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ILLUMINATIONS

An Improved Model for Simulating Obstructive Lung Disease

Cátedra de Fisiología
Facultad de Ciencias Veterinarias
Universidad Nacional de La Plata
La Plata 1900, Argentina

Stephen E. DiCarlo

Department of Physiology
Wayne State University School of Medicine
Detroit, MI 48201
E-mail: sdicarlo{at}med.wayne.edu

Pulmonary function testing with the use of spirometers is useful for enhancing students' understanding of normal lung volumes, capacities, and flow rates. Furthermore, the spirogram can be an excellent tool for understanding how lung diseases alter pulmonary function parameters. For example, physiology programs at several schools have students determine their normal lung volumes, capacities, and flow rates by means of standard spirometry procedures (1). Subsequently, these programs have students simulate obstructive and restrictive lung diseases and repeat the procedures for pulmonary function testing. To simulate an obstructive impairment, a rubber stopper, with a small hole drilled through the center, is placed securely into the spirometer tubing. The stopper adds resistance to both inspiration and expiration, and the resulting spirogram closely resembles a typical obstructive curve (3). However, individuals with obstructive lung impairments experience less airflow resistance during the inspiratory phase due to the effects of radial traction and increased transmural pressure than during the expiratory phase. Importantly, the rubber stopper with the small hole drilled through the center adds equal resistance to both the inspiratory and expiratory phases. To address this concern, we modified the model so that students experience most of the resistance during expiration. The modification consists of altering a one-way valve [Rescuer, CPR Pro (2)] (Fig. 1). The original one-way valve had a small resistance to inflow (R_IF) provided by the radius of the opening in the valve and an infinite resistance to outflow (R_OF) provided by a stopper that blocked flow. By making a hole (with a smaller radius than the internal radius of the inflow valve, e.g., with a heated drill bit of 1/8-in. diameter) in the outflow stopper, outflow was allowed. In addition, it was important to block the valve side opening with glue from a glue gun (Fig. 1). Since the hole in the stopper was smaller than the radius of the inflow valve, it offered more resistance during expiration. Thus, R_OF was higher than R_IF (R_OF > R_IF). With this modification, students are able to feel the differences in resistance between inspiration and expiration (higher resistance during expiration, which simulates the pathological state). The spirometry exercise enhances students' understanding of pulmonary physiology and pathophysiology and allows them to experience the difficulty, discomfort, and apprehension associated with lung disease.

View larger version (130K): [in this window] [in a new window]   Fig. 1. Left: one-way valve with rubber stopper and side opening. The stopper prevents air from flowing out. Expired air passes through the side opening. Right: modified one-way valve with rubber stopper that now has a small hole to allow air to flow out. Note that the small hole in the rubber stopper is much smaller than the radius of the inflow opening. This modification provides significant resistance to expiration without adding resistance to inspiration. Also note that the side opening has been filled with glue from a glue gun.

	REFERENCES

TOP REFERENCES

 

1. Carroll RG. Design and evaluation of a national set of learning objectives: the medical physiology learning objectives project. Adv Physiol Educ 25: 74–79, 2001.[Medline]
2. CPR Pro. CPR-Pro.com. CPR Supplies: Replacement Valves For CPR Masks. Rescuer Replacement Valve for CPR Mask (online). http://www.cpr-pro.com/replacement_valve.html [19 February 2008].
3. Rodenbaugh DW, Collins HL, DiCarlo SE. Spirometry: simulations of obstructive and restrictive lung diseases. Adv Physiol Educ 26: 222–223, 2002.[Abstract/Free Full Text]

This Article Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Giuliodori, M. J. Articles by DiCarlo, S. E. Search for Related Content PubMed PubMed Citation Articles by Giuliodori, M. J. Articles by DiCarlo, S. E.