Abdominal Breathing Increases Tear Secretion in Healthy Women
Adequate production of tears is essential for maintenance of the ocular surface. Tears are primarily produced by the lacrimal glands, which are innervated by the autonomic nervous system, with predominant parasympathetic input. Parasympathetic innervation of the lacrimal gland is considered to be responsible for inducing most of the tear secretion.
Dry eye disease (DED) is a multifactorial disease involving tears and dryness of the ocular surface. It constitutes an important health problem, causing discomfort, visual disturbance, and tear film instability, as well as potential damage to the ocular surface and increased risk of ocular surface infections.
These symptoms frequently interfere with activities such as reading, working on a computer, and driving a car, thus having a negative impact on sychological health and overall sense of well-being. In particular, visual display terminal (VDT) use is a strong risk factor for DED.
Several studies have shown that respiration contributes to modulation of the sympathetic and parasympathetic nervous systems. Slow breathing at 6 cycles/min reduces muscle nerve sympathetic activity and chemoreflex activation. Especially, abdominal breathing is associated with low levels of sympathetic nervous activity and high levels of parasympathetic nervous activity. It has been reported that abdominal breathing for 3 min in the 4-second inhalation and 6-second exhalation pattern decreases the heart rate and increases high-frequency power, an index of parasympathetic nervous activity. In the present study, we hypothesized that abdominal breathing, compared to normal breathing, increases tear meniscus volume as measured by strip meniscometry.
A total of 20 eyes of 20 healthy female volunteers were examined.
The participants were randomly assigned to one of two groups: normal breathing and abdominal breathing. During the first visit, subjects in the normal breathing group performed normal breathing for 3 min, whereas those in the abdominal breathing group performed abdominal breathing (4-second inhalation and 6-second exhalation) for 3 min.
During the second visit, the protocols were swapped between the groups. We compared and estimated the data between the abdominal breathing group and the normal breathing group. Moreover, we compared the data between the several measurement time points and the initial time point (before) in the same group. The subjects were examined while they were seated. The R-R interval, tear meniscus volume, salivary amylase activity, pulse and blood pressure were investigated before and immediately after, 15 min after, and 30 min after the breathing activity was completed . The results of normal breathing were used as the control.
A. Measurement of R-R Interval
The R-R interval was measured by a heartbeat sensor called “myBeat” (UNION TOOL, Tokyo, Japan), which uses a safe and noninvasive technique. The participants wore the monitor on their chest, which was used to analyze the R-R interval on the basis of the heart rate.
B. Measurement of Tear Meniscus Volume
The tear meniscus volume was measured by SM (Echo Electricity, Tokyo, Japan). The tip of the SM apparatus was inserted into the lateral lower tear meniscus for 5 seconds, without touching the ocular surface. The length (in mm) of the stained tear column in the central membrane ditch was regarded as the SM value of that eye.
C. Measurement of Pulse and Blood Pressure
Pulse and blood pressure were measured by a blood pressure monitor (OMRON, Kyoto, Japan), which could record the pulse as well as the systolic and diastolic blood pressure.
D. Measurement of Salivary Amylase Activity
Salivary amylase activity was measured by using a drychemistry system called “COCORO Meter” (NIPRO, Osaka, Japan) to investigate the changes in the sympathetic nervous system. This system used a disposable test-strip equipped with built-in saliva collection, reagent papers, and an automatic saliva transfer mechanism. This method could measure the salivary amylase in 1 min.
This study shows that abdominal breathing increases the marginal tear strip volume compared to normal breathing in healthy Japanese women. Abdominal breathing may decrease dryness of the eyes and is an effective technique for increasing tear meniscus volume.
The abdominal breathing technique can be practiced by anyone, and it requires no machines or specific environment. Although this study needs to be conducted in men and DED patients as well as healthy women in the future, this study shows that abdominal breathing may alleviate discomfort caused by decreased tear volume, especially in VDT users.
KOKORO SANO, RN, PHN, MOTOKO KAWASHIMA, MD, PHD, KAZUHIRO IKEURA, DDS,
REIKO ARITA, MD, PHD, AND KAZUO TSUBOTA, MD, PHD
GARY N. FOULKS, MD, EDITOR
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