Dronkers 2008.

Study characteristics
Methods	Study design: single‐blind randomised controlled trial Number of participants: 20 people were randomised Exclusions post‐randomisation: there were no exclusions post‐randomisation Losses to follow‐up: intervention = 2 (could not be followed up during the first 7 days after surgery because of acute reoperation for blood vessel occlusion in the leg); control = 2 (dropped out because they were not registered at the department of physical therapy when they were admitted to hospital and thus follow‐up was not possible) Intention‐to‐treat analysis: intervention = 10, control = 10 Duration/dates study conducted: not reported
Participants	Country: The Netherlands Setting: Gelderse Vallei Hospital Age, years (SD): intervention = 70 (6), control = 59 (6) Sex: intervention, women/men = 8/2, control, women/men= 7/3 Inclusion criteria: elective surgery for aneurysm of the abdominal aorta with a scheduled delay until surgery of at least two weeks (type of surgery not specified); at least one of the following risk factors: age > 65 years; smoking less than two months before surgery; COPD; and overweight (BMI > 27 kg/m2); proficient in Dutch; able to perform a valid spirometry test. Exclusion criteria: cerebrovascular disorders; immunosuppressive treatment < 30 days before the operation neuromuscular diseases; lung surgery in the medical history; cardiovascular instability; treatment by a physical therapist within 8 weeks before elective abdominal aortic aneurysm surgery.
Interventions	Intervention group (and sample size): n = 10 The intervention group took part in a training programme (6 sessions, 6 days a week for at least 2 weeks before surgery) designed to increase the strength and endurance of the inspiratory muscles. Each session consisted of 15 minutes of inspiratory muscle training; 1 session/week was supervised by the same physical therapist and the other 5 sessions were unsupervised. The participants were instructed to keep a daily diary during the study and were trained to use an inspiratory threshold‐loading device. The intervention group received care as usual 2 to 3 weeks before surgery, consisting of instruction in (a) diaphragmatic breathing, (b) deep inspirations with the aid of incentive spirometer, and (c) coughing and ‘forced expiration techniques’ (FET). Control group (and sample size): n = 10 Care as usual, consisting of instruction in (a) diaphragmatic breathing, (b) deep inspirations with the aid of incentive spirometer, and (c) coughing and FET. The control group received this usual care one day before surgery.
Outcomes	Primary outcome: postoperative pulmonary complications (atelectasis); feasibility (occurrence of adverse events during testing or training and participant satisfaction) Secondary outcomes: postoperative respiratory function (MIP, inspiratory muscle endurance, inspiratory vital capacity); inspiratory muscle strength (MIP at residual volume)
Notes	Funding source not reported. No conflict of interest declared.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Unclear risk	Sealed and numbered envelope. However, it was not mentioned if envelope was opaque.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Due to the nature of the intervention it is not possible to blind participants and this score is for personnel. The main postoperative outcome was atelectasis as diagnosed at the base of X‐rays by a blinded radiologist.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Main outcome assessed by blinded radiologist.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Two participants in control arm dropped out and 2 participants in intervention arm could not be followed up for the first 7 days after surgery. Methods stated ITT analysis was used. Data missing for several participants for each outcome.
Selective reporting (reporting bias)	Low risk	Reported mortality, but was not listed as one of the measured outcomes "The main outcome measure was postoperative pulmonary complications, operationalized as atelectasis," Secondary outcome measures were postoperative respiratory function determined by MIP, and the inspiratory vital capacity. All outcomes reported
Other bias	High risk	"Despite randomization, patients in the intervention group were significantly older than the patients in the control group (70 plus/minus 6 years versus 59 plus/minus 6 years, respectively; P = 0.001)."