title: Exosurf versus Survanta surfactant preparations: proportional-hazards regression analysis of time to successful extubation and discontinuation of oxygen therapy.
abstract: Time to successful extubation (VENT-DC) and time to discontinuation of oxygen therapy (OX-DC) for infants treated with Exosurf and Survanta surfactant preparations were compared in an observational study. Proportional-hazards (Cox) regression was used to adjust for confounding by differences in baseline risk factors between treatment groups. The Exosurf/Survanta hazard ratios, representing the relative instantaneous probabilities of the next event (VENT-DC or OX-DC) occurring in the Exosurf versus Survanta groups, were close to the null value of 1.0 and were not statistically significant. For VENT-DC the ratio was 1.08 (95% confidence interval 0.73 to 1.61, p = 0.60); for OX-DC the ratio was 0.87 (0.58 to 1.30, p = 0.83). By contrast, the hazard ratios for female versus male sex and black versus white race, presented as internal reference values, were further from the null value and were statistically significant. Survival curves showing the estimated proportion of patients in whom VENT-DC or OX-DC was achieved over time were generated from the proportional hazards models. Our findings suggest that any difference between Exosurf and Survanta surfactant for VENT-DC or OX-DC is likely considerably smaller than the differences associated with gender or race. The rationales for (1) using proportional-hazards regression when duration of therapy is an outcome of interest and (2) generating internal reference risk ratios when multivariate analysis is used are discussed in relation to future studies of hyaline membrane disease or other problems of prematurity.
authors.affiliation: Department of Neonatology, Cook-Fort Worth Children's Medical Center, TX 76104, USA.
authors.forename: C
authors.initials: C
authors.lastname: Arnold
authors.forename: E
authors.initials: E
authors.lastname: Adams
authors.forename: E
authors.initials: E
authors.lastname: Torres
authors.forename: R
authors.initials: R
authors.lastname: Sidebottom
mesh_terms: D000368:Aged; D001688:Biological Products; D004338:Drug Combinations; D005233:Fatty Alcohols / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D006819:Hyaline Membrane Disease / Q000628:therapy*; D007231:Infant, Newborn; D007440:Intubation; D008297:Male; D010100:Oxygen / Q000627:therapeutic use*; D010767:Phosphorylcholine; D011092:Polyethylene Glycols / Q000627:therapeutic use*; D016016:Proportional Hazards Models; D011663:Pulmonary Surfactants / Q000627:therapeutic use*; D012044:Regression Analysis; D016019:Survival Analysis; D013997:Time Factors
chemical_list: D001688:Biological Products; D004338:Drug Combinations; D005233:Fatty Alcohols; D011663:Pulmonary Surfactants; D010767:Phosphorylcholine; D011092:Polyethylene Glycols; C047049:dipalmitoylphosphatidylcholine, hexadecanol, tyloxapol drug combination; C072197:beractant; D010100:Oxygen