New generation ventilators

Enhanced notification of critical ventilator events

Mechanical ventilators are designed to generate alarms when patients become disconnected or experience other critical ventilator events. However, these alarms can blend in with other accustomed sounds of the intensive care unit. Ventilator alarms that go unnoticed for extended periods of time often result in permanent patient harm or death. We developed a system to monitor critical ventilator events through our existing hospital network. Whenever an event is identified, the new system takes control of every computer in the patient's intensive care unit and generates an enhanced audio and visual alert indicating that there is a critical ventilator event and identifies the room number. Once the alert is acknowledged or the event is corrected, all the computers are restored back to the pre-alert status and/or application. This paper describes the development and implementation of this system and reports the initial results, user acceptance, and the increase in valuable information and patient safety.

Inspiratory work imposed by demand valve ventilator circuits

The inspiratory work (WI) imposed by three commonly used demand valve ventilator circuits was studied using a lung model to simulate spontaneous ventilation. The CPU-1 and Engstrom Erica circuits recorded WI of 379 mJ/l and 190 mJ/l respectively. A negative WI of -32 mJ/l was recorded for the Servo 900C, denoting that the circuit performed work on the lung. The demand valves recorded a time delay between inspiratory effort and onset of gas flow, of 300 ms (CPU-1), 190 ms (Servo 900c) and 160 ms (Engstrom Erica). Both the Servo 900C and Engstrom Erica demand valves were able to generate a high inspiratory gas flow response, but the CPU-1 lacked such a flow compensation. Expiratory work was also greatest with the CPU-1 (156 mJ/l) with 141 mJ/l and 90 mJ/l recorded for the Servo 900C and Engstrom Erica. Of the three ventilators studied, the Servo 900C appears to be the ventilator circuit of choice for spontaneous ventilation.

Mechanical ventilation in medical and neurological diseases: 11 years of experience

Mechanical ventilation (MV) is imperative in many forms of acute respiratory failure (ARF). The aim of this work was to review all episodes of MV in a Medical Intensive Care Unit (MICU) during the 11-year period 1976-1986. Four per cent (n = 1008) of 24,899 admissions to the MICU were treated with MV. The mean age of ventilator-treated patients was 53 +/- 18 years, and obviously it increased during the period of study. The average duration of MV was 4.7 d. MICU mortality, hospital mortality and 2-year mortality rates for patients subjected to MV were 33%, 38% and 46%, respectively. The mortality rate did not change during the study period. Cerebrovascular and malignant diseases carried the highest mortality rates, 75 and 79%, respectively, whereas mortality in patients ventilated because of drug overdose (n = 313) was only 2%. The results of this study confirm previously published findings concerning the outcome of MV, and we conclude that the effects of MV remain discouraging in medical and neurological patients. Improved quality of ventilator therapy and monitoring, as well as continued research directed at the causes of ARF, are equally important in reducing the mortality in ARF.

Ventilation and ventilators--an update

In the five years which have passed since the previous review, the literature has been concerned more with the ways in which ventilators may be applied to patients and the effects of differing patterns of ventilation than with the design philosophy of the ventilators themselves. This account should be read in conjunction with that of 1982 [1].