The psychophysiological functions of sighing

Although there seems to be consensus on the physiological mechanisms of sighing, little is known about the psychological processes that relate to these physiological functions. Physiologically, sighing is assumed to prevent atelectasis (Bendixen, Smith & Mead, 1964; Reynolds, 1962) and is thought to restore lung compliance (Caro, Butler & Dubois, 1960; Ferris & Pollard, 1960; McIlroy, Butler & Finley, 1962; Mead & Collier, 1959) and gas exchange (Bartlett, 1971; Chemiack, Euler, Glogowska & Homma, 1981; Glogowska, Richardson, Widdicombe & Winning, 1972). Additionally, there are indications that sighing might reset physiological variability (Baldwin et al., 2004; Franco et al., 2003). It appears thus that sighing could function as a physiological resetter to reset homeostasis. The psychological processes of sighing, however, have rarely been studied. Sighing has been shown to be a marker of negative emotions as well as an indicator of positive emotional states. On the one hand, sighing has been shown to be characteristic of pain (Keefe & Block, 1982; Keefe & Hill, 1985; Keefe, Wilkins & Cook, 1984), unpleasant thoughts (Finesinger, 1944) and has been found to be excessive in epilepsia patients (Goldie & Green, 1961), as well as in panic patients (Abelson, Weg, Nesse & Curtis, 2001; Wilhelm, Trabert & Roth, 2001a; Wilhelm, Trabert & Roth, 2001b). On the other hand, sighing has been related to suppressed dyspnea (Hirose, 2000), decreased negative affectivity (McClernon, Westman & Rose, 2004) and relief (Soltysik & Jeelen, 2005). In search for an explanation that could account for these findings, we put forward the hypothesis that sighing might relieve. Considering the physiological functions of sighing, it seems plausible that decreasing lung compliance and a lack of physiological variability could be accompanied by a subjective sensation of chest tightness. In addition, obstructed gas exchange may evoke dyspnea. If sighing can counteract these physiological changes and reset physiological comfort by restoring lung compliance and gas exchange, it seems reasonable that sighing also subjectively causes release of tightness and dyspnea. If sighing indeed would relieve, increased sighing would not only be indicative of a state of relief, but sighing could also function as a way of coping with sustained stress or tension, resulting in increased relief during prolonged stress periods. A possible mediator in this relationship between relief and sighing could be physiological variability. First, decreased heart rate variability has been shown to be indicative of disease (for an overview: Aubert & Ramaekers, 2004; Kazuma, Otsuka, Matsuoka & Murata, 1997; Rother et al., 1987), panic (Friedman, 1998a; Friedman, 1998b) and anxiety (Agelink, Boz, Ullrich & Andrich, 2002; Gorman & Sloan, 2000; Kawachi, Sparrow, Vokonas & Weiss, 1995; Thayer, Friedman & Borkovec, 1996; Yeragani, Balon, Pohl & Ramesh, 1995), whereas increased heart rate variability is characteristic of health (Hedelin, Wiklund, Bjerle & Hendriksson-Larsen, 2000; Pardo et al., 2000) and relaxation (Lehrer, Sasaki & Saito, 1999; Mishima, Kubota, & Nagata, 1999; Murata et al., 2004; Peng et al., 2004; Peng et al., 1999; Travis, 2001; Sakakibara, Takeuchi, & Hayano, 1994; Sawada, 2000). If sighing resets heart rate variability, as has been shown previously (Franco et al., 2003), it seems plausible that this resetting is accompanied with the restoration of relaxation, thus relief. Second, stress and tension might result in decreased respiratory variability or rigid breathing (Van Diest, Thayer, Vandeputte, Van de Woestijne, & Van den Bergh, 2006), causing atelectasis and decreased lung compliance, which might enhance feelings of tightness. Sighing, resetting lung compliance (Caro, Butler & Dubois, 1960; Ferris & Pollard, 1960; McIlroy, Butler & Finley, 1962; Mead & Collier, 1959) and restoring respiratory variability (Baldwin et al., 2004), could counteract these tense feelings and cause feelings of relief. The aim of this project focuses on the hypothesis that sighing relieves. Until now, our approach consisted of comparing sigh frequency during experimentally imposed states of danger (stress) and safety (relief). Three experiments will be described, in which we consistently find increased sighing during relief, compared to periods of stress and relaxation. Additionally, we find that respiratory variability decreases toward a sigh and becomes restored after sighing. Our future directions include imposing sighs in non variable breathing patterns in order to determine its relieving effects by measuring subjective feelings and physiological measures of relaxation, such as EMG and heart rate variability.status: publishe