Preoxygenation
The aim of preoxygenation is to replace the nitrogen that forms the majority of the functional residual capacity with oxygen. This provides an oxygen reservoir in the lungs that will delay the depletion of oxygen in the absence of ventilation (after paralysis). For a healthy adult, this can lead to maintaining a blood oxygen saturation of at least 90% for up to 8 minutes. This time will be significantly reduced in obese patients, ill patients and children. Preoxygenation is usually performed by giving 100% oxygen via a tightly fitting face mask. Preoxygenation or a maximum of eight deep breaths over 60 seconds resulting in blood oxygenation is not different from that of quiet breathing volume for 3 minutes.Newer methods of preoxygenation include the use of a nasal cannula placed on the patient at 15 LPM at least 5 minutes prior to the administration of the sedation and paralytic drugs. High flow nasal oxygen has been shown to flush the nasopharynx with oxygen, and then when patients inspire they inhale a higher percentage of inspired oxygen. Small changes in FiO2 create dramatic changes in the availability of oxygen at the alveolus, and these increases result in marked expansion of the oxygen reservoir in the lungs prior to the induction of apnea. After apnea created by RSI the same high flow nasal cannula will help maintain oxygen saturation during efforts securing the tube (oral intubation). The use of nasal oxygen during pre-oxygenation and continued during apnea can prevent hypoxia before and during intubation, even in extreme clinical cases.
For affected girls who wish (or whose parents wish) to have their hymens preserved, surgical techniques to excise of a central flange of the hymen can be used. The timing of surgical hymen repair is controversial: some doctors believe it is best to intervene immediately after the neonatal period, while others believe that surgical repair should be delayed until puberty, when estrogenization is complete. Epidemiology
Imperforate hymen is the most common vaginal obstruction of congenital origin. Estimates of the frequency of imperforate hymen vary from 1 in 1000 to 1 in 10,000 females. References

Glavan, N; Haller, H; Brnčić-Fischer, A; Glavan-Gačanin, L; Miletić, D; Jonjić, N (2016). "Imperforate hymen presenting as vaginal cyst in a 16-month-old child - considerations for an early diagnosis". Scottish Medical Journal. 61 (1): 48–50. doi:10.1177/0036933015615263. PMID 26659454. S2CID 27077599. Imperforate hymen at Medscape


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