Deterioration of respiratory function is a critical factor in amyotrophic lateral sclerosis (ALS).1 Respiratory tract infections (RTIs) are the principal causes of morbidity and mortality.2 Low level of peak cough expiratory flow (PCEF) is associated with a high risk for pulmonary complications during RTIs,3–5 for hospisalization,6 and is also considered an indicator for spontaneous cough effectiveness during an acute RTI.6–8 PCEF reflects the capacity to expulse debris from the airways (cough efficacy) and values less than 160L/min are associated with extubation failure.9

After RTIs, subjects with neuromuscular diseases have a slow recovery of clinical, functional and oxygenation parameters.3

Studies have also demonstrated the importance of using specific cough assistance techniques9–13 in order to avoid rehospitalisation.4,11,14–18

Although easily evaluable, PCEF is not routinely done at home in subjects with ALS.

The primary aim of this study was to evaluate, in subjects with non-bulbar ALS, the feasibility of a long-term (9 months), home-based, comprehensive protocol involving daily self-monitoring for cough capacity. Changes in objective (PCEF and SpO2) and subjective (respiratory discomfort [RD]) respiratory variables, occurrence of respiratory deterioration events (RDEs) and influence of baseline PCEF and its decline during time on RDEs were evaluated as secondary outcomes.

From April 2009 to July 2012, 18 subjects with ALS who met eligibility criteria were identified. Four subjects refused to participate and two subjects withdrew consent. Therefore, data for 12 subjects were analysed (66.7% of acceptance). Anthropometric, functional and ABG data at baseline are shown in Table 1. During an average period of follow-up of 125±102 days (range 21–270), the 12 subjects performed a total of 1175 measures. The total compliance for all abovementioned parameters was 37±32% (range 8–100%) worsening across time from 63±27% (at months 1–3) to 26±39% (at months 3–6), and (22±35%) at months 6–9. During the study, the subjects sent data reported on the diary mainly by e-mail (69%).

16% of subjects delivered data by personal contact, and the remaining provided over telephone. 58% of subjects, because of delay in delivery, had to be followed up by phone at least once by PT and they performed PCEF with caregiver assistance.

One patient (8%) presented clinical instability not related to respiratory causes. Five out of the 12 subjects studied (42%) reported six episodes of RDEs: one episode of chest infection with fever needing antibiotics at home, three episodes of desaturation and disturbed sleep with urgent need to also increase time of NIV during the day without any change in NIV setting, one episode of severe secretion encumbrance with activation of more frequent use of manual assisted cough manoeuvres without any change in device setting (repetitive two hours application for 36 consecutive hours), one episode of respiratory failure needing hospitalisation and need for 24h NIV use. Two consecutive episodes, both due to urgent need to increase time of NIV, were reported by the same patient after 21 and 92 days from the start of the study. The mean time before the first RDE was 136±108 days (range 21–255 days). None of the subjects received mechanical cough assistance devices or needed tracheostomy during RDEs. Hospitalisation rate was 8.3% while none was admitted to ER and immediately discharged.

Table 2 shows differences in pre-discharge baseline data according to subjects with or without RDEs: among all these data, subjects with RDEs showed a statistically worse FEV1 and more years of disease duration.

The overall decline in PCEF during the study was −46.25±68.37L/min (range 30–190). Level of monthly decline in PCEF was −15.08±32.43 (median value 7.53; range 30–85.5)L/min. In our series, the lower level of PCEF was 40L/min and the minimum SpO2 was 90%. No differences were found in subjects with or without RDEs between subjects with high or low decline (p<0.079), PCEF > or <270L/min (p<0.276).

Subjects with high and low PCEF decline did not differ at the start of the project for any of the baseline variables. Individual trends and values in PCEF, SpO2 and RD at specific time points (16 days before, at the RDEs start and 30 days after RDEs) were available in 4 out of 5 subjects presenting an RDE (80%) (Fig. 1). ANOVA analysis shows that the sensation of discomfort only worsened significantly from 16 days before and 30 days after from 3.0±1.41 to 4.25±1.71 points of Borg score (Tukey Test significant). On the day of the RDE, these subjects had worsened PCEF (from 225±69.5L/min to 177.5±42.7L/min), SpO2 (from 95±1.83 to 93±0%) and subjective RD (from 2.25±0.96 to 4.75±1.89 Borg score) with respect to their pre-discharge data. These changes however did not reach statistical significance.

Figure 1.

Individual trends and values in PCEF, SpO2 and respiratory discomfort by Borg scale 16 days before, the day before and 30 days after four RDEs related to respiratory causes in 4 representative subjects. Borg scale detected wellbeing respiratory sensation (0=absolute wellbeing, no symptoms, 10=maximum perceived feeling of discomfort).

PCEF indicates peak cough expiratory flow; SpO2, oxygen saturation as measured by pulse oxymetry.

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Previous studies have shown that PCEF is a good functional indicator of spontaneous cough effectiveness.6–8

Home patients’ diaries have been proposed for COPD exacerbation24–27 while home variation in peak expiratory flow has been evaluated in asthma28,29 and COPD.30

Sancho et al.6 reported that ALS subjects received a home protocol based on scheduled clinical and functional assessment by a physician and were encouraged to request hospitalisation if they suffered dyspnoea, ineffective cough or decreased oxyhemoglobin saturation.6

A significant decrease of sniff nasal inspiratory pressure (SNIP) and a parallel increase in dyspnoea Borg Score were observed in 14 ALS subjects during a period of 19 months.31

Baseline dyspnoea index was found to be related with a decline in forced vital capacity which was better than that of the revised ALS functional rating scale (ALS-FRS-R) and a visual analogue scale.2

Compliance with the proposed protocol was not high; it was 67% before discharge and it got worse over time; this result is very similar to the compliance with home PCEF monitoring in subjects with asthma.32 Two main reasons can be identified: the long duration of the study and the huge number of measurements requested daily. Psychological and depressive reasons might have further reduced adherence.

In regards to the feasibility of conducting the protocol at home, it is interesting to note that the adherence to the protocol deteriorated, especially after the first three months, and that telephone feedback by the physiotherapist became necessary. Moreover, subjects sent their data through the mail thinking that this method was simpler and more reliable. In more than half of the cases caregivers performed the required measurements: this is not surprising since ALS is a severe disabling disease requiring a high amount of caring by caregivers.

More than 40% of subjects presented 6 episodes of respiratory derangements. Five subjects presenting a RDE were, in general, more compromised in all functional and clinical parameters. Also the decline during follow-up was worse than that of subjects without RDE.

Due to the small sample size, statistical significance was only found for FEV1 and years of diseases. It is also interesting to note that a cut off of baseline PCEF > or < to 270L/min was not predictable for RDEs.

Previous results from literature do not show what could happen to these subjects during a respiratory tract infection.18 Only Poponick et al.3 evaluated respiratory function in subjects with multiple muscular dystrophies during and in the post recovery phase of acute upper respiratory tract infection: whereas we monitored respiratory function, SpO2 and cough ability before, during and for a longer post recovery phase in a more homogeneous ALS population.

As demonstrated in 4 representative subjects (Fig. 1) only the sensation of discomfort worsened significantly from 16 days before and 30 days after the RDEs demonstrating that objective data present a faster recovery time than subjective ones.

Our pilot data do not support the hypothesis that subjects with ALS with low or high decline in PCEF during time and high or low level of baseline PCEF are prone to have a RDE.

The strengths of this study are: (a) proposal for a home daily cough capacity follow-up, (b) information on monthly trends in PCEF decline, (c) documentation of events during a RDE and during recovery time.

An important limitation to this study is the small sample size of the population: as a descriptive case-series we need to temper our interpretation of presented data. Poor protocol adherence prevents definitive conclusions as we need to consider that non-adherent patients could be the patients with the worst disease decline. We cannot exclude the possibility that a simpler and less cumbersome protocol (monitoring variables less frequently, monitoring fewer variables and simplifying the reporting) would improve patient compliance.

In conclusion, in subjects with ALS, good adherence to combined daily self-monitoring for PCEF, SpO2 and respiratory discomfort seems difficult to obtain and does not add further advantages to current practices of advising on clinical derangements; that is use of mechanical cough assistance or increase of ventilatory support immediately SpO2 drops below 95%. Confirmatory larger studies are necessary in this field in order to study new domiciliary monitoring tools and to find predicted clinical variables of respiratory distress events.

The authors have no conflicts of interest to declare.