Pursed lips breathing (PLB), the breathing retraining technique that clinicians learned from their emphysema patients, was initially discouraged. We told our patients to stop working against themselves by creating this extra work to breathe. Eventually, we began to question our own advice. Clinical observation (sometimes clinical acumen) told us that PLB with its occasional audio accompaniment of irritating grunting noises and lip contortions added a measure of comfort to their struggle to breathe.
Theories and insightful descriptions appeared in the literature. Respiratory pioneer Alvan Barach1 in the late 1930s deduced that breathing against an external resistance helped to keep bronchiolar passages open to make way for alveolar emptying. Schmidt and colleagues2 determined that the effect of the back pressure of PLB was to slow exhalation so as to minimize small airway collapse via the Bernoulli effect, not to build alveolar driving pressure. Motley3 compared slow deep breathing with intermittent positive pressure breathing and found that both interventions improved SaO2 by increasing alveolar ventilation. Thoman et al4 determined that patients during PLB increased their tidal volume and reduced their breath rates, a consistent finding in most studies. Inherent in that finding is that it reduces VD/VT and thereby improves alveolar ventilation.
Mueller and coinvestigators5 concluded that PLB improved SaO2 and PaCO2 in both patients who felt the benefit and those who did not. Otherwise stated, the improvement in gas exchange is not necessarily linked to dyspnea relief. Tiep and colleagues6 specifically trained patients to increase their SpO2 via PLB by pulse oximetry biofeedback, a technique now widely incorporated in pulmonary rehabilitation programs. Pursed lips breathing may also be used as an adjunct to improve the effectiveness of oxygen therapy.7 The disconnect between SpO2 improvement and its ability to relieve dyspnea, coupled with the fact that PLB can raise SpO2 in patients with restrictive lung disease as well as normal subjects at altitude, suggests that a mechanism other than preventing airway collapse may be involved.
In considering ventilatory mechanics, there must be a balance between driving pressure of the chest wall and back pressure created by pursing lips. The expiratory airflow should not be so slow as to defeat the purpose of lowering end expiratory lung volume. Rodenstein and Stanescu8 showed that PLB may cause patients to inhale only through their nose and exhale entirely through the mouth. This may lower VD/VT and thus contribute to improved gas exchange. A summary of the mechanical effects of PLB would include but not be limited to slower expiratory flow, improved alveolar ventilation, a reduction in VD/VT, and an improvement in oxygenation and CO2 removal. Some of these factors are related to or emanate from the other.
Desirably, the greatest benefit of PLB should occur when it is incorporated during exercise where the limitation by hyperinflation becomes most pronounced. Patients with COPD become dyspneic during exertion, not at rest. Any intervention that can slow exhalatory flow during exertion will enable alveolar emptying and thereby create a mechanical advantage for the subsequent inhalation. Such known interventions include bronchodilators, oxygen, and exercise training itself.
Spahiji and Grassino9 demonstrated an improvement in lung mechanics for a given work rate (60% of VO2Max). Garrod et al10 determined that PLB during exercise lowers postexercise breath rate and accelerates recovery as compared with exercise with nonpursed lips. When trying to improve a patient's ability to function, dyspnea relief is an important goal. Bianchi and coinvestigators11 showed that PLB reduces dyspnea by both lengthening expiratory time and lengthening the full ventilatory cycle.
The present study from Nield and colleagues12 specifically trained patients during a 12-week period to lengthen their expiratory time in order to ameliorate exercise dyspnea. They compared training and reinforcing PLB versus applying an externally imposed resistance. They tested dyspnea at the end of the 6-minute walk test and showed that PLB rather than the externally applied resistance reduced the dyspnea sensation during exercise. Dyspnea is intimately associated with exercise limitation and their subjects were less dyspneic over time. Considering that PLB is taught differently in each setting, it would have been desirable if this study included changes in the end expiratory lung volume and exercise capacity to clarify that relationship. Also, because their patients trained using SpO26 and given its possible disconnect from the dyspnea benefit, changes in the SpO2 would have also added to our breadth of understanding. However, in an added lesson, this study highlighted the relevance of long-term training and reinforcement that is so necessary in the development of clinical skills.
The major difficulty presented by PLB studies is that there is no standard method of training. Lungs are complex structures. In the quest to gain understanding of the mechanisms involved and perhaps develop refinements of the technique, it is imperative that we understand impact of pressure, flow, and direction of gas travel within the airways. Confusion heightens because clinicians and researchers teach PLB differently. Some investigators focus on back pressures; others target expiratory flow; some teach patients to exhale beyond FRC, whereas still others set their sights on SpO2. For the purpose of gaining understanding of the mechanics involved, it is probably best that we are devoid of a generalized protocol; rather we should specify and measure pressure, volume, timing, gas exchange, and activity. We need to know whether air is flowing through the mouth or nose during inhalation because this can affect dead space.8 Future studies should separate the effect of breathing pattern, VD/VT, gas exchange, DLCO, and other variables to clarify the impact of breathing retraining methods on the complex and interactive physiology of normal and diseased respiratory apparatus.
1. Barach AL. Physiologic advantage of grunting, groaning and pursed lip breathing: adaptive symptoms related to the development of continuous positive pressure breathing. Bull NY Acad Med
2. Schmidt RW, Wasserman K, Lillington GA. The effect of air flow and oral pressure on the mechanics of breathing in patients with asthma and emphysema. Am Rev Respir Dis
3. Motley HL. The effects of slow deep breathing on the blood gas exchange in emphysema. Am Rev Respir Dis
4. Thoman RL, Stoker GL, Ross JC. The efficacy of pursed lips breathing in patients with chronic obstructive pulmonary disease. Am Rev Respir Dis
5. Mueller RE, Petty TL, Filley GF. Ventilation and arterial blood gas changes induced by pursed lips breathing. J Appl Physiol
6. Tiep BL, Burns M, Kao D, Herrera J, Madison R. Pursed lips breathing training using ear oximetry. Chest
7. Tiep BL, Burns M, Hererra J. A new pendant oxygen-conserving cannula which allows pursed lips breathing. Chest
8. Rodenstein DO, Stanescu DC. Absence of nasal air flow during pursed lips breathing. The soft palate mechanisms. Am Rev Respir Dis
9. Spahija JA, Grassino A. Effects of pursed-lips breathing and expiratory resistive loading in healthy subjects. J Appl Physiol
10. Garrod R, Dallimore K, Cook J, Davies V, Quade K. An evaluation of the acute impact of pursed lips breathing on walking distance in nonspontaneous pursed lips breathing chronic obstructive pulmonary disease patients. Chron Respir Dis
11. Bianchi R, Gigliotti F, Romagnoli I, et al. Chest wall kinematics and breathlessness during pursed-lip breathing in patients with COPD. Chest
12. Nield MA, Soo Hoo GW, Roper J, Santiago S. Efficacy of pursed-lips breathing: a breathing pattern retraining strategy for dyspnea reduction. J Cardiopulm Rehabil Prev