Assessment of Respiratory Function and Need for Noninvasive Ventilation in a Cohort of Patients with Myotonic Dystrophy Type 1 Followed at One Single Expert Center

Table 5

Changes per year of respiratory features from the cohort available for follow-up.

	n	Overall cohort (n = 116)
		Median [IQR]
Follow-up period (months)	116	44.90 [26.32–59.20]
Nocturnal oximetry
Mean SpO2	91	−0.02 [−0.50–0.52]
Min SpO2	83	0.00 [−1.39–1.73]
ODI	82	−0.40 [−2.78–0.28]
Morning arterial blood gas analysis
pH	66	0.01 [0.00–0.02]
pCO2	68	−0.59 [−1.42–0.86]
pO2	66	−0.13 [−2.94–2.86]
HCO3-	65	−0.05 [−0.75–1.05]
Spirometry
FVC % sitting	115	−0.99 [−3.98–1.34]
FVC % supine	52	−0.72 [−2.58–2.09]
FEV1%	96	−0.54 [−3.21–2.88]
FEV1/FVC	96	0.02 [−0.01–0.04]
∆ FVC	52	−0.40 [−2.78–1.86]
PCEF	109	6.77 [−4.22–22.08]
MIP	20	1.51 [−4.19–9.83]
MEP	20	1.22 [−9.37–18.90]
6MWT
Meters	65	4.04 [−9.36–18.90]
Mean O2 saturation	45	−0.22 [−1.09–0.54]
Pretest dyspnea	48	0.00 [0.00–0.12]
Post-test dyspnea	45	0.00 [0.00–1.18]

IQR, interquartile range; SpO2, oxygen saturation; ODI, Oxygen Desaturation Index; pH, potential of hydrogen; pCO2, partial pressure of carbon dioxide; pO2, partial pressure of oxygen; HCO3-, bicarbonate; FVC, forced vital capacity; FEV1, forced expiratory volume in 1 second; PCEF, peak cough expiratory flow; MIP, maximal inspiratory pressure; MEP, maximal expiratory pressure; 6MWT, six-minute walk test; NIV, noninvasive ventilation. Pretest dyspnea and post-test dyspnea were calculated using the modified dyspnea Borg scale. This scale asks the patient to rate the difficulty of breathing from 0 (no difficulty) to 10 (maximal difficulty) at the very beginning of the 6MWT and immediately after.