The proposed study will measure the incidence of adverse events and the decrease in time to meet discharge criteria from the post anesthesia care unit when hypercapnic and hyperpnoea are used during emergence.

Hypercapnia has been used in conjunction with hyperpnoea to provide a more rapid return of responsiveness after inhaled anesthesia. The benefits of accelerating patient recovery in the operating room may extend to the post anesthesia care unit if the patient is more alert and easier to care for when they arrive in the unit. Respiratory patterns and gas levels - including CO2, O2, and anesthetic vapor - will be measured in order to better understand a patient's respiratory status during recovery.

In Feb 2009 we finished our first study (IRB 26111) and submitted a publication. The journal reviewers identified a serious limitation: we could not report whether the treated patients recovered from anesthesia faster because the treatment (inspired CO2) caused them to breath more vigorously or because the treatment caused the anesthetic vapors to be cleared more rapidly from the brain. Our new application uses essentially the same study protocol as the former study but adds chest bands to measure the patient's rate of breathing and expired gas monitoring to measure the rate at which the vapors are removed.

Inclusion Criteria:

• adult ASA class I-III subjects of both genders scheduled to undergo eye surgery at the Moran Hospital.

Exclusion Criteria:

• a history of renal or hepatic disease, chronic alcohol or drug abuse, disabling neuropsychiatric disorder, hypersensitivity, or unusual response to other halogenated anesthetics, pulmonary hypertension, increased intracranial pressure, seizure disorder, or personal/familial history of malignant hyperthermia, and current smokers.
• Subjects will also be excluded if they are currently being treated with known hepatic enzyme-inducing drugs (e.g., phenobarbital, dilantin, or isoniazid) or with drugs known to alter anesthetic requirements (e.g., opiates, clonidine, alpha2 agonists, alcohol, anticonvulsants, antidepressants, barbiturates, benzodiazepines or other tranquilizers).
• Subjects will also be excluded if they have intolerance to non-steroidal anti-inflammatories.
• In addition subjects who have received general anesthesia within the previous 7 days, received any investigational drug within the previous 28 days, or participated in a previous isoflurane or desflurane study will be excluded.
• Female subjects can be neither pregnant nor breast feeding.
• Subjects with significant restrictive lung disease will also be excluded.
• Subjects passing these criteria will be further evaluated with a medical history including medications, abbreviated physical examination, clinical laboratory tests (urine drug test), and a urine or serum human chorionic gonadotropin pregnancy test for women with childbearing potential.