Table 1.
Alternative pulmonary function tests (PFTs) for asthmatic children during the Covid-19 pandemic.
| Laboratory (References) | Advantages | Limitations |
|---|---|---|
| FOT (9, 10, 14–21) | • Assess respiratory mechanics and airway resistance during tidal breathing. Help to detect peripheral airway obstruction. • Brief, feasible for children who are unable to cooperate with spirometry. • Baseline outcomes fairly distinguish subjects with recurrent wheeze/asthma from those healthy (see limitations). • Best utility, to assess the BDR and AHR. • Help overtime assessment and prediction of loss of asthma control. |
• Outcomes depend on patient selection and diagnostic criteria. • Sensitive to upper airway shunting. • Multi-ethnic normative values are lacking. • Usefulness for long-term monitoring of patients, further studies needed. • Standardization of the technique and response to bronchodilators (type, drug dose, and timing), should be improved. |
| Rint (9, 14, 18, 22–25) | • Assess respiratory resistance during tidal breathing. Simple, quick, adapted for toddlers. • Reported high values in young children with persistent wheeze as compared with transient wheezers or never wheezers. • Assess the BDR with good sensitivity and specificity. • Relatively useful to assess AHR to cold air or exercise challenge (see limitations). |
• Low sensitivity to detect peripheral airway obstruction. • Sensitive to upper airway shunting. • Does not discriminate well between children with recurrent wheeze and those healthy. • May underestimate resistance in children with severe airway obstruction. • Unclear utility for asthma monitoring. |
| FENO (26–33) | • Assess TH2-type airway inflammation during slow exhalation maneuvers. • Moderate accuracy for asthma diagnosis in subjects 5 yrs. and older. • Patients with FENO >35 ppb are likely to benefit from inhaled corticosteroids (ICs). • Assist correct use of ICs, therapy compliance, and resistance to ICs. • Help to monitor biological therapy. • Raising levels predict disease exacerbations. |
• Positively skewed levels; overlapping between asthmatic and healthy subjects. Low FENO does not exclude asthma. • The optimization of therapy based on FENO has not proven better outcomes. • Several factors can affect its levels (e.g., atopy, infections, comorbidities, age, height, sex, and smoking exposure). • Needs coaching, especially in young children. |
| MBW (18, 34–40) | • Inert gas clearance technique. Assess ventilation distribution inhomogeneity during tidal breathing. Also measures the functional residual capacity (FRC). • Feasible for young children, reproducible. • Useful in severe or uncontrolled asthma. • More sensitive than spirometry to detect small airway disease. • Both MBW and FENO indices can help to assess disease exacerbations and EIB. |
• Prolonged testing, especially in patients with uneven ventilation. • Requires experienced personnel. Preparation of the equipment and data processing is complex. • Insensitive to detect small airway dysfunction in mild asthma. • Multi-ethnic normative values are lacking. • Expensive devices, scarce accessibility. |
| Home (References) | ||
| PEF (41–45) | • Assess airflow limitation during maximal expiratory maneuvers. Hand-held devices. | • Effort dependent. Do not enhance self-management during asthma flare-ups. |
| • Assessment of diurnal variation or changes between visits; variability weakly correlates with asthma symptoms and AHR. • New electronic devices with smartphone applications are feasible for children. |
• Written records are unreliable. • Compliance decreases after 4 weeks. • Often disagrees with spirometric records. • Electronic PEF meters with automatic teletransmission still need validation. |
|
| Spirometry (13, 46–50) | • Assess maximal inspiratory and expiratory volumes; estimate the baseline airway patency and its changes (BDR and AHR). • Flow-volume curves can be evaluated remotely, by an operator. • Acceptability and reproducibility criteria (with instructions to subjects if criterion not met) are available. • Portable devices. |
• Effort dependent; underestimated data. Data quality decreases with younger age, lack of controller therapy, and FEV1 < 80%. • Daily FEV1 telemonitoring does not lead to better symptom control or fewer attacks. • Devices often lack instructive videos and maneuver's quality feedback. • Variable accuracy. Expensive. • Smartphone spirometers need validation. |
| FOT (51) | • As above (Laboratory). Useful for assessing day-to-day variability. | • Expensive. Requires more evidence for long-term monitoring. |
| FENO (52, 53) | • As above (Laboratory). Improves with mobile direct observation of therapy (MDOT). | • Expensive. Needs good quality control, instructions, and online feedback. |
FOT, forced oscillation technique; Rint, respiratory resistance measured with the interrupter technique; FENO, fractional exhaled nitric oxide concentration; MBW, multiple breath washout; PEF, peak expiratory flow; BDR, bronchodilator response; AHR, airway hyperresponsiveness; ICs, inhaled corticosteroids.