Chest
Volume 133, Issue 4, April 2008, Pages 941-947
Journal home page for Chest

Original Research
COPD
Importance of Noninvasively Measured Respiratory Muscle Overload Among the Causes of Hospital Readmission of COPD Patients

https://doi.org/10.1378/chest.07-1796Get rights and content

Aim

To evaluate the influence of respiratory muscle overload and right cardiac overload among the possible risk factors of hospital readmission in a 1-year follow-up of a cohort of patients with moderate-to-severe COPD.

Methods

A total of 112 COPD patients who were admitted consecutively to the hospital for acute exacerbation. At hospital discharge, we evaluated the conventional clinical and functional determinations in addition to the pressure-time index (PTI), which is obtained using the equation PTI = (Pawo/Pimax) × (Ti/Ttot) × 100, where Pawo represents the mean airway pressure measured at the mouth during spontaneous breathing, Pimax is the maximal inspiratory pressure, Ti is the inspiratory time, and Ttot is the total breathing cycle time. A cardiac echo-Doppler examination was carried out when patients were in stable condition and presented clinical signs of right cardiac overload prior to inclusion in the study.

Results

Multivariate analysis showed that the use of long-term oxygen therapy (LTOT) and high PTI (> 0.25) were independently related to the risk of hospital readmission. Patients receiving LTOT had higher Paco2 (p < 0.05), FEV1 percent predicted (p < 0.05), FVC percent predicted (p < 0.05), and Pao2 (p < 0.05), and had higher Paco2 (p < 0.05). An elevated systolic pulmonary arterial pressure (> 40 mm Hg) was also independently related, but only 28 patients had echo-Doppler data that could be used.

Conclusions

At hospital discharge, noninvasively measured respiratory muscle overload as well as the use of LTOT were associated with an increased risk of hospital readmission for exacerbation in patients with moderate-to-severe COPD.

Section snippets

Patients

All of the patients with moderate-to-severe COPD (112 subjects), who were admitted consecutively to a hospital ward between January 2004 and December 2004 for an acute exacerbation of COPD, were included in this study. The patients had COPD confirmed by a medical history including current smoking status or smoking history (ie, history of > 10 pack-years), clinical evaluation, and pulmonary functional testing results showing airflow obstruction (ie, FEV1/FVC ratio < 70) with a change in FEV1 of

Results

The characteristics of the study patients at hospital discharge are shown in Table 1. All patients were men with a mean age of 69.3 ± 7.5 years. The smoking history for the whole group was evaluated at 75 ± 40 pack-years. Airway obstruction was moderate to severe because the mean FEV1 was 43 ± 12% predicted. The group as a whole showed moderate hypoxemia (mean Pao2, 62.7 ± 9.1 mm Hg) and hypercapnia (mean Paco2, 48.01 ± 8.4 mm Hg). Nevertheless, 27 of the 112 patients had a Pao2 of < 60 mm Hg

Discussion

The main findings of our study show that high respiratory muscle load assessed by means of the PTI and treated with LTOT are independent predictive factors for hospital readmission in patients with moderate-to-severe COPD. Cardiac overload assessed by an elevated estimate of SPAP also appears to be a predictive factor, but the low number of patients who had undergone an echo-Doppler examination greatly detracted from the clinical relevance of this statistical finding.

. Functional

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  • Cited by (0)

    The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

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