Hering-Breuer Reflex in Normal Adults and in Patients with Chronic Obstructive Pulmonary Disease and Interstitial Fibrosis

Abstract

Background: It has been suggested that the Hering-Breuer reflex (HBR) is unimportant in adults during normal tidal breathing and that it is elicited only if tidal volume is increased above a certain critical threshold. Objective: The aim of this study was (1) to study the occurrence of the HBR in adults with normal pulmonary function and (2) to examine if changes in lung mechanics have any effect on the HBR. Methods: We examined 11 adults with normal pulmonary function, 8 patients with chronic destructive pulmonary disease (COPD) and 3 with interstitial fibrosis (IF). All subjects were lightly sedated with fentanyl, intubated and ventilated with a Servo-900 ventilator. Inspiratory and expiratory flow (and after integration, volume) and mouth pressure were recorded from the endotracheal tube with a pneumotachograph and a pressure transducer. Pressure support ventilation was applied in all patients and functional residual capacity (FRC) was measured with the N₂ washout method. Mean (Te_mean) and maximal expiratory time (Te_max) were determined for each individual for 20 breaths. Following several breaths to establish a stable baseline the airway was occluded at end inspiration by a shutter. A positive HBR was interpreted as longer Te_occ than Te_max (Te_occ/Te_max, %). Occlusion was maintained until negative airway pressure occurred and the occlusion time (Te_occ) was measured. We attempted occlusions after the addition of 5 cm H₂O positive end-expiratory pressure (PEEP) and subsequently with 10, 15 and 20 cm H₂O PEEP. Te_occ was measured of progressively larger lung volumes. To examine the HBR sensitivity in the three groups, we plotted the lung volumes of occlusion against the corresponding Te_occ/Te_max. Results: The ratio Te_occ/Te_max increased from 167.5 ± 82.5 at normal FRC to 474 ± 200.2 s (PEEP₂₀). On the contrary, in patients with COPD, Te_occ/Te_max increased from 125.2 ± 34 to 193.7 ± 74.2 (p < 0.05). Conclusions: The HBR was positive in all subjects. COPD patients were found to be less sensitive to volume changes when compared with normal controls and with IF patients.

Esophago-Glottal Closure Reflex in Human Infants: A Novel Reflex Elicited With Concurrent Manometry and Ultrasonography

“…The regulation of the inspiration-expiration cycle by chemoreceptors, mechanoreceptors, and nociceptive receptors has been known in human or animal models (26)(27)(28)(29). Glottal closure during inspiration may be protective in that esophageal luminal contents are prevented from being inhaled as in retrograde aspiration.…”

An Official American Thoracic Society Statement: Update on the Mechanisms, Assessment, and Management of Dyspnea

“…In animal models of emphysema, pulmonary stretch receptor discharge is decreased (104). Pulmonary stretch receptor activation alone provides potent relief (100), independent of vagal influences on inspiratory drive (105) and changes in alveolar and arterial blood gas concentrations (106,107).…”

Airway Mechanosensor Behavior during Application of Positive End-Expiratory Pressure

“…Distention of the airway initially leads to increased SAR signals, resulting in decreased phrenic nerve activity [9] and, in turn, prolonged expiration [10]. In COPD patients, the HBR was weakened [8]. Possibly, the intrinsic PEEP present for years in COPD patients leads to an attenuation of SAR responses to elevated pressures.…”

“…PEEP is also used in spontaneous breathing trials during ventilator weaning and in obstructive sleep apnea. Tryfon et al [8] applied PEEP to healthy subjects and patients with chronic obstructive pulmonary disease (COPD) or interstitial fibrosis, and examined the HBR. The HBR was augmented in interstitial fibrosis (decreased lung compliance), but was unaffected in COPD (chronic intrinsic PEEP), even at a PEEP level of 20 cm H 2 O [8].…”

“…Tryfon et al [8] applied PEEP to healthy subjects and patients with chronic obstructive pulmonary disease (COPD) or interstitial fibrosis, and examined the HBR. The HBR was augmented in interstitial fibrosis (decreased lung compliance), but was unaffected in COPD (chronic intrinsic PEEP), even at a PEEP level of 20 cm H 2 O [8]. In 1975, Stanley et al [9] demonstrated that phrenic nerve activity was inhibited by application of a 10-cm H 2 O PEEP, which was independent of blood gases.…”