Prophylactic respiratory physiotherapy after cardiac surgery

Prophylactic respiratory physiotherapy after cardiac surgery Patrick Pasquina; Martin R Tramèr, MD, D. Phil; Bernhard Walder, MD Divisions of Surgical Intensive Care (Mr Pasquina) and Anaesthesia (Drs Tramèr and Walder), Department APSIC (Anaesthesia, Pharmacology & Surgical Intensive Care), Geneva University Hospitals, Geneva, Switzerland It is well established that pulmonary function deteriorates in patients after cardiac surgery and that these patients are prone to pulmonary complications. Postoperative pulmonary complications increase hospital morbidity, prolong hospital stay and contribute to additional healthcare costs. 1 For improved understanding of the potential benefit of prophylactic respiratory physiotherapy after cardiac surgery, four issues need to be addressed. First, what is the impact of cardiac surgery on pulmonary function? Second, what are the mechanisms of pulmonary changes after cardiac surgery? Third, what postoperative pulmonary complications are relevant to the patients? And fourth, can respiratory physiotherapy prevent patientrelevant pulmonary complications after cardiac surgery? 1. what is the impact of cardiac surgery on pulmonary function? 1.1. Pulmonary function tests Patients after cardiac surgery have a marked reduction in vital capacity and forced expiratory volume in one second. On the second postoperative day, when impairment of pulmonary function tests is maximal, vital capacity and forced expiratory volume in one second are about 30% only of preoperative values. 2,3 At the eighth postoperative day, pulmonary function is still about 70% compared with preoperative values. 2 Thus, at hospital discharge, most patients have not yet returned to normal daily activity and their quality of life may still be reduced. 1.2. Radiographic changes Radiographic pulmonary abnormalities vary in function of the type of cardiac surgery; they are more frequent on the left side of the chest radiograph. 4 For instance, left-sided pulmonary alterations were reported in 88% of patients undergoing left internal mammary artery grafting or left pleurotomy (73% atelectasis, 11% infiltrates, 55% effusions). 4 After saphenous vein grafting or valvular surgery, left-sided alterations were observed in 68% of the patients (54% atelectasis, 3% infiltrates, 35% effusions). 4 No data are available on the duration of these radiographic changes. 1.3. Changes of partial pressure of arterial oxygen After cardiac surgery, partial pressure of arterial oxygen (PaO2) is decreased. The impairment in oxygen exchange is most pronounced on the second postoperative day and is still 997

present on the eighth day. 2,5 Therefore, supplementation of oxygen is highly recommended during the postoperative period, particularly during night time. 2. What are the Mechanims of Pulmonary changes after cardiac surgery? Many pulmonary complications seem to be related to disruption of the normal activity of the respiratory muscles, disruption that begins with the induction of anaesthesia and that continues into the postoperative period. Different mechanisms impair the function of respiratory muscles after cardiac surgery. 2.1 Anaesthetics Anaesthetics affect the central regulation of breathing, changing the neural drive to respiratory muscles such as the diaphragm. They reduce the efficiency of the muscles activity inducing hypoventilation and subsequent atelectasis. The effect of anaesthetics may persist into the early postoperative period. 2.2 Phrenic nerve dysfunction Diaphragmatic impairment with atelectasis due to phrenic nerve dysfunction is a well recognised complication of heart surgery. Although several factors have been implicated in this dysfunction, most cases are either due to cold injury or direct damage to the nerve. This nerve dysfunction may persist for many days. 2.3 Chest wall deformation During surgery, the deformation of the chest wall alters the underlying lung, decreasing functional residual capacity and producing atelectases in dependent lungs regions. These intraoperative changes may continue to persist in the postoperative period. 2.4. Surgical trauma Surgical trauma generates multiple impairment of postoperative ventilatory function: disruption of respiratory muscles through incisions, postoperative pain with voluntary limitation of respiratory muscle use, and stimulation of the central nervous system with reflex inhibition of the phrenic and other nerves that are innervating respiratory muscles. These mechanisms lead to a decrease in functional residual and vital capacity for many days, and to atelectases. In an animal study, atelectasis was shown to promote bacterial growth in the lung related to reduced function of alveolar macrophage and reduced functional surfactant, explaining potentially the occurrence of pneumonia. 16 3. What postoperative pulmonary complications are relevant to the patients? A large variety of postoperative pulmonary complications have been reported in clinical studies. However, a few only are clinically relevant, and for most, there are several definitions. 998 Patrick Pasquina, Martin R. Tramèr, D. Phil, Bernhard Walder

3.1 Pneumonia Pneumonia is clearly an outcome that makes a difference to the patient. However, unfortunately, there are different definitions of postoperative pneumonia. Some authors have used the Centre for Disease Control (CDC) criteria involving various combinations of clinical, radiographic, and laboratory signs of infection. And a few authors only have tried to confirm the diagnosis with more invasive interventions, as for instance broncho-alveolar lavage to obtain specimens from the lower respiratory tract for culture and gram stains. 6,8 Despite differences in definitions, there is evidence that pneumonia is the most frequent cause of nosocomial infection after cardiac surgery. The incidence varies between 3% and 6% (with a peak after eight days), 7,8 and mortality reaches 20%. 6 Patients with nosocomial pneumonia have prolonged hospital stays, need additional investigations, treatments and care, and report on increased levels of discomfort. 1,6 3.2 Respiratory failure As with postoperative pneumonia, there are different definitions of postoperative respiratory failure. After cardiac surgery, respiratory failure has often been defined as the need for mechanical ventilatory support for longer than 72 hours. Using this definition of respiratory failure, the incidence was reported to be about 5%; reasons were most often extra-pulmonary, and mortality was 24%. 9 Respiratory failure after cardiac surgery has also been defined as the need for readmission to the intensive care unit related to partial or global respiratory insufficiency. Using this definition, the incidence of respiratory failure was about 2%, it was most often due to nosocomial pneumonia or the patient s inability to clear secretions, and mortality was 15%. 10 Finally, respiratory failure after cardiac surgery has been defined as the presence of an acute respiratory distress syndrome (ARDS). Using this definition, the incidence of was about 1%, and mortality was 15% to 50%. 11,12 3.3 Postoperative pulmonary complications The term postoperative pulmonary complications has often been used in studies that investigated postoperative pulmonary outcomes. However, that endpoint is an amalgamation of several symptoms, and a clear and universally accepted definition is lacking. Almost always that endpoint includes definite or suspected pneumonia and atelectasis (which is often not defined). Sometimes, respiratory failure, acute bronchitis, unexplained fever, excessive bronchial secretions, abnormal breathing sounds, productive cough, need of antibiotics, or hypoxemia is added. 13 This large variety in definitions is most likely responsible for the observed variability in the incidence of postoperative pulmonary complications in patients who do not receive additional care. For instance, in randomised studies testing the impact of respiratory physiotherapy after upper abdominal surgery, the incidence of postoperative pulmonary complications in patients who did not receive any physiotherapy was ranging from 0% to almost 50%. 13,14 The clinical relevance of this composite endpoint remains uncertainty. It has been claimed that composite outcomes are appropriate only when the all symptoms are well defined, when they are of equal importance and occur with similar frequencies, and when the active intervention leads to a comparable relative risk reduction of all components. 15 This is clearly not the case with postoperative pulmonary complications. 999

There is an argument to disregard the composite endpoint postoperative pulmonary complications in this context, and to consider more clearly defined outcomes only, such as pneumonia or respiratory failure. 4. Can respiratory physiotherapy prevent pulmonary complications after cardiac surgery? There is an assumption that prophylactic respiratory physiotherapy after cardiac surgery may reduce the decrease in functional residual capacity and thus prevent pulmonary complications. Westerdhal et al. used computed tomography to show that in patients after cardiac surgery maximum inspirations recruited collapsed lung tissue. 17 However, there were no data on the function of the recruited lung tissue, on duration of this potentially improved function, and on reduced pulmonary complications. Many other methods of prophylactic respiratory physiotherapy have been used for the prevention of pulmonary complications after cardiac surgery: deep breathing exercises with directed cough, incentive spirometry, continuous positive airway pressure, or intermittent positive pressure breathing. However, respiratory physiotherapy is labour-intensive and costly, and some patients may suffer from specific, intervention-related adverse effects. To justify the routine use of prophylactic respiratory physiotherapy after cardiac surgery, we need to be confident that the efficacy is worthwhile and that patient-relevant pulmonary complications and length of hospital stay are reduced. We have performed a systematic review of full reports of randomised trials testing the efficacy of prophylactic respiratory physiotherapy in patients undergoing cardiac surgery. 18 Trials had to compare any technique of prophylactic respiratory physiotherapy (active intervention) with no intervention (inactive control) or with another method of respiratory physiotherapy (active control). Trials had to report on pulmonary outcomes during an observation period of at least two days. Since there is no gold standard intervention in this setting, we assumed that the most valid study design to establish the relative efficacy of respiratory physiotherapy was a randomised comparison between an active intervention and a no intervention control. We analysed data from 18 trials (1,457 patients) that were published between 1978 and 2001. They tested different regimens of physical therapy (13 trials), incentive spirometry (8), continuous positive airway pressure (CPAP) (5), and intermittent positive pressure breathing (3). Four trials only had a no intervention control; none of those showed any significant benefit with physiotherapy. Across all trials and interventions, the average incidence of atelectasis was 15% to 98%, of pneumonia was 0% to 20%, of partial pressure of arterial oxygen per inspired oxygen fraction was 212 mmhg to 329 mmhg, of vital capacity was 37% to 72% of preoperative values, and of forced expiratory volume in one second was 34% to 72% of preoperative values. None of the tested physiotherapies showed superiority for any endpoint. However, there reports of gastric distension, nausea, intolerance of face mask, oxygen desaturation, and tachycardia during physiotherapy sessions. We concluded that the usefulness of prophylactic respiratory physiotherapy after cardiac surgery remained unproved. 18 The doubtful efficacy of prophylactic respiratory physiotherapy after cardiac surgery was recently reinforced by Brasher et al. 19 They tested a physioherapy program with or without deep breathing exercises after cardiac surgery and reported that additional deep breathing exercises had no effect on patient-relevant pulmonary complications but prolonged therapists labour time. 19 Interestingly, all patients in that study were mobilised early after surgery which may explain the reduced incidence of pulmonary complications. 1000 Patrick Pasquina, Martin R. Tramèr, D. Phil, Bernhard Walder

5. Where do we go from here? The research agenda Since the efficacy of prophylactic respiratory physiotherapy after cardiac surgery remains unproven, the research agenda needs to be clear. One option would be to abandon physiotherapy in this setting and to safe money. However, millions of patients are concerned, and it may therefore be justified to reinforce clinical research to define with more confidence the usefulness (or the uselessness) of respiratory physiotherapy to prevent patient-relevant pulmonary complications. For instance, an interesting alternative concept may be to try to strengthen and to improve the endurance of inspiratory muscles through a preoperative physiotherapy program. Weiner et al. observed that the decrease of pulmonary function tests in patients after cardiac surgery may be prevented by preoperative inspiratory muscle training, starting four weeks before surgery. 20 Obviously, this concept is costly if used in all patients that are scheduled for cardiac surgery. However, it may prove to be cost-effective in patients at particular risk for postoperative pulmonary complications, for instance, those with chronic pulmonary diseases. To avoid methodological pitfalls in future clinical studies, some issues need to be addressed that have been identified through our systematic review. 18 5.1. Experimental intervention Patients in the intervention group should be treated with highly standardised and valid respiratory physiotherapy methods. Techniques should be identical, of similar duration, and delivered in a standardised manner by trained physiotherapists. 5.2. Control intervention Since a gold standard intervention has not been defined yet and a no intervention control group is ethically acceptable in this setting, future trials should randomise patients to an experimental physiotherapy group and a no intervention control group. 5.3. Sample size Trials should be of reasonable size to overcome random variations, and to identify with confidence small but clinically relevant benefits and rare adverse effects. 5.4. Control of co-interventions Co-interventions such as analgesia or mobilisation should be strictly controlled. In a large randomised trial, the risk of attrition bias will become negligible. 5.5. Methods of assessment Clinically relevant endpoints should be evaluated using standardised and validated methods of assessment. When ever feasible, assessment should be done by observers who are 1001

unaware of treatment allocation. The observation period should expand until hospital discharge. 5.6. Relevant endpoints Studies should concentrate on the reporting of clinically relevant, well defined endpoints. Surrogate endpoints that do not have a direct impact on outcome (for instance oxygen saturation) should be avoided. Length of stay (in the intensive care unit, in the hospital) has important implications for costs; these data should be reported. 5.7. Patient selection If control patients who do not receive prophylactic respiratory physiotherapy, do not develop pulmonary complications, physiotherapy has no scope to improve this outcome. Thus, pulmonary high-risk patients need to be included in future trials, although, then, applicability of trial results will be of limited value. Risk scores may enable investigators to stratify patients into those who are most likely to profit from prophylactic respiratory physiotherapy. Based on data from cohort studies, and using multivariate analyses, a variety of risk factors have been identified. 9 As an alternative, a multifactorial risk index for predicting postoperative respiratory failure or pneumonia in patients undergoing major non-cardiac surgery, may be used. 21,22 6. Conclusions A variety of intra-operative mechanisms lead to pulmonary modifications and subsequent complications. It has been hypothesised that prophylactic respiratory physiotherapy may reduce those. However, evidence is lacking on the benefit of prophylactic respiratory physiotherapy for the prevention of pulmonary complications after cardiac surgery. Indeed, based on a recently published systematic review of randomised trials, prophylactic physiotherapy after cardiac surgery cannot be recommended for all patients. Nevertheless, in patients undergoing cardiac surgery, regular postoperative pulmonary evaluation remains essentially to detect patient-relevant pulmonary complications, and to initiate adequate care that may include therapeutic respiratory physiotherapy. 7. References 1. Lawrence VA, Hilsenbeck SG, Mulrow CD, et al. Incidence and hospital stay for cardiac and pulmonary complications after abdominal surgery. J Gen Intern Med 1995;10:671-8. 2. Pasquina P, Merlani P, Granier JM, et al. Continuous positive airway pressure versus noninvasive pressure support ventilation to treat atelectasis after cardiac surgery. Anesth Analg 2004;99:1001-8. 3. Ferdinande PG, Beets G, Michels A, et al. Pulmonary function tests after different techniques for coronary artery bypass surgery. Saphenous vein versus single versus double internal mammary artery grafts. Intensive Care Med 1988;14:623-7. 4. Jain U, Rao TL, Kumar P, et al. Radiographic pulmonary abnormalities after different types of cardiac surgery. J Cardiothorac Vasc Anesth 1991;5:592-5. 1002 Patrick Pasquina, Martin R. Tramèr, D. Phil, Bernhard Walder

5. Singh NP, Vargas FS, Cukier A, et al. Arterial blood gases after coronary artery bypass surgery. Chest 1992;102:1337-41. 6. Kollef MH, Sharpless L, Vlasnik J, et al. The impact of nosocomial infections on patient outcomes following cardiac surgery. Chest 1997;112:666-75. 7. Leal-Noval SR, Marquez-Vacaro JA, Garcia-Curiel A, et al. Nosocomial pneumonia in patients undergoing heart surgery. Crit Care Med 2000;28:935-40. 8. Carrel TP, Eisinger E, Vogt M, et al. Pneumonia after cardiac surgery is predictable by tracheal aspirates but cannot be prevented by prolonged antibiotic prophylaxis. Ann Thorac Surg 2001;72:143-8. 9. Canver CC, Chanda J. Intraoperative and postoperative risk factors for respiratory failure after coronary bypass. Ann Thorac Surg 2003;75:853-8. 10. Bardell T, Legare JF, Buth KJ, et al. ICU readmission after cardiac surgery. Eur J Cardiothorac Surg 2003;23:354-9. 11. Messent M, Sullivan K, Keogh BF, et al. Adult respiratory distress syndrome following cardiopulmonary bypass: incidence and prediction. Anaesthesia 1992;47:267-8. 12. Milot J, Perron J, Lacasse Y, et al. Incidence and predictors of ARDS after cardiac surgery. Chest 2001;119:884-8. 13. Celli BR, Rodriguez KS, Snider GL. A controlled trial of intermittent positive pressure breathing, incentive spirometry, and deep breathing exercises in preventing pulmonary complications after abdominal surgery. Am Rev Respir Dis 1984;130:12-5. 14. Lotz P, Heise U, Schaffer J, et al. The effect of intraoperative PEEP ventilation and postoperative CPAP breathing on postoperative lung function following upper abdominal surgery. Anaesthesist 1984;33:177-88. 15. Montori VM, Permanyer-Miralda G, Ferreira-Gonzalez I, et al. Validity of composite end points in clinical trials. BMJ 2005;330:594-6. 16. Van Kaam AH, Lachmann RA, Herting E, et al. Reducing atelectasis attenuates bacterial growth and translocation in experimental pneumonia. Am J Respir Crit Care Med 2004;169:1046-53. 17. Westerdahl E, Lindmark B, Eriksson T, et al. The immediate effects of deep breathing exercises on atelectasis and oxygenation after cardiac surgery. Scand Cardiovasc J 2003;37:363-7. 18. Pasquina P, Tramèr MR, Walder B. : systematic review. BMJ 2003;327:1379-81. 19. Brasher PA, McClelland KH, Denehy L, et al. Does removal of deep breathing exercises from a physiotherapy program including pre-operative education and early mobilisation after cardiac surgery alter patient outcomes? Aust J Physiother 2003;49:165-73. 20. Weiner P, Zeidan F, Zamir D, et al. Prophylactic inspiratory muscle training in patients undergoing coronary artery bypass graft. World J Surg 1998;22:427-31. 21. Arozullah AM, Daley J, Henderson WG, et al. Multifactorial risk index for predicting postoperative respiratory failure in men after major noncardiac surgery. The National Veterans Administration Surgical Quality Improvement Program. Ann Surg 2000;232:242-53. 22. Arozullah AM, Khuri SF, Henderson WG, et al. Development and validation of a multifactorial risk index for predicting postoperative pneumonia after major noncardiac surgery. Ann Intern Med 2001;135:847-57. 1003