Cardio pulmonary exercise testing: Mouthpiece or a mask? Does it matter?

Introduction: Cardio pulmonary exercise test (CPET) parameters can be measured with the use of a mouthpiece or a breathing mask. In clinical practice, patients often complain about a dry mouth when a mouthpiece is used which possibly influences CPET results. A more comfortable alternative, although with an increased change of leakage, is the frequently used breathing mask. Therefore we hypothesised that ventilatory CPET results measured by mouthpiece or breathing mask could be different. Aim: To test this hypothesis we conducted this study to estimate ventilatory CPET differences between mouthpiece and breathing mask measurements. Methods: Twelve healthy subjects performed two (3 minutes/40watt; incremental) maximal CPET measurements with steady state measurements of ventilation (VE) and oxygen consumption (VO 2 ) at sub maximum work levels. The measurements were taken on different days within one week in a different sequence. One using the mouthpiece (deadspace: 50 ml) and the other with a mask (Combitox, deadspace: 100 ml). Results: See Table 1. Table 1 Mouth piece mask p-value VE (l min –1 ) 40 watt 20.7±3.6 23.1±2.5 0.00 80 watt 29.3±2.7 32.6 ± 4.3 0.00 120 watt 40.4±3.6 44.6±5.6 0.00 VO2 (ml –1 ) 40 watt 882±103 884±70 0.94 80 watt 1276±97 1304±84 0.22 120 watt 1698±124 1741±127 0.19 Work (watt) Maximum 230±70 232±73 0.70 Conclusions: Due to the fact that the VO2 values between mouthpiece and mask measurements were not different, we concluded that the Combitox mask does not leak. However, the VE values measured with the mask were higher compared to those of the mouthpiece. This is likely explained by the higher amount of deadspace. The maximum work rate level attained with the mouthpiece or the mask was the same.