Time to achieve desired fraction of inspired oxygen using a T-piece ventilator during resuscitation of preterm infants at birth.

AIM: To determine the time between adjustment of FiO2 at the oxygen blender and the desired FiO2 reaching the preterm infant during respiratory support at birth. METHODS: This observational study was performed using a Neopuff™ T-piece Resuscitator attached to either a test lung (during initial bench tests) or a face mask during the stabilization of infants at birth. FiO2 was titrated following resuscitation guidelines. The duration for the desired FiO2 to reach either the test lung or face mask was recorded, both with and without leakage. A respiratory function monitor was used to record FiO2 and amount of leak. RESULTS: In bench tests, the median (IQR) time taken to achieve a desired FiO2 was 34.2 (21.8-69.1) s. This duration was positively associated with the desired FiO2 difference, the direction of titration (upwards) and the occurrence of no leak (R2 0.863, F 65.016, p < 0.001). During stabilization of infants (median (IQR) gestational age 29+0 (28+2-30+0) weeks, birthweight 1290 (1240-1488) g), the duration (19.0 (0.0-57.0) s) required to reach a desired FiO2 was less, but still evident. In 27/55 (49%) titrations, the desired FiO2 was not achieved before the FiO2 levels were again changed. CONCLUSION: There is a clear delay before a desired FiO2 is achieved at the distal end of the T-piece resuscitator. This delay is clinically relevant as this delay could easily lead to over- and under titration of oxygen, which might result in an increased risk for both hypoxia and hyperoxia.

Correlation of intraocular pressure and central corneal thickness in normal myopic eyes and after laser in situ keratomileusis.

PURPOSE: To determine the relationship of intraocular pressure (IOP) and central corneal thickness (CCT) in normal myopic eyes and after laser in situ keratomileusis (LASIK). SETTING: TLC The Windsor Laser Center, Windsor, Ontario, Canada. METHODS: Intraocular pressure measured by Goldmann applanation tonometry and CCT by ultrasonic pachymetry were determined in a group of untreated corneas of 120 patients (203 eyes) and in 50 patients (85 eyes) pre- and post-LASIK. Statistical analyses were performed with the Pearson correlation coefficient and paired Student t test. RESULTS: In the untreated group of 288 eyes, mean CCT was 544.0 microns +/- 37.3 (SD) (range 461 to 664 microns) and mean IOP, 15.6 +/- 2.7 mm Hg (range 10 to 24 mm Hg). The correlation between IOP and CCT in this group was highly significant (r = 0.44; P < .0001). The slope was 0.032 mm Hg/micron of CCT or an approximate decrease of 1 mm Hg, for a reduction in CCT of 31.3 microns. In the post-LASIK group, mean CCT dropped approximately 73.0 microns to 479.5 +/- 41.2 microns (range 408 to 503 microns) and IOP dropped to a mean of 13.6 +/- 3.3 mm Hg (range 7 to 22 mm Hg). A significant correlation was found between IOP and CCT after LASIK (r = 0.33; P < .002). The difference between the mean pre- and post-LASIK measurements of applanation IOP was 2.5 mm Hg, which was significant (P < .0001). The post-LASIK slope was 0.027 mm Hg/micron, or a decrease of 1.0 mm Hg per 37.8 microns reduction in CCT. CONCLUSION: Central corneal thickness is an important variable in the evaluation of applanation IOP and should be included in the assessment of any case of potential glaucoma or ocular hypertension, particularly in eyes with previous photoablative refractive surgery.