Changes in PUFA and eicosanoid metabolism during/after apnea diving: a prospective single-center study.

Background: The popularity of apneic diving is continually growing. As apnea diving substantially burdens the cardiovascular system, special focus is warranted. Regarding inflammation processes and associated inflammatory-related diseases (e.g., cardiovascular diseases), eicosanoids play an important role. This study aims to investigate polyunsaturated fatty acids (PUFAs) and eicosanoids in voluntary apnea divers, and so to further improve understanding of pathophysiological processes focusing on proinflammatory effects of temporarily hypercapnic hypoxia.. Methods: The concentration of PUFAs and eicosanoids were investigated in EDTA plasma in apnea divers (n=10) before and immediately after apnea, 0.5 hour and four hours later, applying liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results: Mean age was 41±10 years, and divers performed a mean breath-hold time of 317±111 seconds. PUFAs, eicosanoids and related lipids could be classified in four different kinetical reaction groups following apnea. The first group (e.g., Ω-6 and Ω-3-PUFAs) showed an immediate concentration increase followed by a decrease below baseline four hours after apnea. The second group (e.g., thromboxane B2) showed a slower increase, with its maximum concentration 0.5 hour post-apnea followed by a decrease four hours post-apnea. Group 3 (9- and 13-hydroxyoctadecadienoic acid) is characterized by two concentration increase peaks directly after apnea and four hours afterward compared to baseline. Group 4 (e.g., prostaglandin D2) shows no clear response. Conclusion: Changes in the PUFA metabolism after even a single apnea revealed different kinetics of pro- and anti-inflammatory regulations and changes for oxidative stress levels. Due to the importance of these mediators, apnea diving should be evaluated carefully and be performed only with great caution against the background of cardiovascular diseases and inflammation processes.

Preinduction incentive spirometry versus deep breathing to improve apnea tolerance during induction of anesthesia in patients of abdominal sepsis: A randomized trial.

BACKGROUND: Abdominal sepsis is associated with varied degree of hypoxemia and atelactasis in the lung and can enhance the onset of desaturation of arterial blood during apnea. AIMS: This study looked at methods to improve safety margin of apnea during induction of anesthesia in these high-risk patients. SETTINGS AND DESIGN: It was a randomized, single blind study on adult patients presenting for emergency laparotomy due to peritonitis in a university teaching hospital setting. MATERIALS AND METHODS: In group 1 (IS) (n = 32), three sessions of incentive spirometry (IS) were performed within one hour before induction of anesthesia. In group 2 (DB) (n = 34), patients were subjected to deep breathing sessions in a similar manner. All patients received preoxygenation (100%) by mask for 3 min, followed by rapid-sequence induction of anesthesia using fentanyl, thiopental, and suxamethonium and endotracheal intubation. Patients were subjected to a period of apnea by keeping the end of the endotracheal tube open to air till they developed 95% hemoglobin saturation (SpO 2) by pulse oxymetry. Positive pressure ventilation was resumed at the end. We observed for hemodynamic changes, apnea time, and SpO 2 (100%) recovery time on resuming ventilation. Arterial blood gas samples were taken before intervention, after IS or DB, after preoxygenation, and at the end of apnea. STATISTICAL ANALYSIS USED: One-way analysis of variance (ANOVA), X 2 test, Kaplan-Meier graph, and log-rank tests were applied to compare the two study groups. RESULTS: Oxygenation level in group 1 (265 ± 76.7 mmHg) patients was significantly (P < 0.001) higher than in group 2 (221 ± 61.8 mmHg)at the end of preoxygenation. The apnea time (median: lower bound - upper bound Confidence Interval apnea time) (272:240-279 s) in group 1 (IS) patients was significantly higher P < 0.05) than in group 2 (180:163-209 s) patients. Saturation recovery time (35:34-46 s) in group 1 (IS) patients was also quicker than in group 2 patients (48:44-58 s). CONCLUSIONS: IS in the preoperative period is superior to deep breathing sessions for improving apnea tolerance during induction of anesthesia in abdominal sepsis patients.

Effects of dietary inorganic nitrate on static and dynamic breath-holding in humans.

Inorganic nitrate has been shown to reduce oxygen cost during exercise. Since the nitrate-nitrite-NO pathway is facilitated during hypoxia, we investigated the effects of dietary nitrate on oxygen consumption and cardiovascular responses during apnea. These variables were measured in two randomized, double-blind, placebo-controlled, crossover protocols at rest and ergometer exercise in competitive breath-hold divers. Subjects held their breath for predetermined times along with maximum effort apneas after two separate 3-day periods with supplementation of potassium nitrate/placebo. In contrast to our hypothesis, nitrate supplementation led to lower arterial oxygen saturation (SaO(2), 77 ± 3%) compared to placebo (80 ± 2%) during static apnea, along with lower end-tidal fraction of oxygen (FETO(2)) after 4 min of apnea (nitrate 6.9 ± 0.4% vs. placebo 7.6 ± 0.4%). Maximum apnea duration was shorter after nitrate (329 ± 13 s) compared to placebo (344 ± 13 s). During cycle ergometry nitrate had no effect on SaO(2), FETO(2) or maximum apnea duration. The negative effects of inorganic nitrate during static apnea may be explained by an attenuated diving response.

Vitamin C supplementation influences the antioxidant response and nitric oxide handling of erythrocytes and lymphocytes to diving apnea.

OBJECTIVE: We have investigated the influence of vitamin C diet supplementation on the antioxidant response and nitrite levels in lymphocytes and erythrocytes during diving apnea. SUBJECTS: Seven male professional apnea divers participated in a double blind crossover study. Divers were randomly assigned to either vitamin C supplemented or placebo groups. The subjects did not take any other supplements than the ones provided for this study. INTERVENTION: One group was supplemented with vitamin C capsules (1 g per day) for 7 days while the other group took a placebo composed of lactose. The usual dietary habits of participants were assessed using a self-reported 7-days 24-h recall before the day of the study. Blood samples were taken under basal conditions, immediately after diving apnea for 4 h and after 1 h of recovery. RESULTS: Catalase activity increased in erythrocytes (23%) and superoxide dismutase increased in lymphocytes (35%) during the recovery only in the placebo group. Lymphocyte ascorbate levels increased in the supplemented group after diving (85%) and maintained high at recovery. Plasma nitrite levels increased about twofold in both groups during the recovery. Erythrocyte nitrite levels increased after diving (50%) and about twofold during the recovery in the supplemented group. Nitrite levels and iNOS levels in lymphocytes were higher in the placebo group than in the supplemented during the recovery. Erythrocyte carbonyl derivates were unchanged in all situations. CONCLUSIONS: Vitamin C supplementation influenced the antioxidant response and NO handling in erythrocytes and lymphocytes to the oxidative stress induced by hypoxia-reoxygenation.

Hypoxia/reoxygenation and vitamin C intake influence NO synthesis and antioxidant defenses of neutrophils.

Oxidative stress induced by hypoxia/reoxygenation mediates the pathophysiological consequence of ischemia/reperfusion and human diseases. Diving apnea could be a good model of oxidative stress induced by hypoxia/reoxygenation. We studied the influence of vitamin C diet supplementation on the response of neutrophil antioxidant defenses, NO production, and redox status to diving apnea. Seven professional apnea divers participated in a double-blind cross study. Divers were assigned to either vitamin C-supplemented (1 g/d for a week) or placebo groups. Blood samples were taken under basal conditions, immediately after diving apnea for 4 h and after 1 h of recovery. Plasma vitamin C increased only in the supplemented group after diving and was maintained high in recovery. Diving apnea decreased neutrophil GSH/GSSG ratio in both groups, but maintained protein carbonyl derivates. Neutrophil catalase activity and levels and glutathione peroxidase activity were lower in the supplemented group than in the placebo group after diving. iNOS and nitrite levels decreased only in the supplemented group after diving and recovery. Diving apnea induced oxidative stress and initiated neutrophil reactions that resemble the acute-phase immune response with increased myeloperoxidase activity in neutrophils. Diet supplementation with vitamin C reduced neutrophil iNOS levels and NO production.

Role of L-carnitine in apnea of prematurity: a randomized, controlled trial.

OBJECTIVE: Carnitine is thought to be a conditionally essential biological cofactor for premature infants. A preliminary study suggested that carnitine could significantly reduce apnea of prematurity. The objective of this study was to evaluate critically the role of carnitine in idiopathic apnea of prematurity and to determine whether the use of carnitine would facilitate discontinuation of mechanical ventilatory support, shorten the duration of ventilatory support, and reduce the amount of time that such infants are exposed to both mechanical ventilation and oxygen. We also wanted to determine the effects of supplemental carnitine on weight gain, time to regain birth weight, time to achieve full enteral feedings, and length of hospital stay. METHODS: A prospective, randomized, blinded trial was conducted on 44 preterm infants who were from the same neonatal intensive care unit and who were < or =32 weeks' gestational age with a postnatal age <48 hours and a birth weight <1500 g and required total parenteral nutrition (TPN). Infants were randomized to receive carnitine supplementation or placebo without crossover. Carnitine-supplemented infants received 30 mg/kg/d carnitine in their TPN until the they were tolerating 120 mL/kg/d enteral feedings, and then they received 30 mg/kg/d oral carnitine. The placebo group received TPN without supplemental carnitine; when they tolerated 120 mL/kg/d enteral feedings, they received an oral placebo. The 2 groups continued on their respective supplemental carnitine or placebo until 34 weeks' adjusted age, at which time the study period was completed. Twelve-hour cardiorespiratorygrams to record heart rate, respiratory impedance, and oxygen saturation, and a nasal thermistor to detect expiratory airflow were performed every 4 days on 3 occasions and at 30 and 34 weeks' adjusted age. Plasma carnitine levels were measured at day 14. RESULTS: There were no significant differences between the 2 groups in the occurrence of apnea as detected by cardiorespiratorygram or nursing observation. There were no significant differences between the groups in regard to total days on ventilator, days of nasal continuous positive airway pressure, time to regain birth weight, time to reach enteral feedings of 120 mL/kg/d, discharge weight, adjusted age at discharge, need for oxygen at 28 days' and 36 weeks' adjusted age, or length of stay. The plasma carnitine level was a median of 15.5 micromol/L (range: 7.6-30.5) for the placebo infants compared with a median of 195.3 micromol/L (range: 71.7-343.6) for the carnitine infants. CONCLUSIONS: In this blinded, randomized, placebo-controlled study, we found that infants who received supplemental carnitine did not demonstrate any reduction in apnea of prematurity, ventilator or nasal continuous positive airway pressure days, or the need for supplemental oxygen therapy. Although carnitine may be of significant nutritional benefit for very low birth weight infants, our study does not support its use to reduce apnea of prematurity or decrease dependence on mechanical ventilation.

Breath-holding spells in a patient with transient erythroblastopenia of childhood.

We describe a child with transient erythroblastopenia of childhood and breath-holding spells. The spells resolved after oral iron supplementation but before the anemia resolved. The physiologic role of iron in autonomic nervous system regulation and its potential role in the treatment of breath-holding spells are discussed.

[Metabolic, hormonal and nutritional effects of long-term theophylline therapy in preterm infants: a case-control study]. / Effetti metabolici, ormonali e nutrizionali della terapia prolungata con teofillina nei nati pretermine: uno studio caso-controllo.

Theophylline is widely used in preterm newborns for the prevention of idiopathic apnoeas, but few controlled studies have evaluated its effects on the nutritional and hormonal status of the infant. For this reason we have studied the effect of long term theophylline administration on 16 laboratory parameters concerning the metabolism of proteins, glucose, lipids, hormones and the glomerular function (blood: hemoglobin, glucose, albumin, prealbumin, urea nitrogen, creatinine, cholesterol, triglycerides, apolipoproteins A-I and B-100, IGF-I, IGFBP-3; urine: urea nitrogen, creatinine, C-peptide, GH). A case-control study was performed on 18 healthy preterm infants who were receiving oral theophylline for the prevention of idiopathic apnoeas. The mean duration of therapy at the moment of the balance study was 31 days (SD 12, range 12-51), the mean daily dose was 4.2 mg/kg (SD 1.0), the plasma range of theophylline concentration was 5 to 15 mg/l. As controls, 18 healthy preterm infants of comparable post-conceptional age, body weight and calories/protein intake at the moment of the study, were selected if they had been never treated with theophylline. No statistically significant differences were found between the two groups for the growth velocity or any of the parameters studied. The only notable exception was hemoglobin, which was significantly lower in theophylline treated infants (mean values 10.5 vs 12.7 g/dl, p 0.005 at t test). In synthesis, long term theophylline treatment in preterm infants seems to be safe from the point of view of growth, glucose, protein and lipid metabolism, hormones and glomerular function, but further studies are needed on the effects of theophylline on neonatal erythropoiesis.