Leigh M. Seccombe

Effect of simulated commercial flight on oxygenation in patients with interstitial lung disease and chronic obstructive pulmonary disease

Background: Commercial aircraft cabins provide a hostile environment for patients with underlying respiratory disease. Although there are algorithms and guidelines for predicting in-flight hypoxaemia, these relate to chronic obstructive pulmonary disease (COPD) and data for interstitial lung disease (ILD) are lacking. The purpose of this study was to evaluate the effect of simulated cabin altitude on subjects with ILD at rest and during a limited walking task. Methods: Fifteen subjects with ILD and 10 subjects with COPD were recruited. All subjects had resting arterial oxygen pressure (Pao2) of >9.3 kPa. Subjects breathed a hypoxic gas mixture containing 15% oxygen with balance nitrogen for 20 minutes at rest followed by a 50 metre walking task. Pulse oximetry (Spo2) was monitored continuously with testing terminated if levels fell below 80%. Arterial blood gas tensions were taken on room air at rest and after the resting and exercise phases of breathing the gas mixture. Results: In both groups there was a statistically significant decrease in arterial oxygen saturation (Sao2) and Pao2 from room air to 15% oxygen at rest and from 15% oxygen at rest to the completion of the walking task. The ILD group differed significantly from the COPD group in resting 15% oxygen Sao2, Pao2, and room air pH. Means for both groups fell below recommended levels at both resting and when walking on 15% oxygen. Conclusion: Even in the presence of acceptable arterial blood gas tensions at sea level, subjects with both ILD and COPD fall below recommended levels of oxygenation when cabin altitude is simulated. This is exacerbated by minimal exercise. Resting sea level arterial blood gas tensions are similarly poor in both COPD and ILD for predicting the response to simulated cabin altitude.

Abnormal ventilatory control in Parkinson's disease--further evidence for non-motor dysfunction.

There has been increasing recognition of pre-motor manifestations of Parkinsons disease (PD) resulting from early brainstem involvement. We sought to determine whether ventilatory control is abnormal. Patients with PD without respiratory disease were recruited. Spirometry, lung volumes, diffusing capacity and respiratory muscle strength were assessed. Occlusion pressure and ventilation were measured with increasing CO(2). Arterial blood gases were taken at rest and following 20 min exposure to 15% O(2). A linear correlation assessed associations between respiratory function and indices of PD severity. 19 subjects (17 males) with mild-moderate PD were studied (mean (SD) age 66 (8) years). Respiratory flows and volumes were normal in 16/19. Maximum inspiratory and expiratory pressures were below LLN in 13/19 and 15/19 respectively. 7/15 had a reduced ventilatory response to hypercapnia and 11/15 had an abnormal occlusion pressure. There was no correlation between impairment of ventilatory response and reduction in respiratory muscle strength. Response to mild hypoxia was normal and there were no associations between disease severity and respiratory function. Our findings suggest that patients with mild-moderate PD have abnormal ventilatory control despite normal lung volumes and flows.

Oxygen supplementation for chronic obstructive pulmonary disease patients during air travel

Purpose of review By 2008 it is projected that over two billion people will be travelling by commercial aircraft each year. With an ageing population and treatment improvements, many of these travellers will have lung disease, particularly chronic obstructive pulmonary disease. Current guidelines as to whether a patient requires supplemental oxygen during the flight are based on limited research evidence. Awareness of the increased risk has resulted in recent scientific interest in this area. Recent findings Studies have demonstrated a lack of consistency in international guideline recommendations when performing assessments within the respiratory laboratory. This has led to more specific analysis of patients, including in-flight assessments, the inclusion of exercise stress and more interest in actual cabin pressure conditions. Summary Commercial air travel is generally safe for patients with chronic obstructive pulmonary disease when their disease is stable. All current guidelines reflect the considerable uncertainty in relation to the clinical circumstances when oxygen prescription during flight is essential. Currently planned flight outcome studies will provide more precise risk quantification.

Directly measured cabin pressure conditions during Boeing 747–400 commercial aircraft flights

Background and objectives:  In the low pressure environment of commercial aircraft, hypoxaemia may be common and accentuated in patients with lung or heart disease. Regulations specify a cabin pressure not lower than 750 hPa but it is not known whether this standard is met. This knowledge is important in determining the hazards of commercial flight for patients and the validity of current flight simulation tests.

Glossopharyngeal insufflation causes lung injury in trained breath-hold divers

Background and objective:  Glossopharyngeal insufflation (GI) is a technique practised by competitive breath‐hold divers to enhance their performance. Using the oropharyngeal musculature, air is pumped into the lungs to increase the lung volume above physiological TLC. Experienced breath‐hold divers can increase their lung volumes by up to 3 L. Although the potential for lung injury is evident, there is limited information available. The aim of this study was to examine whether there is any evidence of lung injury following GI, independent of diving.

Predicting the response to air travel in passengers with non-obstructive lung disease: Are the current guidelines appropriate?

Background and objective:  Air travel guidelines recommend using baseline arterial oxygen levels and the hypoxic challenge test (HCT) to predict in‐flight hypoxaemia and the requirement for in‐flight oxygen in patients with lung disease. The purpose of the present study was to (i) quantify the hypoxaemic response to air travel and (ii) identify baseline correlate(s) to predict this response in passengers with non‐obstructed lung disease.

Lung perfusion and chest wall configuration is altered by glossopharyngeal breathing

Glossopharyngeal insufflation is used by competitive breath-hold divers to increase lung gas content above baseline total lung capacity (TLC) in order improve performance. Whilst glossopharyngeal insufflation is known to induce hypotension and tachycardia, little is known about the effects on the pulmonary circulation and structural integrity of the thorax. Six male breath-hold divers were studied. Exhaled lung volumes were measured before and after glossopharyngeal insufflation. On two study days, subjects were studied in the supine position at baseline TLC and after maximal glossopharyngeal insufflation above TLC. Tc 99m labelled macro-aggregated albumin was injected and a computed tomography (CT) scan of the thorax was performed during breath-hold. Single photon emission CT images determined flow and regional deposition. Registered CT images determined change in the volume of the thorax. CT and perfusion comparisons were possible in four subjects. Lung perfusion was markedly diminished in areas of expanded lung. 69% of the increase in expired lung volume was via thoracic expansion with a caudal displacement of the diaphragm. One subject who was not proficient at glossopharyngeal insufflation had no change in CT appearance or lung perfusion. We have demonstrated areas of hyperexpanded, under perfused lung created by glossopharyngeal insufflation above TLC.

Right heart function during simulated altitude in patients with pulmonary arterial hypertension.

Objective Patients with pulmonary arterial hypertension (PAH) are often recommended supplemental oxygen for altitude travel due to the possible deleterious effects of hypoxia on pulmonary haemodynamics and right heart function. This includes commercial aircraft travel; however, the direct effects and potential risks are unknown. Methods Doppler echocardiography and gas exchange measures were investigated in group 1 patients with PAH and healthy patients at rest breathing room air and while breathing 15.1% oxygen, at rest for 20 min and during mild exertion. Results The 14 patients with PAH studied were clinically stable on PAH-specific therapy, with functional class II (n=11) and III (n=3) symptoms when tested. Measures of right ventricular size and function were significantly different in the PAH group at baseline as compared to 7 healthy patients (p<0.04). There was no evidence of progressive right ventricular deterioration during hypoxia at rest or under exertion. Pulmonary arterial systolic pressure (PASP) increased in both groups during hypoxia (p<0.01). PASP in hypoxia correlated strongly with baseline PASP (p<0.01). Pressure of arterial oxygen correlated with PASP in hypoxia (p<0.03) but not at baseline, with three patients with PAH experiencing significant desaturation. The duration and extent of hypoxia in this study was tolerated well despite a mild increase in symptoms of breathlessness (p<0.01). Conclusions Non-invasive measures of right heart function in group 1 patients with PAH on vasodilator treatment demonstrated a predictable rise in PASP during short-term simulated hypoxia that was not associated with a deterioration in right heart function.

Maintenance of vital capacity during repetitive breath-hold in a spearfishing competition

Background and objective:  Cough and a reduction in vital capacity have recently been reported following breath‐hold dives to depths of 25–75 m. We sought to investigate whether repetitive dives to depths of less than 30 m would elicit similar effects.

Investigating asthma symptoms in primary care

Even when dyspnoea is accompanied by a history of wheeze, use of spirometry and related tests is needed before making a diagnosis of asthma