BACKGROUND: Cough is part of life in patients with cystic fibrosis (CF). Weak coughing may add to increased respiratory disease that affects the mechanical properties of cough in these patients. In this study, we investigated cough characteristics in relation to forced expiratory flow/volume indices in CF. METHODS: This prospective study included 54 subjects (26 ؎ 10 y old) with CF. Similar indices of the maneuvers were compared. Additionally, other cough characteristics revealed by the maneuvers were investigated. Cough was considered efficient with 6 or more secondary spikes at a flow of > 2.67 L/s. RESULTS: Cough peak flows similar to peak expiratory flows (regardless of FEV 1 severity level) were found in 98% of subjects. The secondary spike flows deteriorated alongside the percent-of-predicted FEV 1 (r 2 ؍ 0.17, P ؍ .002), yet inefficient secondary spike flows could also be found when FEV 1 was within normal range. Mean efficient spike number was low (2.5 ؎ 1.2 spikes/maneuver). Most cough spike flows were very small (< 0.9 L/s), resembling vibration that may contribute to the propulsion of mucus toward the central airways. Cough maneuver duration ended faster than forced expiration duration (3.7 ؎ 1.7 s vs 6.8 ؎ 2.5 s, P < .001), resulting in a smaller cough vital capacity compared with expiratory vital capacity (2.1 ؎ 0.9 l vs 3.1 ؎ 0.7 l, P < .001). Inspiratory volume below 2.23 ؎ 0.07 L reduced efficient secondary spike number. CONCLUSIONS: The cough flow/volume maneuver reveals abnormalities in cough velocities and volume. A low secondary spike correlates with FEV 1 severity level. The method may lead to earlier intervention to assist cough in CF.
EFLTV onset may be an important pathophysiological event that could influence the natural history of lung function decline in subjects with cystic fibrosis. This may lead to a significant deterioration in lung function in the following 2 years alongside an increase in the number of hospitalization days. The monitoring of FEV1 alone does not offer as good a threshold signal, because values are only moderately reduced. Therefore, identifying EFLTV appearance is potentially a signal for therapeutic intervention. Further studies are warranted to confirm our findings.
A reversibility test by an increase of greater than 12% in FEV1 can support a diagnosis of asthma and alter a patient's treatment plan but may not be applicable to the young ages. We retrospectively gathered spirometric data from 85/271 asthmatic children having mild obstruction (FEV1 > 80% predicted), age 2.6–6.9 years. Spirometry was performed before and 20 min after inhalation of 200 mcg Albuterol. We defined a deviation below −1.64 z scores from control as obstruction and an increased above 1.64 scores from control as a positive response to bronchodilators. Sensitivity of the index was considered significant if it captured >68% of the participants. The sensitivity of detecting airway obstruction in these children by FEV1 was 15.3% and 62.4% by FEF25–75. A positive response to Albuterol was an increase of 9.2% for FEV1 (12% for adults) and 18.5% for FEF25–75. The sensitivity for detecting a response to Albuterol in mild asthma was 64.7% by FEV1 and 91.8% by FEF25–75. Young children having normal spirometry can demonstrate airway reversibility. The response of spirometry parameters to bronchodilators may be more sensitive than obstruction detection and may help to support the diagnosis of asthma and adjust treatment plan.
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