The OdonAssist inflatable device for assisted vaginal birth-the ASSIST II study (United Kingdom)

BACKGROUND

Decreasing rates of assisted vaginal birth have been paralleled with increasing rates of cesarean deliveries over the last 40 years. The OdonAssist is a novel device for assisted vaginal birth. Iterative changes to clinical parameters, device design, and technique have been made to improve device efficacy and usability.

OBJECTIVE

This study aimed to determine if the feasibility, safety, and efficacy of the OdonAssist device were sufficient to justify conducting a future randomized controlled trial.

STUDY DESIGN

An open-label nonrandomized study of 104 participants having a clinically indicated assisted vaginal birth using the OdonAssist was undertaken at Southmead Hospital, Bristol, United Kingdom. Data were also collected from participants who consented to participate in the study but for whom trained OdonAssist operators were not available, providing a nested cohort. The primary clinical outcome was the proportion of births successfully expedited with the OdonAssist. Secondary outcomes included clinical, patient-reported, operator-reported, device and health care utilization. Neonatal outcome data were reviewed at day 28, and maternal outcomes were investigated up to day 90. Given that the number of successful OdonAssist births was ≥61 out of 104, the hypothesis of a poor rate of 50% was rejected in favor of a good rate of ≥65%.

RESULTS

Between August 2019 and June 2021, 941 (64%) of the 1471 approached, eligible participants consented to participate. Of these, 104 received the OdonAssist intervention. Birth was assisted in all cephalic vertex fetal positions, at all stations ≥1 cm below the ischial spines (with or without regional analgesia). The OdonAssist was effective in 69 of the 104 (66%) cases, consistent with the hypothesis of a good efficacy rate. There were no serious device-related maternal or neonatal adverse reactions, and there were no serious adverse device effects. Only 4% of neonatal soft tissue bruising in the successful OdonAssist group was considered device-related, as opposed to 20% and 23% in the unsuccessful OdonAssist group and the nested cohort, respectively. Participants reported high birth perception scores. All practitioners found the device use to be straightforward.

CONCLUSION

Recruitment to an interventional study of a new device for assisted vaginal birth is feasible; 64% of eligible participants were willing to participate. The success rate of the OdonAssist was comparable to that of the Kiwi OmniCup when introduced in the same unit in 2002, meeting the threshold for a randomized controlled trial to compare the OdonAssist with current standard practice. There were no disadvantages of study participation in terms of maternal and neonatal outcomes. There were potential advantages of using the OdonAssist, particularly reduced neonatal soft tissue injury. The same application technique is used for all fetal positions, with all operators deeming the device straightforward to use. This study provides important data to inform future study design.

Fetal head position and perineal distension associated with the use of the BD Odon Device™ in operative vaginal birth: a simulation study

Objective

To investigate (i) the placement of the BD Odon Device on the model fetal head, and (ii) perineal distention during simulated operative vaginal births conducted with the BD Odon Device

Design

Observational simulation study

Setting

North Bristol NHS Trust, UK

Population or Sample

440 simulated operative vaginal births

Methods

Three bespoke fetal mannequins were developed to represent (i) bi-parietal diameter of the 50^th centile at term (ii) bi-parietal diameter at the 5^th centile at term and (iii) 50^th centile head with 2 cm of caput. Siting of the BD Odon Device on model heads was determined before and after 400 simulated operative vaginal births. Variables were analysed to determine their effect on device siting and movement during birth.

The fetal mannequins were placed inside a maternal mannequin (PROMPT Flex, Limbs & Things, Bristol, UK) and the BD Odon Device was placed around the fetal head as per the instructions for use. The location of the air cuff was determined before and after the head was delivered. Perineal distension was determined by recording maximum perineal distention during a simulated operative vaginal birth using the same procedure, as well as scenarios employing an inappropriately non-deflated air cuff (for the BD Odon Device), the Kiwi ventouse and non-rotational forceps.

Main Outcome Measures

Site and displacement during birth of the BD Odon Device on a model head. Maximal perineal distension during birth.

Results

The BD Odon Device was reliably sited in a standard over the fetal head position (approximately 40mm above the fetal chin) for all stations, head sizes and positions with no significant displacement. In occipito-posterior births, compared to occipito-anterior or transverse, the BD Odon Device routinely sited further down the fetal head (toward the chin).

The BD Odon Device was not associated with more perineal distension than forceps or Kiwi ventouse (21mm vs 26mm vs 21mm at posterior fourchette).

Conclusions

The BD Odon Device reliably sited over a safe area of the fetal head in 400 simulated births representative of clinical practice. The BD Odon Device generates similar levels of perineal distension compared to Kiwi ventouse when used correctly.

Design and development of the BD Odon DeviceTM : a human factors evaluation process

OBJECTIVE

To (1) determine how intended users interact with and use the BD Odon Device in simulation, (2) use these findings to alter progressively the design of the BD Odon Device and (3) validate that these changes have improved the ability of practitioners to use the BD Odon Device.

DESIGN

Human factors evaluation study.

SETTING

Simulation suite designed to mimic delivery room.

POPULATION OR SAMPLE

Three hundred and ninety simulated operative births, performed by 100 practising clinicians.

METHODS

Simulated operative vaginal births performed using the BD Odon Device and the device Instructions for use were subjected to three formative human factors evaluations and one human factors validation test. Following each evaluation, findings were reviewed and the design of the BD Odon Device and Instructions for use were modified.

MAIN OUTCOME MEASURES

Successful performance of an operative vaginal birth using the BD Odon Device in accordance with provided training and Instructions for use.

RESULTS

Using version two of the BD Odon Device, and following exposure to face-to-face training and written instructions, 25% of accouchers were able successfully to perform a simulated operative vaginal birth. In the final evaluation, following device design and training material alterations, all accouchers were able successfully to perform a simulated operative vaginal birth using version four of the BD Odon Device.

CONCLUSIONS

Human factors evaluations have enabled a multi-professional device and training materials design team to alter the design of the BD Odon Device and the Instructions for use in an evidence-based fashion. This process has resulted in a device which has a predictable and likely safe pattern of use.

TWEETABLE ABSTRACT

Human Factors evaluations help make the BD Odon Device safe and usable for clinical practice.

The ASSIST Study - The BD Odon Device for assisted vaginal birth: a safety and feasibility study

BACKGROUND

Assisted vaginal birth is a vital health intervention that can result in better outcomes for mothers and their babies when complications arise in the second stage of labour. Unfortunately, instruments for assisted vaginal birth (forceps and ventouse) are often not utilised in settings where there is most clinical need, resulting in maternal and neonatal morbidity and mortality which could have been prevented. The BD Odon Device is a new device for assisted vaginal birth that may be able to address this unmet need. However, before dissemination, the device requires evaluation in robust clinical trials. A feasibility study to investigate the clinical impact, safety, and acceptability of the BD Odon Device for assisted vaginal birth is therefore planned. This will provide further information on acceptability, recruitment, and the outcome data required to design a future randomised controlled trial of the BD Odon Device versus Kiwi ventouse.

METHODS

Forty women who require an assisted vaginal birth for a recognised clinical indication will have the birth assisted with the BD Odon Device. The primary outcome is successful vaginal birth completed with the BD Odon Device. Secondary clinical outcomes include maternal and neonatal outcomes, and maternal and practitioner satisfaction. Safety data will be reviewed following every birth.

DISCUSSION

A future randomised controlled trial of the BD Odon Device versus the current standard instrument (the Kiwi ventouse) is planned. The findings of the ASSIST Study will inform the randomised controlled trial design.

TRIAL REGISTRATION

ISRCTN, ISRCTN10203171 . Prospectively registered on 27 July 2018.