RESUMO
Termination of hypoxia results in a transient ventilatory decline referred to as post-hypoxic ventilatory decline (PHVD). We wished to determine whether PHVD is due to changes in ventilatory motor output or upper airway mechanics. We studied 19 healthy normal subjects (15 men, 4 women) during stable non-REM (NREM) sleep. Subjects were exposed to multiple episodes of brief (3 min) hypoxia that terminated with one breath of 100% FI(O2). Minute ventilation (V (I)), tidal volume (V (T)), timing, and upper airway resistance (R (ua)) were measured during the control, hypoxia, and for the first six breaths immediately after cessation of hypoxia. In addition, we measured diaphragmatic electromyograms (EMGdia) via surface electrodes in four subjects. V (I) and V (T) decreased during the recovery period to a nadir of 81 and 83% of room air control, respectively. However, there was no significant change in respiratory frequency or upper airway resistance during the post-hypoxic recovery period. Decreased V (I) was associated with a comparable decrease in EMGdia. We conclude that: (1) PHVD occurs in normal humans during NREM sleep, (2) there is no evidence of post-hypoxic frequency decline in humans during NREM sleep, and (3) PHVD is centrally mediated and not driven by upper airway mechanics.
Assuntos
Hipóxia/fisiopatologia , Polissonografia , Ventilação Pulmonar/fisiologia , Mecânica Respiratória/fisiologia , Fases do Sono/fisiologia , Adulto , Resistência das Vias Respiratórias/fisiologia , Diafragma/fisiopatologia , Feminino , Humanos , Hiperventilação/fisiopatologia , Medidas de Volume Pulmonar , Masculino , Valores de Referência , Músculos Respiratórios/fisiopatologiaRESUMO
TI-201 chloride was used for tumor imaging in patients with head and neck cancer. It is of value in detecting the extent of tumor involvement, the presence of residual tumor after radical courses of treatment, and the presence of local recurrence and distant metastases.
