Aseptic techniques for lung function testing

Journal of Hospital Infection (1981) 2, 369-372

Aseptic techniques for lung function testing M. H. Depledge

and A. Barrett

The Institute of Cancer Research and The Royal Marsden Hospital, Downs Road, Sutton, Surrey Summary: Immuno-incompetent patients may be exposed to an unacceptably high risk of cross-infection when undergoing lung function tests using conventional equipment. Sites of contamination include mouthpieces, nose clips and spirometer bellows. Equipment modifications and disinfection procedures are described which are simple to implement and which effectively minimize this risk. Introduction

In patients with immuno-deficiency disorders or in those who have received immuno-suppressive treatment for malignant disease, recurrent acute or chronic respiratory tract infections are a significant cause of morbidity and mortality (Polmar, 1976). If lung function tests are performed there is a risk of cross-infection from contaminated equipment. We have developed aseptic procedures to monitor the respiratory physiology of patients with acute myeloid leukaemia (AML) treated with cytoreductive chemotherapy, total body irradiation (TBI) and bone marrow transplantation (BMT) (Barrett, Barrett and Powles, 1979). This has enabled functional changes associated with subclinical idiopathic pneumonitis, radiation fibrosis and graft-versus-host disease (GvHD) to be investigated with a low risk of cross-infection (Depledge and Barrett, in prep.). Materials

and methods

Routine lung function tests measure total lung capacity (TLC), ventilatory ability and gas transfer. TLC is usually determined with a whole body plethysmograph (Cotes, 1979) but in our patients is measured by a radiographic technique in which lung volumes are computed from posterior and lateral chest X-rays taken at maximum inspiration (Pierce et al., 1979). No contact with equipment is involved. Standard spirometry is used to assess ventilatory ability but the equipment has been modified as shown in Figure 1. Direct connection with the wedge bellows is avoided by patients breathing in and out of a disposable plastic bag contained within a bell jar. As the bag is inflated by forced expiration, air is driven from the bell jar into the spirometer. During forced inspiration the bag collapses and air is drawn out of the spirometer. Changes in flow and volume are automatically transmitted from the transducers to a microprocessor and plotted as flow-volume loops. Nose clips, disposable mouth pieces and plastic bags are replaced after each test and the or95-67~~1/81/040369

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connecting tube chemically disinfected with O-5 per cent chlorhexidine in alcohol. Diffusing capacity (DLCO) and accessible alveolar volume (VA) are measured using a single breath technique (Cotes, 1979) on a conventional respirameter (PK Morgan). The sterile rubber mouth piece is autoclaved after use and the mouth piece tube, rotary valve and vent tubes washed with 0.5 per cent chlorhexidine in alcohol. Wedge spirometer

i ece

ble

Figure 1. A modified wedge spirometer

for sterile lung function testing.

Special attention is paid to maintaining the cleanliness of the lung function laboratory. The floors and benches are washed thoroughly with dilute chlorhexidine detergent weekly after 10 to 15 tests. Paper towels are used to dry all surfaces. These precautions are desirable when testing profoundly immunosuppressed bone marrow transplant recipients. However, for other patients thorough cleaning is likely to be adequate. Cleanliness of the equipment was assessed by swabbing various sites before and after lung function testing and then again after washing with disinfectant (chlorhexidine, 0.5 per cent in alcohol). Results The results of lung function tests on patients after BMT will be reported elsewhere. Confirmation that inclusion of the ‘bag-in-the-bell jar’ in the spirometer system does not influence flow-volume loops was obtained by testing 15 control subjects. Each volunteer performed consecutive forced expiratory and inspiratory manoeuvres using the spirometer conventionally and then in the modified version. Flow-volume loops were superimposable. Assessment of decontamination procedures Swabs were taken from the equipment at the sites shown in Figure 2a and b. No micro-organisms were at any time cultured from sites 2, 3, 5, 7 or 8. Sites 1 and 6 (the mouth pieces of the spirometer and respirameter) yielded scanty growths of Staphylococcus aureus, Staph. albus and Corynebacteria spp. immediately after use but washing with chlorhexidine and autoclaving the rubber mouth pieces rendered the equipment sterile again. Occasionally, Staph. aurem was cultured from site 4 at the neck of the connecting tube but washing with chlorhexidine effectively decontaminated the tube. Swabs from nose clips invariably yielded growths of Staph. aureus and they were therefore autoclaved after use.

Lung function

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Initial investigations over a period of 3 months indicated that decontamination procedures were satisfactory and only spot checks (every 1 to 3 weeks) are now performed. In the last 2 years there have been no positive cultures from sites 2, 3, 5, 7 and 8 after use of the equipment and only rarely from site 4. (b)

piece

Fi~re 2. Swab sites. (a) Bag in bell jar system; (b) respirameter. Cleanliness

of the laboratory

No attempt was made to maintain aseptic conditions in the laboratory but it was thought that clean conditions might reduce the number of potential pathogens. When settle plates were left in the laboratory for 3 h periods at various times during a routine working day the number of bacterial and fungal colonies increased from 11 between 0900-1200 h to 19 between 1100-1400 h, the period of maximum activity in the laboratory. From plates exposed between 1300-1600 h nine colonies were cultured. No major pathogens (e.g. Clostridia, Klebsiella, etc.) were isolated. Similarly, laboratory dust yielded colonies of common bacteria and fungi but no pathogens. Discussion

The risks of cross-infection among immuno-competent patients performing lung function tests have never been accurately assessed. Houston, Parry and Smith (1981) investigated the bacterial pathogens isolated from the unsterilized tube and spirometer bellows of a Vitalograph used by 1000 patients over a 4 week period. The commonest organisms were: Acinetobacter spp., Flavo-bacterium spp., Staph. albus, Streptococcus spp. and a variety of fungi. The major potential pathogen was K. pneum0nLz-e. The isolation of pathogenic bacteria from the test equipment suggests that aseptic techniques may be advisable for immuno-suppressed patients. Routine lung function laboratories are testing increasing number of immunosuppressed patients who have received chemotherapy for malignant diseases or organ or bone marrow transplants. The techniques described above are simple and reduce the risk of cross-infection without affecting the accuracy of measurements. We should like to thank Dr B. Jameson the manuscript.

for her helpful

advice and Miss Carol Parr for typing

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and A. Barrett

References Cotes, J. E. (1979). Measurement of the transfer factor for the lung. In Lung FunctionAssessment and Application in Medicine, 4th edn, pp. 230-250. Blackwell Scientific Publication, London. Barrett, A., Barrett, A. J. & Powles, R. L. (1979). Total body irradiation and marrow transplantation for acute leukaemia. Pathologie Siologie 27, 357-359. Houston, K., Parry, P. & Smith, A. P. (1981). Have you looked into your spirometer recently? Breath 12, 10-l 1. Pierce, R. J., Brown, D. J., Holmes, M., Cumming, G. & Denison, D. M. (1979). Estimation of lung volumes from chest radiographs using shape information. Thorax 34,726-734. Polmar, S. II. (1976). Immunologic and infectious reactions in the lung, Vol. 1 (Kirkpatrick, C. & Reynolds, H. Y., Eds), pp. 191-209. Dekker, New York.