Modified face mask

Peak exercise capacity defined as peak oxygen consumption (peak V′_O2) was determined using an incremental treadmill (Woodway PPS 55 Med; Woodway, Weil am Rhein, Germany) exercise test according to a modified Bruce protocol [29 (link)] using a Vyntus CPX unit powered by SentrySuite software (Vyaire Medical GmbH, Hoechberg, Germany). Speed and elevation increased every minute, starting from a slow walking phase, until the participants reached their maximum intensity level. The test was stopped when the participant indicated severe exhaustion or was unable to continue due to EILO symptoms, preferably supported by a respiratory exchange ratio (RER) exceeding 1.05 or heart rate exceeding 95% of maximally predicted [30 (link)]. Airflow and gas exchange parameters was measured breath-by-breath through a modified face mask (Hans Rudolph Inc., Kansas City, MO, USA) and averaged over 10 s. The cardiopulmonary exercise test (CPET) parameters recorded at maximal exhaustion are listed in table 1.

A 12‐lead portable electrocardiograph device was attached to the subject. Nostrils and nasal cavity were anesthetized with 4% lidocaine. An endoscopic video camera system (Visera, CLV‐S40; Olympus, Tokyo, Japan) was connected to a fiberoptic laryngoscope (ENF‐V2; Olympus) in a sterile plastic cover with work channel, which was advanced through a hole in a modified facemask (Hans Rudolph, Inc., Kansas City, MO) through the nasal cavity to the oropharynx. Lidocaine (4%) was used to anesthetize the vocal folds and proximal trachea by a dripping technique through the work channel. The laryngoscope was fixed to the headset. Two pressure sensors (Mikro‐Cath 825‐0101; Milar, Houston, TX) were introduced through the work channel. The first was positioned approximately at the first tracheal ring. The second was positioned at the epiglottis tip. The sensors were secured to the headset and connected to a data‐acquisition box (Powerbox 8/35; ADInstruments, Oxford, United Kingdom), and data were collected and stored on a MacBook Pro laptop (Apple Inc., Cupertino, CA) using LabChart 8.0 software (ADInstruments). Data acquisition was set at 40 Hz. A video camera and microphone were placed in front of the subject to document external images and sounds, and the ergo‐spirometry unit was attached to the facemask.