Increased vagal airway tone in fatal asthma

A Retrospective Study on the Reconstruction of Nasal Septal Mucosal Defects after Asian Rhinoplasty

BACKGROUND

Nasal septal mucosal defects following rhinoplasty in Asian patients are uncommon complications. However, the reconstruction of such defects presents a challenging task in plastic surgery. The aim of this study was to present comprehensive surgical strategies for the reconstruction of nasal septal mucosal defect after rhinoplasty.

METHODS

Thirteen cases presenting with nasal septal mucosal defects between January 2016 and October 2021 were retrospectively reviewed. The size, location, and severity of the defect as well as the extent of cartilage exposure were taken into consideration during evaluation, and surgical approaches were employed for repair accordingly. Patient satisfaction was evaluated using a questionnaire with visual analog scale (VAS) and nasal obstruction symptom evaluation scale (NOSE).

RESULTS

The average postoperative follow-up period in this study group was 10.15 months. Reconstruction of nasal septal mucosal defects resulted in successful treatment for all patients. There was no evidence of flap failure or nasal valve stenosis. All patients were satisfied with the reconstruction outcome.

CONCLUSIONS

The successful application of surgical techniques for nasal septal mucosal defects after rhinoplasty requires comprehensive consideration. The utilization of the retrograde-flow superior labial artery mucosal flap appears to be a secure, efficient, and effective technique for nasal septal mucosal defect reconstruction in rhinoplasty, particularly in cases with cartilage exposure.

LEVEL OF EVIDENCE IV

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Circadian rhythm of airways caliber and its autonomic modulation

The autonomic nervous system (ANS) is one of the effector pathways for circadian variation of many physiological parameters. Autonomic tone and airways caliber have been reported to exhibit circadian variation in separate studies. A simultaneous investigation of heart rate variability (HRV) and airway caliber might ascertain how airway caliber is modulated by autonomic tone. This study was planned to identify the variations in airway caliber and autonomic function tone during a 24-hour span. A total of 56 healthy male subjects with almost similar daily routines were studied. Time domain, frequency domain and nonlinear analysis of R-R interval from 5 min electrocardiogram (ECG) was done seven times during the daytime wake span at 3-hour intervals starting at 05:00 h in the morning until 23:00 h in the night. Simultaneously peak expiratory flow rate (PEFR) was determined using a mini Wright's peak flow meter. Rhythmometric analysis was done for PEFR and HRV parameters. Significant circadian variation in low frequency (LF) and high frequency (HF) variance was identified in this group of healthy subjects. The circadian rhythm of LF variance was characterized by a gradual increase and corresponding reciprocal change in HF variance from morning until night. The LF/HF ratio and SD2/SD1 ratio reflecting sympatho-vagal balance showed low to high values from morning to evening. The acrophase of the PEFR temporal pattern is similar to that of LF power and almost opposite in phase to that of HF power. PEFR is positively correlated with LF power. The circadian rhythm of airway caliber co-varies with cardiac autonomic tone. It appears that the temporal pattern of cardiac autonomic tone precedes in time that of airways caliber, thereby suggesting the latter operates under the modulatory effect of the 24-hour pattern in sympatho-vagal balance.

Asthmatic Airway Vagal Hypertonia Involves Chloride Dyshomeostasis of Preganglionic Neurons in Rats

Airway vagal hypertonia is closely related to the severity of asthma; however, the mechanisms of its genesis are unclear. This study aims to prove that asthmatic airway vagal hypertonia involves neuronal Cl^– dyshomeostasis. The experimental airway allergy model was prepared with ovalbumin in male adult Sprague-Dawley rats. Plethysmography was used to evaluate airway vagal response to intracisternally injected γ-aminobutyric acid (GABA). Immunofluorescent staining and Western-blot assay were used to examine the expression of microglia-specific proteins, Na⁺-K⁺-2Cl^– co-transporter 1 (NKCC1), K⁺-Cl^– co-transporter 2 (KCC2) and brain-derived nerve growth factor (BDNF) in airway vagal centers. Pulmonary inflammatory changes were examined with hematoxylin and eosin staining of lung sections and ELISA assay of ovalbumin-specific IgE in bronchoalveolar lavage fluid (BALF). The results showed that histochemically, experimental airway allergy activated microglia, upregulated NKCC1, downregulated KCC2, and increased the content of BDNF in airway vagal centers. Functionally, experimental airway allergy augmented the excitatory airway vagal response to intracisternally injected GABA, which was attenuated by intracisternally pre-injected NKCC1 inhibitor bumetanide. All of the changes induced by experimental airway allergy were prevented or mitigated by chronic intracerebroventricular or intraperitoneal injection of minocycline, an inhibitor of microglia activation. These results demonstrate that experimental airway allergy augments the excitatory response of airway vagal centers to GABA, which might be the result of neuronal Cl^– dyshomeostasis subsequent to microglia activation, increased BDNF release and altered expression of Cl^– transporters. Cl^– dyshomeostasis in airway vagal centers might contribute to the genesis of airway vagal hypertonia in asthma.

Asthmatic Augmentation of Airway Vagal Activity Involves Decreased Central Expression and Activity of CD73 in Rats

The severity of asthma is closely related to the intensity of airway vagal activity; however, it is unclear how airway vagal activity is centrally augmented in asthma. Here we report that in an asthma model of male Sprague-Dawley rats, the expression and activity of ecto-5'-nucleotidase (CD73) were decreased in airway vagal centers, ATP concentration in cerebral spinal fluid was increased, and the inhibitory and excitatory airway vagal responses to intracisternally injected ATP (5 μmol) and CD73 inhibitor AMPCP (5 μmol), respectively, were attenuated. In airway vagal preganglionic neurons (AVPNs) identified in medullary slices of neonatal Sprague-Dawley rats, AMPCP (100 μmol·L^-1) caused excitatory effects, as are shown in patch-clamp by depolarization, increased neuronal discharge, and facilitated spontaneous excitatory postsynaptic currents (sEPSCs). In contrast, exogenous ATP (100 μmol·L^-1, 1 mmol·L^-1) primarily caused inhibitory effects, which are similar to those induced by exogenous adenosine (100 μmol·L^-1). Adenosine A₁ receptor antagonist CPT (5 μmol·L^-1) blocked the inhibition of sEPSCs induced by 100 μmol·L^-1 exogenous ATP and that by 100 μmol·L^-1 exogenous adenosine, whereas 50 μmol·L^-1 CPT converted the inhibition of sEPSCs induced by 1 mmol·L^-1 ATP to facilitation that was blocked by addition of P2X receptor antagonist PPADS (20 μmol·L^-1). These results demonstrate that in rat, the sEPSCs of AVPNs are facilitated by extracellular ATP via activation of P2X receptors and inhibited by extracellular adenosine via activation of A₁ receptors; in experimental asthma, decreased CD73 expression and activity in airway vagal centers contribute to the augmentation of airway vagal activity through imbalanced ATP/ADO modulation of AVPNs.

Can bronchial asthma with an highly prevalent airway (and systemic) vagal tone be considered an independent asthma phenotype? Possible role of anticholinergics

Recently, we studied occurrence and role of non-respiratory symptoms (n-RSs) before a worsening of asthma symptoms. Some n-RSs such as anxiety, reflux, heartburn, abdominal pain, which appeared within 3 h before the onset of an asthma attack, are the likely result of an imbalance between sympathetic/parasympathetic systems with an increase in cholinergic tone. Therefore, it is likely that some of these n-RSs induced by the increased cholinergic tone might be present related with specific parasympathetic-associated respiratory symptoms such as those elicited by airway narrowing. It is likely that, at least in some categories of asthmatics, an increased cholinergic tone, rather than other well-known factors, might play a prevalent role in triggering bronchospasm. If this is the case, it is possible to speculate that the use of anticholinergic agents (mainly those with long-acting activity) in patients suffering from asthma should be more beneficial in individuals characterized by a higher degree of cholinergic tone that, consequently might be the ideal target for the use of long-acting anticholinergics and, possibly, represent a novel asthma phenotype. The presence of parasympathetic-associated n-RSs might help the physician to identify this type of patients, although this might be followed by a more detailed assessment.