Lung Hyperinflation Is Associated with Pulmonary Exacerbations in Adults with Cystic Fibrosis

Background: Forced expiratory volume 1 second (FEV1) has traditionally been used as a readily available marker of health in adult cystic fibrosis (CF). However, due to the obstructive nature of this disease, it is possible that lung hyperinflation could be more closely related to disease severity than is FEV1. The purpose of this study was to determine if hyperinflation is more closely associated with quality of life, functional status, and pulmonary exacerbations than FEV1 in patients with CF. Methods: Sixty-eight adult patients with CF were evaluated in this retrospective study. We used IC and functional residual capacity (FRC) and their ratios to total lung capacity (TLC) as measures of lung hyperinflation. We used bivariate correlations and backwards regression analysis to assess possible associations between FEV1, lung hyperinflation, and measures of disease severity including questionnaire based quality of life, pulmonary exacerbation frequency, and mortality. The respiratory component of the Cystic Fibrosis Questionnaire–Revised (CRQ-R-Respiratory) was used as a measure of quality of life. Results: Both FEV1 and IC were negatively correlated with pulmonary exacerbations over a 3 year period (p = 0.004, r2 = 0.127;p < 0.001, r2 = 0.307, respectively), while FRC/TLC correlated positively with exacerbations (p = 0.007). Backwards regression analysis showed that among pulmonary function variables, IC had the strongest relationship with exacerbations over 3 years. A lower CFQ-R-Respiratory score was associated with greater mortality (p = 0.005). However, no statistically significant relationships were found between lung function and mortality. Conclusions: FEV1 and lung hyperinflation-as measured by IC and FRC/TLC-are both associated with pulmonary exacerbation frequency. This suggests that chronic dynamic hyperinflation contributes significantly to disease severity in adult cystic fibrosis.

Dyspnea and respiratory muscle strength in end-stage liver disease

AIM:To investigate the prevalence of chronic dyspnea and its relationship to respiratory muscle function in end-stage liver disease.METHODS:Sixty-eight consecutive,ambulatory,Caucasian patients with end-stage liver disease,candidates for liver transplantation,were referred for preoperative respiratory function assessment.Forty of these(29 men) were included in this preliminary study after applying strict inclusion and exclusion criteria.Seventeen of 40 patients(42%) had ascites,but none of them was cachectic.Fifteen of 40 patients(38%)had a history of hepatic encephalopathy,though none of them was symptomatic at study time.All patients with a known history and/or presence of co-morbidities were excluded.Chronic dyspnea was rated according to the modified medical research council(mMRC) 6-point scale.Liver disease severity was assessed according to the Model for end-stage liver disease(MELD).Routine lung function tests,maximum static expiratory(Pemax) and inspiratory(Pimax) mouth pressures were measured.Respiratory muscle strength(RMS) was calculated from Pimax and Pemax values.In addition,arterial blood gases and pattern of breathing(VE:minute ventilation;VT:tidal volume;VT/TI:mean inspiratory flow;TI:duration of inspiration) were measured.RESULTS:Thirty-five(88%) of 40 patients aged(mean ± SD) 52 ± 10 years reported various degrees of chronic dyspnea(mMRC),ranging from 0 to 4,with a mean value of 2.0 ± 1.2.MELD score was 14 ± 6.Pemax,percent of predicted(%pred) was 105 ± 35,Pimax,%pred was 90 ± 29,and RMS,%pred was 97 ± 30.These pressures were below the normal limits in 12(30%),15(38%),and 14(35%) patients,respectively.Furthermore,comparing the subgroups of ascites to non-ascites patients,all respiratory muscle indices measured were found significantly decreased in ascites patients.Patients with ascites also had a significantly worse MELD score compared to non-ascites ones(P = 0.006).Significant correlations were found between chronic dyspnea and respiratory muscle function indices in all patients.Specifically,mMRC score was significantly correlated with Pemax,Pimax,and RMS(r =-0.53,P < 0.001;r =-0.42,P < 0.01;r =-0.51,P < 0.001,respectively).These correlations were substantially closer in the non-ascites subgroup(r =-0.82,P < 0.0001;r =-0.61,P < 0.01;r =-0.79,P < 0.0001,respectively) compared to all patients.Similar results were found for the relationship between mMRC vs MELD score,and MELD score vs respiratory muscle strength indices.In all patients the sole predictor of mMRC score was RMS(r =-0.51,P < 0.001).In the subgroup of patients without ascites this relationship becomes closer(r =-0.79,P < 0.001),whilst this relationship breaks down in the subgroup of patients with ascites.The disappearance of such a correlation may be due to the fact that ascites acts as a "confounding" factor.PaCO2(4.4 ± 0.5 kPa) was increased,whereas pH(7.49 ± 0.04) was decreased in 26(65%) and 34(85%) patients,respectively.PaO2(12.3 ± 0.04 kPa) was within normal limits.VE(11.5 ± 3.5 L/min),VT(0.735 ± 0.287 L),and VT/TI(0.449±0.129 L/s) were increased signifying hyperventilation in both subgroups of patients.VT/TI was significantly higher in patients with ascites than without ascites.Significant correlations,albeit weak,were found for PaCO2 with VE and VT/TI(r =-0.44,P < 0.01;r =-0.41,P < 0.01,respectively).CONCLUSION:The prevalence of chronic dyspnea is 88% in end-stage liver disease.The mMRC score closely correlates with respiratory muscle strength.