Effect of preoperative inspiratory muscle training on postoperative outcomes in patients undergoing cardiac surgery: A systematic review and meta-analysis

Table 2 Inspiratory muscle training used in each study

No.	Ref.	Length	Frequency	Duration	Supervision	Intensity
1	Hulzebos et al[12], 2006	≥ 2 wk preoperatively	Once a day	20 mins	6 times a week without supervision and once a week with supervision	30% of MIP. Resistance increases incrementally, based on the RPE scored on the Borg scale
2	Savci et al[17], 2011	5 d preoperatively + 5 d postoperatively	Twice a day	30 mins	Each session was under the supervision of a physical therapist	15% of MIP. The resistance was increased incrementally between 15% and 45% based on patient’s tolerance in the following days
3	Moises et al[18], 2014	Preoperative (length not mentioned)	Once a day	20 mins	Each session was under supervision	40% of MIP. Intensity increase not mentioned
4	Valkenet et al[6], 2016	Not mentioned	Once a day	20 min	6 times a week without supervision and once a week with supervision	30% of MIP. Increased incrementally based on the RPE as scored on the Borg scale. If patients recorded an RPE score < 5 after a training session, they were instructed to increase the inspiratory load of the threshold device by 5% before the next training session. The threshold load was unchanged for RPE scores ≥ 5
5	Chen et al[19], 2019	5 d preoperatively	Twice a day	20 min	Each session was under the supervision of a physical therapist	30% of MIP. Increased incrementally, based on the RPE scored on the Borg18 scale. If the RPE was less than 5, the resistance of the inspiratory threshold trainer was then increased incrementally by 5%. Training loads were adjusted to maintain 30% of the maximal inspiratory pressure every day
6	Weber et al[20], 2021	≥ 2 wk preoperatively	Once a day	20 min	Not mentioned	Not mentioned

MIP: Maximum inspiratory pressure; RPE: Rate of perceived exertion.