Reliability of maximum oxygen uptake in cardiopulmonary exercise testing with continuous laryngoscopy

Abstract

Aims: A cardiopulmonary exercise test (CPET) is the gold standard to evaluate symptom-limiting exercise intolerance, while continuous laryngoscopy performed during exercise (CLE) is required to diagnose exercise-induced laryngeal obstruction. Combining CPET with CLE would save time and resources; however, the CPET data may be distorted by the extra equipment. We therefore aimed to study whether CPET with CLE influences peak oxygen uptake (V'_O2 peak) and other gas exchange parameters when compared to a regular CPET.

Methods: Forty healthy athletes without exercise-related breathing problems, 15-35 years of age, performed CPET to peak exercise with and without an added CLE set-up, in randomised order 2-4 days apart, applying an identical computerised treadmill protocol.

Results: At peak exercise, the mean difference (95% confidence interval) between CPET with and without extra CLE set-up for V'_O2 peak, respiratory exchange ratio (RER), minute ventilation (V'_E) and heart rate (HR) was 0.2 (-0.4 to 0.8) mL·kg^-1·min^-1, 0.01(-0.007 to 0.027) units, 2.6 (-1.3 to 6.5) L·min^-1 and 1.4 (-0.8 to 3.5) beats·min^-1, respectively. Agreement (95% limits of agreement) for V'_O2 peak, RER and V'_E was 0.2 (±3.7) mL·kg^-1·min^-1, 0.01 (±0.10) units and 2.6 (±24.0) L·min^-1, respectively. No systematic or proportional bias was found except for the completed distance, which was 49 m (95% CI 16 to 82 m) longer during CPET.

Conclusion: Parameters of gas exchange, including V'_O2 peak and RER, obtained from a maximal CPET performed with the extra CLE set-up can be used interchangeably with data obtained from standard CPET, thus preventing unnecessary additional testing.

FIGURE 1

Illustration of the set-up for cardiopulmonary exercise test (CPET) with and without continuous video laryngoscopy. The upper left and right images demonstrate the facemask used for ordinary CPET. The middle left and right images demonstrate the modified facemask with a flexible transnasal laryngoscope positioned through a tight-fit opening. A custom-made headgear secures the body of the laryngoscope. The attached transnasal flexible laryngoscope enables video recording of the laryngeal inlet during the maximal exercise treadmill test (bottom image).

FIGURE 2

Agreement between peak oxygen consumption (V′_O2peak), respiratory exchange ratio (RER) and minute ventilation (V′_E) obtained from cardiopulmonary exercise testing (CPET) and continuous laryngoscopy performed during exercise (CLE) test. The horizontal lines depict the mean difference between the variables obtained with the two methods, whereas ±1.96 sd of these differences represent 95% limits of agreement between the two methods. The 95% confidence intervals for the mean, the upper limit of agreement and the lower limit of agreement are indicated by vertical lines. The figures given below in the brackets are the mean difference and the upper and lower limits of agreement, expressed as percentages of the mean of the CPET and CLE value. a) Agreement between V′_O2peak, expressed as mL·kg⁻¹·min⁻¹, obtained from CPET and CLE tests. The mean difference was 0.2 mL·kg⁻¹·min⁻¹ (0.4%), the upper limit of agreement was 4.0 mL·kg⁻¹·min⁻¹ (7.0%), and the lower limit of agreement was −3.5 mL·kg⁻¹·min⁻¹ (−6.2%). b) Agreement between RER obtained from CPET and CLE test at peak exercise. The mean difference was 0.01 units (0.7%), the upper limit of agreement was 0.11 units (9.2%), and the lower limit of agreement was −0.09 units (−7.8%). c) Agreement between V′_E obtained from CPET and CLE test at peak exercise. The mean difference was 2.58 L·min⁻¹ (2.2%), the upper limit of agreement was 26.5 L·min⁻¹ (18.3%), and the lower limit of agreement was −21.4 L·min⁻¹ (−13.9%).