Breath Holding

Severe pallid breath-holding spells (BHSs) are based on parasympathetic hyperactivity, leading to cardiac asystole, pallor, brain ischemia, loss of consciousness, and reflex anoxic seizures. In recent years, an increasing number of patients with severe pallid BHSs have been successfully treated with pacemaker implantation. We present the case of a 13-month-old girl suffering from repeated severe pallid BHSs, causing asystole, loss of consciousness, and generalized anoxic seizures. She underwent treatment with oral glycopyrrolate, an anticholinergic drug, and an oral retard preparation of theophylline. The aim of the treatment was to decrease cardiac inhibition with glycopyrrolate and to bring about a positive chronotropic effect with theophylline. In our case, the combined therapy was effective in suppressing syncope and reflex anoxic seizures associated with BHSs This avoided the need for ventricular pacemaker implantation.

SR. Dive, food, and exercise effects on blood microparticles in Steller sea lions (Eumetopias jubatus): exploring a biomarker for decompression sickness..—Re-cent studies of stranded marine mammals indicate that exposure to underwater military sonar may induce pathophysiological responses consistent with decompression sickness (DCS). However, DCS has been difficult to diagnose in marine mammals. We investigated whether blood microparticles (MPs, measured as number/l plasma), which increase in response to decompression stress in terrestrial mammals, are a suitable biomarker for DCS in marine mammals. We obtained blood samples from trained Steller sea lions (Eumetopias jubatus, 4 adult females) wearing time-depth recorders that dove to predetermined depths (either 5 or 50 meters). We hypothesized that MPs would be positively related to decompression stress (depth and duration underwater). We also tested the effect of feeding and exercise in isolation on MPs using the same blood sampling protocol. We found that feeding and exercise had no effect on blood MP levels, but that diving caused MPs to increase. However, blood MP levels did not correlate with diving depth, relative time underwater, and presumed decompression stress, possibly indicating acclimation following repeated exposure to depth. sea lion; decompression; stress; apnea; diving; bubbles THE PURPOSE OF THIS STUDY was to improve understanding of physiological responses to diving in a breath-hold diving marine mammal, with a particular focus on the pathophysiology of decompression sickness (DCS). DCS is a systemic patho-physiological process that occurs naturally after tissues become supersaturated with N 2 under high atmospheric pressure. In humans, DCS can also occur when N 2 or some alternative gas is used to dilute O 2 in breathing mixtures during activities such as deep-sea diving, high-altitude aviation, and space exploration. Most studies of DCS are performed with terrestrial mammals. We therefore hypothesized that a comparative physiological approach studying bona fide diving mammals would add valuable insight into the physiology of decompression. Such an approach may yield insights into the potential physiological traits that allow breath-hold diving animals to perform prolonged apneas to great depths without apparent pressure-related problems. There are data indicating that diving mammals may sustain DCS, at least when they are subjected to atypical stresses (11, 16, 17). Recent necropsy reports have suggested a link between mass stranding of beaked whales and the use of naval midfre-quency sonar (10). The whales experienced symptoms that were similar to those caused by inert gas bubbles in human divers (4). These reports have increased the concern that anthropogenic sound, such as that created by military sonar or during seismic exploration, may harm marine animals. Specifically , it has been suggested that alteration in physiology or diving behavior may increase the risk of DCS (3, 15). For instance, blood bubble formation has been noted in some turtles that were trapped underwater and hauled rapidly to the surface. Those that received recompression treatment recovered and were released, thereby confirming a clinical diagnosis of DCS in a diving vertebrate (12). Bubble formation is believed to be a crucial event in the etiology of DCS, but the role bubbles play in the disease process remains unclear (22). As more is learned about DCS, it has become apparent that some of the symptoms are similar to those of other disease states (18, 35, 36). There are a few well-defined risk factors that increase the probability of DCS, such as increasing dive duration, dive depth, ascent/decompression rate, body mass, and breathing gas (8, 19, 20, 37). Recent studies have shown that micropar-ticles (MPs) are elevated with decompression stress (31, 32). MPs are cellular fragments between 0.3 and 1 m in size that are shed from various cells. MPs derived from platelets are known to activate leukocytes and cause aggregation and can stimulate proinflammatory cytokines. MPs derived from de-compression stress have been shown to specifically activate neutrophils and cause vascular damage (32). MPs correlate with depth of diving in mice (32), but correlate poorly with depth in humans (31, 33). Studies have also evaluated the effect of exercise on bubble and MP production in human scuba divers. Exercise can increase the number of circulating MPs slightly, whereas diving has a much greater effect and is also impacted by the gas used during the dive (31). The question of potential causal relationships among bubbles , MPs, platelet-neutrophil interactions, and neutrophil activation remains obscure (30). Our study aimed to examine the relationship between decompression stress (depth and time underwater) and blood MP levels in Steller sea lions in a controlled diving experiment, in the context of diving, feeding,

Respiratory motion during PET has a significant effect on the quantification of radiotracer uptake in PET images. Even when respiratory motion is considered using PET gating techniques, inaccuracies in standardized uptake values can be caused by inappropriate attenuation correction due to a spatial mismatch between PET and CT. In this study, the effect of breath-hold CT imaging on the spatial match between CT and amplitude-based respiratory-gated PET images is investigated. Whole-body (18)F-FDG PET/CT imaging was performed in 52 patients with 125 lung lesions. (18)F-FDG PET was performed using optimized, amplitude-based respiratory gating. For CT, 36 patients were randomly assigned to the free-breathing (FB) group and 16 to the rest-expiratory breath-hold (BH) group. Spatial mismatch between the PET and CT images was quantified by measuring the distance between the centroids of PET and CT lesions and calculating the Jaccard similarity coefficient (JSC). In the upper lobes, the avera...

Hyperoxia causes oxidative stress. Breath-hold diving is associated with transient hyperoxia followed by hypoxia and a build-up of carbon dioxide (CO₂), chest-wall compression and significant haemodynamic changes. This study analyses variations in plasma oxidative stress markers after a series of repetitive breath-hold dives. Thirteen breath-hold divers were asked to perform repetitive breath-hold dives to 20 metres' depth to a cumulative breath-hold time of approximately 20 minutes over an hour in the open sea. Plasma nitric oxide (NO), peroxinitrites (ONOO⁻) and thiols (R-SH) were measured before and after the dive sequence. Circulating NO significantly increased after successive breath-hold dives (169.1 ± 58.26% of pre-dive values; P = 0.0002). Peroxinitrites doubled after the dives (207.2 ± 78.31% of pre-dive values; P = 0.0012). Thiols were significantly reduced (69.88 ± 19.23% of pre-dive values; P = 0.0002). NO may be produced by physical effort during breath-hold diving....

Heart-rate (f H) changes during diving and exercise are well documented for marine mammals, but changes in stroke volume (SV) and cardiac output (CO) are much less known. We hypothesized that both SV and CO are also modified following intense exercise. Using transthoracic ultrasound Doppler at the level of the aortic valve, we compared blood flow velocities in the left ventricle and cardiac frequencies during rest and at 1, 3 and 4 min after a bout of exercise in 13 adult bottlenose dolphins (Tursiops truncatus, six male and seven female, body mass range 143–212 kg). Aortic cross-sectional area and ventricle blood velocity at the aortic valve were used to calculate SV, which together with f H provided estimates of left CO at rest and following exercise. f H and SV stabilized approximately 4–7 s following the post-respiratory tachycardia, so only data after the f H had stabilized were used for analysis and comparison. There were significant increases in f H , SV and CO associated with each breath. At rest, f H , SV and CO were uncorrelated with body mass, and averaged 41±9 beats min −1 , 136±19 ml and 5514±1182 l min −1 , respectively. One minute following high intensity exercise, the cardiac variables had increased by 104±43%, 63±11% and 234±84%, respectively. All variables remained significantly elevated in all animals for at least 4 min after the exercise. These baseline values provide the first data on SV and CO in awake and unrestrained cetaceans in water.

Hyperoxia causes oxidative stress. Breath-hold diving is associated with transient hyperoxia followed by hypoxia and a build-up of carbon dioxide (CO₂), chest-wall compression and significant haemodynamic changes. This study analyses variations in plasma oxidative stress markers after a series of repetitive breath-hold dives. Thirteen breath-hold divers were asked to perform repetitive breath-hold dives to 20 metres' depth to a cumulative breath-hold time of approximately 20 minutes over an hour in the open sea. Plasma nitric oxide (NO), peroxinitrites (ONOO⁻) and thiols (R-SH) were measured before and after the dive sequence. Circulating NO significantly increased after successive breath-hold dives (169.1 ± 58.26% of pre-dive values; P = 0.0002). Peroxinitrites doubled after the dives (207.2 ± 78.31% of pre-dive values; P = 0.0012). Thiols were significantly reduced (69.88 ± 19.23% of pre-dive values; P = 0.0002). NO may be produced by physical effort during breath-hold diving....