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Biomedical subjects

V Flook

Publications and source records attributed to V Flook.

16 recordsLinked to original sources
PubMed2004

Venous gas embolism in chamber attendants after hyperbaric exposure.

An initial occupational survey (OS) was initiated to investigate the prevalence of venous gas embolism (VGE) in chamber attendants assisting hyperbaric oxygen (HBO2) treatments. Nine female subjects were exposed for three consecutive days to the routine hospital procedure of compressed air exposure to 240 kPa for approximately 115 min with 12 min of terminal oxygen (O2) breathing. VGE was monitored with ultrasound Doppler in 15 min intervals for 2h after the first and third exposure. A follow-up experimental study was completed to investigate whether changed breathing gases and decompression would affect the high incidence of VGE observed in the OS. Ten female subjects were randomly exposed to the routine or revised profile (12 and 24 min of terminal O2 breathing respectively), and a Nitrox profile (breathing gas 40.5% O2 in Nitrogen during 90 min of the isobaric phase). VGE was monitored with transthoracic ultrasound scanner and Doppler. In the OS precordial VGE grade III (Doppler) was observed in five subjects, but median resting precordial VGE was Grade 0 both days and VGE score at all sites were equal Days 1 and 3. In the experimental study, median resting precordial VGE was Grade 0 (Doppler) and Grade 1 (Scanner). VGE Grade III (Doppler) was observed in all series, but VGE scores were not significantly different between the series. We conclude that chamber attendants assisting HBO2 treatment at 240 kPa for approximately 115 min are exposed to a significant decompression stress using the profiles tested in the present study.

Adult↗
PubMed1998

Effect of oxygen tension and rate of pressure reduction during decompression on central gas bubbles.

Reduction in ascent speed and an increase in the O2 tension in the inspired air have been used to reduce the risk for decompression sickness. It has previously been reported that decompression speed and O2 partial pressure are linearly related for human decompressions from saturation hyperbaric exposures. The constant of proportionality K (K = rate/partial pressure of inspired O2) indicates the incidence of decompression sickness. The present study investigated the relationship among decompression rate, partial pressure of inspired O2, and the number of central gas bubbles after a 3-h dive to 500 kPa while breathing nitrox with an O2 content of 35 kPa. We used transesophageal ultrasonic scanning to determine the number of bubbles in the pulmonary artery of pigs. The results show that, for a given level of decompression stress, decompression rate and O2 tension in the inspired air can be traded off against each other by using pulmonary artery bubbles as an end point. The results also seem to confirm that decompressions that have a high K value are more stressful.

Animals↗
PubMed1989

Inspiratory flow limitation in divers.

Inspiratory dyspnea becomes an important factor in reducing a diver's ability to carry out physical work at depths in excess of 300 m. It is possible that dynamic compression of the trachea occurs when the intratracheal pressure drops below environmental pressure, thereby causing transient reduction in inspiratory flow. Vocal cords form an orifice of variable diameter, and orifice flow is predicted to occur at flow rates as low as 22 liter/min when gas density is 5 kg/m3 or more. Pressure drop across the vocal cords is calculated to range from 70 N/m2 at flow rate 1 liter/sec to 2.8 kN/m2 flow rate 4 liter/sec, aperture of the vocal cords 1.2 X 10(-2) m, gas density range 5-10 kg/m3. A smaller aperture, 0.6 X 10(-2) m, results in a pressure drop range 1.29-41.15 kN/m2 for the same flow rates and density range. Thus the transmural pressures that can occur are high enough to cause tracheal compression. At 300 m, gas density 5.9 kg/m3, 3 of 4 divers showed evidence of sudden inspiratory flow limitation.

Atmospheric Pressure↗
PubMed1988

A computer program to calculate mean skin temperature from measurements available from field trials.

Attempts to estimate mean skin temperature for subjects during prolonged experiments in field conditions are often made difficult because probes become disconnected or cease to function. There are several equations which allow estimation of mean skin temperature from a reduced number of functioning probes. The Fortran program described chooses the appropriate equation, calculates the mean skin temperature using whichever readings are available from the six selected sites and calculates mean body temperature using also rectal temperature. The organization of the program is such that it could easily be modified for use on results from a wide range of experimental conditions.

Electronic Data Processing↗
PubMed1983

An artificial circulation for the study of thrombolysis. The influence of flow rate and pressure on thrombolysis and a comparison between urokinase and tissue activator as thrombolytic agents.

The construction of an artificial circulation for the study of thrombolysis allowing variation in fluid pressure and flow rate is described. The lysis of 125I-fibrin was not influenced by variation in pressure between 10 and 30 cm H2O, but was significantly faster at a flow rate of 25 ml/min than at 40 ml/min or 10 ml/min. At equivalent concentrations as assessed on fibrin plates tissue activator induced greater thrombolysis than urokinase. Thrombolysis by both activators was diminished in the presence of plasma.

Animals↗
PubMed1980

Environmental and body temperatures of 52 divers in hyperbaric heliox.

Rectal and skin temperatures were recorded over periods as long as 24 h on 52 divers at depths as great as 300 m. Chamber temperature and body temperatures are correlated with depth, and the correlation between chamber temperature and mean skin temperature is evaluated. To ensure thermal balance daytime chamber temperatures must change with depth in meters according to the relationship Tch = 28.23 +/- (0.0058 x depth). Nighttime chamber temperatures must change according to the relationship Tch = 27.6 + (0.0074 x depth). Daytime rectal temperatures change significantly with depth in a way described by a 2nd-order regression line. The linear rate of change is 0.0014 degrees C/m increasing from a sea level value of 36.62 degrees C in heliox. Daytime mean body temperature increases with depth by 0.001 degrees C/m from 35.3 degrees C. Daytime mean skin temperatures very with chamber temperature at a rate of 0.34 degrees C/degrees C, which is identical to that found for an unclothed person in 1 ATA air.

Atmospheric Pressure↗