Patients with COPD exhibit greater oxyhemoglobin desaturation during walking than with cycling. The purpose of this investigation was to investigate differences in ventilatory responses and gas exchange as proposed mechanisms for this observation.

Arterial blood gas and lactate levels were measured in 12 patients with COPD (aged 68 ± 6 years) during incremental treadmill and cycle exercise. The primary outcome to assess the ventilatory response to exercise was Pao₂. The primary outcome to assess impairment in exercise gas exchange was the difference between partial pressures of alveolar and arterial oxygen (Pao₂ – Pao₂).

Pao₂ in patients was significantly lower at peak exercise for treadmill walking (51.4 ± 6.8 mm Hg) compared with cycling (60.4 ± 10.7 mm Hg) (P = .002). The initial increase in Pao₂ with cycling occurred prior to the onset of the anaerobic threshold. At peak exercise, Pao₂ was significantly higher with cycling compared with walking (P = .004). The anaerobic threshold occurred at a lower oxygen consumption during cycling than walking (P = .001), and peak lactate levels were higher with cycling (P = .019). With progressive exercise, Pao₂ – Pao₂ increased similarly during treadmill and cycle exercise.

The higher Pao₂ during cycling minimized the magnitude of oxyhemoglobin desaturation compared with walking. The enhanced respiratory stimulation during cycling appears due to an initial neurogenic process, possibly originating in receptors of exercising muscles, and a subsequent earlier onset of anaerobic metabolism with higher lactate levels during cycling.

Lymph node (LN) status is an important component of staging; it provides valuable prognostic information and influences treatment decisions. However, the prognostic significance of the number of positive LNs in N1 non-small cell lung cancer (NSCLC) remains unclear. In this study we evaluated whether a higher number of positive LNs results in worse survival among patients with N1 disease.

The Surveillance, Epidemiology, and End Results database was used to identify 3,399 patients who underwent resection for N1 NSCLC. Subjects were categorized into groups based on the number of positive nodes: one, two to three, four to eight, and more than eight positive LNs. The prognostic significance of the number of positive LNs in relation to survival was evaluated using the Kaplan-Meier method. Stratified and Cox regression analysis were used to evaluate the relationship between the number of positive LNs and survival after adjusting for potential confounders.

Unadjusted survival analysis showed that a greater number of N1 LNs was associated with worse lung cancer-specific (P < .0001) and overall (P < .0001) survival. Mean lung cancer-specific survival was 8.8, 8.2, 6.0, and 3.9 years for patients with one, two to three, four to eight, and more than eight positive LNs, respectively. Stratified and adjusted analysis also showed the number of N1 LNs was an independent predictor of survival after controlling for potential confounders.

The number of positive LNs is an independent prognostic factor of survival in patients with N1 NSCLC. This information may be used to further stratify patients with respect to risk of recurrence in order to determine postoperative management.

The role of Mycoplasma pneumoniae (Mp) in the initiation and persistence of asthma remains elusive. Mp community-acquired respiratory distress syndrome toxin (CARDS Tx) is a unique virulence factor that induces an intense lymphocytic response and exacerbates asthma in animal models. We sought to determine the incidence of Mp infection and the presence of CARDS Tx in subjects with refractory asthma (RA).

We conducted a prospective observational study in 64 subjects with RA. Respiratory secretions (sputum, nasal lavage, and throat swab) and blood were analyzed for the presence of CARDS Tx and P1 adhesin (P1) DNA by polymerase chain reaction (PCR), and CARDS Tx by antigen capture. Serum IgM and IgG antibodies to CARDS Tx were determined by enzyme-linked immunosorbent assay (ELISA).

Thirty-three of 64 subjects (52%) tested positive for Mp: 29 of 33 by CARDS Tx vs 10 of 33 by P1 assays. Ten subjects followed longitudinally for up to 633 days tested persistently positive for Mp. There were no significant differences in Mp-specific IgG responses between Mp-positive and Mp-negative groups. Eight of 10 subjects who tested persistently positive failed to mount a substantial IgG response to CARDS Tx, and up to 8 weeks of clarithromycin failed to eradicate Mp in five subjects.

Subjects with RA may be chronically infected with Mp. PCR for CARDS Tx appears to be the most sensitive method of identifying Mp infection. Despite the persistence of Mp in subjects with RA, some subjects failed to mount an IgG response, and macrolide therapy was insufficient to eradicate Mp.

Both chronic airway obstruction and obesity are increasing in prevalence but the effect of their combination on pulmonary function parameters across the range of airway obstruction is unknown.

We studied the impact of increasing BMI on static lung volumes and airway function in a cohort of 2,265 subjects from a large pulmonary function laboratory database who were 40 to 80 years of age and met GOLD (Global Initiative for Chronic Obstructive Lung Disease) spirometric criteria for COPD (postbronchodilator FEV₁/FVC < 0.7). We also evaluated the influence of severity of airway obstruction (by GOLD criteria) on these relationships.

With increasing BMI in the group as a whole, functional residual capacity, residual volume, expiratory reserve volume, and specific airway resistance (sRaw) decreased exponentially (all P < .001); total lung capacity (TLC) decreased linearly (P < .001); and inspiratory capacity (IC) and IC/TLC increased linearly (P < .001). However, vital capacity was not influenced significantly. The effects of increasing BMI on FEV₁/FVC and sRaw were greatest in GOLD stage III/IV (P < .05), whereas increasing BMI had greater effects on IC in GOLD stage I (P < .001).

With increasing BMI, subjects with airway obstruction had consistent reductions in lung hyperinflation, with significant improvements in IC and the FEV₁/FVC ratio; this effect was greatest in patients with the most severe airway obstruction. These results have important implications for the clinical assessment of patients with combined obesity and airway obstruction.