Exhaled air dispersion during bag-mask ventilation and sputum suctioning - Implications for infection control

Abstract

Mask ventilation and coughing during oro-tracheal suctioning produce aerosols that enhance nosocomial transmission of respiratory infections. We examined the extent of exhaled air dispersion from a human-patient-simulator during mask ventilation by different groups of healthcare workers and coughing bouts. The simulator was programmed to mimic varying severity of lung injury. Exhaled airflow was marked with tiny smoke particles, and highlighted by laser light-sheet. We determined the normalized exhaled air concentration in the leakage jet plume from the light scattered by smoke particles. Smoke concentration ≥20% was considered as significant exposure. Exhaled air leaked from mask-face interface in the transverse plane was most severe (267 ± 44 mm) with Ambu silicone resuscitator performed by nurses. Dispersion was however similar among anesthesiologists/intensivists, respiratory physicians and medical students using Ambu or Laerdal silicone resuscitator, p = 0.974. The largest dispersion was 860 ± 93 mm during normal coughing effort without tracheal intubation and decreased with worsening coughing efforts. Oro-tracheal suctioning reduced dispersion significantly, p < 0.001, and was more effective when applied continuously. Skills to ensure good fit during mask ventilation are important in preventing air leakage through the mask-face interface. Continuous oro-tracheal suctioning minimized exhaled air dispersion during coughing bouts when performing aerosol-generating procedures.

Figure 1

Bag-mask ventilation performed by an anaesthesiologist using (A) Laerdal silicone resuscitator (left panel) and the calculated normalized concentration of the smoke particle in the transverse plane of the expiration port (right panel); (B) Ambu silicone resuscitator and (C) Ambu silicone resuscitator with addition of a breathing filter, respectively.

Figure 2

Results of exhaled air dispersion in the sagittal plane during normal, mild and poor coughing efforts generated by short bursts of oxygen flow at 650, 320, and 220 L/min, respectively, in a human patient simulator with continuous (panels A–C), intermittent oral suctioning (panels D–F) and without oral suctioning (panels G–I).

Figure 3

Results of exhaled air dispersion in the sagittal plane during normal, mild and poor coughing efforts generated by short bursts of oxygen flow at 650, 320, and 220 L/min, respectively, in a human patient simulator following tracheal intubation with (panels A–C) and without tracheal suctioning (panels D–F).

Figure 4

Changes of dispersion distances of exhaled air in the median sagittal plane during normal, mild and poor cough before and after oro-tracheal suction in a human patient simulator with and without tracheal intubation. Box and whiskers plot: the upper and lower edges of the boxes indicate the interquartile ranges, the line through box is the median value, the whiskers are the 5% and 95% centiles and the closed circles are outliers.

Figure 5

Experimental setup of bag-mask ventilation (top panel). Exhaled air dispersion highlighted by the laser light sheet during bag-mask ventilation (lower panel) with (A) Laerdal silicone resuscitator, (B) Ambu silicone resuscitator and (C) Ambu silicone resuscitator with the addition of a breathing filter on the human patient simulator.

Figure 6

Experimental setup to evaluate coughing through a tracheal tube during tracheal suctioning. The human patient simulator was positioned in the supine position. Exhaled air plume was indicated with intrapulmonary smoke and was revealed by laser light sheet in the sagittal plane (shown with the green section/arrows). Images were captured by high-definition camera positioned in a perpendicular position (red area) for data analysis.