If sample sizes need to be determined there are many statistical methods and assumptions related to this so decisions should be carefully considered. Two of the most commonly used sample tables are ISO 2859 for attibutes and ISO 3951 for variables.
FDA: Exemptions, Variances, and Alternate Forms of Adverse Event Reporting for Medical Devices
Manufacturers, importers, and user facilities can request an exemption or variance from any or all of the medical device reporting requirements in 21 CFR Part 803. Read more: https://www.fda.gov/medical-devices/medical-device-reporting-mdr-how-report-medical-device-problems/exemptions-variances-and-alternate-forms-adverse-event-reporting-medical-devices