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 7

Changes per year in the patients’ respiratory parameters based on their NIV adherence.

		NIV nonadherent (n = 40)		NIV adherent (n = 17)	p value
Follow-up period (months)	40	48.20 [31.50–61.35]	17	46.17 [31.17–59.73]	0.6691
Nocturnal oximetry
Mean SpO2	36	0.00 [−0.47–0.71]	16	0.68 [0.07–2.90]	0.0198
Min SpO2	35	0.00 [−2.61–0.99]	13	3.12 [1.34–4.87]	0.0093
ODI	34	−0.41 [−3.04–0.14]	15	−3.66 [−6.88–−2.64]	0.0033
Morning ABG
pH	27	0.01 [0.00–0.02]	11	0.01 [0.00–0.02]	0.9743
pCO2	27	−1.08 [−1.81–0.00]	11	−0.55 [−2.67–0.04]	0.8469
pO2	27	−0.82 [−2.94–1.80]	10	2.72 [0.26–6.12]	0.0175
HCO3-	27	−0.05 [−0.67–1.05]	10	−0.30 [−1.04–0.24]	0.1879
Spirometry
FVC % sitting	40	−1.67 [−4.35 to −0.13]	17	0.92 [−0.85–2.29]	0.0273
FVC % supine	9	−0.66 [−2.37–1.98]	0
FEV1%	36	−0.47 [−4.00–2.44]	14	0.36 [−1.72–2.81]	0.4055
FEV1/FVC	36	0.00 [−0.01–0.02]	14	0.00 [−0.02–0.02]	0.6198
∆ FVC	9	0.00 [−2.84–0.20]	0
PCEF	34	4.12 [−12.43–16.17]	17	−2.66 [−18.96–15.39]	0.5690
MIP	5	1.35 [−3.53–1.66]	0
MEP	5	−0.71 [−1.57–4.74]	0
6MWT
Meters	19	5.36 [−7.86–18.07]	9	−2.42 [−42.63–28.80]	0.5225
Mean O2 saturation	11	0.50 [−1.12–2.19]	6	0.13 [−1.12–0.60]	0.6511
Pretest dyspnea	12	0.00 [−0.28–0.26]	6	0.0 [−0.52–0.00]	0.7688
Post-test dyspnea	11	0.29 [0.00–1.51]	6	0.26 [0.00–0.52]	0.6470

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.