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 6

Changes per year of the respiratory parameters in the 2 cohorts according to NIV indication.

	n	Cohort 1 (n = 59)	n	Cohort 2 (n = 57)	p value
		No NIV indication		NIV indication at baseline
		Median [IQR]		Median [IQR]
Follow-up period (months)	59	38.10 [24.13–55.60]	57	46.17 [31.17–60.83]	0.0758
Nocturnal oximetry
Mean SpO2	39	−0.34 [−0.61–0.04]	52	0.24 [−0.33–1.07]	0.0016
Min SpO2	35	0.27 [−0.74–1.30]	48	0.00 [−2.19–2.47]	0.9742
ODI	33	−0.02 [−0.53–0.71]	49	−2.13 [−4.07–−0.08]	0.0008
Morning ABG
pH	28	0.00 [−0.01–0.02]	38	0.01 [0.00–0.02]	0.1966
pCO2	30	−0.09 [−1.34–1.72]	38	−0.97 [−1.91–0.00]	0.0342
pO2	29	−1.46 [−5.11–3.41]	37	0.26 [−1.96–2.59]	0.5523
HCO3-	28	0.31 [−1.13–1.49]	37	−0.16 [−0.68–0.59]	0.5035
Spirometry
FVC % sitting	58	−1.17 [−3.98–1.43]	57	−0.97 [−3.95–1.19]	0.9354
FVC % supine	42	−0.79 [−2.72–1.97]	10	−0.58 [−2.37–5.56]	0.5081
FEV1%	46	−0.91 [−2.68–2.96]	50	−0.33 [−3.87–2.81]	0.9124
FEV1/FVC	46	0.03 [0.01–0.06]	50	0.00 [−0.01–0.02]	<0.0001
∆ FVC	42	−0.40 [−2.67–2.23]	10	−0.66 [−5.91–0.20]	0.4505
PCEF	58	10.88 [2.99–30.61]	51	1.38 [−17.49–16.12]	0.0048
MIP	14	2.89 [−4.85–17.37]	6	1.51 [−3.53–1.84]	0.5362
MEP	14	−0.01 [−10.10–35.66]	6	2.02 [−1.57–12.45]	0.9671
6MWT
Meters	37	5.09 [−9.61–18.90]	28	2.89 [−8.18–22.48]	0.9525
Mean O2 saturation	28	−0.34 [−1.07–0.08]	17	0.26 [−1.12–0.77]	0.2101
Pretest dyspnea	30	0.00 [0.00–0.00]	18	0.00 [−0.52–0.24]	0.6302
Post-test dyspnea	28	0.00 [−0.12–1.19]	17	0.29 [0.00–1.18]	0.7490

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.