To determine the efficacy of photodynamic therapy (PDT) with meso-tetra (hydroxyphenyl) chlorin (m-THPC) photosensitizer for recurrent respiratory papillomatosis. Design: Parallel-arm, randomized trial of patients requiring surgery at least 3 times yearly with single PDT 6 or 18 months after enrollment and 12-month followup. Disease extent was scored and papillomas were removed during direct endoscopy every 3 months after enrollment. Setting: Tertiary medical centers. Patients: Of 23 patients aged 4 to 60 years enrolled in the study, 15 patients, plus 2 in the late group without PDT owing to airway risk, completed the study. Six patients withdrew voluntarily after PDT. Intervention: Intravenous administration of m-THPC 6 days before direct endoscopic PDT with 80 to 100 J of light for adults and 60 to 80 J for children. Main Outcome Measures: Difference in severity scores between the early and late groups and between pre-and post-PDT scores for all patients. Secondary measures were the associations between baseline characteristics and response and changes in immune response and the prevalence of latent viral DNA. Results: There were significant differences between groups, with marked improvement in laryngeal disease across time after PDT (P=.006). Five of 15 patients were in remission 12 to 15 months after treatment, but there was recurrence of disease after 3 to 5 years. Tracheal disease was not responsive to PDT. No change occurred in the prevalence of latent human papillomavirus DNA. The immune response to virus improved with clinical response. Conclusions: Use of m-THPC PDT reduces the severity of laryngeal papillomas, possibly through an improved immune response. Failure to maintain remission with time suggests that this is not an optimal treatment.

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CH3F, when its ν3 mode is pumped by the P(20) line of the 9.6-μ band of a CO2 Q-switch laser, exhibits fluorescence from the ν1 and ν4 modes at 3000 cm−1. This fluorescence has a risetime ≤ 5  μsec at 1 torr and a decay rate of 0.59± 0.02 msec−1·torr−1. The diffusion coefficient measured from the low pressure fluorescence decay curves is 0.076± 0.011 cm2·torr msec−1. A very efficient near resonant energy transfer process is probably responsible for propagation of energy up the vibrational manifold. Similar processes may be important for laser induced chemical reactions. A square dependence of the intensity of fluorescence on incident cw laser power has been observed. This appears to arise mainly from population changes caused by a general temperature increase in the gas which occurs after absorption of laser energy and equilibration of all degrees of freedom of the molecule.