Airway Dysfunction in Obesity: Response to Voluntary Restoration of End Expiratory Lung Volume

Abstract

IntroductionAbnormality in distal lung function may occur in obesity due to reduction in resting lung volume; however, airway inflammation, vascular congestion and/or concomitant intrinsic airway disease may also be present. The goal of this study is to 1) describe the phenotype of lung function in obese subjects utilizing spirometry, plethysmography and oscillometry; and 2) evaluate residual abnormality when the effect of mass loading is removed by voluntary elevation of end expiratory lung volume (EELV) to predicted FRC.Methods100 non-smoking obese subjects without cardio-pulmonary disease and with normal airflow on spirometry underwent impulse oscillometry (IOS) at baseline and at the elevated EELV.ResultsFRC and ERV were reduced (44±22, 62±14% predicted) with normal RV/TLC (29±9%). IOS demonstrated elevated resistance at 20 Hz (R20, 4.65±1.07 cmH2O/L/s); however, specific conductance was normal (0.14±0.04). Resistance at 5–20 Hz (R5−20, 1.86±1.11 cmH2O/L/s) and reactance at 5 Hz (X5, −2.70±1.44 cmH2O/L/s) were abnormal. During elevation of EELV, IOS abnormalities reversed to or towards normal. Residual abnormality in R5−20 was observed in some subjects despite elevation of EELV (1.16±0.8 cmH2O/L/s). R5−20 responded to bronchodilator at baseline but not during elevation of EELV.ConclusionsThis study describes the phenotype of lung dysfunction in obesity as reduction in FRC with airway narrowing, distal respiratory dysfunction and bronchodilator responsiveness. When R5−20 normalized during voluntary inflation, mass loading was considered the predominant mechanism. In contrast, when residual abnormality in R5−20 was demonstrable despite return of EELV to predicted FRC, mechanisms for airway dysfunction in addition to mass loading could be invoked.

Influence of distinct asthma phenotypes on lung function following weight loss in the obese

“…Indeed, increased airway remodelling has been reported in obese mice following chronic allergen challenge . An effect of obesity on airway calibre independent of lung volume is consistent with the recent finding that resistance remains elevated in two thirds of obese patients during lung inflation to predicted FRC . On the other hand, the extent of weight loss in the T H 2‐low obese asthmatics was somewhat less than the T H 2‐high group, so it is also possible that the T H 2‐low group did not lose enough weight to cause a significant decrease in resistance.…”

“…31 An effect of obesity on airway calibre independent of lung volume is consistent with the recent finding that resistance remains elevated in two thirds of obese patients during lung inflation to predicted FRC. 32 On the other hand, the extent of weight loss in the TH2-low obese asthmatics was somewhat less than the TH2-high group, so it is also possible that the TH2-low group did not lose enough weight to cause a significant decrease in resistance. In fact, FRC does not differ between subjects with a BMI of 35-40 kg/m 2 and those with BMI > 40 kg/m 2 .…”

Effects of a multidisciplinary body weight reduction program on static and dynamic thoraco-abdominal volumes in obese adolescents

“…The last includes breathing at lower lung volumes, decreased thoracic compliance, and increased respiratory resistance secondary to the reduction in lung volumes related to overweight (Babb 1999;DeLorey et al 2005;Parameswaran et al 2006;Babb et al 2011;Chlif et al 2015). These features suggest that in addition to an augmented elastic load due to the mass burdening on the chest wall, obese subjects also have to overcome a higher resistive load (Oppenheimer et al 2014). Respiratory muscles therefore have to cope with increased work of breathing, particularly during exercise (Lin and Lin 2012).…”

Factores comunes e inductores de inflamación en asma y obesidad

“…Algunos autores han observado anormalidades en la resistencia y frecuencia en la oscilometría, a pesar del flujo normal detectado por espirometría, lo que sugiere una disfunción más distal. 82 El aumento en el índice de masa corporal está asociado directamente con el grado de resistencia de las vías aéreas y el trabajo respiratorio. La reducción en la capacidad residual funcional y el volumen de reserva espiratoria están asociados con un estrechamiento temprano de las vías aéreas; esto causa alteraciones en la ventilación-perfusión y consecuentemente hipoxia, lo que se exacerba durante el sueño.…”