Helicopter emergency medical service in out-of-hospital cardiac arrest--a 10-year population-based study.

BACKGROUND: In 1988, Norway established a countrywide, physician staffed helicopter emergency medical service (HEMS). The medical benefit remains controversial. The aim of this study was to estimate the population incidence of HEMS involvement in out-of-hospital cardiac arrest, report the patient outcome and evaluate the contribution of HEMS to survival. METHODS: We studied HEMS operations in central Norway (population 364,000) during a 10-year period (1988-1997). Missions were classified according to type and quality of intervention done by the primary care providers. HEMS witnessed cardiac arrests were not considered. Patient outcome was determined as survival to hospital discharge with cerebral performance category (CPC) score. The contribution made by HEMS in each survivor was assessed from the timing of return of spontaneous circulation (ROSC) and from subsequent need for advanced medical intervention. The relation between survival and HEMS response time was investigated by ordinal correlation. RESULTS: A total of 541 requests (14.9 per 100,000 inhabitants per year) were identified, of which 424 missions were completed. Overall survival to discharge was 36/541 (6.6%), yielding a population survival incidence of 1 per 100,000 per year. Ninety-five percent of survivors made a favourable cerebral outcome (CPC 1 or 2). General practitioners/ambulance personnel resuscitated 29 out of 36 survivors. The remainder achieved ROSC after HEMS arrival. Case by case, HEMS assistance was considered possibly important in 17 survivors. We found no relation between survival and HEMS response time (P=0.77). DISCUSSION: Survival following out-of-hospital cardiac arrest assisted by HEMS in this region is low, but not negligible. While primary care is most important, HEMS may possibly contribute to the additional survival of 0.19 to 0.46 patients per 100,000 per year. This benefit appears to be independent of HEMS response time.

Reduction of peak inflation and positive end-expiratory pressure using pressure control with inverse-ratio ventilation: a case report.

Pressure control with inverse-ratio ventilation (PcIRV) has been shown to reduce peak inspiratory pressure (PIP) and positive end-expiratory pressure while providing adequate oxygenation and ventilation. This case of a 39-year-old man with a perforated colon who required high PIP after surgery demonstrates the effectiveness of PcIRV in reducing PIP from 72 cm H2O to 44 cm H2O and reducing positive end-expiratory pressure from 24 cm H2O to 6 cm H2O. A maximum inverse ratio of 3:1 was established to achieve a PaO2 of 105 mm Hg and PaCO2 of 37 mm Hg. In this case, the mean airway pressure rose from 32 cm H2O with assist-control ventilation to 39 cm H2O with PcIRV at 3:1. Cardiac output decreased from 9.11 L/min to 8.35 L/min with PcIRV at a 3:1 inspiratory/expiratory ratio.

Nasal airway positive pressure in patients with occlusive sleep apnea. Methods and feasibility.

Nasal airway positive pressure (NAPP) effectively eliminates obstructive sleep apnea. This report describes construction and evaluation of a convenient NAPP apparatus used successfully in 15 patients with obstructive sleep apnea. An impeller blower with high flow, low pressure characteristics delivers room air to a flow divider and then to an injector attached to a custom-fitted nose mask. Of the total naris pressure supplied by the system, a large fraction derives from the kinetic energy of the air stream delivered to the naris by the injectors. This, together with the high flow rate of the system, promotes a constant naris pressure. Naris pressure is determined by the size of the flow divider and the aperture of the exhaust port(s) of the injector. A series of 10 flow divider-injector combinations are described that provide a variety of naris pressures between 2.5 and 13.6 cm H2O. Fourteen of 15 patients found the NAPP apparatus acceptable and effective. No maintenance or repair appears to be required.