Nasal airflow and brain activity: is there a link?

Chief Complaint: Nasal Congestion

Nasal obstruction is the subjective perception and objective state of insufficient airflow through the nose. Nasal congestion, conversely, describes a state of not just inadequate airflow or obstructive phenomena but also pressure- and mucus-related states to the patient. Nasal receptors belonging to the transient receptor potential (TRP) protein family mediate the sense of nasal patency via the trigeminal nerve. The transient receptor potential melastatin-8 (TRPM8) responds to temperatures around 8°C to 22°C, and is stimulated by menthol and other cooling agents. The radiant effects of airflow create heat loss to activate these receptors and humans perceive this as nasal patency rather than the direct detection of airflow. The thermovascular state of the mucosa, in conditions such as rhinitis, influence TRPM8 activation. Nasal endoscopy can show signs of rhinitis and should be considered an essential part of the workup of nasal congestion. Efforts to relieve nasal congestion need to manage the mucosal state and surgery needs to ensures that the nasal cavity mucosa is exposed to the cooling effects of airflow rather than simply creating a passage to the nasopharynx.

Breathing Right… or Left! The Effects of Unilateral Nostril Breathing on Psychological and Cognitive Wellbeing: A Pilot Study

The impact of controlled breathing on cognitive and affective processing has been recognized since ancient times, giving rise to multiple practices aimed at achieving different psychophysical states, mostly related to mental clarity and focus, stress reduction, and relaxation. Previous scientific research explored the effects of forced unilateral nostril breathing (UNB) on brain activity and emotional and cognitive functions. Some evidence concluded that it had a contralateral effect, while other studies presented controversial results, making it difficult to come to an unambiguous interpretation. Also, a few studies specifically addressed wellbeing. In the present study, we invited a pilot sample of 20 participants to take part in an 8-day training program for breathing, and each person was assigned to either a unilateral right nostril (URNB) or left nostril breathing condition (ULNB). Then, each day, we assessed the participants' wellbeing indices using their moods and mind wandering scales. The results revealed that, after the daily practice, both groups reported improved wellbeing perception. However, the effect was specifically related to the nostril involved. URNB produced more benefits in terms of stress reduction and relaxation, while ULNB significantly and increasingly reduced mind-wandering occurrences over time. Our results suggest that UNB can be effectively used to increase wellbeing in the general population. Additionally, they support the idea that understanding the effects of unilateral breathing on wellbeing and cognition requires a complex interpretive model with multiple brain networks to address bottom-up and top-down processes.

Neurovascular Compression-Induced Intracranial Allodynia May Be the True Nature of Migraine Headache: an Interpretative Review

PURPOSE OF REVIEW

Surgical deactivation of migraine trigger sites by extracranial neurovascular decompression has produced encouraging results and challenged previous understanding of primary headaches. However, there is a lack of in-depth discussions on the pathophysiological basis of migraine surgery. This narrative review provides interpretation of relevant literature from the perspective of compressive neuropathic etiology, pathogenesis, and pathophysiology of migraine.

RECENT FINDINGS

Vasodilation, which can be asymptomatic in healthy subjects, may produce compression of cranial nerves in migraineurs at both extracranial and intracranial entrapment-prone sites. This may be predetermined by inherited and acquired anatomical factors and may include double crush-type lesions. Neurovascular compression can lead to sensitization of the trigeminal pathways and resultant cephalic hypersensitivity. While descending (central) trigeminal activation is possible, symptomatic intracranial sensitization can probably only occur in subjects who develop neurovascular entrapment of cranial nerves, which can explain why migraine does not invariably afflict everyone. Nerve compression-induced focal neuroinflammation and sensitization of any cranial nerve may neurogenically spread to other cranial nerves, which can explain the clinical complexity of migraine. Trigger dose-dependent alternating intensity of sensitization and its synchrony with cyclic central neural activities, including asymmetric nasal vasomotor oscillations, may explain the laterality and phasic nature of migraine pain. Intracranial allodynia, i.e., pain sensation upon non-painful stimulation, may better explain migraine pain than merely nociceptive mechanisms, because migraine cannot be associated with considerable intracranial structural changes and consequent painful stimuli. Understanding migraine as an intracranial allodynia could stimulate research aimed at elucidating the possible neuropathic compressive etiology of migraine and other primary headaches.

Optimization of sniff nasal inspiratory pressure (SNIP) measurement methodology in healthy subjects

BACKGROUND

Maximal inspiratory pressure (MIP) is currently the most commonly used measure for respiratory muscle strength (RMS) estimation, however, requires significant effort. Falsely low values are therefore common, especially in fatigue-prone subjects, such as neuromuscular disorder patients. In contrast, sniff nasal inspiratory pressure (SNIP) requires a short, sharp sniff; this is a natural manoeuvre, decreasing required effort. Consequently, it has been suggested that use of SNIP could confirm the accuracy of MIP measurements. However, no recent guidelines regarding the optimal method of SNIP measurement exist, and varied approaches have been described.

OBJECTIVES

We compared SNIP values from three conditions, namely with 30, 60 or 90 s time intervals between repeats, the right (SNIP_R) and left (SNIP_L) nostril, and the contralateral nostril occluded (SNIP_O) or non-occluded (SNIP_NO). Additionally, we determined the optimal number of repeats for accurate SNIP measurement.

METHOD

52 healthy subjects (23 males) were recruited for this study, of which a subset of 10 subjects (5 males) completed tests comparing the time interval between repeats. SNIP was measured from functional residual capacity via a probe in one nostril, while MIP was measured from residual volume.

RESULTS

There was no significant difference in SNIP depending on the interval between repeats (P = 0.98); subjects preferred the 30 s. SNIP_O was significantly higher than SNIP_NO (P < 0.00001) but SNIP_L and SNIP_R did not significantly differ (P =  0.60). There was an initial learning effect for the first SNIP test; SNIP did not decline during 80 repeats (P =  0.64).

CONCLUSIONS

We conclude that SNIP_O is a more reliable RMS indicator than SNIP_NO, as there is reduced risk of RMS underestimation. Allowing subjects to choose which nostril to use is appropriate, as this did not significantly affect SNIP, but may increase ease of performance. We suggest that twenty repeats is sufficient to overcome any learning effect and that fatigue is unlikely after this number of repeats. We believe these results are important in aiding the accurate collection of SNIP reference value data in the healthy population.

EEG signatures change during unilateral Yogi nasal breathing

Airflow through the left-and-right nostrils is said to be entrained by an endogenous nasal cycle paced by both poles of the hypothalamus. Yogic practices suggest, and scientific evidence demonstrates, that right-nostril breathing is involved with relatively higher sympathetic activity (arousal states), while left-nostril breathing is associated with a relatively more parasympathetic activity (stress alleviating state). The objective of this study was to further explore this laterality by controlling nasal airflow and observing patterns of cortical activity through encephalographic (EEG) recordings. Thirty subjects participated in this crossover study. The experimental session consisted of a resting phase (baseline), then a period of unilateral nostril breathing (UNB) using the dominant nasal airway, followed by UNB using the non-dominant nasal airway. A 64-channel EEG was recorded throughout the whole session. The effects of nostril-dominance, and nostril-lateralization were assessed using the power spectral density of the neural activity. The differences in power-spectra and source localization were calculated between EEG recorded during UNB and baseline for delta, theta, alpha, beta and gamma bands. Cluster-based permutation tests showed that compared to baseline, EEG spectral power was significantly (1) decreased in all frequency bands for non-dominant nostril UNB, (2) decreased in alpha, beta and gamma bands for dominant nostril UNB, (3) decreased in all bands for left nostril UNB, and (4) decreased in all bands except delta for right nostril UNB. The beta band showed the most widely distributed changes across the scalp. our source localisation results show that breathing with the dominant nostril breathing increases EEG power in the left inferior frontal (alpha band) and left parietal lobule (beta band), whereas non-dominant nostril breathing is related to more diffuse and bilateral effects in posterior areas of the brain.These preliminary findings may stimulate further research in the area, with potential applications to tailored treatment of brain disorders associated with disruption of sympathetic and parasympathetic activity.

Judgements of attractiveness of the opposite sex and nostril differences in self-rated mood: The effects of androstenol

Androstenol has been reported to influence judgements of attractiveness and to affect participants' mood. In the present study, participants were asked to sniff androstenol or a control odour (pure ethanol) unilaterally with the left or right nostril. Subsequently, they rated the attractiveness of photographs of the opposite sex and their own feelings on four mood scales. Participants rated the photographs as significantly more attractive after sniffing androstenol compared with the control odour. This did not depend upon androstenol being perceived as pleasant. Androstenol made male participants feel more lively, and both male and female participants more sexy, when sniffed through the right compared with the left nostril. Participants rated themselves as more irritable and aggressive when exposed to androstenol through the left nostril. The findings are discussed in relation to the effects of arousal on attraction and in the context of current theories of hemispheric differences in emotion.

Empty Nose Syndrome Pathophysiology: A Systematic Review

OBJECTIVE

The pathophysiology of empty nose syndrome (ENS) remains unclear despite significant research. The pathophysiologic mechanism of ENS was systematically reviewed.

DATA SOURCES

MEDLINE and Embase.

REVIEW METHODS

Data were systematically reviewed for studies that provided original data on pathophysiology.

RESULTS

A total of 2476 studies were screened, and 19 met the inclusion criteria: 13 case-control and 6 cross-sectional. Nine pathophysiologic themes were identified.• Demographics: ENS symptoms had no relationship with climatic factors.• Symptomatology: ENS patients demonstrated high symptom severity.• Mental health: Anxiety and depression including hyperventilation were reported in >50% of ENS patients and correlated with ENS symptom severity.• Anatomic features: Structural changes in response to turbinate surgery were similar between ENS and non-ENS patients.• Airflow analysis: Airflow parameters were similar between ENS and non-ENS patients after turbinate surgery. On computational fluid dynamic analysis, differences were found on multiple outcomes.• Diagnostic testing: The menthol detection test was impaired in ENS, and cotton placement in the airway improved ENS symptoms.• Cognitive function: Functional magnetic resonance imaging showed activation in emotional processing area during breathing.• Olfactory function: Subjective impairment was reported in ENS, but quantitative measures were similar to non-ENS patients.• Mucosal physiology/innate immunity: Turbinate histopathology in ENS showed a tissue-remodeling pattern. Nasal nitric oxide level was lower in ENS patients.

CONCLUSION

There is evidence of high comorbid mental health disorders in ENS patients. An abnormal trigeminal-thermoreceptor response may be present in some patients. The influence of altered airflow and the evidence of surgery as the cause for ENS are unclear.

Pranayamas and Their Neurophysiological Effects

Introduction

The millenarian breathing exercises from Yoga, commonly called Pranayamas, are known to induce meditative states, reduce stress, and increase lung capacity. However, the physiological mechanisms by which these practices modulate the human nervous system still need to be unveiled.

Objectives

The aim of this work was to review studies describing the influence of breathing exercises on the brain/mind of humans.

Methodology

We reviewed articles written in English and published between 2008 and 2018. Inclusion and exclusion criteria were based on the PRISMA recommendations to filter articles from Science Direct, PubMed, and Virtual Health Library databases. Patient/Population, Intervention, Comparison, and Outcome technique and Prospective Register of Systematic Reviews registration were also considered.

Results

From a total of 1588 articles, 14 attended the criteria. They were critically compared to each other and presented in a table divided into study; country; sample size; gender; age; objective; technique; outcome.

Discussion

In general, the 14 papers highlight the impact of yogic breathing techniques on emotional and cognitive performance.

Conclusion

In-depth studies focusing on specific aspects of the practices such as retentions, prolonged expiration, attention on fluid respiration, and abdominal/thoracic respiration should better elucidate the effects of Yogic Breathing Techniques (YBT).

Psychophysiological responses to various slow, deep breathing techniques

Deep breathing exercises are commonly used for several health conditions including pain and hypertension. Various techniques are available to practice deep breathing, whereas possible differential psychophysiological effects have not been investigated. We compared four deep breathing techniques and examined outcomes in blood pressure variability, respiratory sinus arrhythmia, baroreflex function, and emotional state. Healthy adult volunteers performed pursed-lips breathing, left and right unilateral nostril breathing, and deep breathing with an inspiratory threshold load (loaded breathing), all at a frequency of 0.1 Hz (i.e., controlled breathing) and for three minutes each. Results showed that blood pressure variability was higher during loaded breathing versus other conditions and higher during pursed-lips breathing versus left and right unilateral nostril breathing. Respiratory sinus arrhythmia was higher during loaded breathing versus other conditions and higher during pursed-lips breathing versus left unilateral nostril breathing. The effect of breathing condition on respiratory sinus arrhythmia was mediated by alterations in blood pressure variability. There was no difference between the breathing conditions in baroreflex sensitivity or effectiveness. Participants rated pursed-lips breathing as more calming and pleasant and with more sense of control (vs. other conditions). Overall, among the four tested deep breathing techniques, loaded breathing was associated with enhanced cardiovascular effects and pursed-lips breathing with better emotional responses, while also enhancing cardiovascular effects (albeit less than loaded breathing). These findings can be informative in applying deep breathing techniques as self-management interventions for health conditions, in which baroreceptors stimulation and autonomic and emotional modulations can be beneficial, such as pain and hypertension.

Effect of Unilateral Left Nostril Breathing (Chandra Anga Pranayama) on Cognitive Function in Healthy Yoga-Naïve Individuals: A Randomized, Controlled, Pilot Study

INTRODUCTION

Breathing modulates cortical neuronal activity. Various breathing exercises are purported to have specific effects on emotional and cognitive functions.

OBJECTIVE

To determine the effect of unilateral left nostril breathing (ULNB) on nonlateralized, overall cognitive functions using computerized psychometric tests.

METHODS

A randomized, controlled, pilot study was conducted among 20 healthy yoga-naïve medical students. ULNB was performed for 15 min by the test group (n = 10) and breath awareness by the control group (n = 10). Attention and processing speed, memory, and executive function were assessed using the Letter-Digit Substitution Test, Sternberg Memory Task, and Victoria Stroop Test, respectively. Baseline, pre- and postintervention scores were recorded.

RESULTS

There was no significant difference between the groups in baseline scores. In the Sternberg Memory Task, a statistically significant decrease in response time was seen in the test (t(9) = 3.855, p = 0.004) as well as the control group (t(9) = 3.120, p = 0.012); there was no significant difference between the groups. No significant effect of UNLB was seen in the Letter-Digit Substitution Test and Stroop Test.

CONCLUSIONS

Our study showed no difference in the effects of 15-min practice of ULNB and breath awareness on cognitive functions; both improved memory but not attention or executive function.

Sleep and Plasticity: Do We Consolidate Memories Separately in Each Hemisphere?

During sleep, our memories are spontaneously reactivated and consolidated. Now it seems that we can influence these reactivations in specific locations of our brain, for example, by sniffing memory-related odors with only one nostril.

The effect of unilateral forced nostril breathing on sleep in healthy right-handed men: a preliminary report

PURPOSE

Although we spend about one-third of our lives in sleep and recognize its necessity for good health, sleep has only been partially elucidated in the last century. The nasal cycle of congestion and decongestion during sleep has various effects on human physiology. The aim of the present study was to investigate the effect of unilateral forced nostril breathing on sleep.

METHODS

Twenty-one healthy male volunteers aged 18-24 years were included in the study. Only individuals with right-hand dominance were included. Subjects were observed during sleep for three nights under different conditions: no obstruction (normal sleep) on the first night, right nasal obstruction on the second night, and left nasal obstruction on the third night.

RESULTS

The main findings of our study are that sleep efficiency, NREM stage III, and total sleep duration were greater during left nasal obstruction (right nostril dominant respiration), while apnea-hypopnea index (AHI), frequency of periodic limb movements, and oxygen desaturation were higher during right nasal obstruction (left nostril dominant respiration).

CONCLUSION

The nasal cycle has a significant impact on sleep which is reflected in sleep recordings. Our result supports that nasal obstructions, due to deviations, concha hypertrophy, or congestion/decongestion, might affect the physiology of respiration and sleep. Nasal obstruction should be taken into consideration when evaluating patients in sleep laboratories and further studies are required to elucidate the situation in the patients with nasal obstruction.