Table 6.

Factors influencing TTI found from the literature research are categorized according to the degree of influence (low, medium and high). An increase (↑) or decrease (↓) in TTI is represented by the respective symbol.

Factors	Section	Influence	Change of TTI	Conclusion
Waveforms	Section 3.4.1	low	no change	The biphasic waveform was found to be less sensitive to changes in TTI. The reduction in TTI for the biphasic waveform compared to the monophasic waveform was minimal.
Serial shocks	Section 3.4.2	low	↓ with shocks	Not all studies are congruent. More studies reported decrease rather than stable TTI. All recorded decreases were small and SD usually high.
Coupling device	Section 3.4.3	high	↓ for good coupling	Correct coupling (with gels/pastes and mechanical coupling of electrodes) at the electrode/tissue layer is a crucial factor for the TTI.
Electrode size	Section 3.4.4	high	↓ with electrode size	All studies are congruent. Of particular significance in pediatric defibrillation with very small electrodes.
Electrode pressure	Section 3.4.5	high	↓ with pressure	All studies are congruent. For adult defibrillation with paddles, 8 kgf is recommended.
Electrode position	Section 3.4.6	medium	↓ in AP	Overall, the TTI was lower in the AP position than in the AA and AL electrode positions (marginal in some studies). The TTI did not differ in the subgroups of the different AA positions nor in the AP positions. A  higher TTI was found for the transverse position compared to the longitudinal position.
Age	Section 3.4.7	medium	↑ with age	Most of the differences are between adults and children, mainly because of body measurements that change with age. Only one study found TTI generally higher with age.
Gender	Section 3.4.8	low	↕	The results are inconsistent and no trends given. Characteristic differences between sexes can be considered: Breast hair should be removed to allow adequate coupling, on breast positioning of electrodes increases TTI, pregnancy does not affect TTI.
Body dimensions	Section 3.4.9	medium	↑ with body dimensions	Different indicators were used in the different studies: weight, chest size, BSA and BMI, making comparison difficult. A small, if any, increase in TTI with increasing body dimensions is indicated. Severely overweight should be considered.
Respiration and lung volume	Section 3.4.10	low	↑ with lung volume	Full lung volume may result in a slight increase in TTI. Measurements can be taken at end-expiratory time points to fully compensate for the of respiration.
Hemoglobin saturation	Section 3.4.11	low	↑ with Hb O2 saturation	Three studies are congruent: Higher Hb O2 saturation has a slightly increasing effect on TTI. Only of clinical interest in combination with pathological symptoms leading to very atypical Hb O2 saturation values.
Pathologies	Section 3.4.12	low	↕	Mainly minor changes of TTI with pathological symptoms were observed. Severe changes were only documented after sternotomy. In general, the more advanced the pathophysiological symptoms, the greater the change in TTI.