In the operating room, attention naturally focuses on surgical technique, antibiotic prophylaxis or instrument asepsis. Yet a far more discreet factor can also influence patient safety: the comings and goings of staff.
Why every door opening matters
A door that opens for a few seconds seems harmless. Yet from the standpoint of hospital airflow engineering, this opening disrupts a carefully designed balance meant to protect the surgical field. For about thirty years, numerous studies have assessed the consequences of door openings on the microbiological quality of the air and on the risk of surgical site infection (SSI).
The literature now shows that, while the direct relationship with infections remains difficult to demonstrate because SSIs are multifactorial, the physical and microbiological mechanisms are well established.
The operating room: a controlled environment
Operating rooms are designed to limit contamination of the surgical site as much as possible. Several systems contribute to this objective:
- air filtration through HEPA filters;
- ventilation with a high air-change rate;
- positive pressure relative to adjacent rooms;
- in some rooms, unidirectional (laminar) airflow above the surgical field;
- an organisation that limits sources of contamination.
The goal is simple: to prevent particles carrying bacteria from settling on operated tissues or implants.
Why does opening a door change the environment?
An operating room is kept under slight positive pressure. This pressure difference creates a permanent movement of air from the room towards the corridor, preventing the entry of potentially contaminated air.
When a door is opened, several phenomena occur simultaneously:
- a transient drop in positive pressure;
- air exchange between the two rooms;
- the appearance of turbulence;
- deflection of the unidirectional airflow;
- re-suspension of particles present on the floor or on clothing;
- possible entry of air from the corridor.
Even when the door is quickly closed again, it takes several seconds to return to a stable ventilation regime.
Particles: the main vector for bacteria
The air itself is rarely infectious. Bacteria, however, are transported by particles:
- skin squames;
- textile fibres;
- microscopic dust.
Each team member releases several thousand particles per minute, even when wearing appropriate attire. Movement further increases this emission through friction of clothing and re-suspension of particles deposited on the floor.
Human traffic is thus one of the main determinants of airborne contamination.
What does the literature show?
Clearly demonstrated airflow disturbances
Studies using gas tracers, pressure measurements or numerical simulations all show that opening a door disrupts air circulation. The observed effects include:
- a drop in differential pressure;
- increased turbulence;
- alteration of the protective airflow trajectories;
- an increase in particle concentration.
These results are found both in conventional rooms and under unidirectional airflow.
An increase in microbiological contamination
Several teams have shown that repeated door openings are accompanied by an increase in:
- the number of particles;
- colony-forming units (CFU/m³);
- contamination of surfaces close to the surgical field.
The number of people present in the room is also strongly correlated with this contamination.
The link with surgical site infections
This is the most important question. Surgical site infections depend simultaneously on many factors:
- the patient’s underlying condition;
- diabetes;
- obesity;
- smoking;
- antibiotic prophylaxis;
- operative duration;
- hypothermia;
- glycaemic control;
- surgical technique;
- the presence of an implant.
Isolating the specific effect of door openings is therefore difficult. Nevertheless, several observational studies suggest an association between heavy traffic and an increase in SSIs, particularly in cardiac and orthopaedic surgery.
A recent meta-analysis covering more than 4,000 patients found a statistically significant increase in SSI risk when the frequency of door openings rises. The individual effect is modest, but it becomes potentially significant when openings are numerous during long procedures.
How many openings are observed?
The figures reported in the literature are often surprising. Depending on the specialty:
- 20 to 50 openings per procedure are common;
- some surgeries exceed 100 openings;
- more than 200 openings have been reported during long procedures.
In several studies, nearly half of these openings were considered avoidable. The main causes were:
- forgotten equipment;
- searching for an implant;
- requests for documents;
- conversations;
- non-essential traffic;
- phone calls.
A problem that goes beyond infection risk alone
Reducing traffic does not only protect against airborne contamination. Each entry or exit also represents:
- a cognitive interruption;
- a distraction for the team;
- a break in concentration;
- an increase in noise;
- a decline in communication quality.
The human-factors literature shows that these interruptions can contribute to organisational errors, independently of infection risk.
How can unnecessary openings be reduced?
The most effective quality-improvement approaches rely above all on organisation. Among the most effective measures:
- prepare all equipment before incision;
- carry out a complete preoperative briefing;
- check implants and consumables;
- limit the number of people present;
- designate an outside runner who can bring in equipment without multiplying movements;
- regularly raise team awareness;
- audit the number of door openings per procedure;
- feed the results back to the teams.
Some teams have achieved a reduction of more than 50% in traffic simply through regular audits and feedback.
What do international guidelines say?
The main professional societies are consistent. The World Health Organization (WHO), the US CDC, AORN and the UK NHS guidelines all stress the need to:
- keep doors closed as much as possible;
- limit unnecessary movement;
- prepare the procedure before it begins;
- preserve the performance of the ventilation system.
Although no guideline sets a maximum number of door openings, the principle is clear: every opening should meet a genuine need.
Conclusion
Unnecessary entries and exits in the operating room are probably not, on their own, the cause of a surgical site infection. They do, however, disrupt an environment designed to minimise microbial contamination.
The available data consistently show that repeated door openings increase the particulate and bacterial contamination of the air. Clinical studies also suggest an association with surgical site infections, even if the effect remains modest when analysed in isolation.
Because this is an avoidable risk factor, inexpensive to correct and directly related to the organisation of care, limiting entries and exits is today a common-sense measure, supported by international guidelines and by an increasingly solid body of scientific literature.
✅ Key takeaways
- ✓ Door openings disrupt positive pressure and the protective airflow.
- ✓ They increase the concentration of airborne particles and bacteria.
- ✓ Staff movement is a major source of airborne contamination.
- ✓ A significant share of the openings observed is avoidable.
- ✓ Reducing traffic improves both infection-risk control and human factors in the operating room.
🇫🇷 Une version française de cet article est disponible : Les entrées et sorties inutiles au bloc opératoire : un facteur de risque infectieux sous-estimé ?
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