Comparative evaluation of the hygienic efficacy of an ultra-rapid hand dryer vs conventional warm air hand dryers

Aims: To compare an ultra‐rapid hand dryer against warm air dryers, with regard to: (A) bacterial transfer after drying and (B) the impact on bacterial numbers of rubbing hands during dryer use. Methods and Results: The Airblade? dryer (Dyson Ltd) uses two air ‘knives’ to strip water from still hands, whereas conventional dryers use warm air to evaporate moisture whilst hands are rubbed together. These approaches were compared using 14 volunteers; the Airblade? and two types of warm air dryer. In study (A), hands were contaminated by handling meat and then washed in a standardized manner. After dryer use, fingers were pressed onto foil and transfer of residual bacteria enumerated. Transfers of 0–10⁷ CFU per five fingers were observed. For a drying time of 10 s, the Airblade? led to significantly less bacterial transfer than the other dryers (P < 0·05; range 0·0003–0·0015). When the latter were used for 30–35 s, the trend was for the Airblade to still perform better, but differences were not significant (P > 0·05, range 0·1317–0·4099). In study (B), drying was performed ± hand rubbing. Contact plates enumerated bacteria transferred from palms, fingers and fingertips before and after drying. When keeping hands still, there was no statistical difference between dryers, and reduction in the numbers released was almost as high as with paper towels. Rubbing when using the warm air dryers inhibited an overall reduction in bacterial numbers on the skin (P < 0·05). Conclusions: Effective hand drying is important for reducing transfer of commensals or remaining contaminants to surfaces. Rubbing hands during warm air drying can counteract the reduction in bacterial numbers accrued during handwashing. Significance and Impact of the Study: The Airblade? was superior to the warm air dryers for reducing bacterial transfer. Its short, 10 s drying time should encourage greater compliance with hand drying and thus help reduce the spread of infectious agents via hands.     

A microbiological evaluation of warm air hand driers with respect to hand hygiene and the washroom environment

A finger rinse technique for counting micro-organisms on hands showed no significant difference in the level of recovered micro-organisms following hand drying using either warm air or paper towels. Contact plate results appeared to reflect the degree of dampness of hands after drying rather than the actual numbers of micro-organisms on the hands. In laboratory tests, a reduction in airborne count of Pseudomonas aeruginosa and Staphylococcus aureus of between 40 and 75% was achieved from 600 readings comparing inlets and outlets of warm air hand driers. In washroom trials, the number of airborne micro-organisms was reduced by between 30 and 75%. Air emitted from the outlet of the driers contained significantly fewer micro-organisms than air entering the driers. Drying of hands with hand driers was no more likely to generate airborne micro-organisms than drying with paper towels. Levels of micro-organisms on external surfaces of hand driers were not significantly different to those on other washroom surfaces. This work shows that warm air hand driers, of the type used in this study, are a hygienic method of drying hands and therefore appropriate for use in both the healthcare and food industry.     

Effect of phentolamine on the relationship between O2 consumption and delivery in sheep.

The oxygen flux challenge test (OFT) has recently been used in critically ill patients as a dynamic test for assessment of the response in oxygen consumption (VO2) to an increase in O2 delivery (QO2). Such a test may indicate whether a patient demonstrates delivery-dependent VO2. However, the increase in whole body VO2 following an increase of QO2 might be due to the agents used for the OFT. In this study, we examined the possibility of obtaining false positive OFT with an alpha-adrenergic antagonist. Five normothermic thiopentone-anaesthetised and mechanically-ventilated (inspired O2 fraction, 0.3; expired CO2 fraction, 0.045-0.055) adult sheep (25-31 kg) were investigated. The QO2 was increased in a stepwise fashion from 200 to 850 ml.min-1 by vasodilatation with intravenous infusion of phentolamine. The VO2 was calculated at each step from the product of arteriovenous. O2 content difference (CO2, a-v) and cardiac output (Qc), the latter being continuously measured with a transit-time ultrasonic flow probe placed around the main pulmonary artery. The VO2 (y) was linearly related to QO2 (x), y = 0.034 (SD 0.024) x + 29.3 (SD 3.9). The relationship between Qc (y) and CO2, a-v (x) was y = 4.6x(-1.12) (n = 69; r2 = 0.75; P = NS compared to the expected relationship for isoconsumption conditions, i.e. where Qc = VO2.(CO2, a-v)(-1). Our data suggested that under stable conditions, an infusion of phentolamine did not sufficiently alter the relationship between Qc and CO2, a-v to invalidate its use for OFT in normal sheep.     

Effect of flow on O2 consumption during progressive hypoxemia

Rabbit hindlimb preparations perfused with blood from donor rabbits were used to determine whether O2 consumption (VO2) during hypoxemia is limited by total O2 transport (TO2) or by capillary O2 driving pressure, as reflected by the venous PO2 (PVO2). The preparations were randomized into two groups: low flow (LF) and high flow (HF), perfused at 18 and 32 ml.min-1.kg of preparation wt-1, respectively. After a 1-h base-line period with arterial PO2 (PaO2) greater than 100 Torr, both groups were exposed to progressive decrements in PaO2 to less than 10 Torr. Sequential sets of arterial and venous blood gases were obtained, and VO2, TO2, and O2 extraction ratio (ERO2) were calculated. A plot of PVO2 vs. TO2 showed higher levels of PVO2 (P less than 0.05) in LF than HF, when compared at similar levels of TO2. Therefore the experimental protocol allowed the comparison of the separate effects of TO2 or PVO2 on VO2. Plotting VO2 as a function of TO2 revealed two distinct curves (P less than 0.05), with LF having a greater VO2 than HF at a given TO2. Conversely, a plot of VO2 as a function of PVO2 did not show a difference between the groups. The ERO2 of LF was greater than HF when compared at similar levels of TO2 (P less than 0.05). We conclude from these data that during progressive hypoxemia VO2 appears to be primarily limited by factors that determine capillary O2 diffusion. This conclusion supports the Kroghian theory of capillary O2 exchange.     

Muscle O(2) consumption by NIRS: a theoretical model.

In the past, the measurement of O(2) consumption ((2)) by the muscle could be carried out noninvasively by near-infrared spectroscopy from oxyhemoglobin and/or deoxyhemoglobin measurements only at rest or during steady isometric contractions. In the present study, a mathematical model is developed allowing calculation, together with steady-state levels of (2), of the kinetics of (2) readjustment in the muscle from the onset of ischemic but aerobic constant-load isotonic exercises. The model, which is based on the known sequence of exoergonic metabolic pathways involved in muscle energetics, allows simultaneous fitting of batched data obtained during exercises performed at different workloads. A Monte Carlo simulation has been carried out to test the quality of the model and to define the most appropriate experimental approach to obtain the best results. The use of a series of experimental protocols obtained at different levels of mechanical power, rather than repetitions of the same load, appears to be the most suitable procedure.     

Effect of duration of exercise on excess postexercise O2 consumption

This study was undertaken to determine the effect of exercise duration on the time course and magnitude of excess postexercise O2 consumption (EPOC). Six healthy male subjects exercised on separate days for 80, 40, and 20 min at 70% of maximal O2 consumption on a cycle ergometer. A control experiment without exercise was performed. O2 uptake, respiratory exchange ratio (R), and rectal temperature were monitored while the subjects rested in bed 24 h postexercise. An increase in O2 uptake lasting 12 h was observed for all exercise durations, but no increase was seen after 24 h. The magnitude of 12-h EPOC was proportional to exercise duration and equaled 14.4 +/- 1.2, 6.8 +/- 1.7, and 5.1 +/- 1.2% after 80, 40, and 20 min of exercise, respectively. On the average, 12-h EPOC equaled 15.2 +/- 2.0% of total exercise O2 consumption (EOC). There was no difference in EPOC:EOC for different exercise durations. A linear decrease with exercise duration was observed in R between 2 and 24 h postexercise. No change was observed in recovery rectal temperature. It is concluded that EPOC increases linearly with exercise duration at a work intensity of 70% of maximal O2 consumption.     

Effects of moderate hypothermia on O2 consumption at various O2 deliveries in a sheep model.

The effects of modest hypothermia on oxygen consumption (VO2) were studied at various levels of oxygen delivery (DO2) in six sheep. Each animal was placed on cardiopulmonary bypass by extrathoracic cannulations. DO2 was varied by changing blood flow through an extracorporeal circuit. VO2 was measured spirometrically across a membrane lung. VO2 was initially measured at various levels of DO2 at normothermic temperatures (39 degrees C). The animals were then cooled to 33 degrees C. DO2 was varied, and the corresponding VO2's were determined. The data at both temperatures demonstrated the biphasic relationship of VO2 to various levels of DO2. A critical level of DO2 (DO2 crit) was defined to reflect the transition area between the dependent and independent portions of the consumption-delivery curve. The average baseline VO2's on the delivery independent portion of the curve were calculated to be 5.33 and 3.17 ml O2.kg-1.min-1 at 39 and 33 degrees C, respectively (P less than 0.001). The corresponding DO2 crit's were 6.17 and 4.57 ml O2.kg-1.min-1 (P less than 0.05). The oxygen extraction ratios at DO2 crit for each of these temperatures did not differ significantly. We conclude that hypothermia, by lowering baseline VO2, reduces DO2 crit. Hypothermia may therefore reduce or eliminate the anaerobic metabolism and subsequent acidosis that would otherwise occur during normothermia at low levels of DO2.     

Effect of beta-blockade on the drift in O2 consumption during prolonged exercise

The effect of beta-adrenergic blockade on the drift in O2 consumption (VO2 drift) typically observed during prolonged constant-rate exercise was studied in 14 healthy males in moderate heat at 40% of maximal O2 consumption (VO2max). After an initial maximum cycle ergometer test to determine the subjects' control VO2max, subjects were administered each of three medications: placebo, atenolol (100 mg once daily), and propranolol (80 mg twice daily), in a randomized double-blind fashion. Each medication period was 5 days in length and was followed by a 4-day washout period. On the 3rd day of each medication period, subjects performed a maximal cycle ergometer test. On the final day of each medication period, subjects exercised at 40% of their control VO2max for 90 min on a cycle ergometer in a warm (31.7 +/- 0.3 degrees C) moderately humid (44.7 +/- 4.7%) environment. beta-Blockade caused significant (P less than 0.05) reductions in VO2max, maximal minute ventilation (VEmax), maximal heart rate (HRmax), and maximal exercise time. Significantly greater decreases in VO2max, VEmax, and HRmax were associated with the propranolol compared with the atenolol treatment. During the 90-min submaximal rides, beta-blockade significantly reduced heart rate. Substantially lower values for O2 consumption (VO2) and minute ventilation (VE) were observed with propranolol compared with atenolol or placebo. Furthermore, VO2 drift and HR drift were observed under atenolol and placebo conditions but not with propranolol. Respiratory exchange ratio decreased significantly over time during the placebo and atenolol trials but did not change during the propranolol trial.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Siberian tree species on N2O production and consumption

The effect of six Siberian tree species on two stages of denitrification—N₂O production and consumption—was studied. Broadleaf species (aspen and birch) proved to have lower rates of N₂O consumption compared to coniferous species. The factors influencing production and consumption of N₂O were also evaluated. The replacement of coniferous forests with broadleaf trees will double the N₂O/N₂ ratio in the denitrification end-products. Doubled N₂O emission from Siberian forest soils to the atmosphere can be expected due to changes in tree species composition of forest ecosystems even without considering changes in water and temperature regimes in soil.     

Effect in vivo of atrazine on haematology and O2 consumption in fish, Tilapia mossambica.

Studies were conducted on haematological constituents such as Red blood cells (RBC), White blood cells (WBC), Haemoglobin (Hb), Packed cell volume (PCV), Mean cell volume (MCV), Mean corpuscular haemoglobin (MCH), Mean corpuscular haemoglobin concentration (MCHC), Blood volume (BV), Blood water content (BWC) and Whole animal oxygen consumption (WAOC) in the fish exposed to sublethal concentration of atrazine. Significant changes were seen in the constituents of the blood and O2 consumption of fish suggesting the existence of respiratory distress in the fish as a consequence of atrazine toxicity.     

Effect of cold and warm dry air hyperventilation on canine airway blood flow

Tracheobronchial blood flow increases with cold air hyperventilation in the dog. The present study was designed to determine whether the cooling or the drying of the airway mucosa was the principal stimulus for this response. Six anesthetized dogs (group 1) were subjected to four periods of eucapnic hyperventilation for 30 min with warm humid air [100% relative humidity (rh)], cold dry air (-12 degrees C, 0% rh), warm humid air, and warm dry air (43 degrees C, 0% rh). Five minutes before the end of each period of hyperventilation, tracheal and central airway blood flow was determined using four differently labeled 15-micron diam radioactive microspheres. We studied another three dogs (group 2) in which 15- and 50-micron microspheres were injected simultaneously to determine whether there were any arteriovenous communications in the bronchovasculature greater than 15 micron diam. After the last measurements had been made, all dogs were killed, and the lungs, including the trachea, were excised and blood flow to the trachea, left lung bronchi, and parenchyma was calculated. Warm dry air hyperventilation produced a consistently greater increase in tracheobronchial blood flow (P less than 0.01) than cold dry air hyperventilation, despite the fact that there was a smaller fall (6 degrees C) in tracheal tissue temperature during warm dry air hyperventilation than during cold dry air hyperventilation (11 degrees C), suggesting that drying may be a more important stimulus than cold for increasing airway blood flow. In group 2, the 15-micron microspheres accurately reflected the distribution of airway blood flow but did not always give reliable measurements of parenchymal blood flow.     

Effect of separate hemidiaphragm contraction on left phrenic artery flow and O2 consumption

Phrenic arterial blood flow has been shown to increase during bilateral phrenic nerve stimulation (BPNS). However, the role of unilateral phrenic nerve stimulation [left (LPNS) or right (RPNS)] on the blood flow and O2 consumption of the contralateral hemidiaphragm is not known and is explored here. In six anesthetized, mechanically hyperventilated dogs, left phrenic arterial blood flow (Qlpha) was measured (Doppler technique). Supramaximal (10 V, 30 Hz, 0.25-ms duration) LPNS, RPNS, and BPNS at a pacing frequency 15/min and duty cycle of 0.50 were delivered in separate runs. Left hemidiaphragmatic blood samples for gas analyses were obtained by left phrenic venous cannulation. During RPNS, Qlpha and left hemidiaphragmatic O2 consumption (VO2ldi) did not change significantly compared with control. During LPNS and BPNS, there was a significant increase in Qlpha and VO2ldi (P less than 0.01). There was no significant difference in Qlpha and VO2ldi between LPNS and BPNS (P greater than 0.05). We conclude 1) that there is a complete independence of left-right hemidiaphragmatic circulation both at rest and during diaphragm pacing and 2) that during unilateral stimulation transdiaphragmatic pressure is not related to diaphragmatic blood flow.     

Dependency of the O2 consumption/O2 transport relationship on amino acid supply in sepsis

Summary In sepsis tissue O₂ uptake may be abnormally limited because of a depressed O₂ consumption/O₂ transport relationship. This study has been performed to assess patterns of O₂ consumption, CO₂ production and O₂ transport in septic patients undergoing total parenteral nutrition; more in particular, this study has investigated the interdependence between the patterns of blood O₂ uptake and simultaneous CO₂ release, and the availability of substrates (amino acids, glucose and fat). It has been shown that the O₂ consumption/O₂ transport relationship is significantly influenced by the exogenous amino acid load, which tends to increase O₂ uptake and O₂ consumption at any given O₂ transport, thus suggesting a favourable effect of amino acid administration on energy metabolism. The data on CO₂ production and CO₂ release, in addition to reconfirming the results of previous studies, have shown that the changes in O₂ uptake and in CO₂ production mediated by substrate doses have a quantifiable impact on blood O₂-CO₂ exchange interactions.     

Effect of ibuprofen and indomethacin on the O2 supply/consumption balance in ischemic rabbit myocardium

The purpose of this study was to determine if differences in the cardioprotective abilities of ibuprofen and indomethacin were due to their differing abilities to alter the O2 supply/consumption ratio in the ischemic myocardium. Experiments were done on 21 anesthetized open-chest rabbits. Regional flow (using radioactive microspheres), O2 extraction, O2 consumption, and O2 supply/consumption ratio were determined 1 hr after occlusion of the left anterior descending coronary artery in controls and animals given iv 10 mg/kg ibuprofen or iv 3 mg/kg indomethacin. Myocardial blood flow was depressed in the occluded region compared to the nonoccluded region after occlusion for all treatments. O2 extraction in the occluded region was elevated compared to the nonoccluded region for all treatments after occlusion. No differences in O2 consumption were noted between any treatment within the occluded or nonoccluded regions. The O2 supply/consumption ratio was lower in the occluded region compared to the nonoccluded region for all treatments. No differences in this ratio were noted between any treatment. Thus, the effects of indomethacin or ibuprofen on ischemia are not related to acute changes in myocardial O2 supply/consumption balance.