scholarly journals The ventilation of operating-theatres

1960 ◽  
Vol 58 (4) ◽  
pp. 449-464 ◽  
Author(s):  
O. M. Lidwell ◽  
R. E. O. Williams
Keyword(s):  
Nitrous Oxide ◽  
Bacterial Contamination ◽  
Heat Dissipation ◽  
Positive Pressure ◽  
Operating Team ◽  
Air Movement ◽  
Downward Displacement ◽  
Operating Theatres ◽  
Gaseous Tracer ◽  
Ventilation Systems

Measurements to assess the performance of the ventilating system have been carried out in a series of twenty six operating theatres using nitrous oxide as a gaseous tracer to simulate the movement of airborne bacterial contamination. In order to prevent local clouds of contamination derived from the activities of the operating-team persisting in the neighbourhood of the operating-site it is desirable that there should be appreciable air movement in the centre of the room. Downward displacement, ‘piston type’, ventilation systems may be an exception to this but the indications for their use are not clear. Other points discussed include the necessity for the limitation of the volume of mechanical exhaust if adequate positive pressure is to be maintained in the theatre and the need to control heat dissipation from sterilizers, autoclaves and other sources.

scholarly journals Negative pressure rooms and COVID-19

2020 ◽  
Vol 31 (1-2) ◽  
pp. 18-23
Author(s):  
Sammy Al-Benna
Keyword(s):  
Negative Pressure ◽  
Health Care Professionals ◽  
Healthcare Professionals ◽  
Clinical Care ◽  
Public Health Emergency ◽  
Positive Pressure ◽  
Global Pandemic ◽  
Operating Theatres ◽  
Novel Coronavirus ◽  
Surrounding Areas

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes 2019 novel coronavirus disease (COVID-19), has rapidly developed into a global pandemic and public health emergency. The transmission and virulence of this new pathogen have raised concern for how best to protect healthcare professionals while effectively providing care to the infected patient requiring surgery. Although negative pressure rooms are ideal for aerosol-generating procedures, such as intubation and extubation, most operating theatres are generally maintained at a positive pressure when compared with the surrounding areas. This article compares negative and positive pressure rooms and the advantages of a negative pressure environment in optimising clinical care and minimising the exposure of patients and health care professionals to SARS-CoV-2.

scholarly journals Effects of nitrous oxide on cardiovascular parameters in pigs anesthetized with propofol and subjected to pressure-controlled ventilation

2017 ◽  
Vol 38 (4) ◽  
pp. 2209
Author(s):  
Rodrigo Lima Carneiro ◽  
Patrícia Cristina Ferro Lopes ◽  
Ana Paula Gering ◽  
Eliselle Gouveia de Faria Biteli ◽  
Paloma Do Espírito Santo Silva ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Resistance Index ◽  
Compressed Air ◽  
Positive Pressure ◽  
Stroke Index ◽  
Cardiovascular Parameters ◽  
Controlled Ventilation ◽  
Pressure Controlled Ventilation ◽  
Bonferroni Test ◽  
Pressure Controlled

This paper evaluated the effects of the ratio of nitrous oxide to oxygen (50% of each) on cardiovascular parameters in pigs anesthetized with propofol and maintained in ventilation with intermittent positive pressure. Sixteen Large White pigs, weighing between 15 and 20 kg, were divided into two groups of eight animals, and designated as follows: GPN (propofol/nitrous oxide) and GPA (propofol/compressed air). In order to allow endotracheal intubation, the animals received azaperone (2 mg kg-1, IM) followed, after 20 minutes, by intravenous propofol. After successful intubation, continuous infusion of propofol was initiated at a dose of 0.4 mg kg-1minute-1. From this point, the GPN group received N2O (diluted in 50% oxygen), while the GPA group received compressed air (diluted in 50% oxygen). Rocuronium was then administered by continuous intravenous infusion at 0.6 mg kg-1h-1. Pressure-controlled ventilation (PCV) was started and adjusted to 15 cmH2O, and the respiratory rate was set to reach capnometry readings between 35-45 mmHg. The measurement of parameters (heart rate, mean arterial pressure, cardiac index, systemic vascular resistance index, stroke index) begun 15 minutes after the administration of rocuronium, and was repeated in 15-minute intervals for 60 minutes. Data were statistically analyzed by ANOVA followed by Bonferroni test. The results showed that the 1:1 ratio combination of nitrous oxide to oxygen (50% each) did not alter the mentioned parameters in pigs anesthetized with propofol and maintained at pressure-controlled ventilation, indicating that it is a safe protocol for the cardiovascular system.

scholarly journals Increases in Cuff Volume and Pressure in Red Rubber Endotracheal Tubes during Anaesthesia

1979 ◽  
Vol 7 (2) ◽  
pp. 152-157 ◽  
Author(s):  
W. R. Thompson ◽  
T. E. Oh
Keyword(s):  
Nitrous Oxide ◽  
Cuff Pressure ◽  
Intermittent Positive Pressure Ventilation ◽  
Spontaneous Respiration ◽  
Oxygen Mixture ◽  
Positive Pressure ◽  
Cuff Volume ◽  
Endotracheal Tubes ◽  
Nitrous Oxide Oxygen ◽  
Pressure Changes

Increases in endotracheal tube cuff volume and pressure during anaesthesia have been reported to be due to the diffusion of nitrous oxide into the cuff. This study compared cuff volume and pressure changes in anaesthetized intubated patients who were ventilated with those allowed to breath spontaneously. The cuffs of Magill red rubber endotracheal tubes were inflated with either air or a nitrous oxide-oxygen mixture. Serial pressure and volume recordings confirmed that both parameters increased when the cuff was inflated with air. The increase in cuff pressure was however, greater during intermittent positive pressure ventilation than for spontaneous respiration. There were no significant changes when the cuff was inflated with the nitrous oxide-oxygen mixture.

scholarly journals Ventilation conditions and air-borne bacteria and particles in operating theatres: proposed safe economies

1985 ◽  
Vol 95 (2) ◽  
pp. 325-335 ◽  
Author(s):  
R. P. Clark ◽  
P. J. Reed ◽  
D. V. Seal ◽  
M. L. Stephenson
Keyword(s):  
Ventilation Rate ◽  
Hospital Environment ◽  
Positive Pressure ◽  
Risk Of Infection ◽  
Flow Conditions ◽  
Increased Risk ◽  
Operating Theatres ◽  
Cleaning Procedures ◽  
Mechanical Cleaning ◽  
Zero Flow

SUMMARYConcentrations of air-borne bacteria and particles have been measured in turbulently ventilated operating theatres in full flow, half flow and zero flow conditions. Increased air-borne challenge produced by human activity and by mechanical cleaning procedures is demonstrated: die-away of this contamination is shown to be related to the ventilation rate. Ventilation can be reduced or turned off at night and during weekends, and cleaning can also be carried out, without increased risk of infection if full flow is restored one hour prior to preparation for surgery. Areas surrounding the theatres should remain at positive pressure with regard to the general hospital environment during low or no flow periods. The implementation of such energy-saving policies will substantially reduce theatre running costs without introducing infection hazards.

scholarly journals Transfer areas and clean zones in operating suites

1969 ◽  
Vol 67 (3) ◽  
pp. 417-425 ◽  
Author(s):  
G. A. J. Ayliffe ◽  
J. R. Babb ◽  
B. J. Collins ◽  
E. J. L. Lowbury
Keyword(s):  
Staphylococcus Aureus ◽  
Bacterial Contamination ◽  
Operating Theatre ◽  
Significant Difference ◽  
High Street ◽  
Operating Theatres ◽  
The Mean ◽  
Operating Suite ◽  
Total Bacteria

SUMMARYThe value of clean zones and of transfer areas in operating suites was assessed by comparisons of the amounts of contamination on floors, trolleys and footwear in suites with and without a clean zone and a transfer area; counts of Clostridium welchii were used as an index of bacterial contamination introduced into the aseptic zone from outside.The mean counts of Cl. welchii on contact plates from the wheels of trolleys used to convey patients from wards to the operating suite (67·9 ± 7·68 per plate) were significantly higher than those from theatre trolleys (i.e. those used only inside a theatre suite provided with a transfer area) (3·13 ± 0·47 per plate); mean counts of total bacteria were only slightly lower on the wheels of theatre trolleys than on those of hospital trolleys. Other surfaces of hospital trolleys showed counts similar to those found on theatre trolleys.Contact plates from floors showed significantly lower counts of Cl. welchii in the aseptic zone and the clean zone than in the hospital corridor, the protective zone and (when present) the transfer area.The mean counts per 100 cm2 of Cl. welchii were approximately the same on the floor of a theatre with a clean zone and a transfer area (0·83) as in one with a clean zone but no transfer area (0·5). Counts of total bacteria were higher in the latter. A suite with no clean zone or transfer area showed a higher mean count of Cl. welchii on contact plates from the aseptic zone (operating theatre) (20·5 ± 12·33 per 100 cm2). These higher levels of contamination were due to sporadic high counts of Cl. welchii found near the door of the theatre with no clean zone; in another theatre with no clean zone the level of Cl. welchii on the floor was not higher than that in the theatres with clean zones.Theatres with plenum ventilation had lower mean counts of airborne Cl. welchii than those ventilated by windows: there was no significant difference in the levels of Cl. welchii on the floors of theatres with the two forms of ventilation.On sampling with contact plates, theatre footwear yielded fewer total organisms, Staphylococcus aureus and Cl. welchii than outdoor shoes removed before entering the clean zone.The hygienic value of transfer areas and clean zones is discussed. Bacteriological support could not be obtained for the former, but the latter appeared to contribute something to the cleanliness of the theatre by preventing heavy sporadic contamination.We wish to thank Mr M. Wilkins for valuable assistance, the staff of the operating theatres for their co-operation and Alne Engineering Limited, 57 High Street, Henley-in-Arden, Solihull, for supplying disposable contact plates.

scholarly journals Ward floors and other surfaces as reservoirs of hospital infection

1967 ◽  
Vol 65 (4) ◽  
pp. 515-536 ◽  
Author(s):  
G. A. J. Ayliffe ◽  
B. J. Collins ◽  
E. J. L. Lowbury ◽  
J. R. Babb ◽  
H. A. Lilly
Keyword(s):  
Bacterial Contamination ◽  
Hospital Infection ◽  
Staph Aureus ◽  
Air Movement ◽  
Large Numbers ◽  
Equilibrium Level ◽  
Rapid Accumulation ◽  
Floor Surfaces ◽  
Contaminated Area

Impression plates from initially clean horizontal surfaces and floor areas in surgical wards showed a rapid accumulation of bacteria, mainly micrococci, which reached a fluctuating equilibrium after about 24 h. A later increase in bacterial contamination (mainly with aerobic sporing bacilli) to a higher equilibrium level after about 14 days occurred on uncleaned areas. Walls, even if left unwashed, acquired very few bacteria, but many were deposited locally when the wall was touched by a subject whose skin carried large numbers of staphylococci; moist exposed plaster was also heavily contaminated.Regular use of a disinfectant (‘Sudol’ 1 in 100) in cleaning a ward floor did not reduce the equilibrium level of bacteria on the floor.The transfer of staphylococci from contaminated to clean areas on the soles of shoes was demonstrated; the use of tacky and disinfectant mats did not appreciably reduce the transfer of bacteria by this route.Staphylococci deposited on a wall by a disperser were shown to be transferred from the contaminated area of wall to the hands of another subject who did not previously carry the organism; this subject was shown to transfer the staphylo-coccus to a wall which he touched.Attempts to redisperse by air movementStaph. aureuswhich had been shed by a disperser or by a contaminated blanket on to the floor surfaces had little effect; neither blowing with a hair dryer nor brisk exercise appeared to lift any of the staphylococci from a vinyl surface, and only small numbers were lifted by these measures from a terrazzo surface.The hazards of infection from the inanimate environment are discussed.

The influence of nitrous oxide anaesthetic on middle-ear fluid

1978 ◽  
Vol 92 (2) ◽  
pp. 131-135 ◽  
Author(s):  
James O. Shaw ◽  
Earl W. Stark ◽  
Stephen D. Gannaway
Keyword(s):  
Nitrous Oxide ◽  
Eustachian Tube ◽  
Middle Ear ◽  
Positive Pressure ◽  
Middle Ear Fluid ◽  
Nitrous Oxide Anaesthesia ◽  
Oxide Anaesthesia

AbstractNITROUS OXIDE anaesthesia invades the middle-ear cavity, resulting in a positive pressure within this cavity. It has been suggested that the pressure may be sufficient to force open the Eustachian tube and evacuate fluid from the middle ear. This study examined the possible influence of nitrous oxide on middle-ear fluid. Pre- and intra-operative tympanograms were obtained on 39 children scheduled for myringotomy surgery. Fluid was found in 83-1 per cent of the operated ears while the absence of fluid was noted in 16-9 per cent. It is possible that the nitrous oxide anaesthetic did cause an evacuation of fluid from this latter group of ears prior to actual surgery.

A Preliminary Study of the Spark Characteristics for Unconventional Cylinder Charge With Strong Air Movement

2011 ◽  
Author(s):  
Shui Yu ◽  
Kelvin Xie ◽  
Xiaoye Han ◽  
Marko Jeftic ◽  
Tongyang Gao ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Heat Dissipation ◽  
Discharge Voltage ◽  
Spark Discharge ◽  
Gas Velocity ◽  
Electrode Gap ◽  
Movement Condition ◽  
Air Movement ◽  
Discharge Duration ◽  
Flow Velocities

Detailed fundamental understanding of spark discharge under strong air movement condition is crucial to optimize the ignition systems for stratified charge engines. In this paper, extensive bench tests of spark discharge under strong air movement condition are conducted by means of both optical and electrical diagnosis. Strong correlations between the physical structures of spark plasma channel and the gas velocity are found in this paper. The spark heat dissipation distance, the plasma stretched distance and the plasma area under various flow velocities are analyzed. The resistance between the electrode gaps is increased with the enhancement of flow velocity. As a result, the discharge voltage is enhanced, while the discharge duration is shortened. When the flow velocity is enhanced substantially, restrikes of spark discharge are observed. The increasing rate of the discharge voltage before the first restrike is found to be a 2-order polynomial relation to the gas velocity. With the enhancement of flow velocity, the delivered discharge energy increases linearly at the velocity below 25m/s, while it tends to be maintained at the higher flow velocities. Both the increase of the electrode gap size and the flow velocity shorten the spark discharge duration.

scholarly journals The ProSeal Laryngeal Mask in Myasthenia Gravis

2002 ◽  
Vol 30 (5) ◽  
pp. 671-674 ◽  
Author(s):  
S. V. Gardner ◽  
N. R. Evans
Keyword(s):  
Nitrous Oxide ◽  
Laryngeal Mask Airway ◽  
Myasthenia Gravis ◽  
Positive Pressure Ventilation ◽  
Muscle Relaxants ◽  
Laryngeal Mask ◽  
Positive Pressure ◽  
Axillary Lymph ◽  
Remifentanil Infusion ◽  
Axillary Lymph Node Clearance

This case describes the anaesthesia management of a patient with myasthenia gravis who required mastectomy with axillary lymph node clearance. After withholding medical therapy for the myasthenia preoperatively on the day of surgery, anaesthesia was maintained with halothane, nitrous oxide and a remifentanil infusion. Muscle relaxants were avoided, facilitated by the use of a ProSeal (Intravent, Orthofix, Maidenhead, United Kingdom) laryngeal mask airway for positive pressure ventilation. The ProSeal laryngeal mask airway is a new laryngeal mask device with a modified cuff and a drainage tube which has been shown to have advantages over older designs for use during positive pressure ventilation. The rationale for the management of this patient with myasthenia is discussed.

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