Reference Equations for Within-Breath Respiratory Oscillometry in White Adults.

BACKGROUND: Within-breath analysis of oscillometry parameters is a growing research area since it increases sensitivity and specificity to respiratory pathologies and conditions. However, reference equations for these parameters in White adults are lacking and devices using multiple sinusoids or pseudorandom forcing stimuli have been underrepresented in previous studies deriving reference equations. The current study aimed to establish reference ranges for oscillometry parameters, including also the within-breath ones in White adults using multi-sinusoidal oscillations. METHODS: White adults with normal spirometry, BMI ≤30 kg/m2, without a smoking history, respiratory symptoms, pulmonary or cardiac disease, neurological or neuromuscular disorders, and respiratory tract infections in the previous 4 weeks were eligible for the study. Study subjects underwent oscillometry (multifrequency waveform at 5-11-19 Hz, Resmon PRO FULL, RESTECH Srl, Italy) in 5 centers in Europe and the USA according to international standards. The within-breath and total resistance (R) and reactance (X), the resonance frequency, the area under the X curve, the frequency dependence of R (R5-19), and within-breath changes of X (ΔX) were submitted to lambda-mu-sigma models for deriving reference equations. For each output parameter, an AIC-based stepwise input variable selection procedure was applied. RESULTS: A total of 144 subjects (age 20.8-86.3 years; height 146-193 cm; BMI 17.42-29.98 kg/m2; 56% females) were included. We derived reference equations for 29 oscillatory parameters. Predicted values for inspiratory and expiratory parameters were similar, while differences were observed for their limits of normality. CONCLUSIONS: We derived reference equations with narrow confidence intervals for within-breath and whole-breath oscillatory parameters for White adults.

Impulse oscillometry and nitrogen washout test in the assessment of small airway dysfunction in asthma: Correlation with quantitative computed tomography.

OBJECTIVE: Small airway dysfunction (SAD) and airway remodeling influence the disease control and progression in asthma. We investigated whether impulse oscillometry (IOS) and single breath nitrogen washout (SBN2W) could be reliable tests in evaluating SAD and airway remodeling by correlating their data with radiological parameters derived from quantitative chest multidetector computed tomography (MDCT) imaging. METHODS: Lung function tests were performed before and after bronchodilator. The MDCT lung scans were acquired at full inspiration and expiration using a portable spirometer to control the respiratory manoeuvres. Symptom control was assessed using the Asthma Control Test (ACT) questionnaire. RESULTS: Twenty six patients were enrolled. The bronchial lumen area (LA) measured with MDCT lung scan, correlated inversely with airway resistance (Raw, p < 0.001) and with total and large airway oscillometric resistance (R5, p = 0.002 and R20, p = 0.006, respectively). However these two last correlations became non-significant after Bonferroni correction for multiple comparisons. The radiological quantification of air trapping correlated with Raw (p < 0.001), residual volume (RV, p < 0.001), and the slope of phase III of SBN2W (DeltaN2, p < 0.001) whereas the correlation with small airway oscillometric resistance (R5-20) was non-significant after Bonferroni adjustment. Finally, air trapping was significantly higher in patients with a fixed bronchial obstruction in comparison to patients with reversible obstruction. CONCLUSIONS: Plethysmographic method remains the main tool to investigate SAD and airway remodeling in asthmatic patients. The integration with the SBN2W test proved useful to better evaluate the small airway involvement whereas IOS showed a weaker correlation with both radiological and clinical data.

Reduced respiratory muscle strength and endurance in type 2 diabetes mellitus.

BACKGROUND: A restrictive lung function pattern is frequently observed in patients with diabetes mellitus (DM) and has been related to respiratory muscle dysfunction in type 1 DM or in mixed population. We aimed to verify whether such a relationship applies also to type 2 DM patients. METHODS: The respiratory muscle function was explored in 75 non-smoking patients with type 2 DM without pulmonary or cardiac diseases and compared with that of 40 healthy non-smoking control subjects matched by age and sex. Maximal inspiratory and expiratory pressures (MIP, MEP) and maximum voluntary ventilation (MVV), which reflect respiratory muscle strength and endurance, respectively, were measured, and a complete respiratory function assessment was recorded. RESULTS: Patients were in stable metabolic conditions and had, on average, normal total lung capacity and diffusing lung capacity for carbon monoxide. However, MIP and MVV were significantly reduced in comparison with those of control subjects. Both MIP/MEP and MVV significantly correlated with lung volumes and diffusing lung capacity for carbon monoxide. The multiple regression analysis identified age (beta coefficient = -0.238, p = 0.046), glycated haemoglobin (beta coefficient = -0.245, p = 0.047) and total lung capacity (beta coefficient = 0.430, p = 0.016) as independent correlates of MIP, whereas male sex (beta coefficient = 0.423, p = 0.004) and diabetic complications (beta coefficient = -0.248, p = 0.044) were independent correlates of MVV. CONCLUSIONS: In type 2 DM, respiratory muscle strength was reduced and significantly related to lung volumes and quality of metabolic control, whereas impaired endurance of respiratory muscles prevailed in patients with microvascular complications.

Decline of the lung function and quality of glycemic control in type 2 diabetes mellitus.

OBJECTIVE: The aim of this study was to verify to which extent in type 2 diabetes mellitus respiratory function and respiratory muscle efficiency decline over time in relation to the quality of glycemic control (GC). METHODS: Forty-five non-smoker diabetic patients without pulmonary diseases performed a complete respiratory function assessment at baseline and after a follow-up of 4.9±0.6 years. The respiratory muscle efficiency was assessed by maximal inspiratory pressure (MIP) and maximum voluntary ventilation (MVV). Patients with an average yearly value of glycosylated hemoglobin≥7.5% at least in two years during follow-up were considered to have a poor GC. RESULTS: Residual volume and pulmonary diffusing capacity significantly declined over time in the whole sample of patients (p=0.049 and 0.025, respectively), but without difference between patients with poor (n. 12) and good (n. 33) GC. MIP declined in patients with poor GC (from 83.75±32.42 to 71.16±30.43% pred), and increased in those with good GC (from 76.22±26.00 to 82.42±30.34% pred), but the difference between groups was not significant (p=0.091). Finally, MVV significantly declined in patients with poor GC (from 70.60±25.49 to 68.10±18.82% pred) and increased in those with good GC (from 66.40±20.39 to 84.00±23.09% pred) with a significant difference between the two groups (p=0.003). CONCLUSION: These results show that, in type 2 diabetic patients, respiratory muscle efficiency, but not lung volumes and diffusing capacity, might suffer from a poor GC over time.