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.

Is ventilatory efficiency dependent on the speed of the exercise test protocol in healthy men and women?

Indices of ventilatory efficiency have proven useful in assessing patients with heart and lung disease. One of these indices is the slope of the ventilation (V(E)) versus carbon dioxide output (VCO(2)) relationship during cardiopulmonary exercise testing (CPET) for work rates where the relationship is linear. However, this relationship is defined not only by the slope but also by the y-intercept. To examine whether this relationship is dependent on the speed of the CPET protocol, 30 healthy subjects (16 males) were administered a rapid CPET with 1-min increment duration (1-min CPET) to the limit of tolerance and a slow CPET with 4-min increment duration (4-min CPET) to the lactate threshold. Ventilation and the gas fractions for oxygen and CO(2) were measured with a Vacumed metabolic cart. The average increment size of both protocols for both sexes was not significantly different (P>0.05). For the males, the mean (SD) slope for the 1- and 4-min CPET was 20.12 (2.61) and 20.37 (2.41), respectively. The corresponding values for the y-intercept were 4..89 (2.08) and 5..10 (2.00) l min(-1). For the females, the mean (SD) slope for the 1- and 4-min CPET was 23.90 (2.38) and 24.16 (2.55), respectively. The corresponding values for the y-intercept were 3.93 (0.39) and 3.77 (0.71) l min(-1). Paired t-test analysis demonstrated for both sexes that the slopes and y-intercepts were not different for the two protocols (P>0.05). The results of this study demonstrate that the V(E) versus VCO(2) relationship is not dependent on the speed of the CPET protocol.

Exercise test mode dependency for ventilatory efficiency in women but not men.

Ventilatory efficiency is commonly defined as the level of ventilation V(E) at a given carbon dioxide output (V(CO(2) )). The slope of the V(E) versus V(CO(2) ) relationship and the lowest V(E)/V(CO(2) ) are two ventilatory efficiency indices that can be measured during cardiopulmonary exercise testing (CPET). A possible CPET mode dependency for these indices was evaluated in healthy men and women. Also evaluated was the relationship between these two indices as, in theory, V(E)/V(CO(2) ) falls hyperbolically towards an asymptote that numerically equals the V(E) versus V(CO(2) ) slope at exercise levels below the ones that cause respiratory compensation for metabolic acidosis. Twenty-eight healthy subjects (14 men) underwent treadmill and cycle ergometer CPET on different days. Ventilation and the gas fractions for oxygen and CO(2) were measured with a vacumed metabolic cart. In men, paired t-test analysis failed to find a mode difference for either ventilatory efficiency index but the opposite was true in the women as each woman had higher values for both indices on the treadmill. For men, the lowest V(E)/V(CO(2) ) was larger than the V(E) versus V(CO(2) ) slope by 1.3 on the treadmill and 0.8 on the cycle ergometer. The corresponding values for women were 1.7 and 1.4. We conclude that in healthy subjects, women, but not men, demonstrate a mode dependency for the two ventilatory efficiency indices investigated in this study. Furthermore, our results are consistent with the theoretical expectation that the lowest V(E)/V(CO(2) ) has a numerical value just above the asymptote of the V(E)/V(CO(2) ) versus V(CO(2) ) relationship.

Comparison of stroke volume estimation for non-steady-state and steady-state graded exercise testing.

The stroke volume (SV) during exercise is an important index of the heart's functional capacity. A new method has been developed for the non-invasive estimation of exercise SV (SVex). It requires the determination of the slope for the oxygen uptake versus heart rate relationship in the steady state of graded exercise testing (GXT). The product of the slope and a constant (reciprocal of an assumed value of the arterial oxygen content) equals an estimated value for SVex. It was validated in a previous study using invasive measurements while subjects were performing steady-state GXT. However, currently the most commonly used GXT protocols are non-steady state, e.g. protocols with 1-min increment durations. We tested the hypothesis that SVex is the same for steady-state and non-steady-state GXT. A total of 30 subjects (15 males and 15 females) served as subjects for the study. Each subject performed two GXTs on different days with different increment durations - 1 and 4 min. Ventilation and gas exchange were measured with the Vacumed metabolic cart. For the male subjects, the mean (SD) SVex values for the 1- and 4-min GXTs were 155.4 (39.5) and 134.6 (27.5) ml, respectively. The corresponding values for the female subjects were 151.6 (37.6) and 134.3 (36.4) ml. Paired t-test analysis demonstrated that for both genders the mean SVex for the 1-min GXT was significantly larger than the 4-min GXT mean value (P<0.05). Hence, the commonly used 1-min GXT does not yield the same values for SVex as the steady-state GXT.