Breathlessness in a virtual world: An experimental paradigm testing how discrepancy between VR visual gradients and pedal resistance during stationary cycling affects breathlessness perception

Abstract

Introduction: The sensation of breathlessness is often attributed to perturbations in cardio-pulmonary physiology, leading to changes in afferent signals. New evidence suggests that these signals are interpreted in the light of prior "expectations". A misalignment between afferent signals and expectations may underly unexplained breathlessness. Using a novel immersive virtual reality (VR) exercise paradigm, we investigated whether manipulating an individual's expectation of effort (determined by a virtual hill gradient) may alter their perception of breathlessness, independent from actual effort (the physical effort of cycling).

Methods: Nineteen healthy volunteers completed a single experimental session where they exercised on a cycle ergometer while wearing a VR headset. We created an immersive virtual cycle ride where participants climbed up 100 m hills with virtual gradients of 4%, 6%, 8%, 10% and 12%. Each virtual hill gradient was completed twice: once with a 4% cycling ergometer resistance and once with a 6% resistance, allowing us to dissociate expected effort (virtual hill gradient) from actual effort (power). At the end of each hill, participants reported their perceived breathlessness. Linear mixed effects models were used to examine the independent contribution of actual effort and expected effort to ratings of breathlessness (0-10 scale).

Results: Expectation of effort (effect estimate ± std. error, 0.63 ± 0.11, P < 0.001) and actual effort (0.81 ± 0.21, P < 0.001) independently explained subjective ratings of breathlessness, with comparable contributions of 19% and 18%, respectively. Additionally, we found that effort expectation accounted for 6% of participants' power and was a significant, independent predictor (0.09 ± 0.03; P = 0.001).

Conclusions: An individuals' expectation of effort is equally important for forming perceptions of breathlessness as the actual effort required to cycle. A new VR paradigm enables this to be experimentally studied and could be used to re-align breathlessness and enhance training programmes.

Fig 1

A. Image of the bicycle ergometer set-up and B. (top) the VR environment (bottom) virtual hands and speedometer.

Fig 2. Illustration of exercise protocol where slope resistance (cycling ergometer resistance) was dissociated from the observed VR hill gradient.

Fig 3. Slope resistance is a significant predictor of power.

Mean power (W) was greater across all levels of VR hill gradient in the 6% vs. 4% slope resistance blocks. Shaded areas represent 95% CIs.

Fig 4. The power (actual effort), virtual hill gradient (expected effort), and BMI are independent predictors of an individual’s breathlessness.

Fig 5. Virtual reality hill gradient, BMI, sex (male) are independent predictors of physical effort (i.e., the power).