Brief Article
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World J Hepatol. Feb 27, 2013; 5(2): 56-63
Published online Feb 27, 2013. doi: 10.4254/wjh.v5.i2.56
Dyspnea and respiratory muscle strength in end-stage liver disease
Georgios Kaltsakas, Efstathios Antoniou, Anastasios F Palamidas, Sofia-Antiopi Gennimata, Panorea Paraskeva, Anastasios Smyrnis, Antonia Koutsoukou, Joseph Milic-Emili, Nickolaos G Koulouris
Georgios Kaltsakas, Anastasios F Palamidas, Sofia-Antiopi Gennimata, Antonia Koutsoukou, Nickolaos G Koulouris, Respiratory Function Lab, 1st Respiratory Medicine Department, “Sotiria” Hospital for Diseases of the Chest, University of Athens, 11527 Athens, Greece
Efstathios Antoniou, Panorea Paraskeva, Anastasios Smyrnis, 2nd Propaedeutic Surgery Department, “Laiko” Hospital, University of Athens, 11526 Athens, Greece
Joseph Milic-Emili, Meakins-Christie Labs, McGill University, Montreal QC H3A 0G4, Canada
Author contributions: Kaltsakas G, Antoniou E, Palamidas AF, Gennimata SA, Paraskeva P, Smyrnis A, Koutsoukou A, and Koulouris NG made measurements on the subjects, analysed the data, and contributed in lengthy discussions during the writing of the paper; Milic-Emili J made constructive criticisms; Kaltsakas G, Antoniou E, and Koulouris NG wrote the paper.
Correspondence to: Nickolaos G Koulouris, MD, PhD, FCCP, Professor of Respiratory Medicine, 1st Respiratory Medicine Department, “Sotiria” Hospital for Diseases of the Chest, University of Athens, 152, Mesogeion Ave, 11527 Athens, Greece.
Telephone: +30-210-7763684 Fax: +30-210-7223420
Received: June 14, 2012
Revised: October 20, 2012
Accepted: November 25, 2012
Published online: February 27, 2013

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.

Keywords: Liver transplantation, Lung function testing, Maximum static mouth pressures, Pattern of breathing, Respiratory muscle strength