Airway responsiveness measured by barometric plethysmography in guinea pigs

Abstract

Barometric plethysmography has become an increasingly used method to indirectly measure respiratory function in unrestrained freely-moving animals. This technique has been criticized because of physiological uncertainty of its major index, the enhanced pause (Penh). Moreover, a recent study raises concerns that during histamine challenges part of the Penh response could be produced by upper airways (nasal) responses. In this study we compared airway responsiveness measured by barometric plethysmography and total lung resistance (RL: ) in guinea pigs, and evaluated the role of upper airways during Penh measurement. Our results showed that intravenous acetylcholine or histamine caused a dose-dependent increase of the Penh values in non-anesthetized guinea pigs, which were correlated with RL: values obtained in separate groups of anesthetized animals. In anesthetized but spontaneously breathing guinea pigs intravenous acetylcholine or histamine also produced a dose-dependent increment of Penh, which was similar regardless if guinea pigs breathed through the nose or through a tracheal tube. Our results suggest that, independently of the physiological meaning of Penh, this index seems to be a useful indirect measurement for evaluating airway responsiveness to intravenous agonists in guinea pigs, and that nasal passage seems not to be involved in this measurement.

Effects of cigarette smoke and chronic hypoxia on airways remodeling and resistance. Clinical significance

“…In sum, although guinea pigs as all mammals in hypoxia appear to have an increased ventilation to metabolism ratio (i.e., hyperventilate in relation to metabolic needs), it would appear that in our experimental conditions (temperature and duration of hypoxia) such hyperventilation would be minimal, but if any, it would be generated exclusively by a decrease in O 2 consumption due to the unresponsiveness of their CB to hypoxia. This abnormal response of guinea pigs, in comparison to other mammals, prevents us from reporting the impact of CS and CSCH on chemosensitivity Literature on the value of Penh as a measure of airways resistance is divided, with some authors been attached to it (Bergren, 2001;Lomask, 2006) and some others neglecting its value (Flandre et al, 2003; for a recent discussion on the significance of Penh please see Vargas et al, 2010). Yet, in present study there are several findings that predicting an increase in airways resistance did indeed cause an increase in Penh values, and vice versa.…”

Respiratory changes during adaptation to stress induced by movement restriction in rabbits

“…Perhaps the most used parameter in barometric plethysmography is Penh, a unitless index that has been employed as a surrogate of lung resistance and airway obstruction [24,25]. We found that Penh in rabbits had a progressive decrease in the first 60 min of recording.…”

“…A potential limitation of our study is that validity of barometric plethysmography, and especially Penh, has been questioned by some authors [26,27]. However, this last parameter has proved to be correlated with acute changes in lung resistance during a cholinergic challenge in some animal species such as guinea pigs and mice [24,25]. Thus, barometric plethysmography seems to be an appropriate tool to measure acute modifications of pulmonary mechanics, such as those expected to occur during confinement of rabbits inside the plethysmograph box.…”

Therapeutic effects of soluble guanylate cyclase stimulation on pulmonary hemodynamics and emphysema development in guinea pigs chronically exposed to cigarette smoke

“…It is plausible that in this time frame, between drug administration and lung assays, the differences in the magnitude of the response could be counteracted. Likewise, Penh is a controversial parameter that not always correctly reflects airway resistance in guinea pigs (37). Factors, such as lung compartmentalization, pharmacokinetics, and pharmacodynamics of BAY 41-2272, administered orally, should be taken into account to determine their efficacy in the airway.…”