Pulmonary Function Measures
Lung volumes during different phases of breathing are used to assess the effects of pathology on ventilation. Remember, ventilation is the volume of air that moves in and out of the airways. PTs and PTAs teach patients interventions that aim to increase air in and improve the force by which air flows out, therefore foundational knowledge in pulmonary function measures provides some insight into the major barriers to ventilation (e.g. restrictive versus obstructive) and how lung volume measures compare to normal values. Measuring pulmonary function is accomplished through spirometry and is typically performed by Respiratory Care.
Shortness of breath is a sign that ventilation is insufficient to meet the oxygen demands of the activity. This can present at rest with advanced lung disease, and after exertion during mild to high intensity exercise and activity. In patients with pulmonary impairments, breathing rate is closely monitored as an indicator of exercise intensity and tolerance. Shortness of breath is one of the indicators of Work of Breathing (WOB).
Airway tissue resistance, elasticity, and compliance are major factors in respiration. PTs and PTAs apply knowledge of respiratory muscle function, posture, and breathing mechanics to optimize pressures for inspiration and exhalation, which can result in improved gas exchange. The video below provides a brief, yet thorough explanation of pulmonary function measures. You should be able to identify the variables in calculating:
- Total Lung Capacity (TLC)
- Vital Capacity (VC)
- Inspiratory Capacity (IC)
- Functional Residual Capacity (FRC)
Active Learning Exercise
As you view the video below, try how you can volitionally assess your own inspiratory capacity and your expiratory reserve. What muscles are you engaging to maximally inhale and maximally exhale?
Critical thinking question: Why do interventions to increase inspiratory capacity positively affect ventilation and respiration? Try your answers in the CAN YOU HELP ME? forum.
Incentive Spirometry
- Incentive spirometry (IS) is a bedside intervention used by a number of disciplines based on a clinical theory that its use decreases risk of post-operative pulmonary embolus or post-operative pulmonary complications due to changes in functional lung capacity
- Respiratory Care refers to this preventative intervention as a form of "Hyperinflation Therapy" and there are protocols that continue to be applied in hospital settings to guide decision-making in the use of IS
- Visual feedback and goal setting to reach a target volume and inhalation control is presumed to provide "incentive" to open alveolar space and optimize respiration
- Best practice is to use incentive spirometry with early mobilization and airway clearance techniques.
- Systematic literature reviews suggest mixed findings on the benefits of using incentive spirometry in a number of post operative situations (Freitas, Soares, Cardoso & Atallah, 2012; Restrepo, Wettstein, Wittnebel, Tracy, 2011).
Freitas, E. R., Soares, B. G., Cardoso, J. R., & Atallah, Á. N. (2012, September). Incentive spirometry for preventing pulmonary complications after coronary artery bypass graft. Cochrane Database of Systematic Reviews (9). doi 10.1002/14651858.CD004466.pub3.
Restrepo, R. D., Wettstein, R., Wittnebel, L., & Tracy, M. (2011). Incentive spirometry: 2011. Respiratory care, 56(10), 1600-1604.