Vascular Responses to Simulated Breath-Hold Diving Involving Multiple Reflexes

Breath-hold diving evokes a complex cardiovascular response. The degrees of hypertension induced by the diving reflex are substantial and accentuated by the underwater swimming. This condition provides a circulatory challenge to properly buffer and cushion cardiac pulsations. We determined hemodynamic changes during the diving maneuver. A total of 20 healthy young adults were studied. Hemodynamics were measured during exercise on a cycle ergometer, apnea, face immersion in cold water (trigeminal stimulation), and simulated breath-hold diving. Dynamic arterial compliance (measured by changes in carotid artery diameter via ultrasound divided by changes in carotid blood pressure as assessed by arterial tonometry) increased with simulated diving compared with rest (p=0.007) and was elevated compared with exercise and apnea alone (p<0.01). A significant increase in heart rate was observed with exercise, apnea, and facial immersion when compared with rest (p<0.001). However, simulated diving brought the heart rate down to resting levels. Cardiac output increased with all conditions (p<0.001), with an attenuated response during simulated diving compared with exercise and facial immersion (p<0.05). Mean blood pressure was elevated during all conditions (p<0.001), with a further elevation observed during simulated diving compared with exercise (p<0.001), apnea (p=0.016), and facial immersion (p<0.001). Total peripheral resistance was decreased during exercise and facial immersion compared with rest (p<0.001) but was increased during simulated diving compared with exercise (p<0.001), apnea (p=0.008), and facial immersion (p=0.003). We concluded that central artery compliance is augmented during simulated breath-hold diving to help buffer cardiac pulsations.

The Human Dive Reflex During Consecutive Apnoeas in Dry and Immersive Environments: Magnitude and Synchronicity

Introduction: The human dive reflex (HDR), an O2 conserving reflex, is characterised by an interplay of central parasympathetic and peripheral sympathetic reactions, which are presumed to operate independently of each other. The HDR is fully activated during apnoea with facial immersion in water and complete immersion in water is thought to increase the magnitude of HDR during consecutive apnoeas. A comparison of HDR activity between consecutive apnoeas in full-body immersion with consecutive apnoeas in dry conditions has not been fully explored. Also, the interplay between parasympathetic and sympathetic reactions involved in the HDR has not been thoroughly analysed.Methods: 11 human volunteers performed 3 consecutive 60 s apnoeas with facial immersion in dry conditions (FIDC) and 3 consecutive apnoeas with facial immersion in full immersion (FIFI). Heart rate (HR), R-R interval (RRI), finger pulse amplitude (FPA), splenic width (SW) and SpO2 were all measured before, during and after apnoeas. A one-way ANOVA using Dunn’s post hoc test was performed to assess HDR activity, and a Pearson’s correlation test was performed to assess HDR synchronisation between physiological parameters during both conditions.Results: Although HDR activity was not significantly different between both conditions, HR and RRI showed progressively greater changes during FIFI compared with FIDC, while SW and FPA changes were relatively equivalent. During FIDC, significant correlations were found between SW &amp; SpO2 and FPA &amp; SpO2. During FIFI, significant correlations were found between RRI &amp; FPA, SW &amp; FPA, HR &amp; SpO2 and FPA &amp; SpO2.Discussion: While there was no significant difference found between HDR activity during FIDC and FIFI, consecutive apnoeas during FIFI triggered a greater magnitude of cardiac activity. Furthermore, significant correlations between RRI and SW with FPA indicate a crosstalk between parasympathetic tone with splenic contraction and increased peripheral sympathetic outflow during FIFI compared to FIDC. In conclusion, HDR activity during consecutive apnoeas does not differ between FIDC and FIFI. There appears to be however a greater level of synchronicity during apnoeas in FIFI compared to FIDC and that this is most likely due to the physiological effects of immersion, which could induce neural recruitment and increased cross talk of HDR pathways.

The Implications of the Diving Response in Reducing Panic Symptoms

Increased CO2 sensitivity is common in panic disorder (PD) patients. Free divers who are known for their exceptional breathing control have lower CO2 sensitivity due to training effects. This study aimed to investigate the immediate effects of cold facial immersion (CFI), breath holding and CO2 challenges on panic symptoms. Healthy participants and patients with PD were subjected to four experimental conditions in a randomly assigned order. The four conditions were (a) breath-holding (BH), (b) CFI for 30 s, (c) CO2 challenge, and (d) CO2 challenge followed by CFI. Participants completed a battery of psychological measures, and physiological data (heart rate and respiration rate) were collected following each experimental condition. Participants with PD were unable to hold their breath for as long as normal controls; however, this finding was not significant, potentially due to a small sample size. Significant reductions in both physiological and cognitive symptoms of panic were noted in the clinical group following the CFI task. As hypothesized, the CFI task exerted demonstrable anxiolytic effects in the clinical group in this study by reducing heart rate significantly and lessening self-reported symptoms of anxiety and panic. This outcome demonstrates the promise of the CFI task for clinical applications.

Using stimulation of the diving reflex in humans to teach integrative physiology

During underwater submersion, the body responds by conserving O2 and prioritizing blood flow to the brain and heart. These physiological adjustments, which involve the nervous, cardiovascular, and respiratory systems, are known as the diving response and provide an ideal example of integrative physiology. The diving reflex can be stimulated in the practical laboratory setting using breath holding and facial immersion in water. Our undergraduate physiology students complete a laboratory class in which they investigate the effects of stimulating the diving reflex on cardiovascular variables, which are recorded and calculated with a Finapres finger cuff. These variables include heart rate, cardiac output, stroke volume, total peripheral resistance, and arterial pressures (mean, diastolic, and systolic). Components of the diving reflex are stimulated by 1) facial immersion in cold water (15°C), 2) breathing with a snorkel in cold water (15°C), 3) facial immersion in warm water (30°C), and 4) breath holding in air. Statistical analysis of the data generated for each of these four maneuvers allows the students to consider the factors that contribute to the diving response, such as the temperature of the water and the location of the sensory receptors that initiate the response. In addition to providing specific details about the equipment, protocols, and learning outcomes, this report describes how we assess this practical exercise and summarizes some common student misunderstandings of the essential physiological concepts underlying the diving response.

VARIASI PERBEDAAN JUMLAH DENYUT NADI PENYELAM TRADISIONALPADA SIMULASI PENYELAMAN

Human dive response aims to conserve oxygen. Direct contact of the water on the forehead, eyes and nose is a strong stimulus for which is innervated by the trigeminal nerve stimulation causes inhibition against respiratory and vasomotor centers and the activation of cardiac vagal motoneuron. The cardiovascular response that causes a decrease in the heart rate and vasoconstriction Facial cold receptors more strongly activated by low water temperature (10 – 150C). The specific objective of this study was to analyze differences in pulse number of healthy male traditional diver before, while, and after simulated dives. This research is an experimental study with 20 analytical samples are housed in Malalayang 2 Data were analyzed using SPSS and Test T. The results of this study found the number of pulses during a breath hold and facial immersion in cold water was significantly lower than that before doing the activity (p = 0.0001) with 17.1±10.2 difference. The number after the pulse raised face of the water was significantly higher than the current hold your breath and facial immersion in cold water (p = 0.0001), with the difference in the amount of as much as 16.6±10.8 pulse. Conclusion : there are significant difference (p = 0.0001) number of pulses in healthy male traditional divers during the interim before and after the while doing simulations hold your breath and dive with facial immersion in cold water. . Keywords : Pulse, Traditional Diving Abstrak.Respon penyelaman manusia bertujuan untuk menghemat oksigen.Kontak langsung terhadap air pada dahi, mata dan hidung merupakan stimulus kuat karena dipersarafi oleh nervus trigeminus dimana stimulasi terhadapnya menyebabkan penghambatan pernafasan dan pengaktifan pusat vasomotor dan motoneuron vagal jantung.Respon kardiovaskuler ini yang menyebabkan penurunan denyut jantung dan terjadinya vasokontriksi.Reseptor dingin wajah lebih kuat teraktivasi dengan air temperatur rendah (10-150C).Tujuan khusus penelitian ini adalah menganalisa perbedaan jumlah denyut nadi laki-laki sehat penyelam tradisional sebelum, sementara, dan sesudah simulasi penyelaman.Penelitian ini merupakan jenis penelitian analitik eksperimental dengan 20 sampel yang bertempat di Malalayang 2. Data dianalisis dengan menggunakanSPSS dan Uji T. Hasil penelitian ini didapatkan jumlah denyut nadi saat melakukan tahan napas dan perendaman wajah dalam air dingin secara bermakna lebih rendah dibandingkan dengan sebelum melakukan kegiatan tersebut (p=0,0001) dengan perbedaan sebanyak 17,1+10,2. Jumlah denyut nadi sesudah wajah diangkat dari dalam air bermakna lebih tinggi daripada saat tahan napas dan perendaman wajah dalam air dingin (p=0,0001), dengan perbedaan jumlah denyut nadi sebanyak 16,6+10,8. Simpulan: ada perbedaan bermakna (p=0,0001) jumlah denyut nadi pada laki-laki sehat penyelam tradisional pada saat sebelum dengan sementara dan sesudah dengan sementara melakukan simulasi penyelaman dengan tahan napas dan perendaman wajah dalam air dingin. Kata Kunci: Denyut Nadi, Penyelaman Tradisional.

Facial immersion in cold water enhances cerebral blood velocity during breath-hold exercise in humans

The diving response is initiated by apnea and facial immersion in cold water and includes, besides bradycardia, peripheral vasoconstriction, while cerebral perfusion may be enhanced. This study evaluated whether facial immersion in 10°C water has an independent influence on cerebral perfusion evaluated as the middle cerebral artery mean flow velocity (MCA Vmean) during exercise in nine male subjects. At rest, a breath hold of maximum duration increased the arterial carbon dioxide tension (PaCO2) from 4.2 to 6.7 kPa and MCA Vmean from 37 to 103 cm/s (mean; ∼178%; P < 0.001). Similarly, during 100-W exercise, a breath hold increased PaCO2 from 5.9 to 8.2 kPa ( P < 0.001) and MCA Vmean from 55 to 113 cm/s (∼105%), and facial immersion further increased MCA Vmean to 122 cm/s (∼88%; both P < 0.001). MCA Vmean also increased during 180-W exercise (from 47 to 53 cm/s), and this increment became larger with facial immersion (76 cm/s, ∼62%; P < 0.001), although PaCO2 did not significantly change. These results indicate that a breath hold diverts blood toward the brain with a >100% increase in MCA Vmean, largely because PaCO2 increases, but the increase in MCA Vmean becomes larger when combined with facial immersion in cold water independent of PaCO2.

Cardiovascular responses to apneic facial immersion during altered cardiac filling

The hypothesis that reduced cardiac filling, as a result of lower body negative pressure (LBNP) and postexercise hypotension (PEH), would attenuate the reflex changes to heart rate (HR), skin blood flow (SkBF), and mean arterial pressure (MAP) normally induced by facial immersion was tested. The purpose of this study was to investigate the cardiovascular control mechanisms associated with apneic facial immersion during different cardiovascular challenges. Six subjects randomly performed 30-s apneic facial immersions in 6.0 ± 1.2°C water under the following conditions: 1) −20 mmHg LBNP, 2) +40 mmHg lower body positive pressure (LBPP), 3) during a period of PEH, and 4) normal resting (control). Measurements included SkBF at one acral (distal phalanx of the thumb) and one nonacral region of skin (ventral forearm), HR, and MAP. Facial immersion reduced HR and SkBF at both sites and increased MAP under all conditions ( P < 0.05). Reduced cardiac filling during LBNP and PEH significantly attenuated the absolute HR nadir observed during the control immersion ( P < 0.05). The LBPP condition did not result in a lower HR nadir than control but did result in a nadir significantly lower than that of the LBNP and PEH conditions ( P < 0.05). No differences were observed in either SkBF or MAP between conditions; however, the magnitude of SkBF reduction was greater at the acral site than at the nonacral site for all conditions ( P < 0.05). These results suggest that the cardiac parasympathetic response during facial immersion can be attenuated when cardiac filling is compromised.