Anne Edvardsen

Hypoxaemia in chronic obstructive pulmonary disease patients during a commercial flight.

The aim of the study was to investigate hypoxaemia in chronic obstructive pulmonary disease patients during a commercial flight. The effect of a commercial flight, lasting 5 h 40 min, on arterial blood gas levels and symptoms in 18 chronic obstructive pulmonary disease patients with a pre-flight percutaneous oxygen saturation of ≥94% and self-reported ability to walk 50 m without severe dyspnoea was studied. The arterial oxygen tension (Pa,O2) decreased from sea level to cruising altitude (10.3±1.2 versus 8.6±0.8 kPa), but, thereafter, except for one patient, remained stable throughout the flight. During light exercise, however, there was further desaturation (percutaneous oxygen saturation 90±4 versus 87±4%). After 4 h, a decrease in arterial carbon dioxide tension (5.0±0.4 versus 4.8±0.4 kPa) and an increase in cardiac frequency (87±13 versus 95±13 beats·min-1) were observed. A pre-flight Pa,O2 of >9.3 kPa did not secure an acceptable in-flight Pa,O2. Aerobic capacity showed the strongest correlation with in-flight Pa,O2. In conclusion, following an initial decrease in arterial oxygen tension, chronic obstructive pulmonary disease patients in a stable state of their disease seem to maintain a stable arterial oxygen tension throughout a flight of intermediate duration, except when walking along the aisle. However, a decrease in arterial carbon dioxide tension, indicating compensatory hyperventilation, could imply a risk of respiratory fatigue during longer flights.

Relationship between exercise desaturation and pulmonary haemodynamics in COPD patients

Pulmonary hypertension (PH) in patients with chronic obstructive pulmonary disease (COPD) has traditionally been explained as an effect of hypoxaemia. Recently, other mechanisms, such as arterial remodelling caused by inflammation, have been suggested. The aim of this study was to investigate whether exercise-induced PH (EIPH) could occur without concurrent hypoxaemia, and whether exercise-induced hypoxaemia (EIH) was regularly accompanied by increased pulmonary artery pressure or pulmonary vascular resistance index (PVRI). Pulmonary haemodynamics in 17 patients with COPD of varying severity, but with no or mild hypoxaemia at rest, were examined during exercise equivalent to the activities of daily living (ADL) and exhaustion. EIPH occurred in 65% of the patients during ADL exercise. Pulmonary arterial pressure during exercise was negatively correlated with arterial oxygen tension, but EIPH was not invariably accompanied by hypoxaemia. Conversely, EIPH was not found in all patients with EIH. The resting PVRI was negatively correlated with arterial oxygen tension during ADL exercise, but an elevated PVRI without EIH occurred in 35% of the patients. In conclusion, exercise-induced pulmonary hypertension occurred during exercise equivalent to the activities of daily living in chronic obstructive pulmonary disease patients with no or mild hypoxaemia at rest. Although pulmonary artery pressure and arterial oxygen tension were negatively correlated during exercise, a consistent relationship between hypoxaemia and pulmonary hypertension could not be demonstrated. This may indicate that mechanisms other than hypoxaemia contribute significantly in the development of pulmonary hypertension in these patients.

Pulse oximetry in the preflight evaluation of patients with chronic obstructive pulmonary disease.

INTRODUCTION In a British Thoracic Society (BTS) statement on preflight evaluation of patients with respiratory disease, sea level pulse oximetry (Spo2sl) is recommended as an initial assessment. The present study aimed to evaluate if the BTS algorithm can be used to identify chronic obstructive pulmonary disease (COPD) patients in need of supplemental oxygen during air travel, i.e. patients with an in-flight PaO2 < 6.6 kPa (50 mmHg). METHODS There were 100 COPD patients allocated to groups according to the BTS algorithm: Spo2sl > 95%, Spo2sl 92-95% without additional risk factors; Spo2sl 92-95% with additional risk factors; Spo2sl < 92%; and patients using domiciliary oxygen. Pulse oximetry, arterial blood gases, and an hypoxia-altitude simulation test (HAST) to simulate a cabin altitude of 2438 m (8000 ft), were performed. RESULTS The percentage of patients in the various groups dropping below 6.6 kPa during HAST were: Spo2sl > 95%: 30%; Spo2sl 92-95% without additional risk factors: 67%; Spo2sl 92-95% with additional risk factors: 70%; Spo2sl < 92%: 83%; and patients using domiciliary oxygen: 81%. In patients dropping below P(a)o(2) 6.6 kPa, supplemental oxygen of median 1 L x min(-1) was needed to exceed this limit. DISCUSSION If in-flight P(a)o(2) > or = 6.6 kPa is regarded as a strict requirement, the use of pulse oximetry as an initial assessment in the preflight evaluation of COPD patients, as suggested by the BTS, might not discriminate adequately between patients who fulfill the indications for supplemental oxygen during air travel, and patients who can travel without such treatment.

COPD and Air Travel: Oxygen Equipment and Preflight Titration of Supplemental Oxygen

BACKGROUND Patients with COPD may need supplemental oxygen during air travel to avoid development of severe hypoxemia. The current study evaluated whether the hypoxia-altitude simulation test (HAST), in which patients breathe 15.1% oxygen simulating aircraft conditions, can be used to establish the optimal dose of supplemental oxygen. Also, the various types of oxygen-delivery equipment allowed for air travel were compared. METHODS In a randomized crossover trial, 16 patients with COPD were exposed to alveolar hypoxia: in a hypobaric chamber (HC) at 2,438 m (8,000 ft) and with a HAST. During both tests, supplemental oxygen was given by nasal cannula (NC) with (1) continuous flow, (2) an oxygen-conserving device, and (3) a portable oxygen concentrator (POC). RESULTS PaO(2) kPa (mm Hg) while in the HC and during the HAST with supplemental oxygen at 2 L/min (pulse setting 2) on devices 1 to 3 was (1) 8.6 ± 1.0 (65 ± 8) vs 12.5 ± 2.4 (94 ± 18) (P < .001), (2) 8.6 ± 1.6 (64 ± 12) vs 9.7 ± 1.5 (73 ± 11) (P < .001), and (3) 7.7 ± 0.9 (58 ± 7) vs 8.2 ± 1.1 (62 ± 8) (P= .003), respectively. CONCLUSIONS The HAST may be used to identify patients needing supplemental oxygen during air travel. However, oxygen titration using an NC during a HAST causes accumulation of oxygen within the facemask and underestimates the oxygen dose required. When comparing the various types of oxygen-delivery equipment in an HC at 2,438 m (8,000 ft), compressed gaseous oxygen with continuous flow or with an oxygen-conserving device resulted in the same PaO(2), whereas a POC showed significantly lower PaO(2) values. TRIAL REGISTRY ClinicalTrials.gov; No.: Identifier: NCT01019538; URL: clinicaltrials.gov.

Air travel and chronic obstructive pulmonary disease: a new algorithm for pre-flight evaluation

Background The reduced pressure in the aircraft cabin may cause significant hypoxaemia and respiratory distress in patients with chronic obstructive pulmonary disease (COPD). Simple and reliable methods for predicting the need for supplemental oxygen during air travel have been requested. Objective To construct a pre-flight evaluation algorithm for patients with COPD. Methods In this prospective, cross-sectional study of 100 patients with COPD referred to hypoxia-altitude simulation test (HAST), sea level pulse oximetry at rest (SpO2 SL) and exercise desaturation (SpO2 6MWT) were used to evaluate whether the patient is fit to fly without further assessment, needs further evaluation with HAST or should receive in-flight supplemental oxygen without further evaluation. HAST was used as the reference method. Results An algorithm was constructed using a combination of SpO2 SL and SpO2 6MWT. Categories for SpO2 SL were >95%, 92–95% and <92%, the cut-off value for SpO2 6MWT was calculated as 84%. Arterial oxygen pressure (PaO2 HAST) <6.6 kPa was the criterion for recommending supplemental oxygen. This algorithm had a sensitivity of 100% and a specificity of 80% when tested prospectively on an independent sample of patients with COPD (n=50). Patients with SpO2 SL >95% combined with SpO2 6MWT ≥84% may travel by air without further assessment. In-flight supplemental oxygen is recommended if SpO2 SL=92–95% combined with SpO2 6MWT <84% or if SpO2 SL <92%. Otherwise, HAST should be performed. Conclusions The presented algorithm is simple and appears to be a reliable tool for pre-flight evaluation of patients with COPD.

COPD and air travel: does hypoxia-altitude simulation testing predict in-flight respiratory symptoms?

The reduced pressure in an aircraft cabin may cause significant hypoxaemia and respiratory symptoms in patients with chronic obstructive pulmonary disease (COPD). The current study evaluated whether there is a relationship between hypoxaemia obtained during hypoxia-altitude simulation testing (HAST), simulating an altitude of 2438 m, and the reporting of respiratory symptoms during air travel. 82 patients with moderate to very severe COPD answered an air travel questionnaire. Arterial oxygen tensions during HAST (PaO2HAST) in subjects with and without in-flight respiratory symptoms were compared. The same questionnaire was answered within 1 year after the HAST. Mean±sd PaO2HAST was 6.3±0.6 kPa and 62 (76%) of the patients had PaO2HAST <6.6 kPa. 38 (46%) patients had experienced respiratory symptoms during air travel. There was no difference in PaO2HAST in those with and those without in-flight respiratory symptoms (6.3±0.7 kPa versus 6.3±0.6 kPa, respectively; p=0.926). 54 (66%) patients travelled by air after the HAST, and patients equipped with supplemental oxygen (n=23, 43%) reported less respiratory symptoms when flying with than those without such treatment (four (17%) versus 11 (48%) patients; p=0.039). In conclusion, no difference in PaO2HAST was found between COPD patients with and without respiratory symptoms during air travel. Hypoxia-altitude simulation testing does not predict in-flight respiratory symptoms in COPD patients http://ow.ly/nUCtF

Arterial oxygen pressure following whole-body vibration at altitude.

INTRODUCTION Most helicopter operations are carried out at altitudes below 10,000 ft. At these altitudes, the risk of the crew experiencing hypoxia is low. For that reason, supplementary oxygen is not standard equipment on board most helicopters. Due to developments in military missions, high-altitude operations have become more frequent-as have the chances of the crew experiencing hypoxia. Helicopter crews are subjected to a higher load of whole-body vibration compared to fixed-wing aircraft crews. Whole-body vibration increases muscle work, with increased oxygen consumption as a result. We hypothesized that whole-body vibration, as experienced by helicopter crews, causes additional lowering of arterial oxygen levels under hypoxic conditions. METHODS Data were collected from 10 subjects. They were all exposed to six different pressure altitudes in a hypobaric chamber, ranging from 1000 ft to 16,000 ft (approximately 305 m to approximately 4877 m). Arterial blood samples were drawn on two occasions at each altitude: after 14 min of rest and followed by 15 min of whole-body vibration (17 Hz, at 1.1 m x s(-2) in the z-axis) at each altitude. RESULTS There was no significant effect of whole-body vibration on arterial oxygen pressure at altitudes up to 16,000 ft (approximately 4877 m), nor was there any effect on ventilation, seen as changes in arterial pressure of CO2. DISCUSSION We contribute the lack of effect to the low vibration intensity used in this study. Since this vibration intensity was higher than experienced by helicopter crews during flight, we conclude that whole-body vibration does not contribute to hypoxia during high-altitude operations in helicopters.