The prevailing view is that exertional dyspnoea in patients with combined idiopathic pulmonary fibrosis (IPF) and emphysema (CPFE) can be largely explained by severe hypoxaemia. However, there is little evidence to support these assumptions.We prospectively contrasted the sensory and physiological responses to exercise in 42 CPFE and 16 IPF patients matched by the severity of exertional hypoxaemia. Emphysema and pulmonary fibrosis were quantified using computed tomography. Inspiratory constraints were assessed in a constant work rate test: capillary blood gases were obtained in a subset of patients.CPFE patients had lower exercise capacity despite less extensive fibrosis compared to IPF (p=0.004 and 0.02, respectively). Exertional dyspnoea was the key limiting symptom in 24 CPFE patients who showed significantly lower transfer factor, arterial carbon dioxide tension and ventilatory efficiency (higher minute ventilation (V′E)/carbon dioxide output (V′CO2) ratio) compared to those with less dyspnoea. However, there were no between-group differences in the likelihood of pulmonary hypertension by echocardiography (p=0.44). High dead space/tidal volume ratio, low capillary carbon dioxide tension emphysema severity (including admixed emphysema) and traction bronchiectasis were related to a high V′E/V′CO2 ratio in the more dyspnoeic group. V′E/V′CO2 nadir >50 (OR 9.43, 95% CI 5.28–13.6; p=0.0001) and total emphysema extent >15% (2.25, 1.28–3.54; p=0.01) predicted a high dyspnoea burden associated with severely reduced exercise capacity in CPFEContrary to current understanding, hypoxaemia per se is not the main determinant of exertional dyspnoea in CPFE. Poor ventilatory efficiency due to increased “wasted” ventilation in emphysematous areas and hyperventilation holds a key mechanistic role that deserves therapeutic attention.

Determination of potentially-reversible factors contributing to exertional dyspnea remains an unmet clinical need in chronic thromboembolic pulmonary hypertension (CTEPH). Therefore, we aimed to evaluate the influence of inspiratory muscle weakness (IMW) on exercise capacity and dyspnea during effort in patients with CTEPH. We performed a prospective cross-sectional study that included thirty-nine consecutive patients with CTEPH (48 ± 15 yrs, 61% female) confirmed by right heart catheterization that underwent an incremental cardiopulmonary exercise test, 6-minute walk test and maximum inspiratory pressure (MIP) measurement. MIP < 70%pred was found in 46% of patients. On a multiple linear regression analysis, MIP was independently associated with 6MWD and . Patients with MIP < 70% presented greater than those with MIP ≥ 70%. Additionally, they also presented stronger sensations of dyspnea throughout exercise, even when adjusted for ventilation. At rest and at different levels of exercise, mean inspiratory flow (VT/TI) was significantly higher in patients with MIP < 70%. In conclusion, IMW is associated with a rapid increase of dyspnea, higher inspiratory load and poor exercise capacity in patients with CTEPH.

Key pointsr Dysfunction of post-exercise cardiac autonomic control is associated with increased mortality risk in healthy adults and in patients with cardiorespiratory diseases.r The afferent mechanisms that regulate the post-exercise cardiac autonomic control remain unclear.r We found that afferent signals from carotid chemoreceptors restrain the post-exercise cardiac autonomic control in healthy adults and patients with pulmonary arterial hypertension (PAH).r Patients with PAH had higher carotid chemoreflex sensitivity, and the magnitude of carotid chemoreceptor restraint of autonomic control was greater in patients with PAH as compared to healthy adults.r The results demonstrate that the carotid chemoreceptors contribute to the regulation of post-exercise cardiac autonomic control, and suggest that the carotid chemoreceptors may be a potential target to treat post-exercise cardiac autonomic dysfunction in patients with PAH.Abstract Dysfunction of post-exercise cardiac autonomic control predicts mortality, but its underlying mechanisms remain unclear. We tested whether carotid chemoreflex activity restrains post-exercise cardiac autonomic control in healthy adults (HA), and whether such restraint is greater in patients with pulmonary arterial hypertension (PAH) who may have both altered carotid chemoreflex and altered post-exercise cardiac autonomic control. Twenty non-hypoxaemic patients with PAH and 13 age-and sex-matched HA pedalled until 90% of peak work rate observed in a symptom-limited ramp-incremental exercise test. Recovery consisted of unloaded pedalling for 5 min followed by seated rest for 6 min. During recovery, subjects randomly inhaled either 100% O 2 (hyperoxia) to inhibit the carotid chemoreceptor activity, or 21% O 2 (normoxia) as control. Post-exercise cardiac autonomic control was examined via heart rate (HR) recovery (HRR; HR change after 30, 60, 120 and 300 s of recovery, using linear and non-linear regressions of HR decay) and HR variability (HRV; time and spectral domain analyses). As expected, the PAH group had higher carotid chemosensitivity and worse post-exercise HRR and HRV than HA. Hyperoxia increased HRR at 30, 60 and 120 s and absolute spectral power HRV in both groups.Additionally, hyperoxia resulted in an accelerated linear HR decay and increased time domain HRV during active recovery only in the PAH group. In conclusion, the carotid chemoreceptors restrained recovery of cardiac autonomic control from exercise in HA and in patients with PAH, with the restraint greater for some autonomic indexes in patients with PAH.

The baroreflex integrity in early-stage pulmonary arterial hypertension (PAH) remains uninvestigated. A potential baroreflex impairment could be functionally relevant and possibly mediated by enhanced peripheral chemoreflex activity. Thus, we investigated 1) the cardiac baroreflex in non-hypoxemic PAH; 2) the association between baroreflex indexes and peak aerobic capacity (i.e., V̇O2peak); and 3) the peripheral chemoreflex contribution to the cardiac baroreflex. Nineteen patients and 13 age- and sex-matched healthy adults (HA) randomly inhaled either 100% O2 (peripheral chemoreceptors inhibition) or 21% O2 (control session), while at rest and during a repeated sit-to-stand maneuver. Beat-by-beat analysis of R-R intervals and systolic blood pressure provided indexes of cardiac baroreflex sensitivity (cBRS) and effectiveness (cBEI). The PAH group had lower cBEIALL at rest (mean ± SD: PAH = 0.5 ± 0.2 vs HA = 0.7 ± 0.1 a.u., P = 0.02) and lower cBRSALL (PAH = 6.8 ± 7.0 vs HA = 9.7 ± 5.0 ms mmHg-1, P < 0.01) and cBEIALL (PAH = 0.4 ± 0.2 vs HA= 0.6 ± 0.1 a.u., P < 0.01) during the sit-to-stand maneuver versus the HA group. The cBEI during the sit-to-stand maneuver was independently correlated to V̇O2peak (partial r = 0.45, P < 0.01). Hyperoxia increased cBRS and cBEI similarly in both groups at rest and during the sit-to-stand maneuver. Therefore, cardiac baroreflex dysfunction was observed under spontaneous and, most notably, provoked blood pressure fluctuations in non-hypoxemic PAH, was not influenced by the peripheral chemoreflex, and was associated with lower V̇O2peak suggesting it could be functionally relevant.

We read with interest the recently published article by Fussner et al. (1) in Liver Transplantation. The authors showed that intrapulmonary vascular dilatations (IPVDs), detected by agitated saline contrast-enhanced transthoracic echocardiography (cTTE), were common in patients with portopulmonary hypertension (POPH)-59% of patients. Moreover, this finding was associated with decreased survival, and the authors suggest the possibility of a pathophysiological overlap between POPH and hepatopulmonary syndrome in patients with end-stage liver disease. (1) Interestingly, this feature was previously described in patients with schistosomiasis. (2,3) Early reports of the disease identified a unique pattern of pulmonary involvement in patients with schistosomiasis: pulmonary hypertension with central cyanosis in the absence of intracardiac shunt. (2) In 1 study, IPVD was found in 20% of patients with schistosomiasis cor pulmonale. (3) According to necroscopic studies, cyanosis was associated with arteriovenous fistulae, possibly due to bypass of Schistosoma eggs in pulmonary circulation. Furthermore, other investigators confirm this finding and hypothesized that it could be related to repeated worm infestation, common in endemic areas. The pathophysiology of schistosomiasis-associated pulmonary arterial hypertension (Sch-PAH) is not completely understood, but it probably shares some similarities with POPH, in a model without liver cirrhosis.Sch-PAH is potentially the most common cause of pulmonary hypertension worldwide and is associated with higher survival rates compared to IPAH. (4) Our group recently published an article contrasting physiological responses to incremental exercise in cardiopulmonary exercise tests (CPETs) between naive patients with Sch-PAH (n 5 8) and with idiopathic pulmonary arterial hypertension (IPAH) (n 5 9) with similar resting hemodynamics. Interestingly, Sch-PAH showed less impaired physiological responses to incremental exercise than IPAH patients, suggesting a more preserved cardiopulmonary response to exercise in Sch-PAH, which could be related to its better clinical course compared to IPAH. (5) However, at that time, the mechanisms involved were not identified. Even though none of the patients with Sch-PAH had cyanosis or hypoxemia (only 3 had SpO 2 90% at the end of the incremental CPET), cTTE was performed after the publication, and IPVD was detected in 6/8 (75%) Sch-PAH patients (data not published). It is noteworthy that despite the high prevalence of IVPD in this study, only 2 patients died to date (1 of them was without IPVD), which contrasts with the poor prognosis of the presence of IPVD in patients with cirrhosis described by Fussner et al. (1) The clinical relevance of the presence of IPVD in patients with Sch-PAH is not clear, but it is possible to hypothesize that IPVD could attenuate right ventricular stress during exercise. Further studies are needed in order to obtain a better understanding of the natural history of IPVD associated with schistosomiasis as well as to assess...