Validity and reliability of seismocardiography for the estimation of cardiorespiratory fitness

Assessing the accuracy of Seismofit® as an estimate of preoperative maximal oxygen consumption in patients with hepato-pancreato-biliary, colorectal, and gastro-oesophageal cancer

Background

Peak oxygen uptake (VO2 peak) measured during cardiopulmonary exercise testing (CPET) is commonly used to objectively assess fitness and inform risk stratification. Preoperative CPET is not always universally available. Seismofit® offers a noninvasive, non-exercise alternative for estimating VO2 peak, though it has not been validated in patients awaiting major abdominal cancer surgery.

Methods

Prospective single-centre blinded observational study in patients with hepato-pancreato-biliary, colorectal, or gastro-oesophageal cancer undergoing preoperative assessment. Patients underwent Seismofit® assessment before routine CPET. Primary outcome was the relationship between Seismofit®-estimated VO2 peak and CPET-measured VO2 peak. Secondary outcomes explored the relationship between Seismofit® and CPET for (i) bias and agreement limits; (ii) surgical subgroup; (iii) commonly reported CPET variables; (iv) patient acceptance.

Results

Thirty-three participants (median [interquartile range] age: 67 yr [58-75 yr]; 20 [61%] males) completed both CPET and Seismofit®. No linear association was found between Seismofit®-estimated VO2 peak and CPET-measured VO2 peak: Pearson r=0.111 (95% confidence interval -0.242 to 0.437), R 2=0.012, P=0.539. Compared with CPET, Seismofit® demonstrated a large bias (standard deviation) 12.8 (8.8); 95% limits of agreement (-4.5 to 30.0). No association existed between Seismofit®-estimated VO2 peak and CPET-measured VO2 peak in the hepato-pancreato-biliary or gastro-oesophageal subgroup or between Seismofit®-estimated VO2 peak and commonly reported CPET variables.

Conclusions

There was no evidence of linear association between Seismofit®-estimated VO2 peak and objectively measured VO2 peak by CPET in patients undergoing assessment for major abdominal cancer surgery. This finding was consistent across all subgroup and exploratory analyses. Seismofit® tended to overestimate VO2 peak with a high degree of bias.

Clinical trial registration

NCT05831488.

V̇O2peak estimation in people with overweight and obesity before and after a 14-week lifestyle intervention

PURPOSE

This study aimed to investigate the validity and applicability of a non-exercise estimation of cardiorespiratory fitness using resting seismocardiography (SCG eV̇O2peak) in people with overweight and obesity before and after a 14-week lifestyle intervention.

METHODS

The study was carried out at a Folk high school that offers 14-week courses on lifestyle changes where participants live at the school and voluntarily participate in daily lectures and activities. Sixty-seven men and women with age and body mass index between 18 and 70 years and 25-50 kg·m-2 were tested at baseline, and 52 had a follow-up test after 14 weeks. Testing included the determination of anthropometric variables, an SCG eV̇O2peak at supine rest, and a gold standard V̇O2peak test on a cycle ergometer until voluntary exhaustion.

RESULTS

Agreement analysis for V̇O2peak at baseline (n = 67, SCG eV̇O2peak: 26.9 ± 1.9 ml·min-1·kg-1, V̇O2peak: 26.6 ± 1.6 ml·min-1·kg-1, mean ± 95% confidence interval) showed a bias of 0.3 ± 1.0 ml·min-1·kg-1 with 95% limits of agreement (LoA) ranging ± 9.8 ml·min-1·kg-1. A Pearson's correlation of r = 0.78 (p < 0.0001) and a standard error of estimate (SEE) of 5.0 ml·min-1·kg-1 were found between methods. At follow-up (n = 52), body mass was reduced by 6.6 ± 1.4 kg (p < 0.0001). V̇O2peak increased by 3.3 ± 0.9 ml·min-1·kg-1 and 175 ± 78 ml·min-1 and SCG eV̇O2peak by 2.6 ± 0.8 ml·min-1·kg-1 and 93 ± 76 ml·min-1 (two-way ANOVA repeated measure: intervention p < 0.0001, method p = 0.939 and interaction p = 0.125, relative V̇O2peak). A Pearson's correlation of r = 0.37 (p < 0.05) was found between changes in relative V̇O2peak but not for absolute V̇O2peak r = 0.10 (p = 0.402).

CONCLUSIONS

The SCG method is accurate for estimating V̇O2peak and appropriate for detecting group changes in both relative and absolute V̇O2peak following a lifestyle intervention in people with overweight and obesity. Furthermore, the method can detect individual changes in V̇O2peak but not independently of body mass changes. Yet, the applicability is still limited by the relatively large variation in LoA and SEE.

Continuous Estimation of Blood Pressure by Utilizing Seismocardiogram Signal Features in Relation to Electrocardiogram

There is an ongoing search for a reliable and continuous method of noninvasive blood pressure (BP) tracking. In this study, we investigate the feasibility of utilizing seismocardiogram (SCG) signals, i.e., chest motion caused by cardiac activity, for this purpose. This research is novel in examining the temporal relationship between the SCG-measured isovolumic moment and the electrocardiogram (PEPIM). Additionally, we compare these results with the traditionally measured pre-ejection period with the aortic opening marked as an endpoint (PEPAO). The accuracy of the BP estimation was evaluated beat to beat against invasively measured arterial BP. Data were collected on separate days as eighteen sets from nine subjects undergoing a medical procedure with anesthesia. Results for PEPIM showed a correlation of 0.67 ± 0.18 (p < 0.001), 0.66 ± 0.17 (p < 0.001), and 0.67 ± 0.17 (p < 0.001) when compared to systolic BP, diastolic BP, and mean arterial pressure (MAP), respectively. Corresponding results for PEPAO were equal to 0.61 ± 0.22 (p < 0.001), 0.61 ± 0.21 (p < 0.001), and 0.62 ± 0.22 (p < 0.001). Values of PEPIM were used to estimate MAP using two first-degree models, the linear regression model (achieved RMSE of 11.7 ± 4.0 mmHg) and extended model with HR (RMSE of 10.8 ± 4.2 mmHg), and two corresponding second-degree models (RMSE of 10.8 ± 3.7 mmHg and RMSE of 8.5 ± 3.4 mmHg for second-degree polynomial and second-degree extended, respectively). In the intrasubject testing of the second-degree model extended with HR based on PEPIM values, the mean error of MAP estimation in three follow-up measurements was in the range of 7.5 to 10.5 mmHg, without recalibration. This study demonstrates the method's potential for further research, particularly given that both proximal and distal pulses are measured in close proximity to the heart and cardiac output. This positioning may enhance the method's capacity to more accurately reflect central blood pressure compared to peripheral measurements.

Accuracy of a non-exercise method using seismocardiography for the estimation of V̇O2peak in sub-elite football players

A non-exercise method equation using seismocardiography for estimating V̇O2peak (SCG V̇O2peak) has previously been validated in healthy subjects. However, the performance of the SCG V̇O2peak within a trained population is unknown, and the ability of the model to detect changes over time is not well elucidated. Forty-seven sub-elite football players were tested at the start of pre-season (SPS) and 36 players completed a test after eight weeks at the end of the pre-season (EPS). Testing included an SCG V̇O2peak estimation at rest and a graded cardiopulmonary exercise test (CPET) on a treadmill for determination of V̇O2peak. Agreement between SCG V̇O2peak and CPET V̇O2peak showed a large underestimation at SPS (bias ± 95% CI: -9.9 ± 1.8, 95% Limits of Agreement: 2.2 to -22.0 mL·min-1 kg-1). At EPS no interaction (p = 0.3590) but a main effect of time (p < 0.0001) and methods (p < 0.0001) was observed between SCG and CPET V̇O2peak. No correlation in V̇O2peak changes was observed between SCG and CPET (r = -20.0, p = 0.2484) but a fair agreement in classifying the correct directional change in V̇O2peak with the SCG method was found (Cohen's κ coefficient = 0.28 ± 0.25). Overall, the SCG V̇O2peak method lacks accuracy and despite being able to estimate group changes, it was incapable of detecting individual changes in V̇O2peak following a pre-season period in sub-elite football players. The SCG algorithm needs to be further adjusted and the accuracy and precision improved for the method to be applicable for use within a trained population.