Effectiveness of a preoperative breathing exercises intervention on patients undergoing cardiac surgery: a systematic review
Authors: Nicola Martins Rodrigues SF , Henriques HR , Henriques MA 
Published: May 2021

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Postoperative pulmonary complications are a common cause of morbidity and mortality in patients undergoing cardiac surgery, leading to an increase of HLOS and health care costs.

Purpose
This systematic literature review aims to determine if patients undergoing cardiac surgery submitted to a preoperative breathing exercises intervention have better postoperative outcomes regarding respiratory parameters, postoperative pulmonary complications, and HLOS.

Methods
Systematic searches were performed at CINAHL, Cochrane Central Register of Controlled Trials, Cochrane Clinical Answers, Cochrane Database of Systematic Reviews, MEDLINE and MedicLatina databases. Studies were included if they examined adult patients scheduled for elective cardiac surgery, who underwent a preoperative breathing exercises intervention aimed at improving breathing parameters, preventing postoperative pulmonary complications, and reducing HLOS. This
review was based on Cochrane and Prisma statement recommendations in the design, literature search, analysis and reporting.

Results
The search yielded 608 records. Inclusion criteria was fulfilled by 11 studies. Ten studies were RCT"s and one was an observational cohort study. Through these studies, data from 1240 participants was retrieved and meta-analysis was performed whenever possible.

Conclusions
A preoperative breathing intervention on patients undergoing cardiac surgery may help improve respiratory performance after surgery, prevent postoperative pulmonary complications and reduce HLOS. However, more trials are needed to support and strengthen the evidence found.
Author, year Study design Surgery Participants N (Age ± SD) (men/woman) Intervention Comparison Outcomes Study quality (Carvalho et al, 2011) RCT CABG N = 32IG 16 (62 ± 9.9)(62.5%/37.5%)CG:16 (62 ± 10.9) (68.8%/31.3%) The IMT in IG was performed with the threshold IMT with workload set to 30% of the MIP, during the 2 weeks prior to surgery. Training was performed 7 days/week, twice a day, 3 sets of 10 repetitions. Unknown. Pneumonia:IG: 5.3% vs CG: 12.3%, p = 0.04Atelectasis:IG: 18.7% vs CG: 43.2%, p = 0.02Pleural effusion:IG: 12.5% vs CG: 31.3% IMT was efficient increasing respiratory muscle strength (MIP/MEP) and function capacity (6MWT), reducing PPC. B (Chen et al, 2019) RCT CABG and/or valve N = 197IG: 98 (61.68 ± 7.73)(74,5%/25.5%)CG: 99 (61.68 ± 8.12) (68.7%/31.3%) A threshold was used for IMT - the IG received IMT at 30% of MIP for 20 min twice a day the last 5 days with supervision. Resistance was increased based on RPE. If the rate was less than 5, the resistance of the device was increased by 5% at a time. Patients were instructed to maintain diaphragmatic breathing with this device for 5 breaths and maintain this pattern for 20 min, twice a day. Both groups performed abdominal breathing training, twice a day at 20 minutes each, last 5 days before surgery. CG used the same protocol of the participants in the IG for the same number of repetitions, frequency, duration and supervision, but the intensity was fixed at the minimum load of the device (9cmH2O). MIP:IG: 100.8 ± 23.36 vs CG 93.12 ± 23.12, p &lt; 0.001HLOS: IG: 7.51 ± 2.83 vs CG: 9.38 ± 3.10, p = 0.039PPC grade≥2:IG: 10.2 vs CG: 27.3, p = 0.002Pneumonia: IG: 3.1 vs CG: 7.1, p = 0.321 A2 (Ferreira et al, 2009) RCT CABG or valve surgery N = 30IG: 15 (62.47 ± 8,06)(60%/40%)CG: 15 (63.91 ± 7.93) (86.7%/13.3%) General advice about surgery and postoperative care. Advised to stop smoking and not to smoke before surgery. Deep inspiration exercises and daily walks within own limits. Patients had to perform 5 series of 10 calm and deep inspirations with at least 1 min intervals between series, with the incentive of threshold IMT, with a load of 40% of MIP. The series were to be repeated thrice a day, until surgery. CG received general advice for surgery. Didn’t perform IMT exercises with threshold. Pneumonia:IG: 1 (6.7%) vs CG: 0 (0%), NS The IMT program resulted in improved forced vital capacity and maximal voluntary ventilation, although its clinical benefits have not been demonstrated. B (Hulzebos et al, 2006) RCT-pilot CABG N = 26IG: 14 (70.14 ± 9.9)(50%/50%)CG: 12 (70.5 ± 10.1) (50%/50%) Subjects in the IG trained daily at home, 7 times/week, for at least 2 weeks before surgery. Each training session consisted of 20 min of IMT. One session a week was supervised. Education about early mobilization and coughing with wound support 1 day before surgery (usual care). Pneumonia:IG: 1 (7.1%) vs CG: 1 (8.3%), NSAtelectasis:IG: 2 (14.2%) vs CG: 6 (50%), p= 0.05HLOS:IG: 7.93 ± 1.94 vs CG: 9.92 ± 5.78, p = 0.24 IMT significantly improved inspiratory muscle strength (increase of 36%) in the preoperative period and seems to prevent postoperative atelectasis B (Hulzebus et al, 2006) RCT CABG (at high risk of PPC) N = 276IG: 139 (66.5 ± 9.0)(77.7%/22.3%)CG:137(67.3 ± 9.2) (78.1%/21.9) IG received preoperatively individualized exercises, IMT, incentive spirometry; education in active cycle of breathing techniques; and forced expiration techniques. The intervention group trained daily, 7 times/ week, for at least 2 weeks before the actual date of surgery. Each session consisted of 20 min of IMT, which was performed 6 times/week without supervision and once a week with supervision (measured the strength and endurance of the inspiratory muscles after each week of training). Instruction in deep breathings, coughing and early mobilization one day prior to surgery (usual care). PPC grade ≥2:IG: 25 (18%) vs CG: 48 (35%), p = 0.02Pneumonia: IG: 9 (6.5%) vs CG: 22 (16.1%), p = 0.01HLOS:IG: 7 (range 5-41) vs CG: 8 (range 6-70), p = 0.02 Physical therapy with IMT administered to patients at high risk of PPC before CABG surgery was associated with an increase in inspiratory force and a decrease in the incidence of PPC and HLOS. A2 (Leguisamo et al, 2005) RCT CABG N = 86IG: 42 (59.3)(73.8%/26.2%)CG:44 (60.6) (80.95%/19.05) IG was evaluated and coached for at least 2 weeks before surgery, written guidelines on ventilatory exercises and coughing were given to continue the exercises at least twice a day until hospital admittance. An individual weekly encounter to monitor and guidance of breathing exercises: 1) diaphragmatic ventilatory pattern; 2) ventilatory pattern with inspiration split in two; 3) ventilatory pattern with inspiration split in three, performed in 2 series of 10 repetitions of each exercise. CG received guidance and was evaluated 24h before surgery. PPC didn’t demonstrate statically significant difference between groups. HLOS:IG: 11.77 ± 6.26 vs CG: 14.65 ± 6.61, p &lt; 0.005 B (Shakuri et al, 2014) RCT CABG N = 60IG: 30 (54.4 ± 10.8)(63.3%/36.7%)CG: 30 (59.3 ± 10.45) (90%/10%) Two-week period before surgery, 15 sessions, consisting of exercises and auxiliary activities for extension and rotation of thoracic vertebrae, breathing exercises, exercises to expand lung lobes, instruction of incentive spirometer, extension exercise for thoracic cavity muscles and muscles with a role in breathing (aerobic exercises) for 25 min at a constant low speed. CG received rehabilitation care only after the surgery (usual care). FEV1: IG: 80.0 ± 12.4 vs CG: 73.8 ± 13.16MWT, meter / spO2%: IG 97,7 ± 16,39 / 96,4 ± 5,34 vs CG 76,3 ± 20,5 / 97,1 ± 1,4Spirometry differences were significant, and higher in IG. Respiratory performance based on 6MWT parameters showed greater difference in the means of spO2 and distance walked in IG. B (Sobrinho et al, 2014) RCT CABG N = 70IG: 35 (58.9 ± 9.53)(65.7%/34.3%)CG: 35 (61.4 ± 8.43) (82.9%/17.1%) IG performed under supervision, once a day, until surgery, breathing exercises (breathing in time, deep breathing followed by prolonged expiration, sustained maximal inspiration with 6 seconds apnea, and diaphragmatic breathing associated with upper limbs mobilization) and breathing exercises with threshold IMT at an intensity of 40% of the initial MIP with 3 sets of 10 repetitions, with 2 min intervals between each series. Received guidelines at ward (usual care). MIP PO5:IG: 100 vs CG: 80, P &lt; 0.05HLOS:IG: 8460min (10080-6730) vs CG: 9970 (19580-6730), p &lt; 0.001Decrease in HLOS of approximately 25h in IG. B (Turky et al, 2017) RCT CABG N = 33IG: 17 (56.9 ± 3.75) (100% males)CG: 16 (56.95 ± 4.35) (100% males) IG received preoperative IMT by a threshold (30% of MIP, threshold training was increased incrementally by 2cmH2O. The resistance was not changed if the RPE was 6-8, the resistance was decreased by 1 to 2 cmH2O if the RPE was 9-10. Patients were encouraged to complete 3 sets of 10 breathings as slow maximal inspirations, with 30-60 second pause between each set, twice a day. Education on coughing and early mobilization to use postoperatively. Preoperative education (usual care) without IMT training. MIP:PO2, NS PO8: IG: 71.58 vs CG 37.44, p = 0.001SpO2%: PO2 - IG: 97.1 vs CG 95,8, p = 0.001 PO8 - IG: 98.85 vs CG 97.85, p = 0.001HLOS:9.05 ± 0.75 days on both groups, NS Preoperative IMT improved the alveolar-arterial gradient of patients who underwent CABG, reducing the risk of PPC. B (Valkenet et al, 2013) Observational Cohort Study CABG and valve surgery (at high risk of PPC) N = 346IG: 94 (66.8 ± 12.5)(61.7%/38.3%)CG: 252 (68.4 ± 9.3) (68.3%/31.7%) Patients visited the outpatient clinic at least 2 weeks before surgery. Received instructions and education concerning postoperative deep breathing exercises, incentive spirometry, coughing with wound support, and the importance of early postoperative mobilization. IG received one instruction session and was told to perform IMT at home until surgery. CG used the same protocol except they did not perform IMT, there was not enough time until surgery. Pneumonia:IG: 1.1% vs CG: 3.2%Ventilation time:IG: 7 [5-9] vs CG 7 [5-10] hoursLOS (ICU):IG: 23 [21-24] vs CG: 23[21-25] hoursHLOS:IG: 7[6-11] vs CG: 7 [5-9] days It cannot be stated that IMT in usual care resulted in less postoperative pneumonia, decreased ventilation time or decreased HLOS. B (Weiner et al, 1998) RCT CABG N = 84(69%/31%)IG:42 (59.2 ± 3.8) CG: 42 (63.8 ± 3.1) IMT resistance (threshold), starting at 15% of patient MIP up to 60% (increased incrementally 5% per session) of MIP, 6 days/week, for 2-4 weeks before surgery, 30 min training. Each session consisted of 0.5h under supervision. Sham training. IMT with no resistance, 6 days/week, 2-4weeks. Pneumonia:IG: 1 (3.4%) vs CG: 3 (7.14%), NSPleural effusion:IG 5 (11.9%) vs CG 3 (7.1%)Hemidiaphragmatic paralysis:IG: 2 (4.8%) vs CG: 3 (7.1%) Significant increase in inspiratory muscle strength and endurance before surgery and significantly better blood gases and pulmonary function after surgery. A2 Summary data from 11 studies