Hypoxic and hypercapnic ventilatory responses in Prader-Willi syndrome

Area of Science:

• Respiratory Physiology
• Neurology
• Genetics

Background:

• Sleep-disordered breathing is common in Prader-Willi syndrome (PWS).
• Abnormalities in ventilatory control are suspected contributors to PWS pathophysiology.
• Obesity is a frequent comorbidity in PWS, potentially exacerbating respiratory issues.

Purpose of the Study:

• To investigate ventilatory control abnormalities in nonobese and obese PWS patients.
• To compare hypercapnic (HCVR) and hypoxic (HPVR) ventilatory responses in PWS patients versus healthy controls.
• To determine the influence of obesity and PWS on ventilatory control.

Main Methods:

• Measured rebreathing hypercapnic and hypoxic ventilatory responses (HCVR and HPVR) during wakefulness.
• Included 8 nonobese PWS (NOB-PWS), 9 obese PWS (OB-PWS), 24 healthy nonobese controls (NOB-CON), and 10 obese controls (OB-CON).
• Analyzed slopes and points of origin for HCVR and HPVR.

Main Results:

• HCVR slope was similar in NOB-PWS and NOB-CON, but significantly lower in OB-PWS compared to OB-CON (P < 0.02).
• PWS patients had higher end-tidal PCO2 at the start of positive HCVR slope.
• Isocapnic HPVR was absent or markedly reduced in PWS patients, independent of obesity (P < 0.006).

Conclusions:

• Nonobese PWS patients have normal HCVR, while obese PWS patients exhibit blunted HCVR.
• Hypoxic ventilatory response (HPVR) is significantly impaired in all PWS patients.
• The primary ventilatory control defect in PWS likely involves peripheral chemoreceptor pathways.