**10. PH in non-CF Bronchiectasis**

the mean PAP by 13.9 mmHg was observed for all patients although only five had PH [19]. This reduction of PAP and hypoxic pulmonary vascular reactivity in OSA following CPAP treatment was associated with improved pulmonary endothelial function due to the elimina‐ tion of intermittent hypoxemia [19]. A randomised controlled cross-over trial using sham and effective CPAP in 23 patients with OSA (AHI = 44 ± 29.3/h) and 10 normal controls concluded that severe OSA was independently associated with PH [86]. The clinical impact of PH in sleepdisordered breathing remains under investigation. PH in OSA patients may lead to dyspnoea and reduction in 6MWD, suggesting functional impairment [91]. In a study of 296 OSA patients (AHI ≥ 20/hr) using nasal CPAP, pulmonary haemodynamics were not independently associated with mortality [42]. There are no consensus guidelines to recommend routine screening for PH in OSA. Although current data suggest improvement in PH when OSA is treated with CPAP therapy, the significance of this improvement in the clinical context remains

unclear, particularly with mild to moderate PH observed in most patients with OSA.

suggested a role of free radical-mediated reduction in NO bioavailability [93, 94].

45 m was observed and sildenafil was well tolerated [95].

**9. PH in Cystic Fibrosis (CF)**

High altitude PH (HAPH) prevalence is between 5 and 18% in those living at ≥3000 metres and may be more common in children than adults [9,11,92]. As mentioned previously, the roles of the endothelin-1 and prostaglandin I2 pathways in the pathophysiology in high altitude associated PH have not been clearly defined [9]. Alteration in trans-membrane transport of K+ and Ca2+ has been implicated in the process. Recent work by Beall et al. has

Migration to a lower altitude reverses HAPH. However, due to family, social and economic reasons, migration is not an option for some patients. As an alternative, sildenafil for 3 months has been shown to reduce PAP, improve 6MWD and cardiac index in patients with HAPH [95]. Reduction in mean PAP of up to -6.9 mmHg and improvement in walking distance of up to

The role of endothelin receptor antagonists in HAPH is yet to be determined. A small rando‐ mised cross-over study of 8 patients on bosentan did not improve pulmonary pressures or functional capacity when initiated prior to ascent during high intensity exercise [96]. Aceta‐ zolamide was successful in reducing pulmonary pressures and improving cardiac output at 6 months of therapy in patients with excessive erythrocytosis and HAPH [97]. Other drugs under evaluation include angiotensin inhibitors and results of the ongoing studies are pending.

PH prevalence in CF population remains uncertain with figures as high as 21-59%. A retro‐ spective study of 179 pre-transplant CF patients revealed that 38.5% had PH with a RHC mean PAP of ≥ 25 mmHg [98]. In a recent series of 57 CF patients with advanced lung disease considered for lung transplant, 36 (63.2%) had PH [99]. Patients with PH were significantly

**8. High altitude PH**

30 Pulmonary Hypertension

There are no systematic studies to determine true prevalence of PH in bronchiectasis, which is defined as a progressive and permanent dilatation of predominantly medium and small airways. Bronchiectasis is often accompanied with significant airway obstruction and airflow limitation, and is associated with considerable morbidity but low mortality.

In a recent study of 94 patients with bronchiectasis, 31 patients (32.9%) had PH, defined as systolic PAP of ≥40 mmHg on Doppler echocardiography [100]. Significant correlation was observed between right ventricular dimensions and systolic PAP (r = 0.74) while RV dimen‐ sions were inversely related to PaO2 values (r = - 0.37) suggesting a role for hypoxemia in the development of PH [100].

CT scan-derived measurements of the pulmonary artery have been shown to correlate favourably with the mean PAP derived from right heart catheterization [101-104]. In a study of 91 patients with bronchiectasis, increasing PH as characterised by CT measurements of PA dimensions was found to be an important prognostic marker [104].

As with CF patients, there is lack of data in managing PH in this group of patients.
