Pressure-controlled ventilation in children with severe status asthmaticus.

OBJECTIVE: The optimum strategy for mechanical ventilation in a child with status asthmaticus is not established. Volume-controlled ventilation continues to be the traditional approach in such children. Pressure-controlled ventilation may be theoretically more advantageous in allowing for more uniform ventilation. We describe our experience with pressure-controlled ventilation in children with severe respiratory failure from status asthmaticus. DESIGN: Retrospective review. SETTING: Pediatric intensive care unit in a university-affiliated children's hospital. PATIENTS: All patients who received mechanical ventilation for status asthmaticus. INTERVENTIONS: Pressure-controlled ventilation was used as the initial ventilatory strategy. The optimum pressure control, rate, and inspiratory and expiratory time were determined based on blood gas values, flow waveform, and exhaled tidal volume. MEASUREMENT AND MAIN RESULTS: Forty patients were admitted for 51 episodes of severe status asthmaticus requiring mechanical ventilation. Before the institution of pressure-controlled ventilation, median pH and Pco(2) were 7.21 (range, 6.65-7.39) and 65 torr (29-264 torr), respectively. Four hours after pressure-controlled ventilation, median pH increased to 7.31 (6.98-7.45, p <.005), and Pco(2) decreased to 41 torr (21-118 torr, p <.005). For patients with respiratory acidosis (Pco(2) >45 torr) within 1 hr of starting pressure-controlled ventilation, the median length of time until Pco(2) decreased to <45 torr was 5 hrs (1-51 hrs). Oxygen saturation was maintained >95% in all patients. Two patients had pneumomediastinum before pressure-controlled ventilation. One patient each developed pneumothorax and subcutaneous emphysema after initiation of pressure-controlled ventilation. All patients survived without any neurologic morbidity. Median duration of mechanical ventilation was 29 hrs (4-107 hrs), intensive care stay was 56 hrs (17-183 hrs), and hospitalization was 5 days (2-20 days). CONCLUSIONS: Based on this retrospective study, we suggest that pressure-controlled ventilation is an effective ventilatory strategy in severe status asthmaticus in children. Pressure-controlled ventilation represents a therapeutic option in the management of such children.

Discrepancies between direct and indirect blood pressure measurements using various recommendations for arm cuff selection.

OBJECTIVE: The current recommendation for choosing an appropriate size cuff for measuring blood pressure (BP) is a bladder width to equal 40% of the upper arm circumference (UAC). However, most physicians use the older two-thirds or three-fourths upper arm length (UAL) recommendations to choose a cuff. The aim of this study was to verify the disparity in cuff size by using two-thirds UAL, three-fourths UAL, and 40% UAC criteria for cuff selection and to compare the indirectly measured BP by these criteria with directly measured radial intra-arterial BP. METHODS: A prospective, cross-sectional, observational study was conducted in 65 hemodynamically stable patients, aged 5 days to 22 years. Direct BP measurements were obtained from a radial intra-arterial catheter. Indirect BP measurements were taken from the same arm as the arterial catheter with a mercury sphygmomanometer and standard-size arm cuffs. UAL and UAC of each patient were measured, and the 3 cuffs closest to two-thirds and three-fourths UAL and 40% UAC were used. For each cuff, 3 direct and 3 indirect BP measurements were taken. Student t test was used to compare mean systolic and diastolic BP for direct and indirect measurements. RESULTS: A total of 172 observations were recorded, including 56 by two-thirds UAL, 55 by three-fourths UAL, and 61 by 40% UAC criteria. There was no significant difference between the means of the ideal cuff size by 40% UAC criterion and the actual cuffs used from the available standard cuffs. However, because of an unavailability of the larger cuffs for UAL criteria, the actual cuffs used were significantly smaller than ideal. Comparison of direct and indirect BP measurements revealed no significant difference in systolic BP when the latter was obtained by 40% UAC criterion. However, the difference in diastolic BP was significant. With available cuffs, a significant difference in systolic as well as diastolic BP was seen with both UAL criteria. CONCLUSIONS: Practitioners are likely to use significantly larger arm cuffs when following the two-thirds and three-fourths UAL criteria than when following the 40% UAC criterion. Of the 3 criteria for cuff selection, systolic BP by 40% UAC criterion most accurately reflects directly measured radial arterial pressure. However, the 40% UAC cuff significantly overestimates the diastolic pressure. Using available cuffs for indirect measurements by two-thirds and three-quarters UAL criteria significantly underestimates systolic as well as diastolic BP when compared with radial intra-arterial BP.