Short-term effects of positive expiratory airway pressure in patients being weaned from mechanical ventilation

Abstract

Objective: To investigate the feasibility and the cardiorespiratory effects of using positive expiratory airway pressure, a physiotherapeutic tool, in comparison with a T-tube, to wean patients from mechanical ventilation.

Methods/design: A prospective, randomized, cross-over study.

Setting: Two intensive care units.

Patients and interventions: We evaluated forty patients who met weaning criteria and had been mechanically-ventilated for more than 48 hours, mean age 59 years, including 23 males. All patients were submitted to the T-tube and Expiratory Positive Airway Pressure devices, at 7 cm H2O, during a 30-minute period. Cardiorespiratory variables including work of breathing, respiratory rate (rr), peripheral oxygen saturation (SpO2), heart rate (hr), systolic, diastolic and mean arterial pressures (SAP, DAP, MAP) were measured in the first and thirtieth minutes. The condition was analyzed as an entire sample set (n=40) and was also divided into subconditions: chronic obstructive pulmonary disease (n=14) and non-chronic obstructive pulmonary disease (non- chronic obstructive pulmonary disease) (n=26) categories. Comparisons were made using a t-test and Analysis of Variance. The level of significance was p < 0.05.

Results: Our data showed an increase in work of breathing in the first and thirtieth minutes in the EPAP condition (0.86+ 0.43 and 1.02+1.3) as compared with the T-tube condition (0.25+0.26 and 0.26+0.35) (p<0.05), verified by the flow-sensor monitor (values in J/L). No statistical differences were observed when comparing the Expiratory Positive Airway Pressure and T-tube conditions with regard to cardiorespiratory measurements. The same result was observed for both chronic obstructive pulmonary disease and non- chronic obstructive pulmonary disease subconditions.

Conclusions: Our study demonstrated that, in weaning patients from mechanical ventilation, the use of a fixed level of Expiratory Positive Airway Pressure caused an increase in work of breathing that was not accompanied by any other significant cardiorespiratory changes. Therefore, we have to be cautious when using Expiratory Positive Airway Pressure as a physiotherapeutic tool during weaning from mechanical ventilation.

Figure 1 -

Work of Breathing in the study population: Comparison between EPAP and T-tube methods. EPAP= Positive Expiratory Airway Pressure. Values expressed in Joules/L. * Student t-test comparing EPAP ant T-tube methods: p<0.05

Figure 2 and 3 -

Work of Breathing: Comparison between EPAP and T-tube methods in subconditions COPD and non-COPD. EPAP= Positive Expiratory Airway Pressure; COPD = Chronic Obstructive Pulmonary Disease; non-COPD = non Chronic Obstructive Pulmonary Disease. Values expressed in Joules/L. * Student t-test comparing EPAP ant T-tube: p<0.05