Is breath-hold time an objective index of exertional dyspnoea in humans?

Abstract

Since dyspnoeic sensation (d) increases progressively with work rate (WR) and the duration of a volitional breath-hold (t BH ) shortens, we wished to explore whether t BH might correlate suciently closely with d to provide a quantitative and descriptor-free index of respiratory sensation during dynamic exercise. Nine healthy males exercised on a cycle ergometer at a series of constant WRs, above and below the lactate threshold. Ventilatory and gas exchange variables were measured breath-by-breath. At each WR, breath-holds to the limit of tolerance were taken; d was recorded (visual-analog scale) immediately prior to and throughout each breath-hold. During breath-holds, d increased with time as a``break-away'' monoexponential characteristic, reaching the maximum (100%) at the breakpoint. Despite end-tidal partial pressure of carbon dioxide at the break-point being higher and end-tidal partial pressure of oxygen being lower with increasing WR, the relationship between WR and t BH declined curvilinearly (i.e. with large falls in t BH occurring in the low WR range, but far smaller reductions at higher WRs). The t BH /minute ventilation relationship had a similar form. The relationship between pre-breath-hold d and t BH was also complex: the large reductions in t BH in the low WR range were associated with only modest increases in pre-BH d while, at higher WRs, the progressively smaller decrements in t BH were associated with progressively larger increases in d. We therefore conclude that breath-hold duration is unlikely to provide a useful correlate of exertional dyspnoea during dynamic exercise. Furthermore, the relative prolongation of t BH at high WRs (accounting for the moreextreme levels of end-tidal gas tensions) may re¯ect the attention-diverting in¯uence of the exercise per se.

Breath‐holding and its breakpoint

“…Increasing metabolic rate also shortens breath‐hold duration (Rodbard, 1947; Cummings, 1962; Lin et al 1974; Ward et al 2001). Figure 4 shows that exercise (bicycle ergometry to at least double metabolic rate) more than halved breath‐hold duration.…”

“…Neither ‘involuntary’ breath‐holding (e.g. central apnoea or suffocation) nor the sensation of breathlessness/air hunger/dyspnoea (Banzett et al 1990; Ward et al 2001) are considered because their precise relationships to the breakpoint are unclear.…”

Relationship between breath-hold time and physical performance in patients with cystic fibrosis

“…Similarly, a high blood lactate (>4 mmol/l), a low alveolar O 2 pressure (<30 mmHg), and a high alveolar CO 2 pressure (>50 mmHg) were registered at the breath-hold breaking in extreme divers by Ferretti (2001). Ward et al (2001) demonstrated that a dyspnoeic sensation has an important role in the length of the BHT during dynamic exercise. They found an exponentially increasing dyspnoeic sensation at a progressively increasing work rate.…”

Symptom perception in asthma

“…Alternatively, the observed effect may be an illustration of the influence of attention on symptom reporting: in the waiting room, patients had nothing to do and could focus their attention on their bodies while they were filling out the questionnaires. During the histamine provocation, there was a lot of equipment in the room and a lot of 'things to do' (inhaling substances, lung function measurements, symptom reports), diverting attention from their internal sensations (Bauldoff, Hoffman, Zullo, & Sciurba, 2002;Ward, Macias, & Whipp, 2001). Some authors doubt the validity of bronchial provocation tests as a laboratory substitute for real life asthma attacks.…”

“…This is in contrast to patients who did not use music as a distracter: the latter could not maintain post-pulmonary rehabilitation program gains (Bauldoff, Hoffman, Zullo, & Sciurba, 2002). Ward, Macias, and Whipp (2001) suggested that even exercise per se could serve as an attention-diverting mechanism, thereby influencing the perception of dyspnea.…”