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Comparison of Patient Comfort During Pressure Support(PSV) and Assist Control(AC) Mechanical Ventilation

Henry Ford Hospital, Detroit, MI

PURPOSE: PSV has been reported to be more comfortable than AC during non-invasive ventilation(1). This may be due to the ability of PSV to allow the patient to control rate, flow, volume and pattern. A previous report has compared physiologic parameters of PSV versus AC in intubated patients, but patient comfort levels were not assessed(2). Our study aims at comparing comfort levels in these modes in intubated patients.

METHODS: We enrolled twelve patients who were intubated, stable, and able to mark a line on a 100 mm visual analog scale(VAS). After randomization, they were ventilated in PSV and AC for 30 minutes each with a washout period between modes. AC volume was 8cc/kg and pressure support level was set at (Plateau Pressure-PEEP) or enough pressure for tidal volume of 8cc/kg. After each mode, patients were asked to mark their comfort level on the VAS (Very comfortable=100, Uncomfortable=0). Physiologic parameters were also recorded. Paired t-testing was used to compare means between the two groups.

RESULTS: After analyzing the data, we have found PSV(mean=83) to be a more comfortable mode than AC(mean=68), with a difference of 15 between the means(p=0.029). However, we didn’t find any statistical difference between the two modes in terms of physiologic parameters including blood pressure, heart rate, respiratory rate, mean airway pressure and minute ventilation.

CONCLUSION: Our data shows that PSV is a more comfortable mode of ventilation for stable intubated patients than AC. Our study is limited by difficulty in finding mechanically ventilated patients who are both clinically stable and able to use a VAS to accurately mark their comfort level. In addition, other modes of mechanical ventilation such as volume support, proportional assist, and pressure-regulated volume control may potentially be more comfortable, but our study is designed only to evaluate PSV and AC.

CLINICAL IMPLICATIONS: Patient comfort is an essential component of medical critical care. Physicians can use this information in making a decision regarding the choice of a specific mode of ventilation for their intubated patients.

Parameter AC PSV p Value Comfort (0-100 scale) 68 83 0.029 Blood pressure-systolic (mmHg) 126 130 0.179 Blood pressure-diastolic (mmHg) 63 64 0.673 Heart rate /min 84 83.5 0.757 Respiratory rate /min 12 14 0.404 Mean airway pressure (cm H2O) 9.6 10.4 0.366 Minute ventilation (L/min) 8.09 8.54 0.367

DISCLOSURE: I. Khalid, None.

REFERENCES

1. Girault C et al. Chest1997; 111 :1639 -48
2. Tejada M et al. Chest1997; 111 :1322 -25