients with COPD, exercise evoked increases in airway resistance and decreases in reactance that were ameliorated by inhaled bronchodilators. The technique of exercise IOS may aid in the clinical assessment of dynamic airway function during exercise.NEW & NOTEWORTHY This study provides a novel, mechanistic insight into dynamic airway function during exercise in COPD, before and after inhaled bronchodilators. The use of impulse oscillometry (IOS) to evaluate airway function is unique among exercise studies. We show strong correlations among IOS variables, dynamic hyperinflation, and shape-changes in the spontaneous expiratory flow-volume curve. This approach may aid in the clinical assessment of airway function during exercise.

Transcutaneous PCO2 for Exercise Gas Exchange Efficiency in Chronic Obstructive Pulmonary Disease

Gas exchange inefficiency and dynamic hyperinflation contributes to exercise limitation in chronic obstructive pulmonary disease (COPD). It is also characterized by an elevated fraction of physiological dead space (V_D/V_T). Noninvasive methods for accurate V_D/V_T assessment during exercise in patients are lacking. The current study sought to compare transcutaneous PCO₂ (TcPCO₂) with the gold standard-arterial PCO₂ (PaCO₂)-and other available methods (end tidal CO₂ and the Jones equation) for estimating V_D/V_T during incremental exercise in COPD. Ten COPD patients completed a symptom limited incremental cycle exercise. TcPCO₂ was measured by a heated electrode on the ear-lobe. Radial artery blood was collected at rest, during unloaded cycling (UL) and every minute during exercise and recovery. Ventilation and gas exchange were measured breath-by-breath. Bland-Altman analysis examined agreement of PCO₂ and V_D/V_T calculated using PaCO₂, TcPCO₂, end-tidal PCO₂ (P_ETCO₂) and estimated PaCO₂ by the Jones equation (PaCO₂-Jones). Lin's Concordance Correlation Coefficient (CCC) was assessed. 114 measurements were obtained from the 10 COPD subjects. The bias between TcPCO₂ and PaCO₂ was 0.86 mmHg with upper and lower limit of agreement ranging -2.28 mmHg to 3.99 mmHg. Correlation between TcPCO₂ and PaCO₂ during rest and exercise was r²=0.907 (p < 0.001; CCC = 0.941) and V_D/V_T using TcPCO₂ vs. PaCO₂ was r²=0.958 (p < 0.0001; CCC = 0.967). Correlation between PaCO₂-Jones and P_ETCO₂ vs. PaCO₂ were r²=0.755, 0.755, (p < 0.001; CCC = 0.832, 0.718) and for V_D/V_T calculation (r²=0.793, 0.610; p < 0.0001; CCC = 0.760, 0.448), respectively. The results support the accuracy of TcPCO₂ to reflect PaCO₂ and calculate V_D/V_T during rest and exercise, but not in recovery, in COPD patients, enabling improved accuracy of noninvasive assessment of gas exchange inefficiency during incremental exercise testing.