The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

THE EFFECTS OF VARIATIONS OF INSPIRATORY FLOW WAVE PATTERN ON CARDIOPULMONARY FUNCTION AND BREATHING COMFORT DURING LONG-TERM MECHANICAL VENTILATION OF PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE.

David C. Shelledy, PhD, RRT, Brenda Galindo, BS, RRT, Dora A. Galvan, BS, RRT, Clarissa M. Villacorta, BS, RRT. Respiratory Care Department, Vencor Hospital of San Antonio and The University of Texas Health Science Center at San Antonio, Texas.

BACKGROUND: Little is known about the advantages, if any, of particular flow wave patterns during mechanical ventilation of long-term ventilator patients. We examined the effects of three inspiratory flow wave patterns on measures related to cardiopulmonary function and breathing comfort. METHOD: A prospective, randomized blocks repeated measures design with subjects serving as their own controls was used to study eleven stable long-term ventilator patients with a primary diagnosis of COPD. Three inspiratory flow wave patterns (square, down ramp, sine) were assigned in a random sequence for a twenty minute period each followed by collection of the following data: peak airway pressure (PIP), mean airway pressure (MAP), dynamic compliance (Cdyn), static compliance (Cst), SpO_{2}, pulse, blood pressure, and breathing comfort. Patients were asked to indicate breathing comfort using a seven-point scale where 7=extremely comfortable and 1=extremely uncomfortable. Mean values for variables were compared using repeated measures ANOVA. A significant difference (p < .05) on ANOVA was followed by a Scheffe' post-hoc significance test. Results: Means, standard deviations, and ANOVA Results:

MEANS (SD)

Variable Down Ramp Square Wave

Peak Airway Pressure 30.68 (7.3) 42.37 (9.0)

Mean Airway Pressure 9.1 (2.9) 8.08 (2.6)

Dynamic Compliance 26.03 (7.7) 17.95 (4.4)

Static Compliance 37.59 (9.8) 33.43 (7.6)

SpO_{2} 96.27 (3.1) 97.09 (2.5)

Pulse 88.45 (17.2) 89.45 (16.6)

Mean Arterial Pressure 80.34 (9.4) 81.94 (14.7)

Breathing Comfort 4.3 (1.6) 4.22 (1.3)

Sine Wave F P

Variable 38.17 (9.2) 21.35 .00001*

Peak Airway Pressure 7.85 (2.4) 2.58 .10

Mean Airway Pressure 20.50 (6.4) 14.46 .0001*

Dynamic Compliance 37.16 (9.9) 2.01 .16

Static Compliance 96.36 (3.2) 3.26 .059

SpO_{2} 84.0 (16.1) 3.26 .059

Pulse 79.93 (11.9) 0.42 .66

Mean Arterial Pressure 5.0 (1.5) 0.69 .51

Breathing Comfort

* p < .05

There were significant differences by flow wave pattern for PIP and Cdyn. Post-hoc comparisons indicated that the down ramp resulted in a significantly lower PIP than the square wave (p = .00001) or sine wave (p = .002). Conclusions: The down ramp flow pattern resulted in a significantly lower PIP and improved Cdyn when compared to the square or sine wave. There were no significant differences by flow wave pattern for MAP, Cst, blood pressure or breathing comfort, though the differences for heart rate and SPO_{2} approached statistical significance. The use of a down ramp flow wave pattern may be useful in reducing peak airway pressures in long-term ventilator patients with COPD.

The 44th International Respiratory Congress Abstracts-On-DiskĀ®, November 7 - 10, 1998, Atlanta, Georgia.

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