Medical Hypotheses 83 (2014) 733–734
Contents lists available at ScienceDirect
Medical Hypotheses journal homepage: www.elsevier.com/locate/mehy
Accuracy of pulmonary auscultation to detect abnormal respiratory mechanics: A cross-sectional diagnostic study Glaciele Nascimento Xavier a,b,⇑, Antonio Carlos Magalhães Duarte c, César Augusto Melo-Silva d, Carlos Eduardo Ventura Gaio dos Santos e, Veronica Moreira Amado e a
Laboratory of Respiratory Physiology, University of Brasília, Brasília, Brazil Instituto de Cardiologia do Distrito Federal, Brasília, DF, Brazil Centro de Integração Funcional, Salvador, Bahia, Brazil d Department of Rehabilitation, Hospital Universitário de Brasília, Brasília, Brazil e Laboratory of Respiratory Physiology, University of Brasília, Brasília, Brazil b c
a r t i c l e
i n f o
Article history: Received 12 May 2014 Accepted 28 September 2014
a b s t r a c t Pulmonary auscultation is a method used in clinical practice for the evaluation and detection of abnormalities relating to the respiratory system. This method has limitations, as it depends on the experience and hearing acuity of the examiner to determine adventitious sounds. In this context, it’s important to analyze whether there is a correlation between auscultation of lung sounds and the behavior of the respiratory mechanical properties of the respiratory system in patients with immediate postoperative cardiac surgery. Ó 2014 Elsevier Ltd. All rights reserved.
Introduction Lung auscultation performed with a stethoscope is a widely used test in clinical practice by health professionals, as it is noninvasive, practical, cheap and able to detect abnormalities of the respiratory system [1–3]. However, this method has limitations due to being a subjective tool, requiring a high level of experience and good hearing ability from health professionals to detect adventitious sounds [4,5]. Studies show a low to moderate agreement between different examiners, even with experienced examiners. This finding has important implications because lung auscultation is a diagnostic tool that is often used to define therapeutic approaches [4,5]. The nomenclature for lung sounds is nonspecific and not standardized. In this manner, studies requiring a standardized terminology for lung sounds analysis have been published [2]. The lung sounds are divided into normal lung sounds and adventitious sounds. The presence of adventitious sounds indicates abnormalities in the respiratory system, in the airway or in the lung parenchyma [4]. The normal range of lung sounds are classified into three different levels of frequency, low (100 < 300 Hz), medium
⇑ Corresponding author at: Laboratory of Respiratory Physiology, University of Brasília, Campus Darcy Ribeiro, Brasília, DF 70910-900, Brazil. Tel.: +55 61 96067941. E-mail address: [email protected] (G.N. Xavier). http://dx.doi.org/10.1016/j.mehy.2014.09.029 0306-9877/Ó 2014 Elsevier Ltd. All rights reserved.
(300 < 600 Hz) and high (600 < 1200 Hz) [4]. The origin of these sounds is related to air turbulence at the level of lobar or segmental bronchi [4]. Crackles are discontinuous, explosive and short sounds that usually arise in cardiorespiratory and infectious diseases. They originate from small airways and might indicate the presence of secretion or airways closing and reopening within 20 ms or less, with a frequency between 100 and 2000 Hz or more [6–8]. Wheezing sounds are continuous and high frequency; they originate in central and peripheral airways and suggest airflow limitation and airway obstruction. The duration is greater than 100 ms, and the frequency is usually above 100 Hz [4,9]. Rhonchus are sounds that suggest secretion and come from large airways. They last longer than 100 ms, with a frequency often lower than 300 Hz [4]. Routinely, health professionals who work in intensive care units (ICU) use auscultation for the assessment of their patients, commonly using the presence of adventitious sounds to define the therapeutic approach. Some studies show that, in addition to auscultation, other parameters should be evaluated at the time of clinical or respiratory therapy decisions in ICUs [4,10,11]. The presence of adventitious sounds without changes in mechanical properties of the respiratory system, in oxygenation or in ventilation cannot be criteria for a therapeutic approach, such as lung expansion therapy, clearance therapy or bronchodilator therapy [4].
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G.N. Xavier et al. / Medical Hypotheses 83 (2014) 733–734
Patients undergoing cardiac surgery frequently present dysfunction and pulmonary complications, including changes in respiratory mechanics. It’s believed that the occurrences of these complications have multifactorial origins, with the Cardiopulmonary bypass (CPB) having the highest impact factor [12–17]. Cardiopulmonary bypass is the largest cause of morbidity in this kind of surgery. The CPB is responsible for the development of the systemic inflammatory response syndrome due to blood contact with the surface of the CPB circuit, triggering the activation of the complement system and release of proinflammatory cytokines IL-6, IL-8 and TNF-a, causing an increasing in vascular permeability and leakage of fluid into the pulmonary interstitium [12,13]. In the lungs, these changes will lead to decreased production of alveolar surfactant and reduced diffusing capacity of the alveolar membrane blood, contributing to the atelectasis, shunt, reduced lung capacity and lung compliance [18,19].
Conclusion Considering that the diseases affecting the respiratory system can lead to changes in respiratory mechanics, it’s necessary to clarify whether the presence of adventitious sounds during auscultation will be able to diagnose an increased respiratory system impedance, determined by increasing resistance and/or decreasing respiratory system compliance. Due to the large number of pulmonary complications and their impact on morbidity and mortality in patients undergoing cardiac surgery, it’s necessary to evaluate the accuracy of auscultation in this population to determine its real value in order to develop a functional diagnosis, as well as a therapeutic decision. Conflicts of interest None declared. Financial support
Hypothesis Not applicable. Although, pulmonary auscultation is a test routinely used for the assessment, monitoring and characterization for clinical interventions in mechanically ventilated patients in the ICU, there is no evidence of any correlation between auscultated adventitious sounds and mechanical properties of the respiratory system in the immediate postoperative period of cardiac surgery. Furthermore, it is unclear whether such lung sounds are able to diagnose an increase of resistance and decrease of static compliance of the respiratory system.
Testing the hypothesis To analyze the correlation between observers, two health professionals with experience in critical care patients will perform the lung auscultation. The examiners will be blind to the responses from each other and to the values found. The mechanical properties of the respiratory system will be assessed by the rapid end-inspiratory occlusion method described by Bates et al. [20]. In this method, the patient under mechanical ventilation with constant volume and flow undergoes an occlusion at the end of inspiration, leading to an inspiratory pause with a rapid decrease in tracheal pressure from a maximum value, the peak inspiratory airway pressure (Ppeak), to a point of inflection (DP1, Rs), and then a slow decline (DP2, Rs) until a plateau is reached. DP1 reflects the energy dissipation in the resistive component of the respiratory system and DP2 the dissipation in viscoelastic components, jointly with pendelluft. Plateau pressure is represented by the elastic recoil pressure of the respiratory system. The correlation between auscultation and changes in respiratory mechanics will be determined as follows: 1. Wheezing and/or rhonchus associated with increased respiratory system resistance. 2. Crackles and abolition/reduction of normal lung sound resulting in decreased respiratory system compliance.
References [1] Murphy RL. In defense of the stethoscope. Respir Care 2008;53:355–69. [2] Bohadana A, Izbicki G, Kraman SS. Fundamentals of lung auscultation. N Engl J Med 2014;370:744–51. [3] Hoffmann C, Falzone E, Verret C, Pasquier P, Leclerc T, Donat N, et al. Brief report: pulmonary auscultation in the operating room: a prospective randomized blinded trial comparing electronic and conventional stethoscopes. Anesth Analg 2013;117:646–8. [4] Marques A, Bruton A, Barney A, Hall A. Are crackles an appropriate outcome measure for airway clearance therapy? Respir Care 2012;57:1468–75. [5] Brooks D, Thomas J. Interrater reliability of auscultation of breath sounds among physical therapists. Phys Ther 1995;75:1082–8. [6] Murphy RL, Sorensen K. Chest auscultation in the diagnosis of pulmonary asbestosis. J Occup Med 1973;15:272–6. [7] Piirilä P, Sovijärvi AR. Crackles: recording, analysis and clinical significance. Eur Respir J 1995;8:2139–48. [8] Epler GR, Carrington CB, Gaensler EA. Crackles (rales) in the interstitial pulmonary diseases. Chest 1978;73:333–9. [9] Scott G, Presswood EJ, Makubate B, Cross F. Lung sounds: how doctors draw crackles and wheeze. Postgrad Med J 2013. [10] Hess DR. The evidence for secretion clearance techniques. Respir Care 2001;46:1276–93. [11] Pasterkamp H, Kraman SS, Wodicka GR. Respiratory sounds. Advances beyond the stethoscope. Am J Respir Crit Care Med 1997;156:974–87. [12] Ng CS, Wan S, Yim AP, Arifi AA. Pulmonary dysfunction after cardiac surgery. Chest 2002;121:1269–77. [13] Groeneveld AB, Jansen EK, Verheij J. Mechanisms of pulmonary dysfunction after on-pump and off-pump cardiac surgery: a prospective cohort study. J Cardiothorac Surg 2007;2:11. [14] Zin WA, Caldeira MP, Cardoso WV, Auler Jr JO, Saldiva PH. Expiratory mechanics before and after uncomplicated heart surgery. Chest 1989;95:21–8. [15] Wynne R, Botti M. Postoperative pulmonary dysfunction in adults after cardiac surgery with cardiopulmonary bypass: clinical significance and implications for practice. Am J Crit Care 2004;13:384–93. [16] Zin WA. Basic research on respiratory mechanics related to anaesthesia and critical care. Minerva Anestesiol 2000;66:603–9. [17] Gropper MA, Sasaki N, Meyer MJ, Eikermann M. Postoperative respiratory muscle dysfunction: only the strong survive. Postoperative respiratory muscle dysfunction: pathophysiology and preventive strategies. Anesthesiology 2013;118:783–4. [18] Rodrigues AC, Moreira LF, de Souza CL, Pettersen PC, Saldiva PH, Zin WA. Effects of thoracotomy on respiratory system, lung, and chest wall mechanics. Chest 1993;104:1882–6. [19] Duggan M, Kavanagh BP. Pulmonary atelectasis: a pathogenic perioperative entity. Anesthesiology 2005;102:838–54. [20] Bates JH, Rossi A, Milic-Emili J. Analysis of the behavior of the respiratory system with constant inspiratory flow. J Appl Physiol 1985;58:1840–8.
Contents lists available at ScienceDirect
Medical Hypotheses journal homepage: www.elsevier.com/locate/mehy
Accuracy of pulmonary auscultation to detect abnormal respiratory mechanics: A cross-sectional diagnostic study Glaciele Nascimento Xavier a,b,⇑, Antonio Carlos Magalhães Duarte c, César Augusto Melo-Silva d, Carlos Eduardo Ventura Gaio dos Santos e, Veronica Moreira Amado e a
Laboratory of Respiratory Physiology, University of Brasília, Brasília, Brazil Instituto de Cardiologia do Distrito Federal, Brasília, DF, Brazil Centro de Integração Funcional, Salvador, Bahia, Brazil d Department of Rehabilitation, Hospital Universitário de Brasília, Brasília, Brazil e Laboratory of Respiratory Physiology, University of Brasília, Brasília, Brazil b c
a r t i c l e
i n f o
Article history: Received 12 May 2014 Accepted 28 September 2014
a b s t r a c t Pulmonary auscultation is a method used in clinical practice for the evaluation and detection of abnormalities relating to the respiratory system. This method has limitations, as it depends on the experience and hearing acuity of the examiner to determine adventitious sounds. In this context, it’s important to analyze whether there is a correlation between auscultation of lung sounds and the behavior of the respiratory mechanical properties of the respiratory system in patients with immediate postoperative cardiac surgery. Ó 2014 Elsevier Ltd. All rights reserved.
Introduction Lung auscultation performed with a stethoscope is a widely used test in clinical practice by health professionals, as it is noninvasive, practical, cheap and able to detect abnormalities of the respiratory system [1–3]. However, this method has limitations due to being a subjective tool, requiring a high level of experience and good hearing ability from health professionals to detect adventitious sounds [4,5]. Studies show a low to moderate agreement between different examiners, even with experienced examiners. This finding has important implications because lung auscultation is a diagnostic tool that is often used to define therapeutic approaches [4,5]. The nomenclature for lung sounds is nonspecific and not standardized. In this manner, studies requiring a standardized terminology for lung sounds analysis have been published [2]. The lung sounds are divided into normal lung sounds and adventitious sounds. The presence of adventitious sounds indicates abnormalities in the respiratory system, in the airway or in the lung parenchyma [4]. The normal range of lung sounds are classified into three different levels of frequency, low (100 < 300 Hz), medium
⇑ Corresponding author at: Laboratory of Respiratory Physiology, University of Brasília, Campus Darcy Ribeiro, Brasília, DF 70910-900, Brazil. Tel.: +55 61 96067941. E-mail address: [email protected] (G.N. Xavier). http://dx.doi.org/10.1016/j.mehy.2014.09.029 0306-9877/Ó 2014 Elsevier Ltd. All rights reserved.
(300 < 600 Hz) and high (600 < 1200 Hz) [4]. The origin of these sounds is related to air turbulence at the level of lobar or segmental bronchi [4]. Crackles are discontinuous, explosive and short sounds that usually arise in cardiorespiratory and infectious diseases. They originate from small airways and might indicate the presence of secretion or airways closing and reopening within 20 ms or less, with a frequency between 100 and 2000 Hz or more [6–8]. Wheezing sounds are continuous and high frequency; they originate in central and peripheral airways and suggest airflow limitation and airway obstruction. The duration is greater than 100 ms, and the frequency is usually above 100 Hz [4,9]. Rhonchus are sounds that suggest secretion and come from large airways. They last longer than 100 ms, with a frequency often lower than 300 Hz [4]. Routinely, health professionals who work in intensive care units (ICU) use auscultation for the assessment of their patients, commonly using the presence of adventitious sounds to define the therapeutic approach. Some studies show that, in addition to auscultation, other parameters should be evaluated at the time of clinical or respiratory therapy decisions in ICUs [4,10,11]. The presence of adventitious sounds without changes in mechanical properties of the respiratory system, in oxygenation or in ventilation cannot be criteria for a therapeutic approach, such as lung expansion therapy, clearance therapy or bronchodilator therapy [4].
734
G.N. Xavier et al. / Medical Hypotheses 83 (2014) 733–734
Patients undergoing cardiac surgery frequently present dysfunction and pulmonary complications, including changes in respiratory mechanics. It’s believed that the occurrences of these complications have multifactorial origins, with the Cardiopulmonary bypass (CPB) having the highest impact factor [12–17]. Cardiopulmonary bypass is the largest cause of morbidity in this kind of surgery. The CPB is responsible for the development of the systemic inflammatory response syndrome due to blood contact with the surface of the CPB circuit, triggering the activation of the complement system and release of proinflammatory cytokines IL-6, IL-8 and TNF-a, causing an increasing in vascular permeability and leakage of fluid into the pulmonary interstitium [12,13]. In the lungs, these changes will lead to decreased production of alveolar surfactant and reduced diffusing capacity of the alveolar membrane blood, contributing to the atelectasis, shunt, reduced lung capacity and lung compliance [18,19].
Conclusion Considering that the diseases affecting the respiratory system can lead to changes in respiratory mechanics, it’s necessary to clarify whether the presence of adventitious sounds during auscultation will be able to diagnose an increased respiratory system impedance, determined by increasing resistance and/or decreasing respiratory system compliance. Due to the large number of pulmonary complications and their impact on morbidity and mortality in patients undergoing cardiac surgery, it’s necessary to evaluate the accuracy of auscultation in this population to determine its real value in order to develop a functional diagnosis, as well as a therapeutic decision. Conflicts of interest None declared. Financial support
Hypothesis Not applicable. Although, pulmonary auscultation is a test routinely used for the assessment, monitoring and characterization for clinical interventions in mechanically ventilated patients in the ICU, there is no evidence of any correlation between auscultated adventitious sounds and mechanical properties of the respiratory system in the immediate postoperative period of cardiac surgery. Furthermore, it is unclear whether such lung sounds are able to diagnose an increase of resistance and decrease of static compliance of the respiratory system.
Testing the hypothesis To analyze the correlation between observers, two health professionals with experience in critical care patients will perform the lung auscultation. The examiners will be blind to the responses from each other and to the values found. The mechanical properties of the respiratory system will be assessed by the rapid end-inspiratory occlusion method described by Bates et al. [20]. In this method, the patient under mechanical ventilation with constant volume and flow undergoes an occlusion at the end of inspiration, leading to an inspiratory pause with a rapid decrease in tracheal pressure from a maximum value, the peak inspiratory airway pressure (Ppeak), to a point of inflection (DP1, Rs), and then a slow decline (DP2, Rs) until a plateau is reached. DP1 reflects the energy dissipation in the resistive component of the respiratory system and DP2 the dissipation in viscoelastic components, jointly with pendelluft. Plateau pressure is represented by the elastic recoil pressure of the respiratory system. The correlation between auscultation and changes in respiratory mechanics will be determined as follows: 1. Wheezing and/or rhonchus associated with increased respiratory system resistance. 2. Crackles and abolition/reduction of normal lung sound resulting in decreased respiratory system compliance.
References [1] Murphy RL. In defense of the stethoscope. Respir Care 2008;53:355–69. [2] Bohadana A, Izbicki G, Kraman SS. Fundamentals of lung auscultation. N Engl J Med 2014;370:744–51. [3] Hoffmann C, Falzone E, Verret C, Pasquier P, Leclerc T, Donat N, et al. Brief report: pulmonary auscultation in the operating room: a prospective randomized blinded trial comparing electronic and conventional stethoscopes. Anesth Analg 2013;117:646–8. [4] Marques A, Bruton A, Barney A, Hall A. Are crackles an appropriate outcome measure for airway clearance therapy? Respir Care 2012;57:1468–75. [5] Brooks D, Thomas J. Interrater reliability of auscultation of breath sounds among physical therapists. Phys Ther 1995;75:1082–8. [6] Murphy RL, Sorensen K. Chest auscultation in the diagnosis of pulmonary asbestosis. J Occup Med 1973;15:272–6. [7] Piirilä P, Sovijärvi AR. Crackles: recording, analysis and clinical significance. Eur Respir J 1995;8:2139–48. [8] Epler GR, Carrington CB, Gaensler EA. Crackles (rales) in the interstitial pulmonary diseases. Chest 1978;73:333–9. [9] Scott G, Presswood EJ, Makubate B, Cross F. Lung sounds: how doctors draw crackles and wheeze. Postgrad Med J 2013. [10] Hess DR. The evidence for secretion clearance techniques. Respir Care 2001;46:1276–93. [11] Pasterkamp H, Kraman SS, Wodicka GR. Respiratory sounds. Advances beyond the stethoscope. Am J Respir Crit Care Med 1997;156:974–87. [12] Ng CS, Wan S, Yim AP, Arifi AA. Pulmonary dysfunction after cardiac surgery. Chest 2002;121:1269–77. [13] Groeneveld AB, Jansen EK, Verheij J. Mechanisms of pulmonary dysfunction after on-pump and off-pump cardiac surgery: a prospective cohort study. J Cardiothorac Surg 2007;2:11. [14] Zin WA, Caldeira MP, Cardoso WV, Auler Jr JO, Saldiva PH. Expiratory mechanics before and after uncomplicated heart surgery. Chest 1989;95:21–8. [15] Wynne R, Botti M. Postoperative pulmonary dysfunction in adults after cardiac surgery with cardiopulmonary bypass: clinical significance and implications for practice. Am J Crit Care 2004;13:384–93. [16] Zin WA. Basic research on respiratory mechanics related to anaesthesia and critical care. Minerva Anestesiol 2000;66:603–9. [17] Gropper MA, Sasaki N, Meyer MJ, Eikermann M. Postoperative respiratory muscle dysfunction: only the strong survive. Postoperative respiratory muscle dysfunction: pathophysiology and preventive strategies. Anesthesiology 2013;118:783–4. [18] Rodrigues AC, Moreira LF, de Souza CL, Pettersen PC, Saldiva PH, Zin WA. Effects of thoracotomy on respiratory system, lung, and chest wall mechanics. Chest 1993;104:1882–6. [19] Duggan M, Kavanagh BP. Pulmonary atelectasis: a pathogenic perioperative entity. Anesthesiology 2005;102:838–54. [20] Bates JH, Rossi A, Milic-Emili J. Analysis of the behavior of the respiratory system with constant inspiratory flow. J Appl Physiol 1985;58:1840–8.
