Prediction of lung function and health-related quality of life using dominant handgrip strength in cardiac patients

Cardiac diseases are the leading cause of mortality globally, with cardiac surgery still a primary treatment for cardiac disease management. Following cardiac surgery, several indicators such as dominant handgrip strength (DHGS), lung function and health-related quality of life (HRQoL) are routinely used in clinical practice to assess/monitor patients’ recovery. Previous studies that investigated these variables after cardiac surgery identified conflicting findings with a better understanding of patients’ recovery after cardiac surgery needed, including the potential of these monitoring tools. The specific aims of this thesis were to: 1) determine the relationships between DHGS, lung function and HRQoL in cardiac surgical patients pre-operatively, at physiotherapy discharge and post-hospital discharge; 2) investigate the changes in these variables; and 3) identify the predictive ability of DHGS for lung function and HRQoL pre-operatively, at hospital discharge and post-hospital discharge.
To gain an understanding of the current knowledge base, a systematic review investigated the relationship between handgrip strength (HGS) and lung function and identified significant weak to moderate associations between these variables in most healthy adults. However, no to moderate associations were identified between these variables in persons living with some chronic diseases, while no study was retrieved in cardiac populations. Further, the use of un-standardised assessment protocols and different brands of HGS and lung function devices were identified as major flaws that hindered the comparison of data across studies.
Consequently, standardised protocols were used to examine the inter-instrument reliability of different DHGS and lung function devices in 113 healthy volunteers. Significant (p A longitudinal study was conducted, which examined: a) acute (within hospital) changes in DHGS, lung function and HRQoL in patients undergoing cardiac surgery (n = 101); b) the association between these variables; c) the predictive ability of DHGS for lung function and HRQoL values (addressing aims 1-3). Assessments were conducted before (1-2 days) cardiac surgery and at the point of physiotherapy discharge. Results showed that cardiac surgery significantly affected DHGS (-15%, p At six weeks and six-months after hospital discharge (intermediate recovery), consenting patients (n = 58) were re-assessed to examine the recovery of DHGS, lung function and HRQoL and the predictive ability of DHGS for lung function and HRQoL (addressing aims 1-3). At six weeks, both lung function and DHGS were significantly reduced, while only lung function improved to pre-operative levels by six-months. Pre-operative and six-week assessments revealed similar HRQoL, which continued to improve by six-months. At these timepoints, significantly moderate associations were identified between DHGS and lung function, but DHGS was not a significant predictor of lung function. No significant association was identified between DHGS and HRQoL. Overall, this thesis confirmed all three aims with DHGS having limited to no predictive value for lung function and HRQoL in post-cardiac surgical patients during acute and intermediate recovery. Future studies may consider other clinical tools (e.g. lower limb muscle strength, six-minute walk test) as predictors of lung function and HRQoL during acute and intermediate recovery in these patients.