Abstract: Slide Presentations |

Hour-to-hour variation of FEV1/FVC FREE TO VIEW

Boris I. Medarov, MD*
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Long Island Jewish Medical Center, New Hyde Park, NY


Chest. 2004;126(4_MeetingAbstracts):744S-b-745S. doi:10.1378/chest.126.4_MeetingAbstracts.744S-b
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PURPOSE:  A number of physiologic functions and parameters have circadian variations. Pulmonary flow and resistance are not an exception. Our study investigates the day-time variations of the major PFT variables by comparing the mean values of those in nine time intervals- from 8 am to 4 pm.

METHODS:  The study population consisted of all PFT’s done in the study period (3/1997 to 5/2002, N=4835), which were divided into nine subgroups according to the time of the day the test was performed (TableTable.

Demographic characteristics of the studied population

Subgroup (time of PFT)Number of studies- nMale/female ratioAge- mean (SD)BMI-mean (SD)8 (8 am-8:59 am)4260.5257.0 (16.5)28.0 (6.3)9 (9 am-9:59 am)7140.4558.7 (16.4)28.1 (6.5)10 (10 am-10:59 am)6690.4659.3 (16.7)28.2 (6.9)11 (11 am-11:59 am)5200.4958.8 (18.1)27.5 (6.1)12 (12 pm-12:59 pm)4130.4961.3 (15.9)27.3 (6.2)13 (13 pm-13:59 pm)8120.4859.7 (17.4)27.5 (6.5)14 (14 pm-14:59 pm)7320.4559.3 (17.2)28.3 (6.9)15 (15 pm-15:59 pm)4410.4155.5 (18.6)28.1 (6.8)16 (16 pm-16:59 pm)1080.4755.7 (16.7)27.8 (6.2)

PFT- pulmonary function test SD- standard deviation

). One-way analysis of variance with Bonferroni pairwise comparisons was applied to evaluate the differences in FEV1, FVC and TLC. Kruskal-Wallis ANOVA was used for the FEV1/FVC ratio with subsequent Dunn’s pairwise multiple comparison procedures. A p-value of 0.05 or less was considered statistically significant. Only one test of a particular individual was allowed into the same subgroup, so the independence of the data in each group was ensured.

RESULTS:  The lowest median FEV1/FVC ratio was found in the 12 pm group (72.8%), the highest- in the 3 pm group (78.6%) [Figure]. Therefore, an absolute difference of 5.8% was detected between them(P<0.05). Similarly, the lowest FEV1 (1.81 l) was found in the 12 pm group and the highest- in the 3pm and 4 pm groups (2.12 and 2.17 l). Those differences were again highly statistically significant (p-values <0.001 and 0.035). The PEF (peak expiratory flow) variability was similar and also statistically significant. FVC showed a similar trend with the lowest value in the 12 pm group and the highest at 4pm. However, no statistically significant variation was detected in the pairwise comparison analysis.

CONCLUSION:  During working hours, the airway resistance appears to be the most prominent at noon and reaches its minimum around 4-5 pm.

CLINICAL IMPLICATIONS:  Along with its pure academic value, this clinically significant variation of the air flow characteristics may have some practical implications, e.g. timing the administration of long-acting bronchodilators, electively extubating patients in the later afternoon hours.

DISCLOSURE:  B.I. Medarov, None.

Tuesday, October 26, 2004

10:30 AM- 12:00 PM




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