Respiratory volume monitor (RVM) (ExSpiron) is superior to continuous pulse oximetry in detection of postoperative respiratory depression in high risk patients.

Aims are to: 1) Estimate the incidence of postoperative respiratory depression in high risk patients as detected by continuous pulse oximetry 2) Estimate the incidence of postoperative respiratory depression in high risk patients as detected by continuous respiratory volume monitor (RVM) (ExSpiron) 3) Assess the agreement between the continuous pulse oximetry and continuous respiratory volume monitor (RVM) (ExSpiron) in detection of postoperative respiratory depression in high risk patients

Inclusion Criteria:

• Patients who suffered rib fractures or patients who are weaned from mechanical ventilation and recently extubated.

Exclusion Criteria:

• Have known contraindication/allergy to neuroaxial/paravertebral nerve block anesthesia
• Patients allergic to morphine.
• Have an ASA class > IV

Group A; which will involve pregnant women with gestational age between 32-40 weeks. It will take place at:

i. Labor and delivery floor/obstetric floor: 100 patients scheduled for cesarean section under neuraxial anesthesia with 150 mcg intrathecal or 3-mg epidural morphine.

ii. Antenatal care: (obstetric floor, Long Wharf women clinic, Women center at Yale)

Group B; in post anesthesia care units (PACU) and surgical floor: 100 patients scheduled to receive General Anesthesia (GA) and planned to receive opioid intravenously (boluses/patient controlled analgesia (PCA).

Group C: in step down/ICU; 50 patients suffered from rib fracture and 50 patients after weaning from mechanical ventilation and extubation.