Home mechanical ventilation in a patient with Duchenne muscular dystrophy

Anthropometry: Height: 178 cm Weight 36 kg BMI: 11.36 kg/m²
Physical examination: eupnoea, normosthenic, kyphoscoliosis, flection conctrations of upper and lower limbs, cold extremities, tachycardia 118/min
Spirometry: “restrictive” ventilatory impairment – based on FVC and FEV1, since body plethysmography could not be conducted due to physical limitations (Figure 1)
Blood gases: arterialised capillary blood: pH 7.393, pCO₂ 6.21 kPa, pO₂ 8.23 kPa, HCO₃ 27.80 mmol/L, SaO₂ 91.30%

Chest X-ray: no infiltrations or shadows, significant deforming sinistrokyphoscoliosis (Figure 2)
Polygraphy: moderate obstructive sleep apnoea with apnoea-hypopnoea index 19.7 episodes/h, oxygen desaturation index 13.3 episodes/h, mean saturation 93%, time with saturation below 90% was 36.5 min (Figure 3).

Patient was treated by mechanical home ventilation, machine that enables to distinct ventilation modes (Figure 4). Primary – nocturnal regime was ventilation by bi-level positive airway pressure (BiPAP) in spontaneous-timed mode (ST), inspiratory pressure was set on 10 cmH₂O, expiratory pressure 5 cmH₂O, backup frequency 12 breaths/min, with nasal mask (Figure 5). Secondary – daytime regime was the mouthpiece ventilation (MPV) with tidal volume of 850 ml (Figure 6). On these settings we achieved good tolerance of the patient, complete elimination of apnoeic and hypopnoeic episodes, reduction of oxygen desaturation index from 13.3 to 0.5 episodes/h, increase of mean nightime saturation from 93% to 95.4%. In blood gases we observed reduction of hypercapnia from 6.21 to 6.13 kPa, elevation of pO₂ from 8.23 to 10.16 kPa and saturation from 91.3 to 94.5% (Figure 7).

Duchenne muscular dystrophy
Severe levokyphoscoliosis
Chronic respiratory failure
Moderate obstructive sleep apnoea

In DMD natural history of illness includes progressive worsening of pulmonary functions and development of respiratory failure. Respiratory failure appears at first during sleep and that is why it is recommended to conduct full overnight polysomnography, preferably with capnography. This allows for monitoring not only night time hypoventilation due to respiratory muscle weakness and decrease of respiratory drive in brainstem, but also apnoeic and hypopnoeic episodes. The episodes occur frequently in DMD and they are predominantly present in REM sleep in the phase of muscle atonia. They are often of central type. Worsening of nocturnal saturations can be effectively predicted by spirometry.

International guidelines for the management of respiratory failure propose a combination of noninvasive ventilation, cough assistant (Figure 8) and home oximetry monitoring. Saturations should be kept over 95% by these methods. Usually the patients are at first ventilated on mask only at night and they use mouthpiece ventilation at daytime as required by their needs. Mouthpiece ventilation is a method that provides deep breath similar to sigh or yawn. It enables patients to talk or eat without exhaustion. However, it requires firm seal of lips around mouthpiece and patient´s cooperation.

Gradually, night time ventilation cedes to be sufficient in keeping adequate blood gases and patients require continuous ventilation on mask. International experience shows that noninvasive ventilation in DMD slows down worsening of pulmonary functions, reduces need of switching to tracheostomy, frequency of hospitalisations and prolongs life. In noninvasively ventilated patients the median of survival is about 27 years with some living up to 40 years.
In Slovakia noninvasive ventilation is recommended in DMD patient with daytime hypercapnia or in presence of signs of respiratory distress.
In this patient we started noninvasive ventilation at the first signs of respiratory failure in order to decrease progression of disease sequelae and improve quality of life.