From the author:
I would like to thank V. Cottin and co-workers for their interest in our recently published study [1]. Their comments emphasise our conclusion that the treatment of the underlying disease should be the favoured strategy.
Since both patients did not have a reduced cardiac index, when treatment with sildenafil and bosentan was started the lack of a significant improvement was not really surprising. The two patients reported by V. Cottin and co-workers showed different reactions. Patient one deteriorated dramatically in World Health Organization (WHO) functional class and 6-min walk distance (6MWD) “despite” (or due to!) a decrease of pulmonary vascular resistance. This patient showed an excessive increase of cardiac index and a worsening of oxygenation, probably the consequence of increasing shunt perfusion resulting from reversing of vasoconstriction.
Patient two showed an early decrease of pulmonary artery pressure, no change in WHO functional class, and stable oxygenation and cardiac index, but a late improvement in 6MWD. It is questionable whether a short-term follow-up period is appropriate for patients with pulmonary hypertension due to obstructive lung disease. Patients with pulmonary hypertension and chronic obstructive pulmonary disease showed a maximum improvement of 6MWD after 8–9 months, thus, it is probable that these patients need a longer period in order to improve their functional capacity rather than decrease their pulmonary artery pressure [2].
As Meyer et al. [3] reported on respiratory muscle dysfunction and respiratory insufficiency in patients with idiopathic pulmonary arterial hypertension, in our daily practice we have to differentiate whether a patient presenting with severe pulmonary hypertension and hypoventilation is a patient with pulmonary hypertension due to hypoventilation or a patient with late diagnosed pulmonary arterial hypertension and consecutive respiratory failure. The treatment is different.
Another open question is how to treat patients with hypoventilation due to hypoventilation and residual pulmonary hypertension following noninvasive positive-pressure ventilation. Is this a vascular abnormality with a prognostic impact? Perhaps a look at cardiac index might be helpful.
For patients with pulmonary hypertension and lung disease, the current statement of the international conference on pulmonary hypertension recommends to separate patients with a predominantly exhausted circulatory or ventilatory reserve [4]. This is difficult in patients with severe pulmonary hypertension and hypoventilation. As we showed, these patients present with a high minute ventilation/carbon dioxide output slope but low respiratory exchange ratio and increasing end-tidal carbon dioxide tension reflecting a pattern which is different to that seen in patients with pulmonary arterial hypertension and patients with pure ventilatory impairment [1].
V. Cottin and co-workers encourage us to treat the underlying disease as stated in our study [1]. However, we believe that an additional prospective study is needed in order to obtain a clear idea of how to manage these specific patients with residual pulmonary hypertension despite effective noninvasive positive-pressure ventilation.
Footnotes
Conflict of interest: Disclosures can be found alongside the online version of this article at erj.ersjournals.com
- Received April 21, 2014.
- Accepted May 25, 2014.
- ©ERS 2014