Influence of awareness of the recording of breathing on respiratory pattern in healthy humans

Abstract

Supported by the Research Council of the University of Leuven (grant OT/93/12).It is known that in healthy subjects breathing through a mouthpiece results in an increase of tidal volume (VT) [1][2][3], of inspiratory (t I) [2,3] and expiratory time (t E) [2], and inspiratory drive (VT/t I) [2,4]. These changes in ventilation have been attributed to: 1) the influence of the additional dead space; 2) stimulation of the nasal and oral mucosa by the noseclip and mouthpiece; 3) shift of respiratory route from unrestricted nose to mouth.For these reasons, an alternative technique, i.e. respiratory inductive plethysmography (Respitrace) is widely used in the study of the breathing pattern to avoid the influence of the mouthpiece and occlusion of the nose.As pointed out by GILBERT et al.[1], a fourth influence which might modify the natural resting ventilation is that of registration itself, by focusing the subject's attention on his breathing. The use of any recording technique, even a noninvasive one, might modify the spontaneous breathing pattern. In the present study, we tried to evaluate this influence. Materials and method SubjectsThe study was performed on two groups of healthy volunteers: 1) 42 subjects ("younger" population), 25 females and 17 males, aged 21-26 (mean 22) yrs, who were (except for two) medical students of K.U. Leuven, Belgium; 2) 32 subjects ("older" population), 15 females and 17 males, aged 35-63 (mean 47) yrs, who were recruited from outside the hospital. All 74 subjects (younger and older population) were naive to the purpose of the study. Anonymity was ensured.Before the experiment, the subjects answered four questionnaires. One dealt with medical history, two screened the level of anxiety, and one the spontaneous complaints of the subjects. To evaluate the anxiety of the subjects, the state and trait versions of the Zelfbeoordelingsvragenlijst (ZBV-DY1, ZBV-DY2) [5], which is the Dutch Seventy four subjects (40 females and 34 males), aged 21-63 yrs, were studied under three different conditions whilst their breathing was being recorded for 5 min by means of inductance plethysmography (Respitrace): 1) subjects were misled into believing that their breathing was not being recorded but that they had to wait for 5 min whilst equipment was calibrated; 2) subjects were instructed that their breathing pattern was being recorded for 5 min; 3) the subject's breathing was recorded for 5 min with mouthpiece and pneumotachograph. The first two conditions were randomized. The Respitrace was calibrated by means of multiple linear regression carried out during the 5 min period of quiet breathing through a mouthpiece.Awareness of the recording of breathing caused prolongation of inspiratory (t I) and expiratory time (t E). Breathing through the mouthpiece resulted in an increase of t I, t E and tidal volume (VT). The breathing irregularities (sighs and end-expiratory pauses) decreased when subjects were aware of the recording of breathing and nearly disappeared when subjects breathed through the mouthpiec...

Fractal fluctuations in human respiration

“…1, B and C, respectively. The variability depicted in these time series is similar to that observed in all of our subjects as well as that reported in previous studies of healthy humans (5,8,18,31). The corresponding frequency distributions of 1,932 peak-topeak breath intervals and 1,933 breath amplitudes recorded from this subject are shown in Fig.…”

“…The results indicate that, in most cases, apparently random fluctuations in respiratory pattern are, in fact, correlated over more than one time scale. Moreover, the data suggest that fractal fluctuations in breath number, respiratory period, and breath amplitude are controlled by separate processes.Allan and Fano factors; breath amplitude and frequency; dispersional analysis; Hurst exponent RESPIRATION IN AWAKE, HEALTHY adult humans is characterized by considerable variability in the frequency, duration, and amplitude of breaths (5,8,18,24,31). The aim of the present study was to define the basis for the variability of these respiratory parameters.…”

“…Allan and Fano factors; breath amplitude and frequency; dispersional analysis; Hurst exponent RESPIRATION IN AWAKE, HEALTHY adult humans is characterized by considerable variability in the frequency, duration, and amplitude of breaths (5,8,18,24,31). The aim of the present study was to define the basis for the variability of these respiratory parameters.…”

“…Upward deflections in the records denote inspiratory movements and downward deflections denote expirations. This methodology is routinely used in human studies to monitor respiratory variability because it avoids having the subject breathe through a mouthpiece, which is known to alter both the duration and depth of breathing (18,25). …”

Spontanous periodic breathing is associated with sympathetic hyperreactivity and baroreceptor dysfunction in hypertension

“…However, the use of a mouthpiece as it is required with the pneumotachograph as well as the awareness of recording substantially influences the breathing pattern. [41] We aimed to identify irregularities in the breathing pattern with minimal awareness of the subjects of the recording rather than to exactly quantify respiratory flow. For this purpose, the strain gauge method used in this study might be more appropriate.…”