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Biomedical subjects

K Tetzlaff

Publications and source records attributed to K Tetzlaff.

At least 19 recordsLinked to original sources
PubMed2003

Noninvasive myocardial contractility monitoring with seismocardiography during simulated dives.

OBJECTIVE: To determine if bradycardia during hyperbaric exposure is accompanied by a negative influence on myocardial contractility. METHODS: Accelerometer-based registration of myocardial compression waves with Seismocardiography (SCG) for noninvasive contractility monitoring. Comparative pulmonary artery (PA) catheter study (9 ICU-patients, mean = 67ys) with ejection-fraction (EF) equivalent versus sum of g-values of contraction phase in SCG, and Preload (leg-positioning). Test with monitoring of changes in Contractility Index (ContrI) derived from the SCG-power spectrum (contraction phases, area under curve). Hyperbaric chamber study (0.6MPa dive-simulation) in 14 healthy divers. Quantitative SCG-(ContrI, power spectra) and ECG-recording. RESULTS: Correlation between changes in EF (PA catheter) and in the g-values (SCG) was r(SP) = 0.87 (p < 0.0001). ContrI increased in the leg-positioning test parallel to preload increase, heart rate remained stable. During hyperbaric exposure (0.6MPa) heart rate decrease was highly significant (68 to 58 min(-1); p < 0.001), ContrI and power spectra remained nearly unchanged, SCG registration was noise free. CONCLUSIONS: Hyperoxic bradycardia during simulated dives is not accompanied by impaired contractility measured with SCG, which is concordant to findings with invasive methods in current literature. SCG is suitable for noninvasive and stress free contractility monitoring and patient surveillance in a hyperbaric chamber.

Adult↗
PubMed2001

Cervico-thoracic disc protrusions in controlled compressed-air diving: clinical and MRI findings.

Prevalence of cervical and thoracic disc protrusions was investigated by MRI in 24 military long-term compressed-air divers and 24 controls. A total of 26 disc protrusions (17 cervical disc protrusions) were detected in 58% of the divers whereas 18 protrusions were detected in 38 % of the controls (13 disc cervical protrusions). There was no significant difference between groups and no correlation with the diving experience. Neurological examination revealed no clinical abnormalities. In contrast to a recent study, our results suggest that long-term divers are at no increased risk for accumulating spinal disc protrusions or intramedullary abnormalities.

Adult↗
PubMed2001

Spatial orientation in construction divers--are there associations with diving experience?

OBJECTIVE: The purpose of this work was to investigate whether or not navigation abilities are impaired in construction divers and if putative deficits can be related to MRT-verified brain lesions and/or to diving experience. METHODS: Nineteen construction divers and 19 controls matched for age, intelligence, and socioeconomic background were studied by use of a "locomotor search through" task which resembled working conditions at ground. The task incorporated a spatial working memory and a spatial reference memory component. Moreover, navigation parameters (i.e., rotational turns, distances traveled, speed of navigation) were derived from the participant's locomotor behavior, which was recorded automatically. Groups were compared by navigation performance, standard neuropsychological tests, and the number of brain lesions obtained by MRT-scans. RESULTS: Divers were widely comparable with respect to neuropsychological test scores, exploration behavior and speed of navigation during testing. Performance deficits in divers were seen in the three test trials with respect to the number of reference memory errors and navigation behavior. Only in controls were age and the number of MRI-verified lesions related to neuropsychological test performance and to maze variables, but in divers the number of lesions seemed to be related to hyperbaric exposure. CONCLUSION: Despite possible positive selection effects in long-term construction divers, these results may have implications for health care of middle-aged divers who are exposed to critical depths of more than 60 meter sea water (msw).

Adult↗
PubMed2001

Cardiac output changes during hyperbaric hyperoxia.

OBJECTIVES: Increased ambient pressure and oxygen partial pressure (pO2) influence cardiovascular regulation during diving and caisson work. We measured the cardiac output (Q) in subjects who practiced moderate work at a usual diving depth of 30 m. METHODS: In 23 healthy male Navy divers who performed steady state bicycle exercises (100 W workload) in a hyperbaric chamber Q was measured by a CO2-rebreathing technique at normal pressure (100 kPa) and at raised ambient pressure (400 kPa), in a random order. During the rebreathing maneuver the subjects were exposed to pO2 values which theoretically may have reached a maximum value of 87 kPa (normobaric) and 388 kPa (hyperbaric). During the experiments the ambient temperature ranged between 22 and 25 degrees C. RESULTS: There was a significant decrease of the directly measured Q, heart rate (HR) and the calculated stroke volume at depth when compared with normoxic and normobaric exercise. The decrease of Q amounted to 64% of the normobaric value (8.9 l min-1 versus 13.9 l min-1). The mean HR decreased from 104.7 min-1 (100 kPa) to 94.0 min-1 (400 kPa). The calculated mean stroke volume decreased from 133 ml (100 kPa) to 96 ml (400 kPa). CONCLUSIONS: During hyperoxic hyperbaria the peripheral vascular tonus increases due to the consecutively increased arterial oxygen content. The cardiac output may correlate to the peripheral vasoconstriction and is therefore indirectly influenced by elevation of inspiratory pO2 i.e. during the rebreathing maneuver.

Adult↗
PubMed2001

Effects of ambient cold and depth on lung function in humans after a single scuba dive.

This study evaluated the subacute respiratory effects of diving, to try to separate the effects of ambient temperature from those of depth. In the first experiment 10 healthy men made a compressed-air dive to 50 m that exposed them to cold. They were compared with 10 matched control subjects who underwent the same dive profile but were exposed to a comfortable temperature. In the second experiment 16 healthy subjects made randomized cold dives to both 50 m and 10 m. Pulmonary function tests were made before, after 1 h, and 24 h after the dives. In the first experiment there was an increase in residual volume (P < 0.05) and a decrease in forced expiratory volume at 1 s (FEV1), in forced vital capacity (FVC) and in mid-expiratory flow at 75% of FVC (MEF75) 1 h after the cold dives (P < 0.05). In the second experiment significant increases in specific airways resistance (sR(AW)) (P < 0.05) and decreases in FEV1 (P<0.01), in MEF75 (P<0.05), and in mid-expiratory flow at 25% of FVC (P<0.05), were obtained after the 50 m-dives, whereas SR(AW) increased after the 10 m-dives (P<0.05). The respiratory pattern observed 1 h after cold dives to 50 m indicated airway narrowing. The changes after cold dives to 10 m, however, were of minor magnitude. Both cold and depth seemed to contribute to the adverse effects of a single compressed-air dive on pulmonary function.

Adult↗
PubMed2001

[Simultaneous transthoracic echocardiography and transcranial doppler ultrasonography with ultrasound contrast agents for the detection of a patent foramen ovale in diving medicine].

OBJECTIVE: Presentation of a non-invasive method for the identification of a patent foramen ovale (PFO) in screening of diving-candidates or for the investigation of diving accidents. METHOD: Simultaneous transthoracic echocardiography and transcranial Doppler sonography of the middle cerebral artery using ultrasound contrast media. RESULTS: In an unselected collective of amateur and professional divers a PFO was identified according to statistical prediction. CONCLUSION: This method can be used in diving medicine for PFO detection as an alternative procedure to transesophageal echocardiography.

Adult↗
PubMed2001

Respiratory effects of a single dive to 50 meters in sport divers with asymptomatic respiratory atopy.

Increasing popularity of sports diving makes it likely that subjects with allergic respiratory diseases will be involved in diving with self contained underwater breathing apparatus (scuba). The present study evaluated the effects of a single scuba-dive on pulmonary function in subjects with respiratory atopy. Specific airways conductance (sGaw), residual volume (RV), forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), mid expiratory flow at 50% of FVC (MEF50), and transfer factor for carbon monoxide (TLCO) were measured in 9 sport divers with a history of hay fever and 9 matched healthy sport divers (control) before, 3 hours and 24 hours after a wet hyperbaric chamber dive to a depth of 50 m. Airway hyperresponsiveness (AHR) was assessed by methacholine challenge 4 weeks after the dive. Atopic subjects and controls did not differ with respect to anthropometric data, diving experience, and predive lung function. A 3% reduction in FVC was found 24h after the dive (p < 0.05) in both groups, whereas sGaw decreased by 15% 24 h after the dive (p < 0.05) in the subjects with respiratory atopy only. Postdive changes in RV, FEV1, MEF50, and TLCO did not reach level of statistical significance. AHR was obtained in 8/9 subjects with respiratory atopy. We conclude that subjects with atopic sensitization and asymptomatic AHR may be more susceptible to effects of diving on pulmonary function.

Adult↗
PubMed2001

Can eustachian tube ventilatory function impairment after oxygen diving be influenced by application of free radical scavenger vitamins C and E?

OBJECTIVES/HYPOTHESIS: To evaluate the influence of free radical scavenger vitamins C and E on eustachian tube ventilatory function changes related to oxygen dives. STUDY DESIGN: Prospective, randomized, double-blind, placebo-controlled study of middle ear impedance changes of oxygen divers being orally treated with free radical scavenger vitamins C and E. METHODS: Fifteen divers were allocated to two groups. Before diving on oxygen on consecutive days (days 1 and 2), divers in group 1 took a daily dose of 1 g ascorbic acid and 600 International Units d-alpha-tocopherol and divers in group 2 were given placebo. Before diving and 2 and 24 hours after diving on days 1 and 2, middle ear impedance was measured. RESULTS: Impedance decreased overnight after dive 1 (P =.04) but not after dive 2 (P =.31). No impedance differences were found between groups after the dive on day 1 (P =.83). Twenty-four hours after the dive on day 1 and after the dive on day 2, impedance values in both groups were different (P =.02 vs. P =.07), emphasizing slightly more negative pressures in the vitamin group. CONCLUSION: Vitamins C and E did not reduce eustachian tube ventilatory function impairment overnight after the dive on day 1, suggesting no evidence of free radical-mediated toxicity affecting the eustachian tube or middle ear mucosa. Repetitive oxygen dives may cause tissue adaptation suggesting other than antioxidant defense mechanisms.

Administration, Oral↗
PubMed2000

Arteriovenous bubbles following cold water sport dives: relation to right-to-left shunting.

Neurologic injury subsequent to decompression from diving may be due to paradoxical arterialization of venous gas emboli. Of 40 divers who performed 53 open water dives after being tested for a patent foramen ovale (PFO), arterial gas emboli were detected in 7 of 13 dives, which resulted in venous bubbles. In five of these seven dives, there was evidence of a PFO by contrast transcranial Doppler sonography, indicating an increased risk of arterializing venous bubbles in divers with a PFO.

Adult↗
PubMed2000

Neurologic outcome of controlled compressed-air diving.

The authors compared the neurologic, neuropsychological, and neuroradiologic status of military compressed-air divers without a history of neurologic decompression illness and controls. No gross differences in the neuropsychometric test results or abnormal neurologic findings were found. There was no correlation between test results, diving experience, and number and size of cerebral MRI lesions. Prevalence of cerebral lesions was not increased in divers. These results suggest that there are no long-term CNS sequelae in military divers if diving is performed under controlled conditions.

Adult↗
PubMed2000

Computed chest tomography in an animal model for decompression sickness: radiologic, physiologic, and pathologic findings.

This study was conducted to investigate the early pulmonary effects of acute decompression in an animal model for human decompression sickness by CT and light microscopy. Ten test pigs were exposed to severe decompression stress in a chamber dive. Three pigs were kept at ambient pressure to serve as controls. Decompression stress was monitored by measurement of pulmonary artery pressure and arterial and venous Doppler recording of bubbles of inert gas. Chest CT was performed pre- and postdive and in addition the inflated lungs were examined after resection. Each lung was investigated by light microscopy. Hemodynamic data and bubble recordings reflected severe decompression stress in the ten test pigs. Computed tomography revealed large quantities of ectopic gas, predominantly intravascular, in three of ten pigs. These findings corresponded to maximum bubble counts in the Doppler study. The remaining test pigs showed lower bubble grades and no ectopic gas by CT. Sporadic interstitial edema was demonstrated in all animals--both test and control pigs--by CT of resected lungs and on histologic examination. A severe compression-decompression schedule can liberate large volumes of inert gas which are detectable by CT. Despite this severe decompression stress, which led to venous microembolism, CT and light microscopy did not demonstrate changes in lung structure related to the experimental dive. Increased extravascular lung water found in all animals may be due to infusion therapy.

Acute Disease↗
PubMed2000

Does diving damage the brain? MR control study of divers' central nervous system.

PURPOSE: To evaluate the prevalence of cerebral white matter changes on MR imaging in healthy elderly compressed air divers with a long diving history in comparison with control subjects who have never dived. MATERIAL AND METHODS: The investigation employed 59 experienced elderly divers and 48 control subjects matched for age, body mass index, alcohol and smoking history. MR studies included a fluid attenuated inversion recovery sequence and T1- and T2-weighted pre- and postcontrast images in axial orientation of the whole brain to localize white matter changes. RESULTS: MR images did not show any morphologic abnormalities in the brains of divers. Both groups - divers and controls - did not differ significantly with respect to white matter changes of the brain. CONCLUSION: No increased prevalence of cerebral white matter changes in compressed air divers compared with a healthy worker sample of similar age were found. Thus, extensive compressed air diving may not necessarily be related to radiological changes on MR.

Adult↗
PubMed2000

Underwater application of nasal decongestants: method for special operations.

A simple method of emergency underwater application of a nasal decongestant in divers to prevent diving-related accidents or even fatalities attributable to sequelae of middle-ear and sinus barotrauma of ascent was evaluated. Eleven military divers had to inject 1 mL of 0.02% methylene blue into a central venous catheter after having inserted the tip between their upper lip and the mask at 1 m depth in a pool. After injection, the head had to be reclined. Blue liquid flowing from a diver's nostril and a "bitter" taste sensation reported immediately after surfacing indicated successful application. All divers were observed to have had blue liquid flowing from the nostril of application, and one diver could not describe the taste. This method of underwater application of nasal decongestants may be useful for emergency prevention in divers, especially during covert operations. Underwater availability of the system in a special kit carried by divers would be required.

Adult↗
PubMed2000

Exposure to soda-lime dust in closed and semi-closed diving apparatus.

BACKGROUND: Chronic exposure to hyperbaric hyperoxia and venous gas microembolism have been shown to contribute to the long term health effects of diving, especially diver's lung function. Factors related to special diving equipment may add to these effects. This study was conducted to evaluate possible additional hazards for respiratory function of divers employing closed and semi-closed diving apparatus. METHODS: We analyzed soda-lime dust found in the air-intake loop of a closed-circuit oxygen rebreathing diving apparatus which had passed through the filter screen of the diving apparatus's soda-lime cartridge. The geometrical characteristics were evaluated by scanning electron microscopy. The amount of dust that passed through the screen during a normal dive profile was measured by an artificial airflow through a filter membrane. After dives by subjects using these devices, the pH-value of water condensate in the air-intake hose was measured. RESULTS: There was a relevant amount of residual soda-lime dust found in the air-intake loop. The dust particles showed diameters down to 1 micron and a rounded structure. The total amount of dust averaged 9.6 mg.m-3 of breathing mixture. During diving, the mean pH-value of condensate in the hose is estimated at 8.87 (+/- 0.12). CONCLUSION: There is a relevant exposure to soda-lime dust in divers using closed-circuit rebreathing apparatus. This occupational exposure may contribute to chronic airway inflammation and subsequent development of small airway disease in divers.

Calcium Compounds↗
PubMed1999

Respiratory pattern after wet and dry chamber dives to 0.6 MPa ambient pressure in healthy males.

The purpose of this study was to evaluate respiratory effects of wet and dry hyperbaric chamber dives to 0.6 MPa ambient pressure in healthy males. There were 19 and 22 subjects who participated in two series of dives with a bottom time of 15 min and decompression times of 28 and 17 min, respectively. Airways conductance, residual volume, forced vital capacity, forced expiratory volume in 1 sec, mid expiratory flow at 25, 50 and 75% of FVC, and diffusion capacity for CO were measured before the dives, after 3 h, and after 24 h. Multivariate analysis of covariance revealed no statistically significant effects of time or the interaction between time and dry or wet environment on the measured lung function parameters. These findings suggest first that even deep air dives may not necessarily affect pulmonary function, and second, that factors related to the particular wet environment do not seem to contribute to lung function changes after dives.

Adult↗
PubMed1999

Blood lactate changes in men during graded workloads at normal atmospheric pressure (100 kPa) and under simulated caisson conditions (400 kPa).

OBJECTIVES: A hyperbaric environment may influence lactate metabolism due to hyperoxia affecting biochemical pathways. The purpose of our study was to determine the blood lactate levels occurring at high workloads in a sample of professional divers under simulated caisson conditions. The ambient air pressure was equivalent to a diving depth of 30 m of seawater (400 kPa). METHODS: A total of 23 healthy male subjects performed graded bicycle exercise in a dry hyperbaric chamber up to a maximum of 3.5 W kg(-1) body weight at normal (100 kPa) and elevated ambient air pressure (400 kPa). The blood lactate level and the heart rate were measured. RESULTS: In comparison with control conditions, the heart rate and the peripheral blood lactate level were significantly lower at depth for all workloads. CONCLUSIONS: The differences between the normobaric and hyperbaric lactate values may be explained by an overall improvement in lactate metabolism at elevated ambient pressure, especially in the working muscles and the organs responsible for the lactate reduction, i.e., the liver. The reduced heart rate may be an effect of the improved tissue oxygen supply at depth.

Adult↗