To the Editors:
In a recent randomised sham-surgery-controlled trial, Koutsourelakis et al. 1 demonstrated that nasal surgery for fixed nasal obstruction did not improve, or even worsened, sleep-disordered breathing in a majority of 27 patients with obstructive sleep apnoea (OSA) syndrome.
Based on previous studies showing that the oral breathing route predisposes to OSA 2, Koutsourelakis et al. 1 compared the proportion of nasal breathing during sleep in responders and nonresponders to nasal surgery.
This post hoc analysis revealed that four responders spent a low proportion of the pre-operative sleep study with nasal breathing, as assessed via nasal cannula/pressure transducer and oral thermistor measurements. Koutsourelakis et al. 1 concluded that analysis of the oral–nasal breathing route during sleep might help to identify favourable candidates for nasal surgery among OSA patients with fixed nasal obstruction. As Koutsourelakis et al. 1 pointed out, their technique for assessing impaired nasal breathing during sleep was not ideal since it could not quantify nasal ventilation, and conventional rhinomanometry was also unhelpful in predicting the success of nasal surgery.
It has previously been shown that nasal resistance (and nasal airflow) is highly variable over time, with changes in body position and during sleep 3. The cyclical changes in side-predominance of nasal airflow over time (the nasal cycles) additionally contribute to the high variability of nasal resistance, particularly in the presence of anatomical obstacles. It is, therefore, unsurprising that the outcome of nasal surgery cannot be reliably predicted from measurement of nasal resistance by rhinomanometry during wakefulness 4 or from qualitative oral–nasal flow recordings. An unobtrusive technique based on a bilateral nasal cannula/pressure transducer system that permits side-selective quantitative measurements of nasal airflow and conductance over the course of a night has recently been developed and validated 3, 5.
We suggest that future studies on the effects of nasal surgery or pharmacological treatment on sleep-disordered breathing should include continuous quantitative nocturnal nasal conductance measurements for the accurate assessment of a subject’s nasal patency as a means of identifying potential responders to treatment.
Statement of interest
None declared.
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