Kay Tetzlaff

Hypoxia and cardiac arrhythmias in breath-hold divers during voluntary immersed breath-holds

The incidence and nature of cardiac arrhythmias during static apnea were studied by monitoring the electrocardiogram (ECG) and oxygen saturation (SaO2) of 16 recreational breath-hold divers. All subjects completed a maximal apnea with a mean (±SD) breath-hold duration of 281 (±73) s without clinical complications. Both heart rate (HR) and SaO2 decreased significantly with breath-hold duration. The decline in SaO2 was inversely related to the decline in HR (rxa0=xa0−0.55, Pxa0<xa00.05). Cardiac arrhythmias (supraventricular and ventricular premature complexes, right bundle branch block) occurred in 12/16 (77%) subjects and were related to breath-hold duration. Subjects with atrial premature complexes (nxa0=xa09) had a reduced BMI (Pxa0=xa00.016) and a higher decline of the terminal SaO2 (Pxa0=xa00.01). In conclusion, ectopic arrhythmias were common during maximal static apneas for training purposes. The results indicate that the occurrence of ectopic beats is associated with individual factors such as the tolerable SaO2 decrease.

One-Year Safety of Olodaterol Once Daily via Respimat® in Patients with GOLD 2–4 Chronic Obstructive Pulmonary Disease: Results of a Pre-Specified Pooled Analysis

Abstract The novel long-acting β2-agonist olodaterol demonstrated an acceptable safety profile in short-term phase II clinical studies. This analysis of four randomized, double-blind, placebo-controlled, parallel-group, phase III studies (1222.11, NCT00782210; 1222.12, NCT00782509; 1222.13, NCT00793624; 1222.14, NCT00796653) evaluated the long-term safety of olodaterol once daily (QD) in a large cohort of patients with moderate to very severe (Global initiative for chronic Obstructive Lung Disease 2–4) chronic obstructive pulmonary disease (COPD). The studies compared olodaterol (5 or 10 μg) QD via Respimat®, formoterol 12 μg twice daily (BID) via Aerolizer® (1222.13 and 1222.14), and placebo for 48 weeks. Patients continued receiving background maintenance therapy, with ∼60% receiving concomitant cardiovascular therapy and 25% having a history of concomitant cardiac disease. Pre-specified analyses of pooled data assessed the adverse events (AEs) and serious AEs in the whole population, and in subgroups with cardiac disease, along with in-depth electrocardiogram and Holter monitoring. In total, 3104 patients were included in the safety analysis: 876 received olodaterol 5 μg, 883 received olodaterol 10 μg, 885 received placebos, and 460 received formoterol 12 μg BID. Overall incidence of on-treatment AEs (71.2%), serious AEs (16.1%), and deaths (1.7%) were balanced across treatment groups. Respiratory and cardiovascular AEs, including major adverse cardiac events, were reported at similar frequencies in placebo and active treatment groups. The safety profiles of both olodaterol 5 μg (marketed and registered dose) and 10 μg QD delivered via Respimat® are comparable to placebo and formoterol BID in this population, with no safety signals identified.

Characteristics of the respiratory mechanical and muscle function of competitive breath-hold divers

Competitive breath-hold divers (BHD) employ glossopharyngeal insufflation (GI) to increase intrapulmonary oxygen stores and prevent the lungs from dangerous compressions at great depths. Glossopharyngeal insufflation is associated with inflation of the lungs beyond total lung capacity (TLC). It is currently unknown whether GI transiently over-distends the lungs or adversely affects lung elastic properties in the long-term. Resting lung function, ventilatory drive, muscle strength, and lung compliance were measured in eight BHD who performed GI since 5.5 (range 2–6)xa0years on average, eight scuba divers, and eight control subjects. In five BHD subsequent measures of static lung compliance (Cstat) were obtained after 1 and 3xa0min following GI. Breath-hold divers had higher than predicted ventilatory flows and volumes and did not differ from control groups with regard to gas transfer, inspiratory muscle strength, and lung compliance. A blunted response to CO2 was obtained in BHD as compared to control groups. Upon GI there was an increase in mean vital capacity (VCGI) by 1.75xa0±xa00.85 (SD)xa0L compared to baseline (pxa0<xa00.001). In five BHD Cstat raised from 3.7 (range 2.9–6.8)xa0L/kPa at baseline to 8.1 (range 3.4–21.2)xa0L/kPa after maximal GI and thereafter gradually decreased to 5.6 (range 3.3–8.1)xa0L/kPa after 1xa0min and 4.2 (range 2.7–6.6)xa0L/kPa after 3xa0min (pxa0<xa00.01). We conclude that in experienced BHD there is a transient alteration in lung elastic recoil. Resting lung function did not reveal a pattern indicative of altered lung ventilatory or muscle function.

Glossopharyngeal insufflation and pulmonary hemodynamics in elite breath hold divers

PURPOSEnAcute voluntary lung hyperinflation provoked by glossopharyngeal insufflation (GI) elicits numerous, possibly deleterious, effects on the cardiopulmonary system by increasing intrathoracic pressures far above normal values. This study quantifies acute pulmonary hemodynamics during GI using phase-contrast magnetic resonance imaging (MRI).nnnMETHODSnHemodynamic parameters were measured in nine elite male breath hold divers with a mean age of 30 yr (range = 20-43 yr) by velocity-encoding cine (VEC)-MRI of the main pulmonary artery (PA) before, during, and after GI. Simultaneously, GI-lung volume (GIVEC-MRI) was measured by MR-compatible spirometry.nnnRESULTSnHemodynamic parameters were associated with GIVEC-MRI. Highly significant changes during GI were shown for the mean flow in the PA, which decreased by 45% (P < 0.007), and right ventricular output and cardiac index, which decreased by 41% and 40%, respectively (P < 0.007). Acceleration time also decreased highly significant by 36% during GI (P < 0.007). All hemodynamic parameters except acceleration time returned to baseline after GI.nnnCONCLUSIONSnAcute voluntary lung hyperinflation mimics changes seen in pulmonary arterial hypertension, but unlike the latter, these changes are fully reversible shortly after cessation of voluntary lung hyperinflation. Persistent changes due to repetitive GI could not be detected.

Detection of dysbaric osteonecrosis in military divers using magnetic resonance imaging

This was a controlled cross-sectional study to investigate the prevalence of dysbaric osteonecrosis (DON) in military divers. MRI examinations of the large joints and adjacent bones were performed in a cross-sectional group of 32 highly experienced military divers and 28 non-divers matched for age and anthropometric data. Additional plain radiographs and follow-up controls were performed in all persons with signs certain or suspicious of DON. In two subject groups (one of divers and one of non-divers), lesions characteristic of DON were detected. From this controlled study, it may be concluded that MRI is a highly sensitive method to detect signs of osteonecrosis. It could be shown that the prevalence of bone lesions characteristic of osteonecrosis in highly experienced military divers is not higher than in non-diving subjects of comparable age. The outcome of this comparably small study group fits to the results of previous extensive studies performed with radiographs. The detected low incidence of DON in this collective may be due to the fact that military divers follow stricter selection criteria, decompression schemes and medical surveillance than commercial divers.

Breath-Hold Diving: Respiratory Function on the Longer Term

PURPOSEnExtensive breath-hold (BH) diving imposes high pulmonary stress by performing voluntary lung hyperinflation maneuvers (glossopharyngeal insufflation, GI), hyperinflating the lung up to 50% of total lung capacity. Breath-hold durations of up to 10 min without oxygen support may also presume cerebral alterations of respiratory drive. Little is known about the long-term effects of GI onto the pulmonary parenchyma and respiratory adaptation processes in this popular extreme sport.nnnMETHODSnLung function assessments and subsequent measures of pulmonary static compliance were obtained for 5 min after GI in 12 elite competitive breath-hold divers (BHD) with a mean apnea diving performance of 6.6 yr. Three-year follow-up measurements were performed in 4 BHD. Respiratory drive was assessed in steady-state measurements for 6% and 9% CO2 in ambient air.nnnRESULTSnShort-term pulmonary stress effects for static compliance during GI (13.75 L·kPa) could be confirmed in these 12 divers without exhibiting permanent changes to the lungs distensibility (7.41 L·kPa) or lung function parameters as confirmed by the follow-up measurements and for 4 BHD after 3 yr (P>0.05). Respiratory drive was significantly reduced in these BHD revealing a characteristic breathing pattern with a significant increase in VE and mouth occlusion pressure (P0.1) between free breathing and 6% CO2, as well as between 6% CO2 and 9% CO2 (all P<0.001).nnnCONCLUSIONnBH diving with performance of GI does not permanently alter pulmonary distensibility or impair ventilatory flows and volumes. A blunted response to elevated CO2 concentrations could be demonstrated, which was supportive of the hypothesis that CO2 tolerance is a training effect due to BH diving rather than being an inherited phenomenon.

Scuba diving and the heart. Cardiac aspects of sport scuba diving

Zusammenfassung.Tauchen mit autonomem Tauchgerät hat sich zu einem beliebten Freizeitsport entwickelt, und es gibt zunehmend Hinweise darauf, dass nicht nur junge, gesunde Menschen, sondern auch solche mit vorbestehenden kardiovaskulären Erkrankungen diese Aktivität aufnehmen. Zur sicheren Ausübung dieses Sports ist nicht unbedingt eine athletische Kondition notwendig, aber die physikalischen Besonderheiten der Umgebung unter Wasser haben physiologische Auswirkungen auf den Organismus und erfordern eine gewisse medizinische Fitness. Dem Herz-Kreislauf-System kommt dabei eine zentrale Bedeutung im Rahmen der Risikoabschätzung bei der Beurteilung der medizinischen Tauchtauglichkeit zu. Die immersionsbedingte Erhöhung von kardialer Vor- und Nachlast führt zu einer besonderen Belastung des Herzens, welche im Fall einer Vorschädigung fatale Konsequenzen haben kann. Venöse Mikrogasblasen können bei Vorliegen eines kardialen Rechts-links-Shunts in das arterielle System gelangen und zur arteriellen Gasembolie führen. Es ist daher wichtig, Tauchkandidaten medizinisch zu untersuchen und bei Vorliegen von kardiovaskulären Kontraindikationen auf die bestehenden Risiken hinzuweisen.Abstract.Diving with self-contained underwater breathing apparatus (scuba) has become a popular recreational sports activity throughout the world. A high prevalence of cardiovascular disorders among the population makes it therefore likely that subjects suffering from cardiovascular problems may want to start scuba diving.Although scuba diving is not a competitive sport requiring athletic health conditions, a certain medical fitness is recommended because of the physical peculiarities of the underwater environment. Immersion alone will increase cardiac preload by central blood pooling with a rise in both cardiac output and blood pressure, counteracted by increased diuresis. Exposure to cold and increased oxygen partial pressure during scuba diving will additionally increase afterload by vasoconstrictive effects and may exert bradyarryhthmias in combination with breath-holds. Volumes of gas-filled body cavities will be affected by changing pressure (Figure 1), and inert gas components of the breathing gas mixture such as nitrogen in case of air breathing will dissolve in body tissues and venous blood with increasing alveolar inert gas pressure. During decompression a free gas phase may form in supersaturated tissues, resulting in the generation of inert gas microbubbles that are eliminated by the venous return to the lungs under normal circumstances.Certain cardiovascular conditions may have an impact on these physiological changes and pose the subject at risk of suffering adverse events from scuba diving. Arterial hypertension may be aggravated by underwater exercise and immersion. Symptomatic coronary artery disease and symptomatic heart rhythm disorders preclude diving. The occurrence of ventricular extrasystoles according to Lown classes I and II, and the presence of atrial fibrillation are considered relative contraindications in the absence of an aggravation following exercise. Asymptomatic subjects with Wolff-Parkinson-White syndrome may be allowed to dive, but in case of paroxysmal supraventricular tachycardia they must refrain from diving. Pacemakers will fail with increasing pressure, but some manufacturers have proven their products safe for pressure equivalents of up to 30 m of seawater, so that patients may dive uneventfully when staying within the 0–20 m depth range. Significant aortic or mitral valve stenosis will preclude diving, whereas regurgitation only will not be a problem. Right-to-left shunts have increasingly gained attention in diving medicine, since they may allow venous gas microbubbles to spill over to the arterial side of the circulation enabling the possibility of arterial gas embolism. Significant shunts thus preclude diving. The highly prevalent patent foramen ovale is considered a relative contraindication only when following certain recommendations for safe diving (Table 2). Metabolic disorders are of concern, since adiposity is associated with both, higher bubble grades in Doppler ultrasound detection after scuba dives when compared to normal subjects, and an increased epidemiologic risk of suffering from decompression illness. In conclusion, cardiovascular aspects are important in the assessment of fitness to dive, and certain cardiovascular conditions preclude scuba diving. Any history of cardiac disease or abnormalities detected during the routine medical examination should prompt to further evaluation and specialist referral.

Should children dive with self‐contained underwater breathing apparatus (SCUBA)?

Diving with self‐contained underwater breathing apparatus (SCUBA) has become a popular recreational activity in children and adolescents. This article provides an extensive review of the current literature.

Pulmonary Function in Children After Open Water SCUBA Dives

An increasing number of children and adolescents is diving with Self-Contained Underwater Breathing Apparatus (SCUBA). SCUBA diving is associated with health risks such as pulmonary barotrauma, especially in children and in individuals with airflow limitation. As no data has been published on the effects of open-water diving on pulmonary function in children, the objective of this study was to evaluate the effects of SCUBA dives on airflow in children. 16 healthy children aged 10-13 years underwent spirometry and a cycle-exercise challenge while breathing cold air. They subsequently performed dives to 1-m and 8-m depth in random order. Pulmonary function was measured before and after the exercise challenge and the dives. There were statistically significant decreases in FEV1, FVC, FEV1/FVC, MEF25 and MEF50 after the cold-air exercise challenge and the dives. Changes in lung function following the exercise challenge did not predict the responses to SCUBA diving. In 3 children the post-dive decrements in FEV1 exceeded 10%. These children had a lower body weight and BMI percentile. SCUBA diving in healthy children may be associated with relevant airflow limitation. A low body mass might contribute to diving-associated bronchoconstriction. In the majority of subjects, no clinically relevant airway obstruction could be observed.

Why predominantly neurological decompression sickness in breath-hold divers?

### Signs and Symptoms Consistent with DCS in Breath-Hold DivingnnIt has been widely believed that human free divers were immune to decompression sickness because the only inert gas added during a breath-hold dive is the nitrogen (N2) that remains in the lungs from the inhalation before submerging.