Vyntus cpx

Breath-by-breath measures of respiratory gases were measured by collection of expired air through a facemask (Hans Rudolph, United States) and analyzed continuously via a metabolic cart (Vyntus CPX, Vyaire Medical). Measures of minute ventilation (V_E), oxygen consumption (VO₂), and P_ETCO₂ were exported for later analysis.

Cardiorespiratory fitness will be measured as VO_2max during maximal walking/running until exhaustion on a treadmill (PPS Med 55, Woodway Inc). The protocols start at 5 km/h with an incline of 5%. The inclination increases with 1% every minute until it reaches 12%, from which the speed increases by 0.5 km/h per minute until exhaustion. Oxygen consumption and minute ventilation will be measured continuously using an oxygen analyzer (Oxycon Pro, Erich Jaeger GmbH; Vyntus CPX, Vyaire Medical GmbH). Heart rate will be measured using a heart rate monitor (T34, Polar Electro KY).

V̇O_2peak is assessed by CPET on a bicycle ergometer (ergometrics er800s, ergoline GmbH, Bitz, Germany). CPET is performed in a fasted state between 8:00 and 9:00 AM and follows a ramp-type protocol. The ramp-type protocol consists of (a) a resting state measurement without pedaling while participants are sitting on the bicycle ergometer (3 minutes); (b) subsequent pedaling at 20 watts (3 minutes); (c) the testing phase with a progressive increment of 5 to 10 watts per minute until subjective exhaustion (8-12 minutes); (d) followed by a cool-down of unloaded pedaling (3 minutes). HR is continuously monitored. Blood pressure and RPE (Borg CR-10 scale) are assessed every two minutes and within the last ten seconds of the test.
V̇O₂ is monitored by direct and continuous measurements (breath by breath) by ergospirometry (Vyaire Medical, Vyntus CPX, Illinois, USA). V̇O_2peak is defined as the highest 15-second averaged V̇O value when the following criteria are attained: respiratory equivalent ratio > 1.10; HR_peak within 10 min⁻¹ of the age-predicted maximum and Borg-CR-10 rating > 8.5 [31 ]. The absolute V̇O_2peak value (mL · min⁻¹) is divided by bodyweight (kg) to obtain the relative V̇O_2peak value (mL · min^− 1 · kg^− 1) as the primary outcome.

Pretest resting spirometry (Vyntus CPX, Vyaire Medical, IL, USA) was performed to measure the forced expired volume in one second (FEV1) and to estimate the maximal voluntary ventilation (MVV) using the formula FEV1 * 40, which is necessary for defining the limit of breathing reserve (BR) during CPET [62 (link)].

VO_2peak was assessed using a ramp-incremental exercise protocol on a cycle ergometer (Excalibur Sport, Lode, Netherlands). This test consisted of a 5 min warm up until the participant indicated a rate of perceived exertion (RPE) of 11 on a Borg Visual Scale (Borg, 1982 (link)), followed by a 3 min ramp protocol in which resistance was increased by 30 W every 3 min until volitional fatigue was reached, or the participant was not able to maintain a consistent cadence above 50 RPM. Oxygen consumption was continuously measured (Vyntus CPX, Vyaire Medical, United Kingdom) and VO_2peak was defined as the highest 30 s average achieved during the test. Continuous measures of HR (Polar H9 HR Sensor, Polar, Finland) were collected for determination of HR_max. Maximal power output W_max was determined as the power output achieved during the final stage of the VO_2peak test.

The CPET was performed on a specialized, electromagnetically braked cycle ergometer (Corival, Lode B.V., Groningen, The Netherlands) using a CPET system (Vyntus CPX powered by SentrySuite, Vyaire Medical, Mettawa IL, USA) with s breath-by-breath gas analyzer by experienced physicians who perform CPET regularly. The CPET system was calibrated following the manufacturer’s recommendations before each test. An integrated Nonin device was used to measure SpO₂ with an ear sensor probe. Stress ECG and HR were monitored at rest and throughout the test using a 12-lead exercise ECG (Mortara Wireless Acquisition Module, Mortara Instrument INC, Milwaukee, WI, USA). Cuff BP was measured every 3 min during exercise and post-exercise recovery, using an adult cuff with a shockproof sphygmomanometer (Gamma G5, HEINE Optotechnik GmbH & Co. KG, Gilching, Germany).

Symptom-limited CPET was performed on a dedicated upright cycle ergometer. Twelve (12) lead ECG was attached and monitored throughout to assess heart rate and rhythm. Pulmonary gas exchange was measured continuously using a metabolic cart (Vyntus CPX, Vyaire Medical). Oxygen consumption (VO₂) and carbon dioxide (VCO₂) production were averaged over 20 s intervals and adjusted to body mass (ml/kg/min). Prior to exercise, participants underwent a 5-minute rest period to obtain baseline values. Participants were then asked to begin cycling at a power of 20 Watts. Power was incrementally increased by 10 Watts per minute. Peak exercise was defined as the point at which the participant felt the need to stop due to symptoms or fatigue. A maximal effort was defined as having reached a respiratory exchange ratio > 1.05. Peak oxygen consumption (VO_2Peak) was identified as the highest attained VO₂ during exercise. A VO_2Peak < 20 ml/kg/min (Weber Class B) was considered objective evidence of reduced exercise capacity as previously described [9] (link).